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  • 251. Perley, Daniel A.
    et al.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Schulze, Steve
    Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Yao, Yuhan
    Fremling, Christoffer
    Gal-Yam, Avishay
    Ho, Anna Y. Q.
    Yang, Yi
    Kool, Erik C.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Irani, Ido
    Yan, Lin
    Andreoni, Igor
    Baade, Dietrich
    Bellm, Eric C.
    Brink, Thomas G.
    Chen, Ting-Wan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Cikota, Aleksandar
    Coughlin, Michael W.
    Dahiwale, Aishwarya
    Dekany, Richard
    Duev, Dmitry A.
    Filippenko, Alexei
    Hoeflich, Peter
    Kasliwal, Mansi M.
    Kulkarni, S. R.
    Lunnan, Ragnhild
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Masci, Frank J.
    Maund, Justyn R.
    Medford, Michael S.
    Riddle, Reed
    Rosnet, Philippe
    Shupe, David L.
    Strotjohann, Nora Linn
    Tzanidakis, Anastasios
    Zheng, WeiKang
    The Type Icn SN 2021csp: Implications for the Origins of the Fastest Supernovae and the Fates of Wolf-Rayet Stars2022Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 927, nr 2, artikkel-id 180Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present observations of SN 2021csp, the second example of a newly identified type of supernova (SN) hallmarked by strong, narrow, P Cygni carbon features at early times (Type Icn). The SN appears as a fast and luminous blue transient at early times, reaching a peak absolute magnitude of −20 within 3 days due to strong interaction between fast SN ejecta (v ≈ 30,000 km s−1) and a massive, dense, fast-moving C/O wind shed by the WC-like progenitor months before explosion. The narrow-line features disappear from the spectrum 10–20 days after explosion and are replaced by a blue continuum dominated by broad Fe features, reminiscent of Type Ibn and IIn supernovae and indicative of weaker interaction with more extended H/He-poor material. The transient then abruptly fades ∼60 days post-explosion when interaction ceases. Deep limits at later phases suggest minimal heavy-element nucleosynthesis, a low ejecta mass, or both, and imply an origin distinct from that of classical Type Ic SNe. We place SN 2021csp in context with other fast-evolving interacting transients, and discuss various progenitor scenarios: an ultrastripped progenitor star, a pulsational pair-instability eruption, or a jet-driven fallback SN from a Wolf–Rayet (W-R) star. The fallback scenario would naturally explain the similarity between these events and radio-loud fast transients, and suggests a picture in which most stars massive enough to undergo a W-R phase collapse directly to black holes at the end of their lives.

  • 252.
    Pessi, Priscila Jael
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). European Southern Observatory, Chile; Universidad Nacional de La Plata (UNLP), Argentina.
    Anderson, J. P.
    Folatelli, G.
    Dessart, L.
    González-Gaitán, S.
    Möller, A.
    Gutiérrez, C. P.
    Mattila, S.
    Reynolds, T. M.
    Charalampopoulos, P.
    Filippenko, A. V.
    Galbany, L.
    Gal-Yam, A.
    Gromadzki, M.
    Hiramatsu, D.
    Howell, D. A.
    Inserra, C.
    Kankare, E.
    Lunnan, Ragnhild
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Martinez, L.
    McCully, C.
    Meza, N.
    Müller-Bravo, T. E.
    Nicholl, M.
    Pellegrino, C.
    Pignata, G.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Tucker, B. E.
    Wang, X.
    Young, D. R.
    Broad-emission-line dominated hydrogen-rich luminous supernovae2023Inngår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 523, nr 4, s. 5315-5340Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hydrogen-rich Type II supernovae (SNe II) are the most frequently observed class of core-collapse SNe (CCSNe). However, most studies that analyse large samples of SNe II lack events with absolute peak magnitudes brighter than −18.5 mag at rest-frame optical wavelengths. Thanks to modern surveys, the detected number of such luminous SNe II (LSNe II) is growing. There exist several mechanisms that could produce luminous SNe II. The most popular propose either the presence of a central engine (a magnetar gradually spinning down or a black hole accreting fallback material) or the interaction of supernova ejecta with circumstellar material (CSM) that turns kinetic energy into radiation energy. In this work, we study the light curves and spectral series of a small sample of six LSNe II that show peculiarities in their H α profile, to attempt to understand the underlying powering mechanism. We favour an interaction scenario with CSM that is not dense enough to be optically thick to electron scattering on large scales – thus, no narrow emission lines are observed. This conclusion is based on the observed light curve (higher luminosity, fast decline, blue colours) and spectral features (lack of persistent narrow lines, broad H α emission, lack of H α absorption, weak, or non-existent metal lines) together with comparison to other luminous events available in the literature. We add to the growing evidence that transients powered by ejecta–CSM interaction do not necessarily display persistent narrow emission lines.

  • 253. Petrushevska, T.
    et al.
    Leloudas, G.
    Ilić, D.
    Bronikowski, M.
    Charalampopoulos, P.
    Jaisawal, G. K.
    Paraskeva, E.
    Pursiainen, M.
    Rakić, N.
    Schulze, Steve
    Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Taggart, K.
    Wedderkopp, C. K.
    Anderson, J. P.
    de Boer, T.
    Chambers, K.
    Chen, Ting-Wan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Damljanović, G.
    Fraser, M.
    Gao, H.
    Gomboc, A.
    Gromadzki, M.
    Ihanec, N.
    Maguire, K.
    Marčun, B.
    Müller-Bravo, T. E.
    Nicholl, M.
    Onori, F.
    Reynolds, T. M.
    Smartt, S. J.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Smith, K. W.
    Wevers, T.
    Wyrzykowski, Ł.
    The rise and fall of the iron-strong nuclear transient PS16dtm2023Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 669, artikkel-id A140Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Context. Thanks to the advent of large-scale optical surveys, a diverse set of flares from the nuclear regions of galaxies has recently been discovered. These include the disruption of stars by supermassive black holes at the centers of galaxies – nuclear transients known as tidal disruption events (TDEs). Active galactic nuclei (AGN) can show extreme changes in the brightness and emission line intensities, often referred to as changing-look AGN (CLAGN). Given the physical and observational similarities, the interpretation and distinction of nuclear transients as CLAGN or TDEs remains difficult. One of the obstacles of making progress in the field is the lack of well-sampled data of long-lived nuclear outbursts in AGN.

    Aims. Here, we study PS16dtm, a nuclear transient in a Narrow Line Seyfert 1 (NLSy1) galaxy, which has been proposed to be a TDE candidate. Our aim is to study the spectroscopic and photometric properties of PS16dtm, in order to better understand the outbursts originating in NLSy1 galaxies.

