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  • 151. Kankare, E.
    et al.
    Kotak, R.
    Pastorello, A.
    Fraser, M.
    Mattila, S.
    Smartt, S. J.
    Bruce, A.
    Chambers, K. C.
    Elias-Rosa, N.
    Flewelling, H.
    Fremling, Christoffer
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Harmanen, J.
    Huber, M.
    Jerkstrand, A.
    Kangas, T.
    Kuncarayakti, H.
    Magee, M.
    Magnier, E.
    Polshaw, J.
    Smith, K. W.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Tomasella, L.
    On the triple peaks of SNHunt248 in NGC 58062015Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 581, artikkel-id L4Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present our findings on a supernova (SN) impostor, SNHunt248, based on optical and near-IR data spanning similar to 15 yr before discovery, to similar to 1 yr post-discovery. The light curve displays three distinct peaks, the brightest of which is at MR similar to -15.0 mag. The post-discovery evolution is consistent with the ejecta from the outburst interacting with two distinct regions of circumstellar material. The 0.5-2.2 mu m spectral energy distribution at -740 d is well-matched by a single 6700 K blackbody with log(L/L-circle dot) similar to 6.1. This temperature and luminosity support previous suggestions of a yellow hypergiant progenitor; however, we find it to be brighter than the brightest and most massive Galactic late-F to early-G spectral type hypergiants. Overall the historical light curve displays variability of up to similar to +/- 1 mag. At current epochs (similar to 1 yr post-outburst), the absolute magnitude (MR similar to -9 mag) is just below the faintest observed historical absolute magnitude similar to 10 yr before discovery.

  • 152. Kann, D. A.
    et al.
    Klose, S.
    Zhang, B.
    Malesani, D.
    Nakar, E.
    Pozanenko, A.
    Wilson, A. C.
    Butler, N. R.
    Jakobsson, P.
    Schulze, S.
    Andreev, M.
    Antonelli, L. A.
    Bikmaev, I. F.
    Biryukov, V.
    Boettcher, M.
    Burenin, R. A.
    Castro Ceron, J. M.
    Castro-Tirado, A. J.
    Chincarini, G.
    Cobb, B. E.
    Covino, S.
    D'Avanzo, P.
    D'Elia, V.
    Della Valle, M.
    Postigo, A. de Ugarte
    Efimov, Yu.
    Ferrero, P.
    Fugazza, D.
    Fynbo, J. P. U.
    Gålfalk, Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Grundahl, F.
    Gorosabel, J.
    Gupta, S.
    Guziy, S.
    Hafizov, B.
    Hjorth, J.
    Holhjem, K.
    Ibrahimov, M.
    Im, M.
    Israel, G. L.
    Jelinek, M.
    Jensen, B. L.
    Karimov, R.
    Khamitov, I. M.
    Kiziloglu, Ue
    Klunko, E.
    Kubanek, P.
    Kutyrev, A. S.
    Laursen, P.
    Levan, A. J.
    Mannucci, F.
    Martin, C. M.
    Mescheryakov, A.
    Mirabal, N.
    Norris, J. P.
    Ovaldsen, J. -E
    Paraficz, D.
    Pavlenko, E.
    Piranomonte, S.
    Rossi, A.
    Rumyantsev, V.
    Salinas, R.
    Sergeev, A.
    Sharapov, D.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Stecklum, B.
    Stella, L.
    Tagliaferri, G.
    Tanvir, N. R.
    Telting, J.
    Testa, V.
    Updike, A. C.
    Volnova, A.
    Watson, D.
    Wiersema, K.
    Xu, D.
    THE AFTERGLOWS OF SWIFT-ERA GAMMA-RAY BURSTS. I. COMPARING PRE-SWIFT AND SWIFT-ERA LONG/SOFT (TYPE II) GRB OPTICAL AFTERGLOWS2010Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 720, nr 2, s. 1513-1558Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have gathered optical photometry data from the literature on a large sample of Swift-era gamma-ray burst (GRB) afterglows including GRBs up to 2009 September, for a total of 76 GRBs, and present an additional three pre-Swift GRBs not included in an earlier sample. Furthermore, we publish 840 additional new photometry data points on a total of 42 GRB afterglows, including large data sets for GRBs 050319, 050408, 050802, 050820A, 050922C, 060418, 080413A, and 080810. We analyzed the light curves of all GRBs in the sample and derived spectral energy distributions for the sample with the best data quality, allowing us to estimate the host-galaxy extinction. We transformed the afterglow light curves into an extinction-corrected z = 1 system and compared their luminosities with a sample of pre-Swift afterglows. The results of a former study, which showed that GRB afterglows clustered and exhibited a bimodal distribution in luminosity space, are weakened by the larger sample. We found that the luminosity distribution of the two afterglow samples (Swift-era and pre-Swift) is very similar, and that a subsample for which we were not able to estimate the extinction, which is fainter than the main sample, can be explained by assuming a moderate amount of line-of-sight host extinction. We derived bolometric isotropic energies for all GRBs in our sample, and found only a tentative correlation between the prompt energy release and the optical afterglow luminosity at 1 day after the GRB in the z = 1 system. A comparative study of the optical luminosities of GRB afterglows with echelle spectra (which show a high number of foreground absorbing systems) and those without, reveals no indication that the former are statistically significantly more luminous. Furthermore, we propose the existence of an upper ceiling on afterglow luminosities and study the luminosity distribution at early times, which was not accessible before the advent of the Swift satellite. Most GRBs feature afterglows that are dominated by the forward shock from early times on. Finally, we present the first indications of a class of long GRBs, which form a bridge between the typical high-luminosity, high-redshift events and nearby low-luminosity events (which are also associated with spectroscopic supernovae) in terms of energetics and observed redshift distribution, indicating a continuous distribution overall.

  • 153. Karambelkar, Viraj R.
    et al.
    Kasliwal, Mansi M.
    Blagorodnova, Nadejda
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Aloisi, Robert
    Anand, Shreya G.
    Andreoni, Igor
    Brink, Thomas G.
    Bruch, Rachel
    Cook, David
    Das, Kaustav Kashyap
    De, Kishalay
    Drake, Andrew
    Filippenko, Alexei V.
    Fremling, Christoffer
    Helou, George
    Ho, Anna
    Jencson, Jacob
    Jones, David
    Laher, Russ R.
    Masci, Frank J.
    Patra, Kishore C.
    Purdum, Josiah
    Reedy, Alexander
    Sit, Tawny
    Sharma, Yashvi
    Tzanidakis, Anastasios
    van der Walt, Stefan J.
    Yao, Yuhan
    Zhang, Chaoran
    Volumetric Rates of Luminous Red Novae and Intermediate-luminosity Red Transients with the Zwicky Transient Facility2023Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 948, nr 2, artikkel-id 137Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Luminous red novae (LRNe) are transients characterized by low luminosities and expansion velocities, and they are associated with mergers or common-envelope ejections in stellar binaries. Intermediate-luminosity red transients (ILRTs) are an observationally similar class with unknown origins, but they are generally believed to be either electron-capture supernovae in super-asymptotic giant branch stars or outbursts in dusty luminous blue variables (LBVs). In this paper, we present a systematic sample of eight LRNe and eight ILRTs detected as part of the Census of the Local Universe (CLU) experiment on the Zwicky Transient Facility (ZTF). The CLU experiment spectroscopically classifies ZTF transients associated with nearby (<150 Mpc) galaxies, achieving 80% completeness for m ( r ) < 20 mag. Using the ZTF-CLU sample, we derive the first systematic LRNe volumetric rate of 7.8-3.7+6.5x10-5 M ( r ) <= -11 mag. We find that, in this luminosity range, the LRN rate scales as dN/dL proportional to L-2.5 +/- 0.3 L (-1.4 +/- 0.3) for lower-luminosity LRNe (M ( V ) >= -10 mag). The steeper power law for LRNe at high luminosities is consistent with the massive merger rates predicted by binary population synthesis models. We find that the rates of the brightest LRNe (M ( r ) <= -13 mag) are consistent with a significant fraction of them being progenitors of double compact objects that merge within a Hubble time. For ILRTs, we derive a volumetric rate of 2.6-1.4+1.8x10-6 M ( r ) <= -13.5 mag, which scales as dN/dL proportional to L-2.5 +/- 0.5

