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  • 201. Mattila, Seppo
    et al.
    Väisänen, Petri
    Farrah, Duncan
    Efstathiou, A
    Meikle, Peter
    Dahlén, Tomas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Fransson, Claes
    Institutionen för astronomi.
    Lira, P
    Lundqvist, Peter
    Institutionen för astronomi.
    Östlin, Göran
    Institutionen för astronomi.
    Ryder, S
    Sollerman, Jesper
    Institutionen för astronomi.
    Adaptive Optics Discovery of Supernova 2004ip in the Nuclear Regions of the Luminous Infrared Galaxy IRAS 18293-34132007Ingår i: The Astrophysical Journal, Vol. 659, nr 1, s. L9-L12Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report a supernova discovery in Ks-band images from the NAOS CONICA adaptive optics (AO) system on the ESO Very Large Telescope. The images were obtained as part of a near-infrared search for highly obscured supernovae in the nuclear regions of luminous and ultraluminous infrared galaxies. SN 2004ip is located within a circumnuclear starburst at 1.4" (or 500 pc) projected distance from the K-band nucleus of the luminous infrared galaxy IRAS 18293-3413. The supernova luminosity and light curve are consistent with a core-collapse event suffering from a host galaxy extinction of up to about 40 mag in the V band, which is as expected for a circumnuclear starburst environment. This is the first supernova to be discovered making use of AO correction and demonstrates the potential of the current 8 m-class telescopes equipped with AO in discovering supernovae from the innermost nuclear regions of luminous and ultraluminous infrared galaxies.

  • 202. Mattila, Seppo
    et al.
    Väisänen, Petri
    Meikle, Peter
    Dahlén, Tomas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Efstathiou, A
    Farrah, Duncan
    Fransson, Claes
    Institutionen för astronomi.
    Lira, P
    Lundqvist, Peter
    Institutionen för astronomi.
    Östlin, Göran
    Institutionen för astronomi.
    Ryder, S
    Sollerman, Jesper
    Institutionen för astronomi.
    Supernova 2004ip in IRAS 18293-3413 = Psn K0409-0012007Övrigt (Övrigt vetenskapligt)
  • 203. Maund, J. R.
    et al.
    Fraser, M.
    Ergon, Mattias
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Pastorello, A.
    Smartt, S. J.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Benetti, S.
    Botticella, M-T
    Bufano, F.
    Danziger, I. J.
    Kotak, R.
    Magill, L.
    Stephens, A. W.
    Valenti, S.
    THE YELLOW SUPERGIANT PROGENITOR OF THE TYPE II SUPERNOVA 2011dh IN M512011Ingår i: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 739, nr 2, artikel-id L37Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present the detection of the putative progenitor of the Type IIb SN 2011dh in archival pre-explosion Hubble Space Telescope images. Using post-explosion Adaptive Optics imaging with Gemini NIRI+ALTAIR, the position of the supernova (SN) in the pre-explosion images was determined to within 23 mas. The progenitor candidate is consistent with an F8 supergiant star (logL/L(circle dot) = 4.92 +/- 0.20 and T(eff) = 6000 +/- 280 K). Through comparison with stellar evolution tracks, this corresponds to a single star at the end of core C-burning with an initial mass of M(ZAMS) = 13 +/- 3 M(circle dot). The possibility of the progenitor source being a cluster is rejected, on the basis of: (1) the source not being spatially extended, (2) the absence of excess H alpha emission, and (3) the poor fit to synthetic cluster spectral energy distributions (SEDs). It is unclear if a binary companion is contributing to the observed SED, although given the excellent correspondence of the observed photometry to a single star SED we suggest that the companion does not contribute significantly. Early photometric and spectroscopic observations show fast evolution similar to the transitional Type IIb SN 2008ax and suggest that a large amount of the progenitor's hydrogen envelope was removed before explosion. Late-time observations will reveal if the yellow supergiant or the putative companion star were responsible for this SN explosion.

  • 204. Maund, J. R.
    et al.
    Fraser, M.
    Smartt, S. J.
    Botticella, M. T.
    Barbarino, C.
    Childress, M.
    Gal-Yam, A.
    Inserra, C.
    Pignata, G.
    Reichart, D.
    Schmidt, B.
    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).
    Tomasella, L.
    Valenti, S.
    Yaron, O.
    Supernova 2012ec: identification of the progenitor and early monitoring with PESSTO2013Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 431, nr 1, s. l102-L106Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present the identification of the progenitor of the Type IIP SN 2012ec in archival pre-explosion Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2) and Advanced Camera for Surveys Wide Field Channel F814W images. The properties of the progenitor are further constrained by non-detections in pre-explosion WFPC2 F450W and F606W images. We report a series of early photometric and spectroscopic observations of SN 2012ec. The r' -band light curve shows a plateau with M-r' = -17.0. The early spectrum is similar to the Type IIP SN 1999em, with the expansion velocity measured at Ha absorption minimum of -11 700 km s(-1) (at 1 d post-discovery). The photometric and spectroscopic evolution of SN 2012ec shows it to be a Type IIP SN, discovered only a few days post-explosion (<6 d). We derive a luminosity for the progenitor, in comparison with MARCS model spectral energy distributions, of log L/L-circle dot = 5.15 +/- 0.19, from which we infer an initial mass range of 14-22M(circle dot). This is the first SN with an identified progenitor to be followed by the Public ESO Spectroscopic Survey of Transient Objects (PESSTO).

  • 205. Maund, J. R.
    et al.
    Leloudas, G.
    Malesani, D. B.
    Patat, F.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    de Ugarte Postigo, A.
    Polarimetry of the superluminous transient ASASSN-15lh2020Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 498, nr 3, s. 3730-3735Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    ASASSN-15lh is the intrinsically brightest transient observed to date. Despite being the subject of concerted photometric and spectroscopic observing campaigns, there is still significant debate about the true nature of this transient and the mechanism responsible for its great luminosity. Here we report five epochs of imaging polarimetry and two epochs of spectropolarimetry conducted with the ESO Very Large Telescope (VLT) FOcal Reducer and low dispersion Spectrograph (FORS) polarimeter, spanning +28-91 d (rest frame) with respect to the light-curve maximum. The overall level of polarization across this period is seen to be low similar to 0.5-0.8 per cent, however at +51.6 d, approximately corresponding to a dip in the ultraviolet (UV) photometric light curve, the polarization is seen to briefly rise to 1.2 per cent in the observed V band. We discuss this behaviour in the context of previous polarimetric observations of superluminous supernovae (SLSNe) and tidal disruption events (TDEs). Although the level of polarization could be consistent with polarization observed for SLSNe, the behaviour around the UV light-curve dip could also be consistent with a TDE observed almost edge on.

  • 206. Mazzali, P. A.
    et al.
    Benetti, S.
    Altavilla, G.
    Blanc, G.
    Cappellaro, E.
    Elias-Rosa, N.
    Garavini, G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Goobar, A.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Harutyunyan, A.
    Kotak, R.
    Leibundgut, B.
    Lundqvist, P.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Mattila, S.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Mendez, J.
    Nobili, S.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Pain, R.
    Pastorello, A.
    Patat, F.
    Pignata, G.
    Podsiadlowski, Ph.
    Ruiz-Lapuente, P.
    Salvo, M.
    Schmidt, B. P.
    Sollerman, J.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Stanishev, V.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Stehle, M.
    Tout, C.
    Turatto, M.
    Hillebrandt, W.
    High-Velocity Features: A Ubiquitous Property of Type Ia Supernovae2005Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 623, s. L37-L40Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Evidence of high-velocity features (HVFs) such as those seen in the near-maximum spectra of some Type Ia supernovae (SNe Ia; e.g., SN 2000cx) has been searched for in the available SN Ia spectra observed earlier than 1 week before B maximum. Recent observational efforts have doubled the number of SNe Ia with very early spectra. Remarkably, all SNe Ia with early data (seven in our Research Training Network sample and 10 from other programs) show signs of such features, to a greater or lesser degree, in Ca II IR and some also in the Si II λ6355 line. HVFs may be interpreted as abundance or density enhancements. Abundance enhancements would imply an outer region dominated by Si and Ca. Density enhancements may result from the sweeping up of circumstellar material (CSM) by the highest velocity SN ejecta. In this scenario, the high incidence of HVFs suggests that a thick disk and/or a high-density companion wind surrounds the exploding white dwarf, as may be the case in single degenerate systems. Large-scale angular fluctuations in the radial density and abundance distribution may also be responsible: this could originate in the explosion and would suggest a deflagration as the more likely explosion mechanism. CSM interaction and surface fluctuations may coexist, possibly leaving different signatures on the spectrum. In some SNe, the HVFs are narrowly confined in velocity, suggesting the ejection of blobs of burned material.