    Methods. Our extensive multiwavelength follow-up that spans around 2000 days includes photometry and spectroscopy in the UV/optical, as well as mid-infrared (MIR) and X-ray observations. Furthermore, we improved an existing semiempirical model in order to reproduce the spectra and study the evolution of the spectral lines.

    Results. The UV/optical light curve shows a double peak at ∼50 and ∼100 days after the first detection, and it declines and flattens afterward, reaching preoutburst levels after 2000 days of monitoring. The MIR light curve rises almost simultaneously with the optical, but unlike the UV/optical which is approaching the preoutburst levels in the last epochs of our observations, the MIR emission is still rising at the time of writing. The optical spectra show broad Balmer features and the strongest broad Fe II emission ever detected in a nuclear transient. This broad Fe II emission was not present in the archival preoutburst spectrum and almost completely disappeared +1868 days after the outburst. We found that the majority of the flux of the broad Balmer and Fe II lines is produced by photoionization. We detect only weak X-ray emission in the 0.5−8 keV band at the location of PS16dtm, at +848, +1130, and +1429 days past the outburst. This means that the X-ray emission continues to be lower by at least an order of magnitude, compared to archival, preoutburst measurements.

    Conclusions. We confirm that the observed properties of PS16dtm are difficult to reconcile with normal AGN variability. The TDE scenario continues to be a plausible explanation for the observed properties, even though PS16dtm shows differences compared to TDE in quiescent galaxies. We suggest that this event is part of a growing sample of TDEs that show broad Balmer line profiles and Fe II complexes. We argue that the extreme variability seen in the AGN host due to PS16dtm may have easily been misclassified as a CLAGN, especially if the rising part of the light curve had been missed. This implies that some changing look episodes in AGN may be triggered by TDEs. Imaging and spectroscopic data of AGN with good sampling are needed to enable testing of possible physical mechanisms behind the extreme variability in AGN.

  • 254. Polshaw, J.
    et al.
    Kotak, R.
    Dessart, L.
    Fraser, M.
    Gal-Yam, A.
    Inserra, C.
    Sim, S. A.
    Smartt, S. J.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Baltay, C.
    Rabinowitz, D.
    Benetti, S.
    Botticella, M. T.
    Campbell, H.
    Chen, T. -W.
    Galbany, L.
    McKinnon, R.
    Nicholl, M.
    Smith, K. W.
    Sullivan, M.
    Takats, K.
    Valenti, S.
    Young, D. R.
    LSQ13fn: A type II-Plateau supernova with a possibly low metallicity progenitor that breaks the standardised candle relation2016Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 588, artikkel-id A1Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present optical imaging and spectroscopy of supernova (SN) LSQ13fn, a type II supernova with several hitherto-unseen properties. Although it initially showed strong symmetric spectral emission features attributable to He II, N III, and C III, reminiscent of some interacting SNe, it transitioned into an object that would fall more naturally under a type II-Plateau (IIP) classification. However, its spectral evolution revealed several unusual properties: metal lines appeared later than expected, were weak, and some species were conspicuous by their absence. Furthermore, the line velocities were found to be lower than expected given the plateau brightness, breaking the SN IIP standardised candle method for distance estimates. We found that, in combination with a short phase of early-time ejecta-circumstellar material interaction, metal-poor ejecta, and a large progenitor radius could reasonably account for the observed behaviour. Comparisons with synthetic model spectra of SNe IIP of a given progenitor mass would imply a progenitor star metallicity as low as 0.1 Z(circle dot). LSQ13fn highlights the diversity of SNe II and the many competing physical e ff ects that come into play towards the final stages of massive star evolution immediately preceding core-collapse.

  • 255. Postigo, A. de Ugarte
    et al.
    Thone, C. C.
    Rowlinson, A.
    Garcia-Benito, R.
    Levan, A. J.
    Gorosabel, J.
    Goldoni, P.
    Schulze, S.
    Zafar, T.
    Wiersema, K.
    Sanchez-Ramirez, R.
    Melandri, A.
    D'Avanzo, P.
    Oates, S.
    D'Elia, V.
    De Pasquale, M.
    Kruehler, T.
    van der Horst, A. J.
    Xu, D.
    Watson, D.
    Piranomonte, S.
    Vergani, S. D.
    Milvang-Jensen, B.
    Kaper, L.
    Malesani, D.
    Fynbo, J. P. U.
    Cano, Z.
    Covino, S.
    Flores, H.
    Greiss, S.
    Hammer, F.
    Hartoog, O. E.
    Hellmich, S.
    Heuser, C.
    Hjorth, J.
    Jakobsson, P.
    Mottola, S.
    Sparre, M.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Tagliaferri, G.
    Tanvir, N. R.
    Vestergaard, M.
    Wijers, R. A. M. J.
    Spectroscopy of the short-hard GRB 130603B The host galaxy and environment of a compact object merger2014Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 563, s. A62-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Context. Short duration gamma-ray bursts (SGRBs) are thought to be related to the violent merger of compact objects, such as neutron stars or black holes, which makes them promising sources of gravitational waves. The detection of a kilonova-like signature associated to the Swift-detected GRB 130603B has suggested that this event is the result of a compact object merger. Aims. Our knowledge on SGRB has been, until now, mostly based on the absence of supernova signatures and the analysis of the host galaxies to which they cannot always be securely associated. Further progress has been significantly hampered by the faintness and rapid fading of their optical counterparts (afterglows), which has so far precluded spectroscopy of such events. Afterglow spectroscopy is the key tool to firmly determine the distance at which the burst was produced, crucial to understand its physics, and study its local environment. Methods. Here we present the first spectra of a prototypical SGRB afterglow in which both absorption and emission features are clearly detected. Together with multi-wavelength photometry we study the host and environment of GRB 130603B. Results. From these spectra we determine the redshift of the burst to be z = 0.3565 +/- 0.0002, measure rich dynamics both in absorption and emission, and a substantial line of sight extinction of A(V) = 0.86 +/- 0.15 mag. The GRB was located at the edge of a disrupted arm of a moderately star forming galaxy with near-solar metallicity. Unlike for most long GRBs (LGRBs), N-HX/A(V) is consistent with the Galactic ratio, indicating that the explosion site differs from those found in LGRBs. Conclusions. The merger is not associated with the most star-forming region of the galaxy; however, it did occur in a dense region, implying a rapid merger or a low natal kick velocity for the compact object binary.