  • 154. Karambelkar, Viraj R.
    et al.
    Kasliwal, Mansi M.
    Maguire, Kate
    Anand, Shreya G.
    Andreoni, Igor
    De, Kishalay
    Drake, Andrew
    Duev, Dmitry A.
    Graham, Matthew J.
    Kool, Erik C.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Laher, Russ R.
    Magee, Mark R.
    Mahabal, Ashish A.
    Medford, Michael S.
    Perley, Daniel
    Rigault, Mickael
    Rusholme, Ben
    Schulze, Steve
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Sharma, Yashvi
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Tzanidakis, Anastasios
    Walters, Richard
    Yao, Yuhan
    Faintest of Them All: ZTF 21aaoryiz/SN 2021fcg-Discovery of an Extremely Low Luminosity Type Iax Supernova2021Inngår i: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 921, nr 1, artikkel-id L6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present the discovery of ZTF 21aaoryiz/SN 2021fcg-an extremely low luminosity Type Tax supernova. SN 2021fcg was discovered by the Zwicky Transient Facility in the star-forming galaxy IC0512 at a distance of approximate to 27 Mpc. It reached a peak absolute magnitude of M-r = -12.66 +/- 0.20 mag, making it the least luminous thermonuclear supernova discovered to date. The E(B - V) contribution from the underlying host galaxy is unconstrained. However, even if it were as large as 0.5 mag, the peak absolute magnitude would be M-r = -13.78 +/- 0.20 mag-still consistent with being the lowest-luminosity SN. Optical spectra of SN 2021fcg taken at 37 and 65 days post-maximum show strong [Ca II], Ca II, and Na I D emission and several weak [Fe II] emission lines. The [Ca II] emission in the two spectra has extremely low velocities of approximate to 1300 and 1000 km s(-1), respectively. The spectra very closely resemble those of the very low luminosity Type Tax supernovae SN 2008 ha, SN 2010ae, and SN 2019gsc taken at similar phases. The peak bolometric luminosity of SN 2021fcg is approximate to 2.5(-0.3)(+1.5) x 10(40) erg s(-1), which is a factor of 3 lower than that for SN 2008 ha. The bolometric lightcurve of SN 2021fcg is consistent with a very low ejected nickel mass (M-Ni approximate to 0.8(-0.5)(+0.4) x 10(-3) M-circle dot). The low luminosity and nickel mass of SN 2021fcg pose a challenge to the picture that low-luminosity SNe Tax originate from deflagrations of near-M-ch hybrid carbon-oxygen-neon white dwarfs. Instead, the merger of a carbon-oxygen and oxygen-neon white dwarf is a promising model to explain SN 2021fcg.

  • 155.
    Karamehmetoglu, Emir
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Aarhus University, Denmark.
    Fransson, Claes
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Tartaglia, Leonardo
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Taddia, Francesco
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    De, K.
    Fremling, C.
    Bagdasaryan, A.
    Barbarino, Cristina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Bellm, E. C.
    Dekany, R.
    Dugas, A. M.
    Giomi, M.
    Goobar, Ariel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Graham, M.
    Ho, A.
    Laher, R. R.
    Masci, F. J.
    Neill, J. D.
    Perley, D.
    Riddle, R.
    Rusholme, B.
    Soumagnac, M. T.
    The luminous and rapidly evolving SN 2018bcc: Clues toward the origin of Type Ibn SNe from the Zwicky Transient Facility2021Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 649, artikkel-id A163Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Context. Supernovae (SNe) Type Ibn are rapidly evolving and bright ( MR;peak similar to 19) transients interacting with He-rich circumstellar material (CSM). SN 2018bcc, detected by the ZTF shortly after explosion, provides the best constraints on the shape of the rising light curve (LC) of a fast Type Ibn.

    Aims. We used the high-quality data set of SN 2018bcc to study observational signatures of the class. Additionally, the powering mechanism of SN 2018bcc o ffers insights into the debated progenitor connection of Type Ibn SNe.

    Methods. We compared well-constrained LC properties obtained from empirical models with the literature. We fit the pseudobolometric LC with semi-analytical models powered by radioactive decay and CSM interaction. Finally, we modeled the line profiles and emissivity of the prominent He i lines, in order to study the formation of P-Cygni profiles and to estimate CSM properties.

    Results. SN 2018bcc had a rise time to peak of the LC of 5:6+0:2 0:1 days in the restframe with a rising shape power-law index close to 2, and seems to be a typical rapidly evolving Type Ibn SN. The spectrum lacked signatures of SN-like ejecta and was dominated by over 15 He emission features at 20 days past peak, alongside Ca and Mg, all with VFWHM similar to 2000 km s 1. The luminous and rapidly evolving LC could be powered by CSM interaction but not by the decay of radioactive 56Ni. Modeling of the He i lines indicated a dense and optically thick CSM that can explain the P-Cygni profiles.

    Conclusions. Like other rapidly evolving Type Ibn SNe, SN 2018bcc is a luminous transient with a rapid rise to peak powered by shock interaction inside a dense and He-rich CSM. Its spectra do not support the existence of two Type Ibn spectral classes. We also note the remarkable observational match to pulsational pair instability SN models.

  • 156.
    Karamehmetoglu, Emir
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Aarhus University, Denmark.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Taddia, Francesco
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Aarhus University, Denmark.
    Barbarino, Cristina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Feindt, Ulrich
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Fremling, C.
    Gal-Yam, A.
    Kasliwal, M. M.
    Petrushevska, T.
    Schulze, Steve
    Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Stritzinger, M. D.
    Zapartas, E.
    A population of Type Ibc supernovae with massive progenitors Broad lightcurves not uncommon in (i)PTF2023Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 678, artikkel-id A87Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    If high-mass stars (≳20 − 25 M) are the progenitors of stripped-envelope (SE) supernovae (SNe), their massive ejecta should lead to broad, long-duration lightcurves. Instead, literature samples of SE SNe have reported relatively narrow lightcurves corresponding to ejecta masses between 1 − 4 M that favor intermediate-mass progenitors (≲20 − 25 M). Working with an untargeted sample from a single telescope to better constrain their rates, we searched the Palomar Transient Factory (PTF) and intermediate-PTF (iPTF) sample of SNe for SE SNe with broad lightcurves. Using a simple observational marker of g- or r-band lightcurve stretch compared to a template to measure broadness, we identified eight significantly broader Type Ibc SNe after applying quantitative sample selection criteria. The lightcurves, broad-band colors, and spectra of these SNe are found to evolve more slowly relative to typical Type Ibc SNe, proportional with the stretch parameter. Bolometric lightcurve modeling and their nebular spectra indicate high ejecta masses and nickel masses, assuming radioactive decay powering. Additionally, these objects are preferentially located in low-metallicity host galaxies with high star formation rates, which may account for their massive progenitors, as well as their relative absence from the literature. Our study thus supports the link between broad lightcurves (as measured by stretch) and high-mass progenitor stars in SE SNe with independent evidence from bolometric lightcurve modeling, nebular spectra, host environment properties, and photometric evolution. In the first systematic search of its kind using an untargeted sample, we used the stretch distribution to identify a higher than previously appreciated fraction of SE SNe with broad lightcurves (∼13%). Correcting for Malmquist and lightcurve duration observational biases, we conservatively estimate that a minimum of ∼6% of SE SNe are consistent with high-mass progenitors. This result has implications for the progenitor channels of SE SNe, including late stages of massive stellar evolution, the origin of the observed oxygen fraction in the universe, and formation channels for stellar-mass black holes.

  • 157.
    Karamehmetoglu, Emir
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Taddia, Francesco
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Wyrzykowski, L.
    Schmidl, S.
    Fraser, Morgan
    Fremling, Christoffer
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Greiner, J.
    Inserra, Cosimo
    Kostrzewa-Rutkowska, Z.
    Maguire, K.
    Smartt, S.
    Sullivan, M.
    Young, D. R.
    OGLE-2014-SN-131: A long-rising Type Ibn supernova from a massive progenitor2017Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 602, artikkel-id A93Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Context. Type Ibn supernovae (SNe Ibn) are thought to be the core-collapse explosions of massive stars whose ejecta interact with He-rich circumstellar material (CSM). Aims. We report the discovery of a SN Ibn, with the longest rise-time ever observed, OGLE-2014-SN-131. We discuss the potential powering mechanisms and the progenitor nature of this peculiar stripped-envelope (SE), circumstellar-interacting SN. Methods. Optical photometry and spectroscopy were obtained with multiple telescopes including VLT, NTT, and GROND. We compare light curves and spectra with those of other known SNe Ibn and Ibc. CSM velocities are derived from the spectral analysis. The SN light curve is modeled under di ff erent assumptions about its powering mechanism (56Ni decay, CSM-interaction, magnetar) in order to estimate the SN progenitor parameters. Results. OGLE-2014-SN-131 spectroscopically resembles SNe Ibn such as SN 2010al. Its peak luminosity and post-peak colors are also similar to those of other SNe Ibn. However, it shows an unprecedentedly long rise-time and a much broader light curve compared to other SNe Ibn. Its bolometric light curve can be reproduced by magnetar and CSM-interaction models, but not by a 56Ni-decay powering model. Conclusions. To explain the unusually long rise-time, the broad light curve, the light curve decline, and the spectra characterized by narrow emission lines, we favor a powering mechanism where the SN ejecta are interacting with a dense CSM. The progenitor of OGLE-2014-SN-131 was likely a Wolf-Rayet star with a mass greater than that of a typical SN Ibn progenitor, which expelled the CSM that the SN is interacting with.

  • 158. Kasliwal, M. M.
    et al.
    Kasen, D.
    Lau, R. M.
    Perley, D. A.
    Rosswog, Stephan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Ofek, E. O.
    Hotokezaka, K.
    Chary, R.-R.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Goobar, Ariel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Kaplan, D. L.
    Spitzer mid-infrared detections of neutron star merger GW170817 suggests synthesis of the heaviest elements2022Inngår i: Monthly Notices of the Royal Astronomical Society: Letters, ISSN 1745-3925, Vol. 510, nr 1, s. L7-L12Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report our Spitzer Space Telescope observations and detections of the binary neutron star merger GW170817. At 4.5 μm, GW170817 is detected at 21.9 mag AB at +43 days and 23.9 mag AB at +74 days after merger. At 3.6 μm, GW170817 is not detected to a limit of 23.2 mag AB at +43 days and 23.1 mag AB at +74 days. Our detections constitute the latest and reddest constraints on the kilonova/macronova emission and composition of heavy elements. The 4.5 μm luminosity at this late phase cannot be explained by elements exclusively from the first abundance peak of the r-process. Moreover, the steep decline in the Spitzer band, with a power-law index of 3.4 ± 0.2, can be explained by a few of the heaviest isotopes with half-life around 14 d dominating the luminosity (e.g. 140Ba, 143Pr, 147Nd, 156Eu, 191Os, 223Ra, 225Ra, 233Pa, 234Th) or a model with lower deposition efficiency. This data offers evidence that the heaviest elements in the second and third r-process abundance peak were indeed synthesized. Our conclusion is verified by both analytics and network simulations and robust despite intricacies and uncertainties in the nuclear physics. Future observations with Spitzer and James Webb Space Telescope will further illuminate the relative abundance of the synthesized heavy elements.