  • 207. McBrien, Owen R.
    et al.
    Smartt, Stephen J.
    Chen, Ting-Wan
    Inserra, Cosimo
    Gillanders, James H.
    Sim, Stuart A.
    Jerkstrand, Anders
    Rest, Armin
    Valenti, Stefano
    Roy, Rupak
    Gromadzki, Mariusz
    Taubenberger, Stefan
    Flörs, Andreas
    Huber, Mark E.
    Chambers, Ken C.
    Gal-Yam, Avishay
    Young, David R.
    Nicholl, Matt
    Kankare, Erkki
    Smith, Ken W.
    Maguire, Kate
    Mandel, Ilya
    Prentice, Simon
    Rodríguez, Ósmar
    Pineda Garcia, Jonathan
    Gutiérrez, Claudia P.
    Galbany, Lluís
    Barbarino, Cristina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Clark, Peter S. J.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Kulkarni, Shrinivas R.
    De, Kishalay
    Buckley, David A. H.
    Rau, Arne
    SN2018kzr: A Rapidly Declining Transient from the Destruction of a White Dwarf2019Ingår i: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 885, nr 1, artikel-id L23Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present SN2018kzr, the fastest declining supernova-like transient, second only to the kilonova, AT2017gfo. SN2018kzr is characterized by a peak magnitude of M-r & xfffd;=& xfffd;?17.98, a peak bolometric luminosity of ?1.4 & xfffd;& x5e0;10(43) erg s(?1), and a rapid decline rate of 0.48 & xfffd;& xfffd;0.03 mag day(?1) in the r band. The bolometric luminosity evolves too quickly to be explained by pure Ni-56 heating, necessitating the inclusion of an alternative powering source. Incorporating the spin-down of a magnetized neutron star adequately describes the lightcurve and we estimate a small ejecta mass of M-ej & xfffd;=& xfffd;0.10 & xfffd;& xfffd;0.05 M. Our spectral modeling suggests the ejecta is composed of intermediate mass elements including O, Si, and Mg and trace amounts of Fe-peak elements, which disfavors a binary neutron star merger. We discuss three explosion scenarios for SN2018kzr, given the low ejecta mass, intermediate mass element composition, and high likelihood of additional powering?the core collapse of an ultra-stripped progenitor, the accretion induced collapse (AIC) of a white dwarf, and the merger of a white dwarf and neutron star. The requirement for an alternative input energy source favors either the AIC with magnetar powering or a white dwarf?neutron star merger with energy from disk wind shocks.

  • 208. McClelland, Colin M.
    et al.
    Garnavich, Peter M.
    Galbany, Lluís
    Miquel, Ramon
    Foley, Ryan J.
    Filippenko, Alexei V.
    Bassett, Bruce
    Wheeler, J. Craig
    Goobar, Ariel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Jha, Saurabh W.
    Sako, Masao
    Frieman, Joshua A.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Vinko, Jozsef
    Schneider, Donald P.
    The Subluminous Supernova 2007qd: A Missing Link in a Family of Low-luminosity Type Ia Supernovae2010Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 720, nr 1, s. 704-716Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present multi-band photometry and multi-epoch spectroscopy of the peculiar Type Ia supernova (SN Ia) 2007qd, discovered by the SDSS-II Supernova Survey. It possesses physical properties intermediate to those of the peculiar SN 2002cx and the extremely low-luminosity SN 2008ha. Optical photometry indicates that it had an extraordinarily fast rise time of lsim10 days and a peak absolute B magnitude of -15.4 ± 0.2 at most, making it one of the most subluminous SN Ia ever observed. Follow-up spectroscopy of SN 2007qd near maximum brightness unambiguously shows the presence of intermediate-mass elements which are likely caused by carbon/oxygen nuclear burning. Near maximum brightness, SN 2007qd had a photospheric velocity of only 2800 km s-1, similar to that of SN 2008ha but about 4000 and 7000 km s-1 less than that of SN 2002cx and normal SN Ia, respectively. We show that the peak luminosities of SN 2002cx like objects are highly correlated with both their light-curve stretch and photospheric velocities. Its strong apparent connection to other SN 2002cx like events suggests that SN 2007qd is also a pure deflagration of a white dwarf, although other mechanisms cannot be ruled out. It may be a critical link between SN 2008ha and the other members of the SN 2002cx like class of objects.

  • 209. Medler, K.
    et al.
    Mazzali, P. A.
    Teffs, J.
    Prentice, S. J.
    Ashall, C.
    Amenouche, M.
    Anderson, J. P.
    Burke, J.
    Chen, Ting-Wan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Galbany, L.
    Gromadzki, M.
    Gutierrez, C. P.
    Hiramatsu, D.
    Howell, D. A.
    Inserra, C.
    Kankare, E.
    McCully, C.
    Müller-Bravo, T. E.
    Nicholl, M.
    Pellegrino, C.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    SN2020cpg: an energetic link between Type IIb and Ib supernovae2021Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 506, nr 2, s. 1832-1849Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Stripped-envelope supernovae (SE-SNe) show a wide variety of photometric and spectroscopic properties. This is due to the different potential formation channels and the stripping mechanism that allows for a large diversity within the progenitors outer envelope compositions. Here, the photometric and spectroscopic observations of SN 2020cpg covering ∼130 d from the explosion date are presented. SN 2020cpg (z = 0.037) is a bright SE-SNe with the B-band peaking at MB = −17.75 ± 0.39 mag and a maximum pseudo-bolometric luminosity of Lmax = 6.03 ± 0.01 × 1042 erg s−1. Spectroscopically, SN 2020cpg displays a weak high- and low-velocity H α feature during the photospheric phase of its evolution, suggesting that it contained a detached hydrogen envelope prior to explosion. From comparisons with spectral models, the mass of hydrogen within the outer envelope was constrained to be ∼0.1 M. From the pseudo-bolometric light curve of SN 2020cpg a 56Ni mass of MNi ∼ 0.27 ± 0.08 M was determined using an Arnett-like model. The ejecta mass and kinetic energy of SN 2020cpg were determined using an alternative method that compares the light curve of SN 2020cpg and several modelled SE-SNe, resulting in an ejecta mass of Mejc ∼ 5.5 ± 2.0 M and a kinetic energy of EK ∼ 9.0 ± 3.0 × 1051 erg. The ejected mass indicates a progenitor mass of 18−25 M. The use of the comparative light curve method provides an alternative process to the commonly used Arnett-like model to determine the physical properties of SE-SNe.

  • 210. Meikle, Peter
    et al.
    Mattila, Seppo
    Pastorello, A
    Gerardy, Christopher
    Kotak, Rubina
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    van Dyk, S. D.
    Farrah, Duncan
    Filippenko, Alexei
    Höflich, Peter
    Lundqvist, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Pozzo, Monica
    Wheeler, J. Craig
    A Spitzer Space Telescope Study of SN 2003gd: Still No Direct Evidence that Core-Collapse Supernovae are Major Dust Factories2007Ingår i: The Astrophysical Journal, Vol. 665, nr 1, s. 608-617Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a new, detailed analysis of late-time mid-infrared observations of the Type II-P supernova (SN) 2003gd. At about 16 months after the explosion, the mid-IR flux is consistent with emission from 4×10-5 Msolar of newly condensed dust in the ejecta. At 22 months emission from pointlike sources close to the SN position was detected at 8 and 24 μm. By 42 months the 24 μm flux had faded. Considerations of luminosity and source size rule out the ejecta of SN 2003gd as the main origin of the emission at 22 months. A possible alternative explanation for the emission at this later epoch is an IR echo from preexisting circumstellar or interstellar dust. We conclude that, contrary to the claim of Sugerman and coworkers, the mid-IR emission from SN 2003gd does not support the presence of 0.02 Msolar of newly formed dust in the ejecta. There is, as yet, no direct evidence that core-collapse supernovae are major dust factories.

  • 211. Meikle, W. P. S.
    et al.
    Kotak, R.
    Farrah, D.
    Mattila, Seppo
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Van Dyk, S. D.
    Andersen, A. C.
    Fesen, R.
    Filippenko, A. V.
    Foley, R. J.
    Fransson, Claes
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Gerardy, C. L.
    Hoeflich, P. A.
    Lundqvist, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Pozzo, M.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Wheeler, J. C.
    Dust and the type II-Plateau supernova 2004dj2011Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 732, nr 2, s. 109-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present mid-infrared (MIR) spectroscopy of a Type II-plateau supernova, SN 2004dj, obtained with the Spitzer Space Telescope, spanning 106-1393 days after explosion. MIR photometry plus optical/near-IR observations are also reported. An early-time MIR excess is attributed to emission from non-silicate dust formed within a cool dense shell (CDS). Most of the CDS dust condensed between 50 days and 165 days, reaching a mass of 0.3 x 10(-5) M(circle dot). Throughout the observations, much of the longer wavelength (> 10 mu m) part of the continuum is explained as an IR echo from interstellar dust. The MIR excess strengthened at later times. We show that this was due to thermal emission from warm, non-silicate dust formed in the ejecta. Using optical/near-IR line profiles and the MIR continua, we show that the dust was distributed as a disk whose radius appeared to be shrinking slowly. The disk radius may correspond to a grain destruction zone caused by a reverse shock which also heated the dust. The dust-disk lay nearly face-on, had high opacities in the optical/near-IR regions, but remained optically thin in the MIR over much of the period studied. Assuming a uniform dust density, the ejecta dust mass by 996 days was (0.5 +/- 0.1) x 10(-4) M(circle dot) and exceeded 10(-4) M(circle dot) by 1393 days. For a dust density rising toward the center the limit is higher. Nevertheless, this study suggests that the amount of freshly synthesized dust in the SN 2004dj ejecta is consistent with that found from previous studies and adds further weight to the claim that such events could not have been major contributors to the cosmic dust budget.