  • 256. Pozzo, M.
    et al.
    Meikle, W. P. S.
    Fassia, A.
    Geballe, T.
    Lundqvist, P.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Chugai, N. N.
    Sollerman, J.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Dust Signatures from Late-time Infrared and Optical Observations of SN 1998S2005Inngår i: 1604-2004: Supernovae as Cosmological Lighthouses: ASP Conference Series, Vol. 342, Proceedings of the conference held 15-19 June, 2004 in Padua, Italy, San Francisco: Astronomical Society of the Pacific , 2005, Vol. 342, s. 337-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present late-time IR (1-5 µm) and optical observations of the type IIn SN 1998S up to about 1200 days post-explosion. The shape and evolution of the Hα and He I 1.083 µm line profiles indicate a powerful interaction with a massive progenitor wind and provide evidence of dust condensation within the ejecta. 1.5-2.5 µm spectra and HKL'M' photometry reveal strong IR emission due to hot dust in the ejecta and/or circumstellar medium (CSM). For the origin of the IR emission we favour dust condensation (at least 10^{-3} M_{sun}) in a cool dense shell (CDS) as the main IR source but do not rule out a contribution from the CSM. The late-time evolution of the intrinsic (K-L') colour of type II supernovae (SNe) may be a potentially useful tool for determining the presence or absence of a massive CSM around their progenitors.

  • 257. Pozzo, M.
    et al.
    Meikle, W. P. S.
    Fassia, A.
    Geballe, T.
    Lundqvist, P.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Chugai, N. N.
    Sollerman, J.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    On the source of the late-time infrared luminosity of SN 1998S and other Type II supernovae2004Inngår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 352, s. 457-477Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present late-time near-infrared (NIR) and optical observations of the Type IIn SN 1998S. The NIR photometry spans 333-1242 d after explosion, while the NIR and optical spectra cover 333-1191 and 305-1093 d, respectively. The NIR photometry extends to the M' band (4.7 μm), making SN 1998S only the second ever supernova for which such a long IR wavelength has been detected. The shape and evolution of the Hα and HeI 1.083-μm line profiles indicate a powerful interaction with a progenitor wind, as well as providing evidence of dust condensation within the ejecta. The latest optical spectrum suggests that the wind had been flowing for at least 430 yr. The intensity and rise of the HK continuum towards longer wavelengths together with the relatively bright L' and M' magnitudes show that the NIR emission was due to hot dust newly formed in the ejecta and/or pre-existing dust in the progenitor circumstellar medium (CSM). The NIR spectral energy distribution (SED) at about 1 yr is well described by a single-temperature blackbody spectrum at about 1200 K. The temperature declines over subsequent epochs. After ~2 yr, the blackbody matches are less successful, probably indicating an increasing range of temperatures in the emission regions. Fits to the SEDs achieved with blackbodies weighted with λ-1 or λ-2 emissivity are almost always less successful. Possible origins for the NIR emission are considered. Significant radioactive heating of ejecta dust is ruled out, as is shock/X-ray-precursor heating of CSM dust. More plausible sources are (a) an IR echo from CSM dust driven by the ultraviolet/optical peak luminosity, and (b) emission from newly-condensed dust which formed within a cool, dense shell produced by the ejecta shock/CSM interaction. We argue that the evidence favours the condensing dust hypothesis, although an IR echo is not ruled out. Within the condensing-dust scenario, the IR luminosity indicates the presence of at least 10-3 Msolar of dust in the ejecta, and probably considerably more. Finally, we show that the late-time (K-L')0 evolution of Type II supernovae may provide a useful tool for determining the presence or absence of a massive CSM around their progenitor stars.

  • 258. Prentice, S. J.
    et al.
    Ashall, C.
    James, P. A.
    Short, L.
    Mazzali, P. A.
    Bersier, D.
    Crowther, P. A.
    Barbarino, Cristina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Chen, T. -W.
    Copperwheat, C. M.
    Darnley, M. J.
    Denneau, L.
    Elias-Rosa, N.
    Fraser, M.
    Galbany, L.
    Gal-Yam, A.
    Harmanen, J.
    Howell, D. A.
    Hosseinzadeh, G.
    Inserra, C.
    Kankare, E.
    Karamehmetoglu, Emir
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Lamb, G. P.
    Limongi, M.
    Maguire, K.
    McCully, C.
    Olivares E., F.
    Piascik, A. S.
    Pignata, G.
    Reichart, D. E.
    Rest, A.
    Reynolds, T.
    Rodríguez, Ó.
    Saario, J. L. O.
    Schulze, S.
    Smartt, S. J.
    Smith, K. W.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Stalder, B.
    Sullivan, M.
    Taddia, Francesco
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Valenti, S.
    Vergani, S. D.
    Williams, S. C.
    Young, D. R.
    Investigating the properties of stripped-envelope supernovae; what are the implications for their progenitors?2019Inngår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 485, nr 2, s. 1559-1578Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present observations and analysis of 18 stripped-envelope supernovae observed during 2013-2018. This sample consists of five H/He-rich SNe, sixH-poor/He-rich SNe, three narrow lined SNe Ic, and four broad lined SNe Ic. The peak luminosity and characteristic time-scales of the bolometric light curves are calculated, and the light curves modelled to derive Ni-56 and ejecta masses (M-Ni and M-cj). Additionally, the temperature evolution and spectral line velocity curves of each SN are examined. Analysis of the [O I] line in the nebular phase of eight SNe suggests their progenitors had initial masses < 20 M-circle dot. The bolometric light curve properties are examined in combination with those of other SE events from the literature. The resulting data set gives the M-ej distribution for 80 SE-SNe, the largest such sample in the literature to date, and shows that SNe Ib have the lowest median M-ej, followed by narrow-lined SNe Ic, H/He-rich SNe, broad-lined SNe Ic, and finally gamma-ray burst SNe. SNe Ic-6/7 show the largest spread of M-ej ranging from similar to 1.2-11 M-circle dot, considerably greater than any other subtype. For all SE-SNe <M-ej> = 2.8 +/- 1.5 M-circle dot which further strengthens the evidence that SE-SNe arise from low-mass progenitors which are typically <5 M-circle dot at the time of explosion, again suggesting M-ZAMS < 25 M-circle dot. The low <M-ej> and lack of clear bimodality in the distribution implies < 30 M-circle dot progenitors and that envelope stripping via binary interaction is the dominant evolutionary pathway of these SNe.