  • 159. Kasliwal, M. M.
    et al.
    Nakar, E.
    Singer, L. P.
    Kaplan, D. L.
    Cook, D. O.
    Van Sistine, A.
    Lau, R. M.
    Fremling, C.
    Gottlieb, O.
    Jencson, J. E.
    Adams, S. M.
    Feindt, Ulrich
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hotokezaka, K.
    Ghosh, S.
    Perley, D. A.
    Yu, P-C.
    Piran, T.
    Allison, J. R.
    Anupama, G. C.
    Balasubramanian, A.
    Bannister, K. W.
    Bally, J.
    Barnes, J.
    Barway, S.
    Bellm, E.
    Bhalerao, V.
    Bhattacharya, D.
    Blagorodnova, N.
    Bloom, J. S.
    Brady, P. R.
    Cannella, C.
    Chatterjee, D.
    Cenko, S. B.
    Cobb, B. E.
    Copperwheat, C.
    Corsi, A.
    De, K.
    Dobie, D.
    Emery, S. W. K.
    Evans, P. A.
    Fox, O. D.
    Frail, D. A.
    Frohmaier, C.
    Goobar, Ariel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hallinan, G.
    Harrison, F.
    Helou, G.
    Hinderer, T.
    Ho, A. Y. Q.
    Horesh, A.
    Ip, W-H.
    Itoh, R.
    Kasen, D.
    Kim, H.
    Kuin, N. P. M.
    Kupfer, T.
    Lynch, C.
    Madsen, K.
    Mazzali, P. A.
    Miller, A. A.
    Mooley, K.
    Murphy, T.
    Ngeow, C-C.
    Nichols, D.
    Nissanke, S.
    Nugent, P.
    Ofek, E. O.
    Qi, H.
    Quimby, R. M.
    Rosswog, Stephan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Rusu, F.
    Sadler, E. M.
    Schmidt, P.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Steele, I.
    Williamson, A. R.
    Xu, Y.
    Yan, L.
    Yatsu, Y.
    Zhang, C.
    Zhao, W.
    Illuminating gravitational waves: A concordant picture of photons from a neutron star merger2017Inngår i: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 358, nr 6370, s. 1559-+Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Merging neutron stars offer an excellent laboratory for simultaneously studying strong-field gravity and matter in extreme environments. We establish the physical association of an electromagnetic counterpart (EM170817) with gravitational waves (GW170817) detected from merging neutron stars. By synthesizing a panchromatic data set, we demonstrate that merging neutron stars are a long-sought production site forging heavy elements by r-process nucleosynthesis. The weak gamma rays seen in EM170817 are dissimilar to classical short gamma-ray bursts with ultrarelativistic jets. Instead, we suggest that breakout of a wide-angle, mildly relativistic cocoon engulfing the jet explains the low-luminosity gamma rays, the high-luminosity ultraviolet-optical-infrared, and the delayed radio and x-ray emission. We posit that all neutron star mergers may lead to a wide-angle cocoon breakout, sometimes accompanied by a successful jet and sometimes by a choked jet.

  • 160. Kasliwal, Mansi M.
    et al.
    Anand, Shreya
    Ahumada, Tomás
    Stein, Robert
    Sagués Carracedo, Ana
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Andreoni, Igor
    Coughlin, Michael W.
    Singer, Leo P.
    Kool, Erik C.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    De, Kishalay
    Kumar, Harsh
    AlMualla, Mouza
    Yao, Yuhan
    Bulla, Mattia
    Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita).
    Dobie, Dougal
    Reusch, Simeon
    Perley, Daniel A.
    Cenko, S. Bradley
    Bhalerao, Varun
    Kaplan, David L.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Goobar, Ariel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Copperwheat, Christopher M.
    Bellm, Eric C.
    Anupama, G. C.
    Corsi, Alessandra
    Nissanke, Samaya
    Agudo, Iván
    Bagdasaryan, Ashot
    Barway, Sudhanshu
    Belicki, Justin
    Bloom, Joshua S.
    Bolin, Bryce
    Buckley, David A. H.
    Burdge, Kevin B.
    Burruss, Rick
    Caballero-García, Maria D.
    Cannella, Chris
    Castro-Tirado, Alberto J.
    Cook, David O.
    Cooke, Jeff
    Cunningham, Virginia
    Dahiwale, Aishwarya
    Deshmukh, Kunal
    Dichiara, Simone
    Duev, Dmitry A.
    Dutta, Anirban
    Feeney, Michael
    Franckowiak, Anna
    Frederick, Sara
    Fremling, Christoffer
    Gal-Yam, Avishay
    Gatkine, Pradip
    Ghosh, Shaon
    Goldstein, Daniel A.
    Golkhou, V. Zach
    Graham, Matthew J.
    Graham, Melissa L.
    Hankins, Matthew J.
    Helou, George
    Hu, Youdong
    Ip, Wing-Huen
    Jaodand, Amruta
    Karambelkar, Viraj
    Kong, Albert K. H.
    Kowalski, Marek
    Khandagale, Maitreya
    Kulkarni, S. R.
    Kumar, Brajesh
    Laher, Russ R.
    Li, K. L.
    Mahabal, Ashish
    Masci, Frank J.
    Miller, Adam A.
    Mogotsi, Moses
    Mohite, Siddharth
    Mooley, Kunal
    Mroz, Przemek
    Newman, Jeffrey A.
    Ngeow, Chow-Choong
    Oates, Samantha R.
    Patil, Atharva Sunil
    Pandey, Shashi B.
    Pavana, M.
    Pian, Elena
    Riddle, Reed
    Sánchez-Ramírez, Rubén
    Sharma, Yashvi
    Singh, Avinash
    Smith, Roger
    Soumagnac, Maayane T.
    Taggart, Kirsty
    Tan, Hanjie
    Tzanidakis, Anastasios
    Troja, Eleonora
    Valeev, Azamat F.
    Walters, Richard
    Waratkar, Gaurav
    Webb, Sara
    Yu, Po-Chieh
    Zhang, Bin-Bin
    Zhou, Rongpu
    Zolkower, Jeffry
    Kilonova Luminosity Function Constraints Based on Zwicky Transient Facility Searches for 13 Neutron Star Merger Triggers during O32020Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 905, nr 2, artikkel-id 145Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a systematic search for optical counterparts to 13 gravitational wave (GW) triggers involving at least one neutron star during LIGO/Virgo's third observing run (O3). We searched binary neutron star (BNS) and neutron star black hole (NSBH) merger localizations with the Zwicky Transient Facility (ZTF) and undertook follow-up with the Global Relay of Observatories Watching Transients Happen (GROWTH) collaboration. The GW triggers had a median localization area of 4480 deg(2), a median distance of 267 Mpc, and false-alarm rates ranging from 1.5 to 10(-25) yr(-1). The ZTF coverage in the g and r bands had a median enclosed probability of 39%, median depth of 20.8 mag, and median time lag between merger and the start of observations of 1.5 hr. The O3 follow-up by the GROWTH team comprised 340 UltraViolet/Optical/InfraRed (UVOIR) photometric points, 64 OIR spectra, and three radio images using 17 different telescopes. We find no promising kilonovae (radioactivity-powered counterparts), and we show how to convert the upper limits to constrain the underlying kilonova luminosity function. Initially, we assume that all GW triggers are bona fide astrophysical events regardless of false-alarm rate and that kilonovae accompanying BNS and NSBH mergers are drawn from a common population; later, we relax these assumptions. Assuming that all kilonovae are at least as luminous as the discovery magnitude of GW170817 (-16.1 mag), we calculate that our joint probability of detecting zero kilonovae is only 4.2%. If we assume that all kilonovae are brighter than -16.6 mag (the extrapolated peak magnitude of GW170817) and fade at a rate of 1 mag day(-1) (similar to GW170817), the joint probability of zero detections is 7%. If we separate the NSBH and BNS populations based on the online classifications, the joint probability of zero detections, assuming all kilonovae are brighter than -16.6 mag, is 9.7% for NSBH and 7.9% for BNS mergers. Moreover, no more than <57% (<89%) of putative kilonovae could be brighter than -16.6 mag assuming flat evolution (fading by 1 mag day(-1)) at the 90% confidence level. If we further take into account the online terrestrial probability for each GW trigger, we find that no more than <68% of putative kilonovae could be brighter than -16.6 mag. Comparing to model grids, we find that some kilonovae must have M-ej M, X-lan > 10(-4), or > 30 degrees to be consistent with our limits. We look forward to searches in the fourth GW observing run; even 17 neutron star mergers with only 50% coverage to a depth of -16 mag would constrain the maximum fraction of bright kilonovae to <25%.