  • 212. Meikle, W. P. S.
    et al.
    Mattila, S.
    Gerardy, C. L.
    Kotak, R.
    Pozzo, M.
    van Dyk, S. D.
    Farrah, D.
    Fesen, R. A.
    Filippenko, A. V.
    Fransson, C.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Lundqvist, P.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Sollerman, J.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Wheeler, J. C.
    A Spitzer Space Telescope Study of SN 2002hh: An Infrared Echo from a Type IIP Supernova2006Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 649, s. 332-344Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present late-time (590-994 days) mid-IR photometry of the normal but highly reddened Type IIP supernova SN 2002hh. Bright, cool, slowly fading emission is detected from the direction of the supernova. Most of this flux appears not to be driven by the supernova event but instead probably originates in a cool, obscured star formation region or molecular cloud along the line of sight. We also show, however, that the declining component of the flux is consistent with an SN-powered IR echo from a dusty progenitor CSM. Mid-IR emission could also be coming from newly condensed dust and/or an ejecta/CSM impact, but their contributions are likely to be small. For the case of a CSM-IR echo, we infer a dust mass of as little as 0.036 Msolar with a corresponding CSM mass of 3.6(0.01/rdg) Msolar, where rdg is the dust-to-gas mass ratio. Such a CSM would have resulted from episodic mass loss whose rate declined significantly about 28,000 years ago. Alternatively, an IR echo from a surrounding, dense, dusty molecular cloud might also have been responsible for the fading component. Either way, this is the first time that an IR echo has been clearly identified in a Type IIP supernova. We find no evidence for or against the proposal that Type IIP supernovae produce large amounts of dust via grain condensation in the ejecta. However, within the CSM-IR echo scenario, the mass of dust derived implies that the progenitors of the most common of core-collapse supernovae may make an important contribution to the universal dust content.

  • 213. Melandri, A.
    et al.
    Malesani, D. B.
    Izzo, L.
    Japelj, J.
    Vergani, S. D.
    Schady, P.
    Sagues Carracedo, A.
    de Ugarte Postigo, A.
    Anderson, J. P.
    Barbarino, Cristina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Bolmer, J.
    Breeveld, A.
    Calissendorff, Per
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Campana, S.
    Cano, Z.
    Carini, R.
    Covino, S.
    D'Avanzo, P.
    D'Elia, V.
    della Valle, M.
    De Pasquale, M.
    Fynbo, J. P. U.
    Gromadzki, M.
    Hammer, F.
    Hartmann, D. H.
    Heintz, K. E.
    Inserra, C.
    Jakobsson, P.
    Kann, D. A.
    Kotilainen, J.
    Maguire, K.
    Masetti, N.
    Nicholl, M.
    Olivares E, F.
    Pugliese, G.
    Rossi, A.
    Salvaterra, R.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Stone, M. B.
    Tagliaferri, G.
    Tomasella, L.
    Thone, C. C.
    Xu, D.
    Young, D. R.
    GRB171010A/SN 2017htp: a GRB-SN at z=0.332019Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 490, nr 4, s. 5366-5374Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The number of supernovae known to be connected with long-duration gamma-ray bursts (GRBs) is increasing and the link between these events is no longer exclusively found at low redshift (z less than or similar to 0.3) but is well established also at larger distances. We present a new case of such a liaison at z = 0.33 between GRB171010A and SN 2017htp. It is the second closest GRB with an associated supernova of only three events detected by Fermi-LAT. The supernova is one of the few higher redshift cases where spectroscopic observations were possible and shows spectral similarities with the well-studied SN 1998bw, having produced a similar Ni mass (M-Ni = 0.33 +/- 0.02 M-circle dot) with slightly lower ejected mass (M-ej = 4.1 +/- 0.7 M-circle dot) and kinetic energy (E-K = 8.1 +/- 2.5 x 10(51) erg). The host-galaxy is bigger in size than typical GRB host galaxies, but the analysis of the region hosting the GRB revealed spectral properties typically observed in GRB hosts and showed that the progenitor of this event was located in a very bright H II region of its face-on host galaxy, at a projected distance of similar to 10 kpc from its galactic centre. The star-formation rate (SFRGRB similar to 0.2 M-circle dot yr(-1)) and metallicity (12 + log(O/H) similar to 8.15 +/- 0.10) of the GRB star-forming region are consistent with those of the host galaxies of previously studied GRB-SN systems.

  • 214.
    Melinder, Jens
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Dahlen, T.
    Mencia-Trinchant, Laia
    Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Östlin, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Mattila, S.
    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).
    Fransson, Claes
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hayes, M.
    Nasoudi-Shoar, S.
    The discovery and classification of 16 supernovae at high redshifts in ELAIS-S1 The Stockholm VIMOS Supernova Survey II2011Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 532, s. A29-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Supernova surveys can be used to study a variety of subjects such as: (i) cosmology through type Ia supernovae (SNe), (ii) star-formation rates through core-collapse SNe, and (iii) supernova properties and their connection to host galaxy characteristics. The Stockholm VIMOS Supernova Survey (SVISS) is a multi-band imaging survey aiming to detect supernovae at redshift similar to 0.5 and derive thermonuclear and core-collapse supernova rates at high redshift. In this paper we present the supernovae discovered in the survey along with light curves and a photometric classification into thermonuclear and core-collapse types. To detect the supernovae in the VLT/VIMOS multi-epoch images, we used difference imaging and a combination of automatic and manual source detection to minimise the number of spurious detections. Photometry for the found variable sources was obtained and careful simulations were made to estimate correct errors. The light curves were typed using a Bayesian probability method and Monte Carlo simulations were used to study misclassification. We detected 16 supernovae, nine of which had a core-collapse origin and seven had a thermonuclear origin. The estimated misclassification errors are quite small, in the order of 5%, but vary with both redshift and type. The mean redshift of the supernovae is 0.58. Additionally, we found a variable source with a very extended light curve that could possibly be a pair instability supernova.

  • 215.
    Melinder, Jens
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Dahlen, Tomas
    Space Telescope Science Institute.
    Fransson, Claes
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Mencia Trinchant, Laia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Mattila, Seppo
    Tuorla Observatory.
    Hayes, Matthew
    CNRS, Universite de Toulouse.
    Östlin, Göran
    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).
    Nasoudi-Shoar, Soroush
    Argelander-Institut fur Astronomie, Universität Bonn.
    The Rate of Supernovae at Redshift 0.1 − 1.0: the Stockholm VIMOS Supernova Survey IV2012Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 545, nr A96Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    We present supernova rate measurements at redshift 0.1–1.5 from the Stockholm VIMOS Supernova Survey (SVISS). The sample contains 16 supernovae in total. The discovered supernovae have been classified into core collapse or thermonuclear (Ia) types based on their light curves, colour evolution and host galaxy photometric redshift. The rates we find for the core collapse supernovae are 1.25 (+2.27 +0.85 −0.97 −0.78) - with statistical and systematic errors, respectively - at z = 0.39 and 6.90 (+5.24 +3.04 −3.25 −2.14) at z = 0.73. For the Ia supernovae the rates are 2.02 (+1.57 +0.53−0.96 −0.57) at z = 0.39 and 1.03 (+0.92 +0.31−0.54 −0.36) at z = 0.80. All of these rate estimates have been corrected for host galaxy extinction. Using Monte Carlo simulations we make a thorough study of the systematic effects from assumptions made when calculating the rates and find that the most important errors comes from misclassification, the assumed mix of faint and bright supernova types and uncertainties in redshift. We compare our rates to other observations, to the star formation history for core collapse rates and to different models of the delay time distribution for Ia rates. Overall, our measurements agree quite well with these other rates when using redshift-dependent corrections for extinction. We do not find any evidence of a missing fraction of core collapse supernovae.