  • 259. Prentice, S. J.
    et al.
    Inserra, C.
    Schulze, Steve
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Nicholl, M.
    Mazzali, P. A.
    Vergani, S. D.
    Galbany, L.
    Anderson, J. P.
    Ashall, C.
    Chen, Ting-Wan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Deckers, M.
    Mancheño, M. Delgado
    Díaz, R. González
    González-Gaitán, S.
    Gromadzki, M.
    Gutiérrez, C. P.
    Harvey, L.
    Kozyreva, A.
    Magee, M. R.
    Maguire, K.
    Müller-Bravo, T. E.
    Muñoz Torres, S.
    Pessi, P. J.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Teffs, J.
    Terwel, J. H.
    Young, D. R.
    Transitional events in the spectrophotometric regime between stripped envelope and superluminous supernovae2021Inngår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 508, nr 3, s. 4342-4358Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The division between stripped-envelope supernovae (SE-SNe) and superluminous supernovae (SLSNe) is not well-defined in either photometric or spectroscopic space. While a sharp luminosity threshold has been suggested, there remains an increasing number of transitional objects that reach this threshold without the spectroscopic signatures common to SLSNe. In this work, we present data and analysis on four SNe transitional between SE-SNe and SLSNe; the He-poor SNe 2019dwa and 2019cri, and the He-rich SNe 2019hge and 2019unb. Each object displays long-lived and variable photometric evolution with luminosities around the SLSN threshold of Mr < −19.8 mag. Spectroscopically however, these objects are similar to SE-SNe, with line velocities lower than either SE-SNe and SLSNe, and thus represent an interesting case of rare transitional events.

  • 260. Prentice, S. J.
    et al.
    Maguire, K.
    Boian, I.
    Groh, J.
    Anderson, J.
    Barbarino, Cristina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Bostroem, K. A.
    Burke, J.
    Clark, P.
    Dong, Y.
    Fraser, M.
    Galbany, L.
    Gromadzki, M.
    Gutiérrez, C. P.
    Howell, D. A.
    Hiramatsu, D.
    Inserra, C.
    James, P. A.
    Kankare, E.
    Kuncarayakti, H.
    Mazzali, P. A.
    McCully, C.
    Müller-Bravo, T. E.
    Nichol, M.
    Pellegrino, C.
    Smartt, S. J.
    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). INAF - Osservatorio Astronomico di Padova, Italy.
    Valenti, S.
    Young, D. R.
    SN 2018gjx reveals that some SNe Ibn are SNe IIb exploding in dense circumstellar material2020Inngår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 499, nr 1, s. 1450-1467Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present the data and analysis of SN 2018gjx, an unusual low-luminosity transient with three distinct spectroscopic phases. Phase I shows a hot blue spectrum with signatures of ionized circumstellar material (CSM), Phase II has the appearance of broad SN features, consistent with those seen in a Type IIb supernova at maximum light, and Phase III is that of a supernova interacting with helium-rich CSM, similar to a Type Ibn supernova. This event provides an apparently rare opportunity to view the inner workings of an interacting supernova. The observed properties can be explained by the explosion of a star in an aspherical CSM. The initial light is emitted from an extended CSM (similar to 4000 R-circle dot), which ionizes the exterior unshocked material. Some days after, the SN photosphere envelops this region, leading to the appearance of a SN IIb. Over time, the photosphere recedes in velocity space, revealing interaction between the supernova ejecta and the CSM that partially obscures the supernova nebular phase. Modelling of the initial spectrum reveals a surface composition consistent with compact H-deficient Wolf-Rayet and Luminous Blue Variable (LBV) stars. Such configurations may not be unusual, with SNe IIb being known to have signs of interaction so at least some SNe IIb and SNe Ibn may be the same phenomena viewed from different angles, or possibly with differing CSM configurations.

  • 261. Prentice, S. J.
    et al.
    Mazzali, P. A.
    Pian, E.
    Gal-Yam, A.
    Kulkarni, S. R.
    Rubin, A.
    Corsi, A.
    Fremling, Christoffer
    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).
    Yaron, O.
    Arcavi, I.
    Zheng, W.
    Kasliwal, M. M.
    Filippenko, A. V.
    Cenko, S. B.
    Cao, Y.
    Nugent, P. E.
    The bolometric light curves and physical parameters of stripped-envelope supernovae2016Inngår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 458, nr 3, s. 2973-3002Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The optical and optical/near-infrared pseudo-bolometric light curves of 85 stripped-envelope supernovae (SNe) are constructed using a consistent method and a standard cosmology. The light curves are analysed to derive temporal characteristics and peak luminosity L-p, enabling the construction of a luminosity function. Subsequently, the mass of Ni-56 synthesized in the explosion, along with the ratio of ejecta mass to ejecta kinetic energy, are found. Analysis shows that host-galaxy extinction is an important factor in accurately determining luminosity values as it is significantly greater than Galactic extinction in most cases. It is found that broad-lined SNe Ic (SNe Ic-BL) and gamma-ray burst SNe are the most luminous subtypes with a combined median L-p, in erg s(-1), of log(L-p)= 43.00 compared to 42.51 for SNe Ic, 42.50 for SNe Ib, and 42.36 for SNe IIb. It is also found that SNe Ic-BL synthesize approximately twice the amount of 56Ni compared with SNe Ic, Ib, and IIb, with median M-Ni = 0.34, 0.16, 0.14, and 0.11 M-circle dot, respectively. SNe Ic-BL, and to a lesser extent SNe Ic, typically rise from L-p/2 to L-p more quickly than SNe Ib/IIb; consequently, their light curves are not as broad.

  • 262. Pursiainen, M.
    et al.
    Leloudas, G.
    Cikota, A.
    Bulla, M.
    Inserra, C.
    Patat, F.
    Wheeler, J. C.
    Aamer, A.
    Gal-Yam, A.
    Maund, J.
    Nicholl, M.
    Schulze, Steve
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Yang, Y.
    Polarimetry of hydrogen-poor superluminous supernovae2023Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 674, artikkel-id A81Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present linear polarimetry for seven hydrogen-poor superluminous supernovae (SLSNe-I) of which only one has previously published polarimetric data. The best-studied event is SN 2017gci, for which we present two epochs of spectropolarimetry at +3 d and +29 d post-peak in rest frame, accompanied by four epochs of imaging polarimetry up to +108 d. The spectropolarimetry at +3 d shows increasing polarisation degree P towards the redder wavelengths and exhibits signs of axial symmetry, but at +29 d, P similar to 0 throughout the spectrum, implying that the photosphere of SN 2017gci evolved from a slightly aspherical configuration to a more spherical one in the first month post-peak. However, an increase of P to similar to 0.5% at similar to+55 d accompanied by a different orientation of the axial symmetry compared to +3 d implies the presence of additional sources of polarisation at this phase. The increase in polarisation is possibly caused by interaction with circumstellar matter (CSM), as already suggested by a knee in the light curve and a possible detection of broad H alpha emission at the same phase. We also analysed the sample of all 16 SLSNe-I with polarimetric measurements to date. The data taken during the early spectroscopic phase show consistently low polarisation, indicating at least nearly spherical photospheres. No clear relation between the polarimetry and spectral phase was seen when the spectra resemble Type Ic SNe during the photospheric and nebular phases. The light-curve decline rate, which spans a factor of eight, also shows no clear relation with the polarisation properties. While only slow-evolving SLSNe-I have shown non-zero polarisation, the fast-evolving ones have not been observed at sufficiently late times to conclude that none of them exhibit changing P. However, the four SLSNe-I with increasing polarisation degree also have irregular light-curve declines. For up to half of them, the photometric, spectroscopic, and polarimetric properties are affected by CSM interaction. As such, CSM interaction clearly plays an important role in understanding the polarimetric evolution of SLSNe-I.