  • 161. Kessler, Richard
    et al.
    Becker, Andrew C.
    Cinabro, David
    Vanderplas, Jake
    Frieman, Joshua A.
    Marriner, John
    Davis, Tamara M.
    Dilday, Benjamin
    Holtzman, Jon
    Jha, Saurabh W.
    Lampeitl, Hubert
    Sako, Masao
    Smith, Mathew
    Zheng, Chen
    Nichol, Robert C.
    Bassett, Bruce
    Bender, Ralf
    Depoy, Darren L.
    Doi, Mamoru
    Elson, Ed
    Filippenko, Alexei V.
    Foley, Ryan J.
    Garnavich, Peter M.
    Hopp, Ulrich
    Ihara, Yutaka
    Ketzeback, William
    Kollatschny, W.
    Konishi, Kohki
    Marshall, Jennifer L.
    Mc Millan, Russet J.
    Miknaitis, Gajus
    Morokuma, Tomoki
    Mörtsell, Edvard
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Pan, Kaike
    Prieto, Jose Luis
    Richmond, Michael W.
    Riess, Adam G.
    Romani, Roger
    Schneider, Donald P.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Takanashi, Naohiro
    Tokita, Kouichi
    van der Heyden, Kurt
    Wheeler, J. C.
    Yasuda, Naoki
    York, Donald
    First-Year Sloan Digital Sky Survey-II Supernova Results: Hubble Diagram and Cosmological Parameters2009Inngår i: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 185, nr 1, s. 32-84Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present measurements of the Hubble diagram for 103 Type Ia supernovae (SNe) with redshifts 0.04 < z < 0.42, discovered during the first season (Fall 2005) of the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey. These data fill in the redshift "desert" between low- and high-redshift SN Ia surveys. Within the framework of the MLCS2K2 light-curve fitting method, we use the SDSS-II SN sample to infer the mean reddening parameter for host galaxies, RV = 2.18 ± 0.14stat ± 0.48syst, and find that the intrinsic distribution of host-galaxy extinction is well fitted by an exponential function, P(AV ) = exp(-AV /τV), with τV = 0.334 ± 0.088 mag. We combine the SDSS-II measurements with new distance estimates for published SN data from the ESSENCE survey, the Supernova Legacy Survey (SNLS), the Hubble Space Telescope (HST), and a compilation of Nearby SN Ia measurements. A new feature in our analysis is the use of detailed Monte Carlo simulations of all surveys to account for selection biases, including those from spectroscopic targeting. Combining the SN Hubble diagram with measurements of baryon acoustic oscillations from the SDSS Luminous Red Galaxy sample and with cosmic microwave background temperature anisotropy measurements from the Wilkinson Microwave Anisotropy Probe, we estimate the cosmological parameters w and ΩM, assuming a spatially flat cosmological model (FwCDM) with constant dark energy equation of state parameter, w. We also consider constraints upon ΩM and ΩΛ for a cosmological constant model (ΛCDM) with w = -1 and non-zero spatial curvature. For the FwCDM model and the combined sample of 288 SNe Ia, we find w = -0.76 ± 0.07(stat) ± 0.11(syst), ΩM = 0.307 ± 0.019(stat) ± 0.023(syst) using MLCS2K2 and w = -0.96 ± 0.06(stat) ± 0.12(syst), ΩM = 0.265 ± 0.016(stat) ± 0.025(syst) using the SALT-II fitter. We trace the discrepancy between these results to a difference in the rest-frame UV model combined with a different luminosity correction from color variations; these differences mostly affect the distance estimates for the SNLS and HST SNe. We present detailed discussions of systematic errors for both light-curve methods and find that they both show data-model discrepancies in rest-frame U band. For the SALT-II approach, we also see strong evidence for redshift-dependence of the color-luminosity parameter (β). Restricting the analysis to the 136 SNe Ia in the Nearby+SDSS-II samples, we find much better agreement between the two analysis methods but with larger uncertainties: w = -0.92 ± 0.13(stat)+0.10 -0.33(syst) for MLCS2K2 and w = -0.92 ± 0.11(stat)+0.07 -0.15 (syst) for SALT-II.

  • 162. Khazov, D.
    et al.
    Yaron, O.
    Gal-Yam, A.
    Manulis, I.
    Rubin, A.
    Kulkarni, S. R.
    Arcavi, I.
    Kasliwal, M. M.
    Ofek, E. O.
    Cao, Y.
    Perley, D.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Horesh, A.
    Sullivan, M.
    Filippenko, A. V.
    Nugent, P. E.
    Howell, D. A.
    Cenko, S. B.
    Silverman, J. M.
    Ebeling, H.
    Taddia, Francesco
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Joel
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Laher, R. R.
    Surace, J.
    Rebbapragada, U. D.
    Wozniak, P. R.
    Matheson, T.
    FLASH SPECTROSCOPY: EMISSION LINES FROM THE IONIZED CIRCUMSTELLAR MATERIAL AROUND < 10-DAY-OLD TYPE II SUPERNOVAE2016Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 818, nr 1, artikkel-id 3Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Supernovae (SNe) embedded in dense circumstellar material (CSM) may show prominent emission lines in their early-time spectra (<= 10 days after the explosion), owing to recombination of the CSM ionized by the shock-breakout flash. From such spectra (flash spectroscopy), we can measure various physical properties of the CSM, as well as the mass-loss rate of the progenitor during the year prior to its explosion. Searching through the Palomar Transient Factory (PTF and iPTF) SN spectroscopy databases from 2009 through 2014, we found 12 SNe II showing flash-ionized (FI) signatures in their first spectra. All are younger than 10 days. These events constitute 14% of all 84 SNe in our sample having a spectrum within 10 days from explosion, and 18% of SNe. II observed at ages <5 days, thereby setting lower limits on the fraction of FI events. We classified as blue/featureless (BF) those events having a first spectrum that is similar to that of a blackbody, without any emission or absorption signatures. It is possible that some BF events had FI signatures at an earlier phase than observed, or that they lack dense CSM around the progenitor. Within 2 days after explosion, 8 out of 11 SNe in our sample are either BF events or show FI signatures. Interestingly, we found that 19 out of 21 SNe brighter than an absolute magnitude M-R = -18.2 belong to the FI or BF groups, and that all FI events peaked above M-R = -17.6 mag, significantly brighter than average SNe II.

  • 163. Kim, Y.-L.
    et al.
    Rigault, M.
    Neill, J. D.
    Briday, M.
    Copin, Y.
    Lezmy, J.
    Nicolas, N.
    Riddle, R.
    Sharma, Y.
    Smith, M.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Walters, R.
    New Modules for the SEDMachine to Remove Contaminations from Cosmic Rays and Non-target Light: BYECR and CONTSEP2022Inngår i: Publications of the Astronomical Society of the Pacific, ISSN 0004-6280, E-ISSN 1538-3873, Vol. 134, nr 1032, artikkel-id 024505Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Currently time-domain astronomy can scan the entire sky on a daily basis, discovering thousands of interesting transients every night. Classifying the ever-increasing number of new transients is one of the main challenges for the astronomical community. One solution that addresses this issue is the robotically controlled Spectral Energy Distribution Machine (SEDM) which supports the Zwicky Transient Facility (ZTF). SEDM with its pipeline pysedm demonstrates that real-time robotic spectroscopic classification is feasible. In an effort to improve the quality of the current SEDM data, we present here two new modules, byecr and contsep. The first removes contamination from cosmic rays, and the second removes contamination from non-target light. These new modules are part of the automated pysedm pipeline and fully integrated with the whole process. Employing byecr and contsep modules together automatically extracts more spectra than the current pysedm pipeline. Using SNID classification results, the new modules show an improvement in the classification rate and accuracy of 2.8% and 1.7%, respectively, while the strength of the cross-correlation remains the same. Improvements to the SEDM astrometry would further boost the improvement of the contsep module. This kind of robotic follow-up with a fully automated pipeline has the potential to provide the spectroscopic classifications for the transients discovered by ZTF and also by the Rubin Observatory's Legacy Survey of Space and Time.

  • 164.
    Kool, Erik C.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Karamehmetoglu, E.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Schulze, S.
    Lunnan, Ragnhild
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Reynolds, T. M.
    Barbarino, Cristina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Bellm, E. C.
    De, K.
    Duev, D. A.
    Fremling, C.
    Golkhou, V. Z.
    Graham, M. L.
    Green, D. A.
    Horesh, A.
    Kaye, S.
    Kim, Y. -L.
    Laher, R. R.
    Masci, F. J.
    Nordin, J.
    Perley, D. A.
    Phinney, E. S.
    Porter, M.
    Reiley, D.
    Rodriguez, H.
    van Roestel, J.
    Rusholme, B.
    Sharma, Y.
    Sfaradi, I.
    Soumagnac, M. T.
    Taggart, K.
    Tartaglia, Leonardo
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Williams, D. R. A.
    Yan, L.
    SN 2020bqj: A Type Ibn supernova with a long-lasting peak plateau2021Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 652, artikkel-id A136Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Context. Type Ibn supernovae (SNe Ibn) are a rare class of stripped envelope supernovae interacting with a helium-rich circumstellar medium (CSM). The majority of the SNe Ibn reported in the literature display a surprising homogeneity in their fast-evolving lightcurves and are typically found in actively starforming spiral galaxies.