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  • 216.
    Melinder, Jens
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Dahlen, Tomas
    Space Telescope Science Institute.
    Mencia Trinchant, Laia
    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).
    Mattila, Seppo
    Tuorla Observatory.
    Sollerman, Jesper
    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).
    Hayes, Matthew
    CNRS, Universite de Toulouse.
    Nasoudi-Shoar, Soroush
    Argelander-Institut fur Astronomie, Universität Bonn.
    The Discovery and Classification of 16 Supernovae at High Redshifts in ELAIS-S1: the Stockholm VIMOS Supernova Survey IIIngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Supernova surveys can be used to study a variety of subjects, such as: (i) cosmology using type Ia supernovae, (ii) star formationrates using core-collapse SNe, (iii) supernova properties and their connection to host galaxy characteristics. The Stockholm VIMOSSupernova Survey (SVISS) is a multi-band imaging survey aiming to detect supernovae at redshift 0.5 and derive thermonuclearand core-collapse supernova rates at high redshift. In this paper we present the supernovae discovered in the survey along with lightcurves and a photometric classification into thermonuclear and core-collapse types. To detect the supernovae in the VLT/VIMOSmulti-epoch images we used difference imaging and a combination of automatic and manual source detection to minimise the numberof spurious detections. Photometry for the found variable sources was obtained and careful simulations done to estimate correct errors.The light curves were typed using a Bayesian probability method and Monte Carlo simulations were used to study misclassification.We detected 16 supernovae, eight of which had a core-collapse origin and eight that had a thermonuclear origin. The estimatedmisclassification errors are quite small, on the order of 5%, but vary with both redshift and type. The mean redshift of the supernovaeis 0.64. Additionally, we found a variable source with a very extended light curve that could possibly be a pair instability supernova.

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  • 217. Michalowski, M. J.
    et al.
    Castro Ceron, J. M.
    Wardlow, J. L.
    Karska, A.
    Messias, H.
    van der Werf, P.
    Hunt, L. K.
    Baes, M.
    Castro-Tirado, A. J.
    Gentile, G.
    Hjorth, J.
    Le Floc'h, E.
    Perez-Martinez, R.
    Guelbenzu, A. Nicuesa
    Rasmussen, J.
    Rizzo, J. R.
    Rossi, A.
    Sanchez-Portal, M.
    Schady, P.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Xu, D.
    GRB 980425 host: [C II], [O I], and CO lines reveal recent enhancement of star formation due to atomic gas inflow2016Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 595, artikel-id A72Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Context. Accretion of gas from the intergalactic medium is required to fuel star formation in galaxies. We have recently suggested that this process can be studied using host galaxies of gamma-ray bursts (GRBs). Aims. Our aim is to test this possibility by studying in detail the properties of gas in the closest galaxy hosting a GRB (980425). Methods. We obtained the first ever far-infrared (FIR) line observations of a GRB host, namely Herschel/PACS resolved [C II] 158 mu m and [O I] 63 mu m spectroscopy, and an APEX/SHeFI CO(2-1) line detection and ALMA CO(1-0) observations of the GRB980425 host. Results. The GRB980425 host has elevated [CII]/FIR and [O I]/FIR ratios and higher values of star formation rates (SFR) derived from line ([C II], [O I], H alpha) than from continuum (UV, IR, radio) indicators. [C II] emission exhibits a normal morphology, peaking at the galaxy centre, whereas [O I] is concentrated close to the GRB position and the nearby Wolf-Rayet region. The high [O I] flux indicates that there is high radiation field and high gas density at these positions, as derived from modelling of photo-dissociation regions. The [C II]/CO luminosity ratio of the GRB980425 host is close to the highest values found for local star-forming galaxies. Indeed, its CO-derived molecular gas mass is low given its SFR and metallicity, but the [C II]-derived molecular gas mass is close to the expected value. Conclusions. The [O I] and H I concentrations and the high radiation field and density close to the GRB position are consistent with the hypothesis of a very recent (at most a few tens of Myr ago) inflow of atomic gas triggering star formation. In this scenario dust has not had time to build up (explaining high line-to-continuum ratios). Such a recent enhancement of star formation activity would indeed manifest itself in high SFRline/SFRcontinuum ratios because the line indicators are sensitive only to recent (less than or similar to 10 Myr) activity, whereas the continuum indicators measure the SFR averaged over much longer periods (similar to 100 Myr). Within a sample of 32 other GRB hosts, 20 exhibit SFRline/SFRcontinuum > 1 with a mean ratio of 1.74 +/- 0.32. This is consistent with a very recent enhancement of star formation that is common among GRB hosts, so galaxies that have recently experienced inflow of gas may preferentially host stars exploding as GRBs. Therefore GRBs may be used to select a unique sample of galaxies that is suitable for the investigation of recent gas accretion.

  • 218. Michalowski, M. J.
    et al.
    Gentile, G.
    Hjorth, J.
    Krumholz, M. R.
    Tanvir, N. R.
    Kamphuis, P.
    Burlon, D.
    Baes, M.
    Basa, S.
    Berta, S.
    Castro Ceron, J. M.
    Crosby, D.
    D'Elia, V.
    Elliott, J.
    Greiner, J.
    Hunt, L. K.
    Klose, S.
    Koprowski, M. P.
    Le Floc'h, E.
    Malesani, D.
    Murphy, T.
    Guelbenzu, A. Nicuesa
    Palazzi, E.
    Rasmussen, J.
    Rossi, A.
    Savaglio, S.
    Schady, P.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    de Ugarte Postigo, A.
    Watson, D.
    van der Werf, P.
    Vergani, S. D.
    Xu, D.
    Massive stars formed in atomic hydrogen reservoirs: H i observations of gamma-ray burst host galaxies2015Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 582, artikel-id A78Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Long gamma-ray bursts (GRBs), among the most energetic events in the Universe, are explosions of massive and short-lived stars, so they pinpoint locations of recent star formation. However, several GRB host galaxies have recently been found to be deficient in molecular gas (H-2), believed to be the fuel of star formation. Moreover, optical spectroscopy of GRB afterglows implies that the molecular phase constitutes only a small fraction of the gas along the GRB line of sight. Here we report the first ever 21 cm line observations of GRB host galaxies, using the Australia Telescope Compact Array, implying high levels of atomic hydrogen (HI), which suggests that the connection between atomic gas and star formation is stronger than previously thought. In this case, it is possible that star formation is directly fuelled by atomic gas (or that the HI- to- H-2 conversion is very efficient, which rapidly exhaust molecular gas), as has been theoretically shown to be possible. This can happen in low-metallicity gas near the onset of star formation because cooling of gas (necessary for star formation) is faster than the HI- to- H-2 conversion. Indeed, large atomic gas reservoirs, together with low molecular gas masses, stellar, and dust masses are consistent with GRB hosts being preferentially galaxies which have very recently started a star formation episode after accreting metal-poor gas from the intergalactic medium. This provides a natural route for forming GRBs in low-metallicity environments. The gas inflow scenario is also consistent with the existence of the companion HI object with no optical counterpart similar to 19 kpc from the GRB 060505 host, and with the fact that the HI centroids of the GRB 980425 and 060505 hosts do not coincide with optical centres of these galaxies, but are located close to the GRB positions.

  • 219. Michalowski, M. J.
    et al.
    Hunt, L. K.
    Palazzi, E.
    Savaglio, S.
    Gentile, G.
    Rasmussen, J.
    Baes, M.
    Basa, S.
    Bianchi, S.
    Berta, S.
    Burlon, D.
    Castro Ceron, J. M.
    Covino, S.
    Cuby, J. -G
    D'Elia, V.
    Ferrero, P.
    Goetz, D.
    Hjorth, J.
    Koprowski, M. P.
    Le Borgne, D.
    Le Floc'h, E.
    Malesani, D.
    Murphy, T.
    Pian, E.
    Piranomonte, S.
    Rossi, A.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Tanvir, N. R.
    de Ugarte Postigo, A.
    Watson, D.
    van der Werf, P.
    Vergani, S. D.
    Xu, D.
    Spatially-resolved dust properties of the GRB 980425 host galaxy2014Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 562, s. A70-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Gamma-ray bursts (GRBs) have been proposed as a tool for studying star formation in the Universe, so it is crucial to investigate whether their host galaxies and immediate environments are in any way special compared with other star-forming galaxies. Here we present spatially resolved maps of dust emission of the host galaxy of the closest known GRB 980425 at z = 0.0085 using our new high-resolution observations from Herschel, Atacama Pathfinder Experiment (APEX), Atacama Large Millimeter Array (ALMA) and Australia Telescope Compact Array (ATCA). We modelled the spectral energy distributions of the host and of the star-forming region displaying the Wolf-Rayet signatures in the spectrum (WR region), located 800 pc from the GRB position. The host is characterised by low dust content and a high fraction of UV-visible star formation, similar to other dwarf galaxies. These galaxies are abundant in the local universe, so it is not surprising to find a GRB in one of them, assuming the correspondence between the GRB rate and star formation. The WR region contributes substantially to the host emission at the far-infrared, millimetre, and radio wavelengths and we propose that this is a consequence of its high gas density. If dense environments are also found close to the positions of other GRBs, then the ISM density should also be considered, along with metallicity, an important factor influencing whether a given stellar population can produce a GRB.