  • 263. Pérez-García, M. A.
    et al.
    Izzo, L.
    Barba-González, D.
    Bulla, Mattia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Sagués-Carracedo, Ana
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Pérez, E.
    Albertus, C.
    Dhawan, S.
    Prada, F.
    Agnello, A.
    Angus, C. R.
    Bruun, S. H.
    del Burgo, C.
    Dominguez-Tagle, C.
    Gall, C.
    Goobar, Ariel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hjorth, J.
    Jones, D.
    López-Sánchez, A. R.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hubble constant and nuclear equation of state from kilonova spectro-photometric light curves2022Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 666, artikkel-id A67Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The merger of two compact objects of which at least one is a neutron star is signalled by transient electromagnetic emission in a kilonova (KN). This event is accompanied by gravitational waves and possibly other radiation messengers such as neutrinos or cosmic rays. The electromagnetic emission arises from the radioactive decay of heavy r-process elements synthesized in the material ejected during and after the merger. In this paper we show that the analysis of KNe light curves can provide cosmological distance measurements and constrain the properties of the ejecta. In this respect, MAAT, the new Integral Field Unit in the OSIRIS spectrograph on the 10.4 m Gran Telescopio CANARIAS (GTC), is well suited for the study of KNe by performing absolute spectro-photometry over the entire 3600 − 10 000 Å spectral range. Here, we study the most representative cases regarding the scientific interest of KNe from binary neutron stars, and we evaluate the observational prospects and performance of MAAT on the GTC to do the following: (a) study the impact of the equation of state on the KN light curve, and determine to what extent bounds on neutron star (NS) radii or compactness deriving from KN peak magnitudes can be identified and (b) measure the Hubble constant, H0, with precision improved by up to 40%, when both gravitational wave data and photometric-light curves are used. In this context we discuss how the equation of state, the viewing angle, and the distance affect the precision and estimated value of H0.

  • 264. Quadri, U.
    et al.
    Strabla, L.
    Girelli, R.
    Quadri, A.
    Itoh, R.
    Ui, T.
    Siviero, A.
    Tomasella, L.
    Pastorello, A.
    Benetti, S.
    Munari, U.
    Ergon, Mattias
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Taddia, Francesco
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Barisevicius, G.
    Supernova 2012aw in M95 = Psn J10435372+11401772012Rapport (Annet vitenskapelig)
    Abstract [en]

    CBET 3054 available at Central Bureau for Astronomical Telegrams.

  • 265. Reusch, Simeon
    et al.
    Stein, Robert
    Kowalski, Marek
    van Velzen, Sjoert
    Franckowiak, Anna
    Lunardini, Cecilia
    Murase, Kohta
    Winter, Walter
    Miller-Jones, James C. A.
    Kasliwal, Mansi M.
    Gilfanov, Marat
    Garrappa, Simone
    Paliya, Vaidehi S.
    Ahumada, Tomás
    Anand, Shreya
    Barbarino, Cristina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Bellm, Eric C.
    Brinnel, Valéry
    Buson, Sara
    Cenko, S. Bradley
    Coughlin, Michael W.
    De, Kishalay
    Dekany, Richard
    Frederick, Sara
    Gal-Yam, Avishay
    Gezari, Suvi
    Giroletti, Marcello
    Graham, Matthew J.
    Karambelkar, Viraj
    Kimura, Shigeo S.
    Kong, Albert K. H.
    Kool, Erik C.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Laher, Russ R.
    Medvedev, Pavel
    Necker, Jannis
    Nordin, Jakob
    Perley, Daniel A.
    Rigault, Mickael
    Rusholme, Ben
    Schulze, Steve
    Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Schweyer, Tassilo
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Singer, Leo P.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Strotjohann, Nora Linn
    Sunyaev, Rashid
    van Santen, Jakob
    Walters, Richard
    Zhang, B. Theodore
    Zimmerman, Erez
    Candidate Tidal Disruption Event AT2019fdr Coincident with a High-Energy Neutrino2022Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 128, nr 22, artikkel-id 221101Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The origins of the high-energy cosmic neutrino flux remain largely unknown. Recently, one high-energy neutrino was associated with a tidal disruption event (TDE). Here we present AT2019fdr, an exceptionally luminous TDE candidate, coincident with another high-energy neutrino. Our observations, including a bright dust echo and soft late-time x-ray emission, further support a TDE origin of this flare. The probability of finding two such bright events by chance is just 0.034%. We evaluate several models for neutrino production and show that AT2019fdr is capable of producing the observed high-energy neutrino, reinforcing the case for TDEs as neutrino sources.