    Aims. We present the discovery and the study of SN 2020bqj (ZTF20aalrqbu), a SN Ibn with a long-duration peak plateau lasting 40 days and hosted by a faint low-mass galaxy. We aim to explain its peculiar properties using an extensive photometric and spectroscopic data set.

    Methods. We compare the photometric and spectral evolution of SN 2020bqj with regular SNe Ibn from the literature, as well as with other outliers in the SN Ibn subclass. We fit the bolometric and multi-band lightcurves with powering mechanism models such as radioactive decay and CSM interaction. We also model the host galaxy of SN 2020bqj.

    Results. The risetime, peak magnitude and spectral features of SN 2020bqj are consistent with those of most SNe Ibn, but the SN is a clear outlier in the subclass based on its bright, long-lasting peak plateau and the low mass of its faint host galaxy. We show through modeling that the lightcurve of SN 2020bqj can be powered predominantly by shock heating from the interaction of the SN ejecta and a dense CSM, combined with radioactive decay. The peculiar Type Ibn SN 2011hw is a close analog to SN 2020bqj in terms of lightcurve and spectral evolution, suggesting a similar progenitor and CSM scenario. In this scenario a very massive progenitor star in the transitional phase between a luminous blue variable and a compact Wolf-Rayet star undergoes core-collapse, embedded in a dense helium-rich CSM with an elevated opacity compared to normal SNe Ibn, due to the presence of residual hydrogen. This scenario is consistent with the observed properties of SN 2020bqj and the modeling results.

    Conclusions. SN 2020bqj is a compelling example of a transitional SN Ibn/IIn based on not only its spectral features, but also its lightcurve, host galaxy properties and the inferred progenitor properties. The strong similarity with SN 2011hw suggests this subclass may be the result of a progenitor in a stellar evolution phase that is distinct from those of progenitors of regular SNe Ibn.

  • 165.
    Kool, Erik C.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Pearson Johansson, Joel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Moldón, Javier
    Moriya, Takashi J.
    Mattila, Seppo
    Schulze, Steve
    Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Chomiuk, Laura
    Pérez-Torres, Miguel
    Harris, Chelsea
    Lundqvist, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Graham, Matthew
    Yang, Sheng
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Henan Academy of Sciences, China.
    Perley, Daniel A.
    Strotjohann, Nora Linn
    Fremling, Christoffer
    Gal-Yam, Avishay
    Lezmy, Jeremy
    Maguire, Kate
    Omand, Conor M. B.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Smith, Mathew
    Andreoni, Igor
    Bellm, Eric C.
    Bloom, Joshua S.
    De, Kishalay
    Groom, Steven L.
    Kasliwal, Mansi M.
    Masci, Frank J.
    Medford, Michael S.
    Park, Sungmin
    Purdum, Josiah
    Reynolds, Thomas M.
    Riddle, Reed
    Robert, Estelle
    Ryder, Stuart D.
    Sharma, Yashvi
    Stern, Daniel
    A radio-detected type Ia supernova with helium-rich circumstellar material2023Inngår i: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 617, nr 7961, s. 477-482Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Type Ia supernovae (SNe Ia) are thermonuclear explosions of degenerate white dwarf stars destabilized by mass accretion from a companion star1, but the nature of their progenitors remains poorly understood. A way to discriminate between progenitor systems is through radio observations; a non-degenerate companion star is expected to lose material through winds2 or binary interaction3 before explosion, and the supernova ejecta crashing into this nearby circumstellar material should result in radio synchrotron emission. However, despite extensive efforts, no type Ia supernova (SN Ia) has ever been detected at radio wavelengths, which suggests a clean environment and a companion star that is itself a degenerate white dwarf star4,5. Here we report on the study of SN 2020eyj, a SN Ia showing helium-rich circumstellar material, as demonstrated by its spectral features, infrared emission and, for the first time in a SN Ia to our knowledge, a radio counterpart. On the basis of our modelling, we conclude that the circumstellar material probably originates from a single-degenerate binary system in which a white dwarf accretes material from a helium donor star, an often proposed formation channel for SNe Ia (refs. 6,7). We describe how comprehensive radio follow-up of SN 2020eyj-like SNe Ia can improve the constraints on their progenitor systems.

  • 166. Kotak, R.
    et al.
    Meikle, W. P. S.
    Farrah, D.
    Gerardy, C. L.
    Foley, R. J.
    Van Dyk, S. D.
    Fransson, C.
    Lundqvist, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Fesen, R.
    Filippenko, A. V.
    Mattila, S.
    Silverman, J. M.
    Andersen, A. C.
    Höflich, P. A.
    Pozzo, M.
    Wheeler, J. C.
    Dust and The Type II-Plateau Supernova 2004et2009Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 704, nr 1, s. 306-323Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present mid-infrared (MIR) observations of the Type II-plateau supernova (SN) 2004et, obtained with the Spitzer Space Telescope between 64 and 1406 days past explosion. Late-time optical spectra are also presented. For the period 300-795 days past explosion, we argue that the spectral energy distribution (SED) of SN 2004et comprises (1) a hot component due to emission from optically thick gas, as well as free-bound radiation; (2) a warm component due to newly formed, radioactively heated dust in the ejecta; and (3) a cold component due to an IR echo from the interstellar-medium dust of the host galaxy, NGC 6946. There may also have been a small contribution to the IR SED due to free-free emission from ionized gas in the ejecta. We reveal the first-ever spectroscopic evidence for silicate dust formed in the ejecta of a supernova. This is supported by our detection of a large, but progressively declining, mass of SiO. However, we conclude that the mass of directly detected ejecta dust grew to no more than a few times 10-4 M sun. We also provide evidence that the ejecta dust formed in comoving clumps of fixed size. We argue that, after about two years past explosion, the appearance of wide, box-shaped optical line profiles was due to the impact of the ejecta on the progenitor circumstellar medium and that the subsequent formation of a cool, dense shell was responsible for a later rise in the MIR flux. This study demonstrates the rich, multifaceted ways in which a typical core-collapse supernova and its progenitor can produce and/or interact with dust grains. The work presented here adds to the growing number of studies that do not support the contention that SNe are responsible for the large mass of observed dust in high-redshift galaxies.

  • 167. Kotak, Rubina
    et al.
    Meikle, Peter
    Pozzo, Monica
    van Dyk, Schuyler
    Farrah, Duncan
    Fesen, Robert
    Filippenko, Alexei
    Foley, Ryan
    Fransson, Claes
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Gerardy, Christopher
    Höflich, Peter
    Lundqvist, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Mattila, Seppo
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Wheeler, J. Craig
    Spitzer Measurements of Atomic and Molecular Abundances in the Type IIP SN 2005af2006Inngår i: The Astrophysical Journal, ISSN 0004-637X, Vol. 651, nr 2, s. L117-L120Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present results based on mid-infrared (3.6-30 μm) observations with the Spitzer Space Telescope of the nearby Type IIP supernova 2005af. We report the first ever detection of the SiO molecule in a Type IIP supernova. Together with the detection of the CO fundamental, this is an exciting finding as it may signal the onset of dust condensation in the ejecta. From a wealth of fine-structure lines we provide abundance estimates for stable Ni, Ar, and Ne that, via spectral synthesis, may be used to constrain nucleosynthesis models.

  • 168.
    Kromer, Markus
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Fremling, Christoffer
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Pakmor, R.
    Taubenberger, S.
    Amanullah, Rahman
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Cenko, S. B.
    Fransson, Claes
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Goobar, Ariel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Leloudas, G.
    Taddia, Francesco
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Roepke, F. K.
    Seitenzahl, I. R.
    Sim, S. A.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    The peculiar Type Ia supernova iPTF14atg: Chandrasekhar-mass explosion or violent merger?2016Inngår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 459, nr 4, s. 4428-4439Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    iPTF14atg, a subluminous peculiar Type Ia supernova (SN Ia) similar to SN 2002es, is the first SN Ia for which a strong UV flash was observed in the early-time light curves. This has been interpreted as evidence for a single-degenerate (SD) progenitor system, where such a signal is expected from interactions between the SN ejecta and the non-degenerate companion star. Here, we compare synthetic observables of multidimensional state-of-the-art explosion models for different progenitor scenarios to the light curves and spectra of iPTF14atg. From our models, we have difficulties explaining the spectral evolution of iPTF14atg within the SD progenitor channel. In contrast, we find that a violent merger of two carbon-oxygen white dwarfs with 0.9 and 0.76 M-aS (TM), respectively, provides an excellent match to the spectral evolution of iPTF14atg from 10 d before to several weeks after maximum light. Our merger model does not naturally explain the initial UV flash of iPTF14atg. We discuss several possibilities like interactions of the SN ejecta with the circumstellar medium and surface radioactivity from an He-ignited merger that may be able to account for the early UV emission in violent merger models.