  • 220. Michalowski, M. J.
    et al.
    Kamble, A.
    Hjorth, J.
    Malesani, D.
    Reinfrank, R. F.
    Bonavera, L.
    Ceron, J. M. Castro
    Ibar, E.
    Dunlop, J. S.
    Fynbo, J. P. U.
    Garrett, M. A.
    Jakobsson, P.
    Kaplan, D. L.
    Kruhler, T.
    Levan, A. J.
    Massardi, M.
    Pal, S.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Tanvir, N. R.
    van der Horst, A. J.
    Watson, D.
    Wiersema, K.
    THE OPTICALLY UNBIASED GRB HOST (TOUGH) SURVEY. VI. RADIO OBSERVATIONS AT z less than or similar to 1 AND CONSISTENCY WITH TYPICAL STAR-FORMING GALAXIES2012Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 755, nr 2, s. 85-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The objective of this paper is to determine the level of obscured star formation activity and dust attenuation in a sample of gamma-ray burst (GRB) hosts, and to test the hypothesis that GRB hosts have properties consistent with those of the general star-forming galaxy populations. We present a radio continuum survey of all z < 1 GRB hosts in The Optically Unbiased GRB Host (TOUGH) sample supplemented with radio data for all (mostly pre-Swift) GRB-SN hosts discovered before 2006 October. We present new radio data for 22 objects and have obtained a detection for three of them (GRB 980425, 021211, 031203; none in the TOUGH sample), increasing the number of radio-detected GRB hosts from two to five. The star formation rate (SFR) for the GRB 021211 host of similar to 825 M-circle dot yr(-1), the highest ever reported for a GRB host, places it in the category of ultraluminous infrared galaxies. We found that at least similar to 63% of GRB hosts have SFR < 100 M-circle dot yr(-1) and at most similar to 8% can have SFR > 500 M-circle dot yr(-1). For the undetected hosts the mean radio flux (<35 mu Jy 3 sigma) corresponds to an average SFR < 15 M-circle dot yr(-1). Moreover, greater than or similar to 88% of the z less than or similar to 1 GRB hosts have ultraviolet dust attenuation A(UV) < 6.7 mag (visual attenuation A(V) < 3 mag). Hence, we did not find evidence for large dust obscuration in a majority of GRB hosts. Finally, we found that the distributions of SFRs and A(UV) of GRB hosts are consistent with those of Lyman break galaxies, H alpha emitters at similar redshifts, and of galaxies from cosmological simulations. The similarity of the GRB population with other star-forming galaxies is consistent with the hypothesis that GRBs, a least at z less than or similar to 1, trace a large fraction of all star formation, and are therefore less biased indicators than once thought.

  • 221. Michalowski, Michal J.
    et al.
    Karska, A.
    Rizzo, J. R.
    Baes, M.
    Castro-Tirado, A. J.
    Hjorth, J.
    Hunt, L. K.
    Kamphuis, P.
    Koprowski, M. P.
    Krumholz, M. R.
    Malesani, D.
    Guelbenzu, A. Nicuesa
    Rasmussen, J.
    Rossi, A.
    Schady, P.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    van der Werf, P.
    Molecular gas masses of gamma-ray burst host galaxies2018Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 617, artikel-id A143Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Context. Long gamma-ray bursts (GRBs) can potentially be used as a tool to study star formation and recent gas accretion onto galaxies. However, the information about gas properties of GRB hosts is scarce. In particular, very few carbon monoxide (CO) line detections of individual GRB hosts have been reported. It has also been suggested that GRB hosts have lower molecular gas masses than expected from their star formation rates (SFRs). Aims. The objectives of this paper are to analyse molecular gas properties of the first substantial sample of GRB hosts and test whether they are deficient in molecular gas. Methods. We obtained CO(2-1) observations of seven GRB hosts with the APEX and IRAM 30 m telescopes. We analysed these data together with all other hosts with previous CO observations. From these observations we calculated the molecular gas masses of these galaxies and compared them with the expected values based on their SFRs and metallicities. Reults. We obtained detections for 3 GRB hosts (980425, 080207, and 111005A) and upper limits for the remaining 4 (031203, 060505, 060814, and 100316D). In our entire sample of 12 CO-observed GRB hosts, 3 are clearly deficient in molecular gas, even taking into account their metallicity (980425, 060814, and 080517). Four others are close to the best-fit line for other star-forming galaxies on the SFR-M-H2 plot (051022, 060505, 080207, and 100316D). One host is clearly molecule rich (111005A). Finally, the data for 4 GRB hosts are not deep enough to judge whether they are molecule deficient (000418, 030329, 031203, and 090423). The median value of the molecular gas depletion time, M-H2/SFR, of GRB hosts is similar to 0.3 dex below that of other star-forming galaxies, but this result has low statistical significance. A Kolmogorov-Smirnov test performed on M-H2/SFR shows an only similar to 2 sigma difference between GRB hosts and other galaxies. This difference can partly be explained by metallicity effects, since the significance decreases to similar to 1 sigma for M-H2/SFR versus metallicity. Conclusions. We found that any molecular gas deficiency of GRB hosts has low statistical significance and that it can be attributed to their lower metallicities; and thus the sample of GRB hosts has molecular properties that are consistent with those of other galaxies, and they can be treated as representative star-forming galaxies. However, the molecular gas deficiency can be strong for GRB hosts if they exhibit higher excitations and/or a lower CO-to-H-2 conversion factor than we assume, which would lead to lower molecular gas masses than we derive. Given the concentration of atomic gas recently found close to GRB and supernova sites, indicating recent gas inflow, our results about the weak molecular deficiency imply that such an inflow does not enhance the SFRs significantly, or that atomic gas converts efficiently into the molecular phase, which fuels star formation. Only if the analysis of a larger GRB host sample reveals molecular deficiency (especially close to the GRB position) would this support the hypothesis of star formation that is directly fuelled by atomic gas.

  • 222. Miknaitis, G.
    et al.
    Pignata, G.
    Rest, A.
    Wood-Vasey, W. M.
    Blondin, S.
    Challis, P.
    Smith, R. C.
    Stubbs, C. W.
    Suntzeff, N. B.
    Foley, R. J.
    Matheson, T.
    Tonry, J. L.
    Aguilera, C.
    Blackman, J. W.
    Becker, A. C.
    Clocchiatti, A.
    Covarrubias, R.
    Davis, T. M.
    Filippenko, A. V.
    Garg, A.
    Garnavich, P. M.
    Hicken, M.
    Jha, S.
    Krisciunas, K.
    Kirshner, R. P.
    Leibundgut, B.
    Li, W.
    Miceli, A.
    Narayan, G.
    Prieto, J. L.
    Riess, A. G.
    Salvo, M. E.
    Schmidt, B. P.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Spyromilio, J.
    Zenteno, A.
    The ESSENCE supernova survey: Survey optimization, observations, and supernova photometry2007Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 666, nr 2, s. 674-693Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    We describe the implementation and optimization of the ESSENCE supernova survey, which we have undertaken to measure the dark energy equation-of-state parameter, w = P/(rho c(2)). We present a method for optimizing the survey exposure times and cadence to maximize our sensitivity to w for a given fixed amount of telescope time. For our survey on the CTIO 4 m telescope, measuring the luminosity distances and redshifts for supernovae at modest redshifts (z approximate to 0: 5 +/- 0: 2) is optimal for determining w. We describe the data analysis pipeline based on using reliable and robust image subtraction to find supernovae automatically and in nearly real time. Since making cosmological inferences with supernovae relies crucially on accurate measurement of their apparent brightnesses, we describe our efforts to establish a thorough calibration of the CTIO 4 m telescope's natural photometric system. In its first four years, ESSENCE has discovered and spectroscopically confirmed 102 Type Ia supernovae, at redshifts from 0.10 to 0.78, identified through an impartial, effective methodology for spectroscopic classification and redshift determination. We present the resulting light curves for all of the Type Ia supernovae found by ESSENCE and used in our measurement of w, presented in a companion paper by Wood-Vasey and coworkers.