  • 266. Rigault, M.
    et al.
    Neill, J. D.
    Blagorodnova, N.
    Dugas, A.
    Feeney, M.
    Walters, R.
    Brinnel, V.
    Copin, Y.
    Fremling, C.
    Nordin, J.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Fully automated integral field spectrograph pipeline for the SEDMachine: pysedm2019Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 627, artikkel-id A115Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Current time domain facilities are discovering hundreds of new galactic and extra-galactic transients every week. Classifying the ever-increasing number of transients is challenging, yet crucial to furthering our understanding of their nature, discovering new classes, and ensuring sample purity, for instance, for Supernova Ia cosmology. The Zwicky Transient Facility is one example of such a survey. In addition, it has a dedicated very-low resolution spectrograph, the SEDMachine, operating on the Palomar 60-inch telescope. This spectrograph's primary aim is object classification. In practice most, if not all, transients of interest brighter than similar to 19 mag are typed. This corresponds to approximately 10-15 targets a night. In this paper, we present a fully automated pipeline for the SEDMachine. This pipeline has been designed to be fast, robust, stable and extremely flexible. PYSEDM enables the fully automated spectral extraction of a targeted point source object in less than five minutes after the end of the exposure. The spectral color calibration is accurate at the few percent level. In the 19 weeks since PYSEDM entered production in early August of 2018, we have classified, among other objects, about 400 Type Ia supernovae and 140 Type II supernovae. We conclude that low resolution, fully automated spectrographs such as the SEDMachine with pysedm installed on 2-m class telescopes within the southern hemisphere could allow us to automatically and simultaneously type and obtain a redshift for most (if not all) bright transients detected by LSST within z < 0.2, notably potentially all Type Ia Supernovae. In comparison with the current SEDM design, this would require higher spectral resolution (R greater than or similar to 1000) and slightly improved throughput. With this perspective in mind, pysedm is designed to easily be adaptable to any IFU-like spectrograph.

  • 267.
    Rosswog, Stephan
    et al.
    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).
    Korobkin, O.
    Wu, M-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).
    Martinez-Pinedo, G.
    Detectability of compact binary merger macronovae2017Inngår i: Classical and quantum gravity, ISSN 0264-9381, E-ISSN 1361-6382, Vol. 34, nr 10, artikkel-id 104001Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study the optical and near-infrared luminosities and detectability of radioactively powered electromagnetic transients ('macronovae') occuring in the aftermath of binary neutron star and neutron star black hole mergers. We explore the transients that result from the dynamic ejecta and those from different types of wind outflows. Based on full nuclear network simulations we calculate the resulting light curves in different wavelength bands. We scrutinize the robustness of the results by comparing (a) two different nuclear reaction networks and (b) two macronova models. We explore in particular how sensitive the results are to the production of alpha-decaying trans-lead nuclei. We compare two frequently used mass models: the finite-range Droplet model (FRDM) and the nuclear mass model of Duflo and Zuker (DZ31). We find that the abundance of alpha-decaying trans-lead nuclei has a significant impact on the observability of the resulting macronovae. For example, the DZ31 model yields considerably larger abundances resulting in larger heating rates and thermalization efficiencies and therefore predicts substantially brighter macronova transients. We find that the dynamic ejecta from NSNS models can reach peak K-band magnitudes in excess of -15 while those from NSBH cases can reach beyond -16. Similar values can be reached by some of our wind models. Several of our models (both wind and dynamic ejecta) yield properties that are similar to the transient that was observed in the aftermath of the short GRB 130603B. We further explore the expected macronova detection frequencies for current and future instruments such as VISTA, ZTF and LSST.

  • 268.
    Rosswog, Stephan
    et al.
    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).
    Feindt, Ulrich
    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).
    Korobkin, O.
    Wollaeger, R.
    Fremling, C.
    Kasliwal, M. M.
    The first direct double neutron star merger detection: Implications for cosmic nucleosynthesis2018Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 615, artikkel-id A132Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Context. The astrophysical r-process site where about half of the elements, heavier than iron are produced, has been a puzzle for several decades. Here we discuss the role of one of the leading ideas - neutron star mergers (NSMs) - in the light of the first direct detection of such an event in both gravitational (GW) and electromagnetic (EM) waves. Aims. Our aim is to understand the implications of the first GW/EM observations of a NSM for cosmic nucleosynthesis. Methods. We analyse bolometric and NIR lightcurves of the first detected double NSM and compare them to nuclear reaction network-based macronova models. Results. The slope of the bolometric lightcurve is consistent with the radioactive decay of neutron star ejecta with Y-e less than or similar to 0.3 (but not larger), which provides strong evidence for an r-process origin of the electromagnetic emission. This rules out in particular nickel winds as major source of the emission. We find that the NIR lightcurves can be well fitted either with or without lanthanide-rich ejecta. Our limits on the ejecta mass together with estimated rates directly confirm earlier purely theoretical or indirect observational conclusions that double neutron star mergers are indeed a major site of cosmic nucleosynthesis. If the ejecta mass was typical, NSMs can easily produce all of the estimated Galactic r-process matter, and - depending on the real rate - potentially even more. This could be a hint that the event ejected a particularly large amount of mass, maybe due to a substantial difference between the component masses. This would be compatible with the mass limits obtained from the GW-observation. Conclusions. The recent observations suggests that NSMs are responsible for a broad range of r-process nuclei and that they are at least a major, but likely the dominant r-process site in the Universe.

  • 269.
    Roy, Rupak
    et al.
    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).
    Silverman, J. M.
    Pastorello, A.
    Fransson, Claes
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Drake, A.
    Taddia, Francesco
    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).
    Kankare, E.
    Kumar, B.
    Cappellaro, E.
    Bose, S.
    Benetti, S.
    Filippenko, A. V.
    Valenti, S.
    Nyholm, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Ergon, Mattias
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Sutaria, F.
    Kumar, B.
    Pandey, S. B.
    Nicholl, M.
    Garcia-Alvarez, D.
    Tomasella, L.
    Karamehmetoglu, Emir
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Migotto, Katia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    SN 2012aa: A transient between Type Ibc core-collapse and superluminous supernovae2016Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 596, artikkel-id A67Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Context. Research on supernovae (SNe) over the past decade has confirmed that there is a distinct class of events which are much more luminous (by similar to 2 mag) than canonical core-collapse SNe (CCSNe). These events with visual peak magnitudes less than or similar to-21 are called superluminous SNe (SLSNe). The mechanism that powers the light curves of SLSNe is still not well understood. The proposed scenarios are circumstellar interaction, the emergence of a magnetar after core collapse, or disruption of a massive star through pair production. Aims. There are a few intermediate events which have luminosities between these two classes. They are important for constraining the nature of the progenitors of these two different populations and their environments and powering mechanisms. Here we study one such object, SN 2012aa. Methods. We observed and analysed the evolution of the luminous Type Ic SN 2012aa. The event was discovered by the Lick Observatory Supernova Search in an anonymous galaxy (z approximate to 0.08). The optical photometric and spectroscopic follow-up observations were conducted over a time span of about 120 days. Results. With an absolute V-band peak of similar to-20 mag, the SN is an intermediate-luminosity transient between regular SNe Ibc and SLSNe. SN 2012aa also exhibits an unusual secondary bump after the maximum in its light curve. For SN 2012aa, we interpret this as a manifestation of SN-shock interaction with the circumstellar medium (CSM). If we assume a Ni-56-powered ejecta, the quasi-bolometric light curve requires roughly 1.3 M-circle dot of Ni-56 and an ejected mass of similar to 14 M-circle dot. This also implies a high kinetic energy of the explosion, similar to 5.4 x 10(51) erg. On the other hand, the unusually broad light curve along with the secondary peak indicate the possibility of interaction with CSM. The third alternative is the presence of a central engine releasing spin energy that eventually powers the light curve over a long time. The host of SN 2012aa is a star-forming Sa/Sb/Sbc galaxy. Conclusions. Although the spectral properties of SN 2012aa and its velocity evolution are comparable to those of normal SNe Ibc, its broad light curve along with a large peak luminosity distinguish it from canonical CCSNe, suggesting that the event is an intermediate-luminosity transient between CCSNe and SLSNe at least in terms of peak luminosity. In comparison to other SNe, we argue that SN 2012aa belongs to a subclass where CSM interaction plays a significant role in powering the SN, at least during the initial stages of evolution.