  • 169. Kuncarayakti, Hanindyo
    et al.
    Maeda, Keiichi
    Ashall, Christopher J.
    Prentice, Simon J.
    Mattila, Seppo
    Kankare, Erkki
    Fransson, Claes
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Lundqvist, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Pastorello, Andrea
    Leloudas, Giorgos
    Anderson, Joseph P.
    Benetti, Stefano
    Bersten, Melina C.
    Cappellaro, Enrico
    Cartier, Regis
    Denneau, Larry
    Della Valle, Massimo
    Elias-Rosa, Nancy
    Folatelli, Gaston
    Fraser, Morgan
    Galbany, Lluis
    Gall, Christa
    Gal-Yam, Avishay
    Gutierrez, Claudia P.
    Hamanowicz, Aleksandra
    Heinze, Ari
    Inserra, Cosimo
    Kangas, Tuomas
    Mazzali, Paolo
    Melandri, Andrea
    Pignata, Giuliano
    Rest, Armin
    Reynolds, Thomas
    Roy, Rupak
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Inter-University Centre for Astronomy and Astrophysics (IUCAA), India.
    Smartt, Stephen J.
    Smith, Ken W.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Somero, Auni
    Stalder, Brian
    Stritzinger, Maximilian
    Taddia, Francesco
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Tomasella, Lina
    Tonry, John
    Weiland, Henry
    Young, David R.
    SN 2017dio: A Type-Ic Supernova Exploding in a Hydrogen-rich Circumstellar Medium2018Inngår i: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 854, nr 1, artikkel-id L14Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    SN 2017dio shows both spectral characteristics of a type-Ic supernova (SN) and signs of a hydrogen-rich circumstellar medium (CSM). Prominent, narrow emission lines of H and He are superposed on the continuum. Subsequent evolution revealed that the SN ejecta are interacting with the CSM. The initial SN Ic identification was confirmed by removing the CSM interaction component from the spectrum and comparing with known SNe Ic and, reversely, adding a CSM interaction component to the spectra of known SNe Ic and comparing them to SN 2017dio. Excellent agreement was obtained with both procedures, reinforcing the SN Ic classification. The light curve constrains the pre-interaction SN Ic peak absolute magnitude to be around M-g = -17.6 mag. No evidence of significant extinction is found, ruling out a brighter luminosity required by an SN Ia classification. These pieces of evidence support the view that SN 2017dio is an SN Ic, and therefore the first firm case of an SN Ic with signatures of hydrogen-rich CSM in the early spectrum. The CSM is unlikely to have been shaped by steady-state stellar winds. The mass loss of the progenitor star must have been intense, M similar to 0.02 (epsilon(H alpha)/0.01)(-1) (nu(wind)/500 km s(-1)) (nu(shock)/10,000 km s(-1))M--3(circle dot) yr(-1), peaking at a few decades before the SN. Such a high mass-loss rate might have been experienced by the progenitor through eruptions or binary stripping.

  • 170. Lampeitl, H.
    et al.
    Nichol, R. C.
    Seo, H.-J.
    Giannantonio, T.
    Shapiro, C.
    Bassett, B.
    Percival, W. J.
    Davis, T. M.
    Dilday, B.
    Frieman, J.
    Garnavich, P.
    Sako, M.
    Smith, M.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. University of Copenhagen, Denmark.
    Becker, A. C.
    Cinabro, D.
    Filippenko, A. V.
    Foley, R. J.
    Hogan, C. J.
    Holtzman, J. A.
    Jha, S. W.
    Konishi, K.
    Marriner, J.
    Richmond, M. W.
    Riess, A. G.
    Schneider, D. P.
    Stritzinger, M.
    van der Heyden, K. J.
    Vanderplas, J. T.
    Wheeler, J. C.
    Zheng, C.
    First-year Sloan Digital Sky Survey-II supernova results: consistency and constraints with other intermediate-redshift data sets2010Inngår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 401, nr 4, s. 2331-2342Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present an analysis of the luminosity distances of Type Ia Supernovae (SNe) from the Sloan Digital Sky Survey-II (SDSS-II) SN Survey in conjunction with other intermediate-redshift (z < 0.4) cosmological measurements including redshift-space distortions from the Two-Degree Field Galaxy Redshift Survey (2dFGRS), the integrated Sachs–Wolfe (ISW) effect seen by the SDSS and the latest baryon acoustic oscillation (BAO) distance scale from both the SDSS and 2dFGRS. We have analysed the SDSS-II SN data alone using a variety of ‘model-independent’ methods and find evidence for an accelerating Universe at a >97 per cent level from this single data set. We find good agreement between the SN and BAO distance measurements, both consistent with a Λ-dominated cold dark matter cosmology, as demonstrated through an analysis of the distance duality relationship between the luminosity (dL) and angular diameter (dA) distance measures. We then use these data to estimate w within this restricted redshift range (z < 0.4). Our most stringent result comes from the combination of all our intermediate-redshift data (SDSS-II SNe, BAO, ISW and redshift-space distortions), giving w=−0.81+0.16−0.18 (stat) ± 0.15 (sys) and ΩM= 0.22+0.09−0.08 assuming a flat universe. This value of w and associated errors only change slightly if curvature is allowed to vary, consistent with constraints from the cosmic microwave background. We also consider more limited combinations of the geometrical (SN, BAO) and dynamical (ISW, redshift-space distortions) probes. 

  • 171. Lampeitl, Hubert
    et al.
    Smith, Mathew
    Nichol, Robert C.
    Bassett, Bruce
    Cinabro, David
    Dilday, Benjamin
    Foley, Ryan J.
    Frieman, Joshua A.
    Garnavich, Peter M.
    Goobar, Ariel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Im, Myungshin
    Jha, Saurabh W.
    Marriner, John
    Miquel, Ramon
    Nordin, Jakob
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Östman, Linda
    Riess, Adam G.
    Sako, Masao
    Schneider, Donald P.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Stritzinger, Maximilian
    The Effect of Host Galaxies on Type Ia Supernovae in the SDSS-II Supernova Survey2010Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 722, s. 566-576Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present an analysis of the host galaxy dependences of Type Ia Supernovae (SNe Ia) from the full three year sample of the SDSS-II Supernova Survey. We re-discover, to high significance, the strong correlation between host galaxy type and the width of the observed SN light curve, i.e., fainter, quickly declining SNe Ia favor passive host galaxies, while brighter, slowly declining Ia's favor star-forming galaxies. We also find evidence (at between 2σ and 3σ) that SNe Ia are sime0.1 ± 0.04 mag brighter in passive host galaxies than in star-forming hosts, after the SN Ia light curves have been standardized using the light-curve shape and color variations. This difference in brightness is present in both the SALT2 and MCLS2k2 light-curve fitting methodologies. We see evidence for differences in the SN Ia color relationship between passive and star-forming host galaxies, e.g., for the MLCS2k2 technique, we see that SNe Ia in passive hosts favor a dust law of RV = 1.0 ± 0.2, while SNe Ia in star-forming hosts require RV = 1.8+0.2 -0.4. The significance of these trends depends on the range of SN colors considered. We demonstrate that these effects can be parameterized using the stellar mass of the host galaxy (with a confidence of >4σ) and including this extra parameter provides a better statistical fit to our data. Our results suggest that future cosmological analyses of SN Ia samples should include host galaxy information.

  • 172. Larsson, J.
    et al.
    Fransson, Claes
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Alp, D.
    Challis, P.
    Chevalier, R. A.
    France, K.
    Kirshner, R. P.
    Lawrence, S.
    Leibundgut, B.
    Lundqvist, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Mattila, S.
    Migotto, Katia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Sonneborn, G.
    Spyromilio, J.
    Suntzeff, N. B.
    Wheeler, J. C.
    The Matter Beyond the Ring: The Recent Evolution of SN 1987A Observed by the Hubble Space Telescope2019Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 886, nr 2, artikkel-id 147Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The nearby SN 1987A offers a spatially resolved view of the evolution of a young supernova (SN) remnant. Here we present recent Hubble Space Telescope imaging observations of SN 1987A, which we use to study the evolution of the ejecta, the circumstellar equatorial ring (ER), and the increasing emission from material outside the ER. We find that the inner ejecta have been brightening at a gradually slower rate and that the western side has been brighter than the eastern side since similar to 7000 days. This is expected given that the X-rays from the ER are most likely powering the ejecta emission. At the same time, the optical emission from the ER continues to fade linearly with time. The ER is expanding at 680 50 km s(-1), which reflects the typical velocity of transmitted shocks in the dense hot spots. A dozen spots and a rim of diffuse H alpha emission have appeared outside the ER since 9500 days. The new spots are more than an order of magnitude fainter than the spots in the ER and also fade faster. We show that the spots and diffuse emission outside the ER may be explained by fast ejecta interacting with high-latitude material that extends from the ER toward the outer rings. Further observations of this emission will make it possible to determine the detailed geometry of the high-latitude material and provide insight into the formation of the rings and the mass-loss history of the progenitor.

  • 173. Larsson, J.
    et al.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Lyman, J. D.
    Spyromilio, J.
    Tenhu, L.
    Fransson, Claes
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Lundqvist, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Clumps and Rings of Ejecta in SNR 0540-69.3 as Seen in 3D2021Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 922, nr 2, artikkel-id 265Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The distribution of ejecta in young supernova remnants offers a powerful observational probe of their explosions and progenitors. Here we present a 3D reconstruction of the ejecta in SNR 0540-69.3, which is an O-rich remnant with a pulsar wind nebula located in the LMC. We use observations from the Very Large Telescope (VLT)/MUSE to study Hβ, [O iii] λλ4959, 5007, Hα, [S ii] λλ6717, 6731, [Ar iii] λ7136, and [S iii] λ9069. This is complemented by 2D spectra from VLT/X-shooter, which also cover [O ii] λλ3726, 3729, and [Fe ii] λ12567. We identify three main emission components: (i) clumpy rings in the inner nebula (≲1000 km s−1) with similar morphologies in all lines; (ii) faint extended [O iii] emission dominated by an irregular ring-like structure with radius ∼1600 km s−1 and inclination ∼40°, but with maximal velocities reaching ∼3000 km s−1; and (iii) a blob of Hα and Hβ located southeast of the pulsar at velocities ∼1500–3500 km s−1. We analyze the geometry using a clump-finding algorithm and use the clumps in the [O iii] ring to estimate an age of 1146 ± 116 yr. The observations favor an interpretation of the [O iii] ring as ejecta, while the origin of the H-blob is more uncertain. An alternative explanation is that it is the blown-off envelope of a binary companion. From the detection of Balmer lines in the innermost ejecta we confirm that SNR 0540 was a Type II supernova and that hydrogen was mixed down to low velocities in the explosion.