  • 223. Miller, A. A.
    et al.
    Cao, Y.
    Piro, A. L.
    Blagorodnova, N.
    Bue, B. D.
    Cenko, S. B.
    Dhawan, Suhail
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Ferretti, Raphael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Fox, O. D.
    Fremling, Christoffer
    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).
    Howell, D. A.
    Hosseinzadeh, G.
    Kasliwal, M. M.
    Laher, R. R.
    Lunnan, R.
    Masci, F. J.
    McCully, C.
    Nugent, P. E.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Taddia, Fransesco
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Kulkarni, S. R.
    Early Observations of the Type Ia Supernova iPTF 16abc: A Case of Interaction with Nearby, Unbound Material and/or Strong Ejecta Mixing2018Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 852, nr 2, artikel-id 100Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Early observations of Type Ia supernovae (SNe Ia) provide a unique probe of their progenitor systems and explosion physics. Here we report the intermediate Palomar Transient Factory (iPTF) discovery of an extraordinarily young SN Ia, iPTF 16abc. By fitting a power law to our early light curve, we infer that first light for the SN, that is, when the SN could have first been detected by our survey, occurred only 0.15 +/-(0.15)(0.07) days before our first detection. In the similar to 24 hr after discovery, iPTF 16abc rose by similar to 2mag, featuring a near-linear rise in flux for. greater than or similar to 3 days. Early spectra show strong C II absorption, which disappears after similar to 7 days. Unlike the extensively observed Type Ia SN 2011fe, the (B - V)(0) colors of iPTF 16abc are blue and nearly constant in the days after explosion. We show that our early observations of iPTF 16abc cannot be explained by either SN shock breakout and the associated, subsequent cooling or the SN ejecta colliding with a stellar companion. Instead, we argue that the early characteristics of iPTF 16abc, including (i) the rapid, near-linear rise, (ii) the nonevolving blue colors, and (iii) the strong C II absorption, are the result of either ejecta interaction with nearby, unbound material or vigorous mixing of radioactive Ni-56 in the SN ejecta, or a combination of the two. In the next few years, dozens of very young normal SNe Ia will be discovered, and observations similar to those presented here will constrain the white dwarf explosion mechanism.

  • 224. Miller, A. A.
    et al.
    Kasliwal, M. M.
    Cao, Y.
    Adams, S. M.
    Goobar, Ariel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Knezevic, S.
    Laher, R. R.
    Lunnan, R.
    Masci, F. J.
    Nugent, P. E.
    Perley, D. A.
    Petrushevska, Tanja
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Quimby, R. M.
    Rebbapragada, U. D.
    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).
    Kulkarni, S. R.
    Color Me Intrigued: The Discovery of iPTF 16fnm, an SN 2002cx-like Object2017Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 848, nr 1, artikel-id 59Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    0 Modern wide-field, optical time-domain surveys must solve a basic optimization problem: maximize the number of transient discoveries or minimize the follow-up needed for the new discoveries. Here, we describe the Color Me Intrigued experiment, the first from the intermediate Palomar Transient Factory (iPTF) to search for transients simultaneously in the g(PTF') and R-PTF bands. During the course of this experiment, we discovered iPTF 16fnm, a new member of the 02cx-like subclass of Type Ia supernovae (SNe). iPTF 16fnm peaked at Mg-PTF = -15.09 +/- 0.17 mag, making it the second-least-luminous known SN Ia. iPTF 16fnm exhibits all the hallmarks of the 02cx-like class: (i) low luminosity at peak, (ii) low ejecta velocities, and (iii) a non-nebular spectrum several months after peak. Spectroscopically, iPTF 16fnm exhibits a striking resemblance to two other low-luminosity 02cx-like SNe: SN. 2007qd and SN 2010ae. iPTF 16fnm and SN 2005hk decline at nearly the same rate, despite a 3 mag difference in brightness at peak. When considering the full subclass of 02cx-like SNe, we do not find evidence for a tight correlation between peak luminosity and decline rate in either the g ' or r ' band. We measure the relative rate of 02cx-like SNe to normal SNe Ia and find r(N02cx/NIa) = 33(-25)(+158)%. We further examine the g ' - r ' evolution of 02cx-like SNe and find that their unique color evolution can be used to separate them from 91bg-like and normal SNe Ia. This selection function will be especially important in the spectroscopically incomplete Zwicky Transient Facility/Large Synoptic Survey Telescope (LSST) era. Finally, we close by recommending that LSST periodically evaluate, and possibly update, its observing cadence to maximize transient science.

  • 225. Miller, A. A.
    et al.
    Magee, M. R.
    Polin, A.
    Maguire, K.
    Zimmerman, E.
    Yao, Y.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Schulze, S.
    Perley, D. A.
    Kromer, M.
    Dhawan, Suhail
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Bulla, Mattia
    Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita).
    Andreoni, I
    Bellm, E. C.
    De, K.
    Dekany, R.
    Delacroix, A.
    Fremling, C.
    Gal-Yam, A.
    Goldstein, D. A.
    Golkhou, V. Z.
    Goobar, Ariel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Graham, M. J.
    Irani, I.
    Kasliwal, M. M.
    Kaye, S.
    Kim, Y-L
    Laher, R. R.
    Mahabal, A. A.
    Masci, F. J.
    Nugent, P. E.
    Ofek, E.
    Phinney, E. S.
    Prentice, S. J.
    Riddle, R.
    Rigault, M.
    Rusholme, B.
    Schweyer, Tassilo
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Shupe, D. L.
    Soumagnac, M. T.
    Terreran, G.
    Walters, R.
    Yan, L.
    Zolkower, J.
    Kulkarni, S. R.
    The Spectacular Ultraviolet Flash from the Peculiar Type Ia Supernova 2019yvq2020Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 898, nr 1, artikel-id 56Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Early observations of Type Ia supernovae (SNe Ia) provide essential clues for understanding the progenitor system that gave rise to the terminal thermonuclear explosion. We present exquisite observations of SN 2019yvq, the second observed SN Ia, after iPTF 14atg, to display an early flash of emission in the ultraviolet (UV) and optical. Our analysis finds that SN 2019yvq was unusual, even when ignoring the initial flash, in that it was moderately underluminous for an SN Ia ( mag at peak) yet featured very high absorption velocities ( km s−1 for Si ii λ6355 at peak). We find that many of the observational features of SN 2019yvq, aside from the flash, can be explained if the explosive yield of radioactive 56Ni is relatively low (we measure ) and it and other iron-group elements are concentrated in the innermost layers of the ejecta. To explain both the UV/optical flash and peak properties of SN 2019yvq we consider four different models: interaction between the SN ejecta and a nondegenerate companion, extended clumps of 56Ni in the outer ejecta, a double-detonation explosion, and the violent merger of two white dwarfs. Each of these models has shortcomings when compared to the observations; it is clear additional tuning is required to better match SN 2019yvq. In closing, we predict that the nebular spectra of SN 2019yvq will feature either H or He emission, if the ejecta collided with a companion, strong [Ca ii] emission, if it was a double detonation, or narrow [O i] emission, if it was due to a violent merger.

  • 226. Moriya, Takashi J.
    et al.
    Maeda, Keiichi
    Taddia, Francesco
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Blinnikov, Sergei I.
    Sorokina, Elena I.
    Mass-loss histories of Type IIn supernova progenitors within decades before their explosion2014Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 439, nr 3, s. 2917-2926Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present results of a systematic study of the mass-loss properties of Type IIn supernova progenitors within decades before their explosion. We apply an analytic light-curve model to 11 Type IIn supernova bolometric light curves to derive the circumstellar medium properties. We reconstruct the mass-loss histories based on the estimated circumstellar medium properties. The estimated mass-loss rates are mostly higher than 10(-3) M-circle dot yr(-1) and they are consistent with those obtained by other methods. The mass-loss rates are often found to be constantly high within decades before their explosion. This indicates that there exists some mechanism to sustain the high mass-loss rates of Type IIn supernova progenitors for at least decades before their explosion. Thus, the shorter eruptive mass-loss events observed in some Type IIn supernova progenitors are not always responsible for creating their dense circumstellar media. In addition, we find that Type IIn supernova progenitors may tend to increase their mass-loss rates as they approach to the time of their explosion. We also show a detailed comparison between our analytic prediction and numerical results.