  • 270. Rubin, Adam
    et al.
    Gal-Yam, Avishay
    De Cia, Annalisa
    Horesh, Assaf
    Khazov, Danny
    Ofek, Eran O.
    Kulkarni, S. R.
    Arcavi, Iair
    Manulis, Ilan
    Yaron, Ofer
    Vreeswijk, Paul
    Kasliwal, Mansi M.
    Ben-Ami, Sagi
    Perley, Daniel A.
    Cao, Yi
    Cenko, S. Bradley
    Rebbapragada, Umaa D.
    Wozniak, P. R.
    Filippenko, Alexei V.
    Clubb, K. I.
    Nugent, Peter E.
    Pan, Y-C.
    Badenes, C.
    Howell, D. Andrew
    Valenti, Stefano
    Sand, David
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Joel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Leonard, Douglas C.
    Horst, J. Chuck
    Armen, Stephen F.
    Fedrow, Joseph M.
    Quimby, Robert M.
    Mazzali, Paulo
    Pian, Elena
    Sternberg, Assaf
    Matheson, Thomas
    Sullivan, M.
    Maguire, K.
    Lazarevic, Sanja
    TYPE II SUPERNOVA ENERGETICS AND COMPARISON OF LIGHT CURVES TO SHOCK-COOLING MODELS2016Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 820, nr 1, artikkel-id 33Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    During the first few days after explosion, Type II supernovae (SNe) are dominated by relatively simple physics. Theoretical predictions regarding early-time SN light curves in the ultraviolet (UV) and optical bands are thus quite robust. We present, for the first time, a sample of 57 R-band SN II light curves that are well-monitored during their rise, with > 5 detections during the first 10 days after discovery, and a well-constrained time of explosion to within 1-3 days. We show that the energy per unit mass (E/M) can be deduced to roughly a factor of five by comparing early-time optical data to the 2011 model of Rabinak & Waxman, while the progenitor radius cannot be determined based on R-band data alone. We find that SN II explosion energies span a range of E/M = (0.2-20) x 10(51) erg/(10 M-circle dot), and have a mean energy per unit mass of < E/M > = 0.85 x 10(51) erg/(10 M-circle dot), corrected for Malmquist bias. Assuming a small spread in progenitor masses, this indicates a large intrinsic diversity in explosion energy. Moreover, E/M is positively correlated with the amount of Ni-56 produced in the explosion, as predicted by some recent models of core-collapse SNe. We further present several empirical correlations. The peak magnitude is correlated with the decline rate (Delta m(15)), the decline rate is weakly correlated with the rise time, and the rise time is not significantly correlated with the peak magnitude. Faster declining SNe are more luminous and have longer rise times. This limits the possible power sources for such events.

  • 271. Sako, Masao
    et al.
    Bassett, Bruce
    Becker, Andrew C.
    Brown, Peter J.
    Campbell, Heather
    Wolf, Rachel
    Cinabro, David
    D'Andrea, Chris B.
    Dawson, Kyle S.
    DeJongh, Fritz
    Depoy, Darren L.
    Dilday, Ben
    Doi, Mamoru
    Filippenko, Alexei V.
    Fischer, John A.
    Foley, Ryan J.
    Frieman, Joshua A.
    Galbany, Lluis
    Garnavich, Peter M.
    Goobar, Ariel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Gupta, Ravi R.
    Hill, Gary J.
    Hayden, Brian T.
    Hlozek, Renee
    Holtzman, Jon A.
    Hopp, Ulrich
    Jha, Saurabh W.
    Kessler, Richard
    Kollatschny, Wolfram
    Leloudas, Giorgos
    Marriner, John
    Marshall, Jennifer L.
    Miquel, Ramon
    Morokuma, Tomoki
    Mosher, Jennifer
    Nichol, Robert C.
    Nordin, Jakob
    Olmstead, Matthew D.
    Östman, Linda
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Prieto, Jose L.
    Richmond, Michael
    Romani, Roger W.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Stritzinger, Max
    Schneider, Donald P.
    Smith, Mathew
    Wheeler, J. Craig
    Yasuda, Naoki
    Zheng, Chen
    The Data Release of the Sloan Digital Sky Survey-II Supernova Survey2018Inngår i: Publications of the Astronomical Society of the Pacific, ISSN 0004-6280, E-ISSN 1538-3873, Vol. 130, nr 988, artikkel-id 064002Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper describes the data release of the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey conducted between 2005 and 2007. Light curves, spectra, classifications, and ancillary data are presented for 10,258 variable and transient sources discovered through repeat ugriz imaging of SDSS Stripe 82, a 300 deg(2) area along the celestial equator. This data release is comprised of all transient sources brighter than r similar or equal to 22.5 mag with no history of variability prior to 2004. Dedicated spectroscopic observations were performed on a subset of 889 transients, as well as spectra for thousands of transient host galaxies using the SDSS-III BOSS spectrographs. Photometric classifications are provided for the candidates with good multi-color light curves that were not observed spectroscopically, using host galaxy redshift information when available. From these observations, 4607 transients are either spectroscopically confirmed, or likely to be, supernovae, making this the largest sample of supernova candidates ever compiled. We present a new method for SN host-galaxy identification and derive host-galaxy properties including stellar masses, star formation rates, and the average stellar population ages from our SDSS multi-band photometry. We derive SALT2 distance moduli for a total of 1364 SN. Ia with spectroscopic redshifts as well as photometric redshifts for a further 624 purely photometric SN. Ia candidates. Using the spectroscopically confirmed subset of the three-year SDSS-II SN. Ia sample and assuming a flat.CDM cosmology, we determine Omega(M) = 0.315 +/- 0.093 (statistical error only) and detect a non-zero cosmological constant at 5.7 sigma.