  • 174. Larsson, Josefin
    et al.
    Fransson, Claes
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Kjaer, Karina
    Jerkstrand, Anders
    Kirshner, Robert P.
    Leibundgut, Bruno
    Lundqvist, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Mattila, Seppo
    McCray, Richard
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Spyromilio, Jason
    Wheeler, J. Craig
    THE MORPHOLOGY OF THE EJECTA IN SUPERNOVA 1987A: A STUDY OVER TIME AND WAVELENGTH2013Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 768, nr 1, s. 89-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a study of the morphology of the ejecta in Supernova 1987A based on images and spectra from the Hubble Space Telescope (HST) as well as integral field spectroscopy from VLT/SINFONI. The HST observations were obtained between 1994 and 2011 and primarily probe the outer H-rich zones of the ejecta. The SINFONI observations were obtained in 2005 and 2011 and instead probe the [Si I]+[Fe II] emission from the inner regions. We find a strong temporal evolution of the morphology in the HST images, from a roughly elliptical shape before similar to 5000 days, to a more irregular, edge-brightened morphology with a hole in the middle thereafter. This transition is a natural consequence of the change in the dominant energy source powering the ejecta, from radioactive decay before similar to 5000 days to X-ray input from the circumstellar interaction thereafter. The [Si I]+[Fe II] images display a more uniform morphology, which may be due to a remaining significant contribution from radioactivity in the inner ejecta and the higher abundance of these elements in the core. Both the Ha and the [Si I]+[Fe II] line profiles show that the ejecta are distributed fairly close to the plane of the inner circumstellar ring, which is assumed to define the rotational axis of the progenitor star. The Ha emission extends to higher velocities than [Si I]+[Fe II], as expected from theoretical models. There is no clear symmetry axis for all the emission. Instead, we find that the emission is concentrated to clumps and that the emission is distributed somewhat closer to the ring in the north than in the south. This north-south asymmetry may be partially explained by dust absorption. We compare our results with explosion models and find some qualitative agreement, but note that the observations show a higher degree of large-scale asymmetry.

  • 175. Larsson, Josefin
    et al.
    Fransson, Claes
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Spyromilio, J.
    Leibundgut, B. .
    Challis, P.
    Chevalier, R. A.
    France, K.
    Jerkstrand, A.
    Kirshner, R. P.
    Lundqvist, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Matsuura, M.
    McCray, R.
    Smith, N.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Garnavich, P.
    Heng, K.
    Lawrence, S.
    Mattila, S.
    Migotto, Katia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Sonneborn, G.
    Taddia, Francesco
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Wheeler, J. C.
    THREE-DIMENSIONAL DISTRIBUTION OF EJECTA IN SUPERNOVA 1987A AT 10,000 DAYS2016Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 833, nr 2, artikkel-id 147Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Due to its proximity, SN. 1987A offers a unique opportunity to directly observe the geometry of a stellar explosion as it unfolds. Here we present spectral and imaging observations of SN. 1987A obtained similar to 10,000 days after the explosion with HST/STIS and VLT/SINFONI at optical and near-infrared wavelengths. These observations allow us to produce the most detailed 3D map of Ha to date, the first 3D maps for [Ca II] lambda lambda 7292, 7324, [O I] lambda lambda 6300, 6364, and Mg. II lambda lambda 9218, 9244, as well as new maps for [Si I]+[Fe II] 1.644 mu m and He I 2.058 mu m. A comparison with previous observations shows that the [Si I]+[Fe II] flux and morphology have not changed significantly during the past ten years, providing evidence that this line is powered by Ti-44. The time evolution of Ha shows that it is predominantly powered by X-rays from the ring, in agreement with previous findings. All lines that have sufficient signal show a similar large-scale 3D structure, with a north-south asymmetry that resembles a broken dipole. This structure correlates with early observations of asymmetries, showing that there is a global asymmetry that extends from the inner core to the outer envelope. On smaller scales, the two brightest lines, Ha and [Si I]+[Fe II] 1.644 mu m, show substructures at the level of similar to 200-1000 km s(-1) and clear differences in their 3D geometries. We discuss these results in the context of explosion models and the properties of dust in the ejecta.

  • 176.
    Larsson, Josefin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Fransson, Claes
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Östlin, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Gröningsson, P.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Jerkstrand, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Kozma, Cecilia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Challis, P.
    Kirshner, R. P.
    Chevalier, R. A.
    Heng, K.
    McCray, R.
    Suntzeff, N. B.
    Bouchet, P.
    Crotts, A.
    Danziger, J.
    Dwek, E.
    France, K.
    Garnavich, P. M.
    Lawrence, S. S.
    Leibundgut, B.
    Lundqvist, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Panagia, N.
    Pun, C. S. J.
    Smith, N.
    Sonneborn, G.
    Wang, L.
    Wheeler, J. C.
    X-ray illumination of the ejecta of supernova 1987A2011Inngår i: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 474, nr 7352, s. 484-486Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    When a massive star explodes as a supernova, substantial amounts of radioactive elements-primarily (56)Ni, (57)Ni and (44)Ti-are produced(1). After the initial flash of light from shock heating, the fading light emitted by the supernova is due to the decay of these elements(2). However, after decades, the energy powering a supernova remnant comes from the shock interaction between the ejecta and the surrounding medium(3). The transition to this phase has hitherto not been observed: supernovae occur too infrequently in the Milky Way to provide a young example, and extragalactic supernovae are generally too faint and too small. Here we report observations that show this transition in the supernova SN 1987A in the Large Magellanic Cloud. From 1994 to 2001, the ejecta faded owing to radioactive decay of (44)Ti as predicted. Then the flux started to increase, more than doubling by the end of 2009. We show that this increase is the result of heat deposited by X-rays produced as the ejecta interacts with the surrounding material. In time, the X-rays will penetrate farther into the ejecta, enabling us to analyse the structure and chemistry of the vanished star.

  • 177.
    Leloudas, G.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Chatzopoulos, E.
    Dilday, B.
    Gorosabel, J.
    Vinko, J.
    Gallazzi, A.
    Wheeler, J. C.
    Bassett, B.
    Fischer, J. A.
    Frieman, J. A.
    Fynbo, J. P. U.
    Goobar, Ariel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Jelinek, M.
    Malesani, D.
    Nichol, R. C.
    Nordin, J.
    Oestman, L.
    Sako, M.
    Schneider, D. P.
    Smith, M.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Stritzinger, Maximilian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Thoene, C. C.
    Postigo, A. de Ugarte
    SN 2006oz: rise of a super-luminous supernova observed by the SDSS-II SN Survey2012Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 541, s. A129-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Context. A new class of super-luminous transients has recently been identified. These objects reach absolute luminosities of M-u < -21, lack hydrogen in their spectra, and are exclusively discovered by non-targeted surveys because they are associated with very faint galaxies. Aims. We aim to contribute to a better understanding of these objects by studying SN 2006oz, a newly-recognized member of this class. Methods. We present multi-color light curves of SN 2006oz from the SDSS-II SN Survey that cover its rise time, as well as an optical spectrum that shows that the explosion occurred at z similar to 0.376. We fitted black-body functions to estimate the temperature and radius evolution of the photosphere and used the parametrized code SYNOW to model the spectrum. We constructed a bolometric light curve and compared it with explosion models. In addition, we conducted a deep search for the host galaxy with the 10 m GTC telescope. Results. The very early light curves show a dip in the g-and r-bands and a possible initial cooling phase in the u-band before rising to maximum light. The bolometric light curve shows a precursor plateau with a duration of 6-10 days in the rest-frame. A lower limit of M-u < -21.5 can be placed on the absolute peak luminosity of the SN, while the rise time is constrained to be at least 29 days. During our observations, the emitting sphere doubled its radius to similar to 2 x 10(15) cm, while the temperature remained hot at similar to 15 000 K. As for other similar SNe, the spectrum is best modeled with elements including O II and Mg II, while we tentatively suggest that Fe III might be present. The host galaxy is detected in gri with 25.74 +/- 0.19, 24.43 +/- 0.06, and 24.14 +/- 0.12, respectively. It is a faint dwarf galaxy with M-g = -16.9. Conclusions. We suggest that the precursor plateau might be related to a recombination wave in a circumstellar medium (CSM) and discuss whether this is a common property of all similar explosions. The subsequent rise can be equally well described by input from a magnetar or by ejecta-CSM interaction, but the models are not well constrained owing to the lack of post-maximum observations, and CSM interaction has difficulties accounting for the precursor plateau self-consistently. Radioactive decay is less likely to be the mechanism that powers the luminosity. The host is a moderately young and star-forming, but not a starburst, galaxy.