  • 227. Müller-Bravo, Tomás E.
    et al.
    Gutiérrez, Claudia P.
    Sullivan, Mark
    Jerkstrand, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Max-Planck Institut für Astrophysik, Germany.
    Anderson, Joseph P.
    González-Gaitán, Santiago
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Arcavi, Iair
    Burke, Jamison
    Galbany, Lluís
    Gal-Yam, Avishay
    Gromadzki, Mariusz
    Hiramatsu, Daichi
    Hosseinzadeh, Griffin
    Howell, D. Andrew
    Inserra, Cosimo
    Kankare, Erki
    Kozyreva, Alexandra
    McCully, Curtis
    Nicholl, Matt
    Smartt, Stephen
    Valenti, Stefano
    Young, Dave R.
    The low-luminosity Type II SN2016aqf: a well-monitored spectral evolution of the Ni/Fe abundance ratio2020Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 497, nr 1, s. 361-377Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Low-luminosity Type II supernovae (LL SNe II) make up the low explosion energy end of core-collapse SNe, but their study and physical understanding remain limited. We present SN 2016aqf, an LL SN II with extensive spectral and photometric coverage. We measure a V-band peak magnitude of −14.58 mag, a plateau duration of ∼100 d, and an inferred 56Ni mass of 0.008 ± 0.002 M. The peak bolometric luminosity, Lbol ≈ 1041.4 erg s−1, and its spectral evolution are typical of other SNe in the class. Using our late-time spectra, we measure the [O i] λλ6300, 6364 lines, which we compare against SN II spectral synthesis models to constrain the progenitor zero-age main-sequence mass. We find this to be 12 ± 3 M. Our extensive late-time spectral coverage of the [Fe ii] λ7155 and [Ni ii] λ7378 lines permits a measurement of the Ni/Fe abundance ratio, a parameter sensitive to the inner progenitor structure and explosion mechanism dynamics. We measure a constant abundance ratio evolution of 0.081+0.009−0.010 and argue that the best epochs to measure the ratio are at ∼200–300 d after explosion. We place this measurement in the context of a large sample of SNe II and compare against various physical, light-curve, and spectral parameters, in search of trends that might allow indirect ways of constraining this ratio. We do not find correlations predicted by theoretical models; however, this may be the result of the exact choice of parameters and explosion mechanism in the models, the simplicity of them, and/or primordial contamination in the measured abundance ratio.

  • 228. Nadolny, Jakub
    et al.
    Michałowski, Michał Jerzy
    Rizzo, J. Ricardo
    Karska, Agata
    Rasmussen, Jesper
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hjorth, Jens
    Rossi, Andrea
    Solar, Martín
    Wróblewski, Radosław
    Leśniewska, Aleksandra
    Main Sequence to Starburst Transitioning Galaxies: Gamma-Ray Burst Hosts at z ∼ 22023Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 952, nr 2, artikel-id 125Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Star-forming galaxies populate a main sequence (MS), a well-defined relation between stellar mass (M*) and star formation rate (SFR). Starburst (SB) galaxies lie significantly above the relation, whereas quenched galaxies lie below the sequence. In order to study the evolution of galaxies on the SFR–M* plane and its connection to the gas content, we use the fact that recent episodes of star formation can be pinpointed by the existence of gamma-ray bursts (GRBs). Here we present sensitive [C i] nondetections of z ∼ 2 ultraluminous infrared (ULIRG) GRB host galaxies. We find that our GRB hosts have similar molecular masses to those of other ULIRGs. However, unlike other ULIRGs, the GRB hosts are located at the MS or only a factor of a few above it. Hence, our GRB hosts are caught in the transition toward the SB phase. This is further supported by the estimated depletion times, which are similar to those of other transitioning galaxies. The GRB hosts are [C i]-dark galaxies, defined as having a [C i]/CO temperature brightness ratio of <0.1. Such a low [C i]/CO ratio has been found in high-density environments (nH > 104 cm−3) where CO is shielded from photodissociation, leading to underabundances of [C i]. This is consistent with the merger process that is indeed suggested for our GRB hosts by their morphologies.

  • 229. Narayan, G.
    et al.
    Rest, A.
    Tucker, B. E.
    Foley, R. J.
    Wood-Vasey, W. M.
    Challis, P.
    Stubbs, C.
    Kirshner, R. P.
    Aguilera, C.
    Becker, A. C.
    Blondin, S.
    Clocchiatti, A.
    Covarrubias, R.
    Damke, G.
    Davis, T. M.
    Filippenko, A. V.
    Ganeshalingam, M.
    Garg, A.
    Garnavich, P. M.
    Hicken, M.
    Jha, S. W.
    Krisciunas, K.
    Leibundgut, B.
    Li, W.
    Matheson, T.
    Miknaitis, G.
    Pignata, G.
    Prieto, J. L.
    Riess, A. G.
    Schmidt, B. P.
    Silverman, J. M.
    Smith, R. C.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Spyromilio, J.
    Suntzeff, N. B.
    Tonry, J. L.
    Zenteno, A.
    LIGHT CURVES OF 213 TYPE Ia SUPERNOVAE FROM THE ESSENCE SURVEY2016Ingår i: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 224, nr 1, artikel-id 3Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The ESSENCE survey discovered 213 Type Ia supernovae at redshifts 0.1 < z < 0.81 between 2002 and 2008. We present their R- and I-band photometry, measured from images obtained using the MOSAIC II camera at the CTIO Blanco, along with rapid-response spectroscopy for each object. We use our spectroscopic follow-up observations to determine an accurate, quantitative classification, and precise redshift. Through an extensive calibration program we have improved the precision of the CTIO Blanco natural photometric system. We use several empirical metrics to measure our internal photometric consistency and our absolute calibration of the survey. We assess the effect of various potential sources of systematic bias on our measured fluxes, and estimate the dominant term in the systematic error budget from the photometric calibration on our absolute fluxes is similar to 1%.

  • 230. Nicholl, M.
    et al.
    Smartt, S. J.
    Jerkstrand, A.
    Inserra, C.
    Anderson, J. P.
    Baltay, C.
    Benetti, S.
    Chen, T. -W
    Elias-Rosa, N.
    Feindt, U.
    Fraser, M.
    Gal-Yam, A.
    Hadjiyska, E.
    Howell, D. A.
    Kotak, R.
    Lawrence, A.
    Leloudas, G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. University of Copenhagen, Denmark.
    Margheim, S.
    Mattila, S.
    McCrum, M.
    McKinnon, R.
    Mead, A.
    Nugent, P.
    Rabinowitz, D.
    Rest, A.
    Smith, K. W.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Sullivan, M.
    Taddia, Francesco
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Valenti, S.
    Walker, E. S.
    Young, D. R.
    Superluminous supernovae from PESSTO2014Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 444, nr 3, s. 2096-2113Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present optical spectra and light curves for three hydrogen-poor superluminous supernovae followed by the Public ESO Spectroscopic Survey of Transient Objects (PESSTO). Time series spectroscopy from a fewdays aftermaximum light to 100 d later shows them to be fairly typical of this class, with spectra dominated by Ca II, MgII, FeII, and Si II, which evolve slowly over most of the post-peak photospheric phase. We determine bolometric light curves and apply simple fitting tools, based on the diffusion of energy input by magnetar spin-down, Ni-56 decay, and collision of the ejecta with an opaque circumstellar shell. We investigate how the heterogeneous light curves of our sample (combined with others from the literature) can help to constrain the possible mechanisms behind these events. We have followed these events to beyond 100-200 d after peak, to disentangle host galaxy light from fading supernova flux and to differentiate between the models, which predict diverse behaviour at this phase. Models powered by radioactivity require unrealistic parameters to reproduce the observed light curves, as found by previous studies. Both magnetar heating and circumstellar interaction still appear to be viable candidates. A large diversity is emerging in observed tail-phase luminosities, with magnetar models failing in some cases to predict the rapid drop in flux. This would suggest either that magnetars are not responsible, or that the X-ray flux from the magnetar wind is not fully trapped. The light curve of one object shows a distinct rebrightening at around 100 d after maximum light. We argue that this could result either from multiple shells of circumstellar material, or from a magnetar ionization front breaking out of the ejecta.

  • 231. Nicholl, M.
    et al.
    Smartt, S. J.
    Jerkstrand, A.
    Inserra, C.
    McCrum, M.
    Kotak, R.
    Fraser, M.
    Wright, D.
    Chen, T-W
    Smith, K.
    Young, D. R.
    Sim, S. A.
    Valenti, S.
    Howell, D. A.
    Bresolin, F.
    Kudritzki, R. P.
    Tonry, J. L.
    Huber, M. E.
    Rest, A.
    Pastorello, A.
    Tomasella, L.
    Cappellaro, E.
    Benetti, S.
    Mattila, S.
    Kankare, E.
    Kangas, T.
    Leloudas, Georgios
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). University of Copenhagen, 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).
    Berger, E.
    Chornock, R.
    Narayan, G.
    Stubbs, C. W.
    Foley, R. J.
    Lunnan, R.
    Söderberg, A.
    Sanders, N.
    Milisavljevic, D.
    Margutti, R.
    Kirshner, R. P.
    Elias-Rosa, N.
    Morales-Garoffolo, A.
    Taubenberger, S.
    Botticella, M. T.
    Gezari, S.
    Urata, Y.
    Rodney, S.
    Riess, A. G.
    Scolnic, D.
    Wood-Vasey, W. M.
    Burgett, W. S.
    Chambers, K.
    Flewelling, H. A.
    Magnier, E. A.
    Kaiser, N.
    Metcalfe, N.
    Morgan, J.
    Price, P. A.
    Sweeney, W.
    Waters, C.
    Slowly fading super-luminous supernovae that are not pair-instability explosions2013Ingår i: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 502, nr 7471, s. 346-+Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Super-luminous supernovae(1-4) that radiate more than 1044 ergs per second at their peak luminosity have recently been discovered in faint galaxies at redshifts of 0.1-4. Some evolve slowly, resembling models of 'pair-instability' supernovae(5,6). Such models involve stars with original masses 140-260 times that of the Sun that now have carbon-oxygen cores of 65-130 solar masses. In these stars, the photons that prevent gravitational collapse are converted to electron-positron pairs, causing rapid contraction and thermonuclear explosions. Many solar masses of Ni-56 are synthesized; this isotope decays to Fe-56 via Co-56, powering bright light curves(7,8). Such massive progenitors are expected to have formed from metal-poor gas in the early Universe(9). Recently, supernova 2007bi in a galaxy at redshift 0.127 (about 12 billion years after the Big Bang) with a metallicity one-third that of the Sun was observed to look like a fading pair-instability supernova(1,10). Here we report observations of two slow-to-fade super-luminous supernovae that show relatively fast rise times and blue colours, which are incompatible with pair-instability models. Their late-time light-curve and spectral similarities to supernova 2007bi call the nature of that event into question. Our early spectra closely resemble typical fast-declining super-luminous supernovae(2,11,12), which are not powered by radio-activity. Modelling our observations with 10-16 solar masses of magnetar-energized(13,14) ejecta demonstrates the possibility of a common explosion mechanism. The lack of unambiguous nearby pair-instability events suggests that their local rate of occurrence is less than 6 x 10(-6) times that of the core-collapse rate.