  • 178. Leloudas, G.
    et al.
    Fraser, M.
    Stone, N. C.
    van Velzen, S.
    Jonker, P. G.
    Arcavi, I.
    Fremling, Christoffer
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Maund, J. R.
    Smartt, S. J.
    Krühler, T.
    Miller-Jones, J. C. A.
    Vreeswijk, P. M.
    Gal-Yam, A.
    Mazzali, P. A.
    De Cia, A.
    Howell, D. A.
    Inserra, C.
    Patat, F.
    de Ugarte Postigo, A.
    Yaron, O.
    Ashall, C.
    Bar, I.
    Campbell, H.
    Chen, T. -W.
    Childress, M.
    Elias-Rosa, N.
    Harmanen, J.
    Hosseinzadeh, G.
    Johansson, J.
    Kangas, T.
    Kankare, E.
    Kim, S.
    Kuncarayakti, H.
    Lyman, J.
    Magee, M. R.
    Maguire, K.
    Malesani, D.
    Mattila, S.
    McCully, C. V.
    Nicholl, M.
    Prentice, S.
    Romero-Cañizales, C.
    Schulze, S.
    Smith, K. W.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Sullivan, M.
    Tucker, B. E.
    Valenti, S.
    Wheeler, J. C.
    Young, D. R.
    The superluminous transient ASASSN-15lh as a tidal disruption event from a Kerr black hole2016Inngår i: Nature Astronomy, E-ISSN 2397-3366, Vol. 1, nr 1, artikkel-id 0002Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    When a star passes within the tidal radius of a supermassive black hole, it will be torn apart1. For a star with the mass of the Sun (M-circle dot) and a non-spinning black hole with a mass <10(8)M(circle dot), the tidal radius lies outside the black hole event horizon2 and the disruption results in a luminous flare(3-6). Here we report observations over a period of ten months of a transient, hitherto interpreted(7) as a superluminous supernova(8). Our data show that the transient rebrightened substantially in the ultraviolet and that the spectrum went through three different spectroscopic phases without ever becoming nebular. Our observations are more consistent with a tidal disruption event than a superluminous supernova because of the temperature evolution(6), the presence of highly ionized CNO gas in the line of sight(9) and our improved localization of the transient in the nucleus of a passive galaxy, where the presence of massive stars is highly unlikely(10,11). While the supermassive black hole has a mass >10(8)M(circle dot)(12,13), a star with the same mass as the Sun could be disrupted outside the event horizon if the black hole were spinning rapidly(14). The rapid spin and high black hole mass can explain the high luminosity of this event.

  • 179. Leloudas, G.
    et al.
    Gallazzi, A.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Stritzinger, Maximilian D.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Fynbo, J. P. U.
    Hjorth, J.
    Malesani, D.
    Michalowski, M. J.
    Milvang-Jensen, B.
    Smith, M.
    The properties of SN Ib/c locations2011Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 530, s. A95-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aims. We seek to gain a deeper understanding of stripped-envelope, core-collapse supernovae through studying their environments. Methods. We obtained low-resolution optical spectroscopy with the New Technology Telescope (+EFOSC2) at the locations of 20 type Ib/c supernovae. We measured the flux of emission lines in the stellar-continuum-subtracted spectra from which local metallicities are computed. For the supernova regions, we estimate both the mean stellar age, by interpreting the stellar absorption with population synthesis models, and the age of the youngest stellar populations using the Ha equivalent width as an age indicator. These estimates are compared with the lifetimes of single massive stars. Results. Based on our sample, we detect a tentative indication that type Ic supernovae might explode in environments that are more metal-rich than those of type Ib supernovae (average difference of 0.08 dex), but this is not a statistically significant result. The lower limits placed on the ages of the supernova birthplaces are generally young, although there are several cases where these appear older than what is expected for the evolution of single stars that are more massive than 25-30 M(circle dot). This is only true, however, when assuming that the supernova progenitors were born during an instantaneous (not continuous) episode of star formation. Conclusions. These results do not conclusively favor any of the two evolutionary paths (single or binary) leading to stripped supernovae. We do note a fraction of events for which binary evolution is more likely due to their associated age limits; however, the supernova environments contain areas of recent (<15 Myr) star formation, and the environmental metallicities at least do not contradict the single evolutionary scenario, suggesting that this channel is also broadly consistent with the observations.

  • 180. Leloudas, G.
    et al.
    Patat, F.
    Maund, J. R.
    Hsiao, E.
    Malesani, D.
    Schulze, S.
    Contreras, C.
    de Ugarte Postigo, A.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Stritzinger, M. D.
    Taddia, F.
    Wheeler, J. C.
    Gorosabel, J.
    Polarimetry of the Superluminous Supernova LSQ14mo: No Evidence for Significant Deviations from Spherical Symmetry2015Inngår i: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 815, nr 1, artikkel-id L10Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present the first polarimetric observations of a Type I superluminous supernova (SLSN). LSQ14mo was observed with VLT/FORS2 at five different epochs in the V band, with the observations starting before maximum light and spanning 26 days in the rest frame (z. = 0.256). During this period, we do not detect any statistically significant evolution (<2 sigma) in the Stokes parameters. The average values we obtain, corrected for interstellar polarization in the Galaxy, are Q = -0.01% (+/- 0.15%) and U = -0.50% (+/- 0.14%). This low polarization can be entirely due to interstellar polarization in the SN host galaxy. We conclude that, at least during the period of observations and at the optical depths probed, the photosphere of LSQ14mo does not present significant asymmetries, unlike most lower-luminosity hydrogen-poor SNe Ib/c. Alternatively, it is possible that we may have observed LSQ14mo from a special viewing angle. Supporting spectroscopy and photometry confirm that LSQ14mo is a typical SLSN I. Further studies of the polarization of Type I SLSNe are required to determine whether the low levels of polarization are a characteristic of the entire class and to also study the implications for the proposed explosion models.

  • 181. Leloudas, G.
    et al.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Levan, A. J.
    Fynbo, J. P. U.
    Malesani, D.
    Maund, J. R.
    Do Wolf-Rayet stars have similar locations in hosts as type Ib/c supernovae and long gamma-ray bursts?2010Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 518, nr July-August, s. A29-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aims: We study the distribution of Wolf-Rayet (WR) stars and their subtypes with respect to their host galaxy light distribution. We thus want to investigate whether WR stars are potential progenitors of stripped-envelope core-collapse supernovae (SNe) and/or long-duration gamma-ray bursts (LGRBs). Methods: We derived the relative surface brightness (fractional flux) at the locations of WR stars and compared with similar results for LGRBs and SNe. We examined two nearby galaxies, M 83 and NGC 1313, for which a comprehensive study of the WR population exists. These two galaxies contain a sufficiently large number of WR stars and sample different metallicities. To enable the comparison, the images of the galaxies were processed to make them appear as they would look at a higher redshift. The robustness of our results against several sources of uncertainty was investigated with the aid of Monte Carlo simulations. Results: We find that the WC star distribution favours brighter pixels than the WN star population. WC stars are more likely drawn from the same distribution as SNe Ic than from other SN distributions, while WN stars show a higher degree of association with SNe Ib. It can also not be excluded that WR (especially WC) stars are related to LGRBs. Some differences between the two galaxies do exist, especially in the subtype distributions, and may stem from differences in metallicity. Conclusions: Although a conclusive answer is not possible, the expectation that WR stars are the progenitors of SNe Ib/c and LGRBs survives this test. The trend observed between the distributions of WN and WC stars, as compared to those of SNe Ib and Ic, is consistent with the theoretical picture that SNe Ic result from progenitors that have been stripped of a larger part of their envelope. Table A.1 is only available in electronic form at http://www.aanda.org

  • 182. Leloudas, G.
    et al.
    Stritzinger, M. D.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Burns, C. R.
    Kozma, Cecilia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Krisciunas, K.
    Maund, J. R.
    Milne, P.
    Filippenko, A. V.
    Fransson, Claes
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Ganeshalingam, M.
    Hamuy, M.
    Li, W.
    Phillips, M. M.
    Schmidt, B. P.
    Skottfelt, J.
    Taubenberger, S.
    Boldt, L.
    Fynbo, J. P. U.
    Gonzalez, L.
    Salvo, M.
    Thomas-Osip, J.
    The normal Type Ia SN 2003hv out to very late phases2009Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 505, nr 1, s. 265-279Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aims: We study a thermonuclear supernova (SN), emphasizing very late phases. Methods: An extensive dataset for SN 2003hv that covers the flux evolution from maximum light to day +786 is presented. This includes 82 epochs of optical imaging, 24 epochs of near-infrared (NIR) imaging, and 10 epochs of optical spectroscopy. These data are combined with published nebular-phase IR spectra, and the observations are compared to model light curves and synthetic nebular spectra. Results: SN 2003hv is a normal Type Ia supernova (SN Ia) with photometric and spectroscopic properties consistent with its rarely observed B-band decline-rate parameter, Δ m15(B) = 1.61 ± 0.02. The blueshift of the most isolated [Fe ii] lines in the nebular-phase optical spectrum appears consistent with those observed in the IR at similar epochs. At late times there is a prevalent color evolution from the optical toward the NIR bands. We present the latest-ever detection of a SN Ia in the NIR in Hubble Space Telescope images. The study of the ultraviolet/optical/infrared (UVOIR) light curve reveals that a substantial fraction of the flux is “missing” at late times. Between 300 and 700 days past maximum brightness, the UVOIR light curve declines linearl