  • 232. Nicholl, M.
    et al.
    Smartt, S. J.
    Jerkstrand, A.
    Inserra, C.
    Sim, S. A.
    Chen, T. -W
    Benetti, S.
    Fraser, M.
    Gal-Yam, A.
    Kankare, E.
    Maguire, K.
    Smith, K.
    Sullivan, M.
    Valenti, S.
    Young, D. R.
    Baltay, C.
    Bauer, F. E.
    Baumont, S.
    Bersier, D.
    Botticella, M. -T
    Childress, M.
    Dennefeld, M.
    Della Valle, M.
    Elias-Rosa, N.
    Feindt, U.
    Galbany, L.
    Hadjiyska, E.
    Le Guillou, L.
    Leloudas, G.
    Mazzali, P.
    McKinnon, R.
    Polshaw, J.
    Rabinowitz, D.
    Rostami, S.
    Scalzo, R.
    Schmidt, B. P.
    Schulze, S.
    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).
    Yuan, F.
    On the diversity of superluminous supernovae: ejected mass as the dominant factor2015Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 452, nr 4, s. 3869-3893Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We assemble a sample of 24 hydrogen-poor superluminous supernovae (SLSNe). Parameterizing the light-curve shape through rise and decline time-scales shows that the two are highly correlated. Magnetar-powered models can reproduce the correlation, with the diversity in rise and decline rates driven by the diffusion time-scale. Circumstellar interaction models can exhibit a similar rise-decline relation, but only for a narrow range of densities, which may be problematic for these models. We find that SLSNe are approximately 3.5 mag brighter and have light curves three times broader than SNe Ibc, but that the intrinsic shapes are similar. There are a number of SLSNe with particularly broad light curves, possibly indicating two progenitor channels, but statistical tests do not cleanly separate two populations. The general spectral evolution is also presented. Velocities measured from Fe II are similar for SLSNe and SNe Ibc, suggesting that diffusion time differences are dominated by mass or opacity. Flat velocity evolution in most SLSNe suggests a dense shell of ejecta. If opacities in SLSNe are similar to other SNe Ibc, the average ejected mass is higher by a factor 2-3. Assuming. = 0.1 cm(2) g(-1), we estimate a mean (median) SLSN ejecta mass of 10 M-circle dot (6 M-circle dot), with a range of 3-30 M-circle dot. Doubling the assumed opacity brings the masses closer to normal SNe Ibc, but with a high-mass tail. The most probable mechanism for generating SLSNe seems to be the core collapse of a very massive hydrogen-poor star, forming a millisecond magnetar.

  • 233. Nordin, J.
    et al.
    Brinnel, V.
    van Santen, J.
    Bulla, Mattia
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. 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).
    Franckowiak, A.
    Fremling, C.
    Gal-Yam, A.
    Giomi, M.
    Kowalski, M.
    Mahabal, A.
    Miranda, N.
    Rauch, L.
    Reusch, S.
    Rigault, M.
    Schulze, S.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Stein, R.
    Yaron, O.
    van Velzen, S.
    Ward, C.
    Transient processing and analysis using AMPEL: alert management, photometry, and evaluation of light curves2019Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 631, artikel-id A147Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Context. Both multi-messenger astronomy and new high-throughput wide-field surveys require flexible tools for the selection and analysis of astrophysical transients.

    Aims. Here we introduce the alert management, photometry, and evaluation of light curves (AMPEL) system, an analysis framework designed for high-throughput surveys and suited for streamed data. AMPEL combines the functionality of an alert broker with a generic framework capable of hosting user-contributed code; it encourages provenance and keeps track of the varying information states that a transient displays. The latter concept includes information gathered over time and data policies such as access or calibration levels.

    Methods. We describe a novel ongoing real-time multi-messenger analysis using AMPEL to combine IceCube neutrino data with the alert streams of the Zwicky Transient Facility (ZTF). We also reprocess the first four months of ZTF public alerts, and compare the yields of more than 200 different transient selection functions to quantify efficiencies for selecting Type Ia supernovae that were reported to the Transient Name Server (TNS).

    Results. We highlight three channels suitable for (1) the collection of a complete sample of extragalactic transients, (2) immediate follow-up of nearby transients, and (3) follow-up campaigns targeting young, extragalactic transients. We confirm ZTF completeness in that all TNS supernovae positioned on active CCD regions were detected.

    Conclusions. AMPEL can assist in filtering transients in real time, running alert reaction simulations, the reprocessing of full datasets as well as in the final scientific analysis of transient data. This is made possible by a novel way of capturing transient information through sequences of evolving states, and interfaces that allow new code to be natively applied to a full stream of alerts. This text also introduces a method by which users can design their own channels for inclusion in the AMPEL live instance that parses the ZTF stream and the real-time submission of high-quality extragalactic supernova candidates to the TNS.

  • 234.
    Nordin, Jakob
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Östman, Linda
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. 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).
    Amanullah, Rahman
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Nichol, R. C.
    Smith, M.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Basset, B. A.
    Frieman, J. A.
    Garnavich, P. M.
    Leloudas, G.
    Sako, M.
    Schneider, D. P.
    Spectral properties of Type Ia supernovae up to z~0.32011Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 526, s. A119-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Aims: Spectroscopic observations of type Ia supernovae obtained at the New Technology Telescope (NTT) and the Nordic Optical Telescope (NOT), in conjunction with the SDSS-II Supernova Survey, are analysed. We use spectral indicators measured up to a month after the lightcurve peak luminosity to characterise the supernova properties, and examine these for potential correlations with host galaxy type, lightcurve shape, colour excess, and redshift.

    Methods: Our analysis is based on 89 type Ia supernovae at a redshift interval z = 0.05-0.3, for which multiband SDSS photometry is available. A lower-z spectroscopy reference sample was used for comparisons over cosmic time. We present measurements of time series of pseudo equivalent widths and line velocities of the main spectral features in type Ia supernovae.

    Results: Supernovae with shallower features are found predominantly among the intrinsically brighter slow declining supernovae. We detect the strongest correlation between lightcurve stretch and the Si ii λ4000 absorption feature, which also correlates with the estimated mass and star formation rate of the host galaxy. We also report a tentative correlation between colour excess and spectral properties. If confirmed, this would suggest that moderate reddening of type Ia supernovae is dominated by effects in the explosion or its immediate environment, as opposed to extinction by interstellar dust.

  • 235.
    Nordin, Jakob
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Östman, Linda
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Goobar, Ariel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Balland, C.
    Lampeitl, H.
    Nichol, R. C.
    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).
    Wheeler, J. C.
    EVIDENCE FOR A CORRELATION BETWEEN THE Si II lambda 4000 WIDTH AND TYPE Ia SUPERNOVA COLOR2011Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 734, nr 1, s. 42-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study the pseudo-equivalent width of the Si II lambda 4000 feature of Type Ia supernovae (SNe Ia) in the redshift range 0.0024 <= z <= 0.634. We find that this spectral indicator correlates with the light curve color excess (SALT2c) as well as previously defined spectroscopic subclasses (Branch types) and the evolution of the Si II lambda 6150 velocity, i.e., the so-called velocity gradient. Based on our study of 55 objects from different surveys, we find indications that the Si II lambda 4000 spectral indicator could provide important information to improve cosmological distance measurements with SNe Ia.