  • 272. Sako, Masao
    et al.
    Bassett, Bruce
    Connolly, Brian
    Dilday, Benjamin
    Cambell, Heather
    Frieman, Joshua A.
    Gladney, Larry
    Kessler, Richard
    Lampeitl, Hubert
    Marriner, John
    Miquel, Ramon
    Nichol, Robert C.
    Schneider, Donald P.
    Smith, Mathew
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Photometric Type Ia Supernova Candidates from the Three-year SDSS-II SN Survey Data2011Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 738, s. 162-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We analyze the three-year Sloan Digital Sky Survey II (SDSS-II) Supernova (SN) Survey data and identify a sample of 1070 photometric Type Ia supernova (SN Ia) candidates based on their multiband light curve data. This sample consists of SN candidates with no spectroscopic confirmation, with a subset of 210 candidates having spectroscopic redshifts of their host galaxies measured while the remaining 860 candidates are purely photometric in their identification. We describe a method for estimating the efficiency and purity of photometric SN Ia classification when spectroscopic confirmation of only a limited sample is available, and demonstrate that SN Ia candidates from SDSS-II can be identified photometrically with ~91% efficiency and with a contamination of ~6%. Although this is the largest uniform sample of SN candidates to date for studying photometric identification, we find that a larger spectroscopic sample of contaminating sources is required to obtain a better characterization of the background events. A Hubble diagram using SN candidates with no spectroscopic confirmation, but with host galaxy spectroscopic redshifts, yields a distance modulus dispersion that is only ~20%-40% larger than that of the spectroscopically confirmed SN Ia sample alone with no significant bias. A Hubble diagram with purely photometric classification and redshift-distance measurements, however, exhibits biases that require further investigation for precision cosmology.

  • 273.
    Sandberg, A.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Sollerman, J.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Optical and infrared observations of the Crab Pulsar and its nearby knot2009Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 504, s. 525-530Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aims: We study the spectral energy distribution (SED) of the Crab Pulsar and its nearby knot in the optical and in the infrared (IR) regime. We want to investigate how the contribution from the knot affects the pulsar SED in that regime, and examine the evidence for synchrotron self-absorption in the IR. We also draw the attention to the predicted secular decrease in luminosity of the Crab Pulsar, and attempt to investigate this with CCD observations. Methods: We present high-quality UBVRIz, as well as adaptive optics JHK_sL' photometry, achieved under excellent conditions with the FORS1 and NAOS/CONICA instruments at the VLT. We combine these data with re-analyzed archival Spitzer Space Telescope data to construct a SED for the pulsar, and quantify the contamination from the knot. We have also gathered optical imaging data from 1988 to 2008 from several telescopes in order to examine the predicted secular decrease in luminosity. Results: For the Crab Pulsar SED we find a spectral slope of α_ν = 0.27 ± 0.03 in the optical/near-IR regime, when we exclude the contribution from the knot. For the knot itself, we find a much redder slope of α_ν = -1.3 ± 0.1. Our best estimate of the average decrease in luminosity for the pulsar is 2.9 ± 1.6 mmag per year. Conclusions: We have demonstrated the importance of the nearby knot in precision measurements of the Crab Pulsar SED, in particular in the near-IR. We have scrutinized the evidence for the traditional view of a synchrotron self-absorption roll-over in the infrared, and find that these claims are unfounded. We also find evidence for a secular decrease in the optical light for the Crab Pulsar, in agreement with current pulsar spin-down models. However, although our measurements of the decrease significantly improve on previous investigations, the detection is still tentative. We finally point to future observations that can improve the situation significantly. Based on observations made with ESO Telescopes under programme ID 072.D-0029. Tables 3, 4 and Fig. 4 are only available in electronic form at http://www.aanda.org

  • 274. Scalzo, R. A.
    et al.
    Childress, M.
    Tucker, B.
    Yuan, F.
    Schmidt, B.
    Brown, P. J.
    Contreras, C.
    Morre, N.
    Hsiao, E.
    Burns, C.
    Phillips, M. M.
    Campillay, A.
    Gonzalez, C.
    Krisciunas, K.
    Stritzinger, M.
    Graham, M. L.
    Parrent, J.
    Valenti, S.
    Lidman, C.
    Schaefer, B.
    Scott, N.
    Fraser, M.
    Gal-Yam, A.
    Inserra, C.
    Maguire, K.
    Smartt, S. J.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Sullivan, M.
    Taddia, Francesco
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Yaron, O.
    Young, D. R.
    Taubenberger, S.
    Baltay, C.
    Ellman, N.
    Feindt, U.
    Hadjiyska, E.
    McKinnon, R.
    Nugent, P. E.
    Rabinowitz, D.
    Walker, E. S.
    Early ultraviolet emission in the Type Ia supernova LSQ12gdj: No evidence for ongoing shock interaction2014Inngår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 445, nr 1, s. 30-48Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present photospheric-phase observations of LSQ12gdj, a slowly declining, UV-bright Type Ia supernova. Classified well before maximum light, LSQ12gdj has extinction-corrected absolute magnitude M-B = -19.8, and pre-maximum spectroscopic evolution similar to SN 1991T and the super-Chandrasekhar-mass SN 2007if. We use ultraviolet photometry from Swift, ground-based optical photometry, and corrections from a near-infrared photometric template to construct the bolometric (1600-23 800 angstrom) light curve out to 45 d past B-band maximum light. We estimate that LSQ12gdj produced 0.96 +/- 0.07 M-circle dot of Ni-56, with an ejected mass near or slightly above the Chandrasekhar mass. As much as 27 per cent of the flux at the earliest observed phases, and 17 per cent at maximum light, is emitted bluewards of 3300 angstrom. The absence of excess luminosity at late times, the cutoff of the spectral energy distribution bluewards of 3000 angstrom and the absence of narrow line emission and strong Na I D absorption all argue against a significant contribution from ongoing shock interaction. However, similar to 10 per cent of LSQ12gdj's luminosity near maximum light could be produced by the release of trapped radiation, including kinetic energy thermalized during a brief interaction with a compact, hydrogen-poor envelope (radius < 10(13) cm) shortly after explosion; such an envelope arises generically in double-degenerate merger scenarios.

  • 275. Schulze, S.
    et al.
    Levan, A. J.
    Malesani, D.
    Fynbo, J. P. U.
    Tanvir, N. R.
    Milvang-Jensen, B.
    de Ugarte Postigo, A.
    D'Elia, V.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hjorth, J.
    GRB 120422A: VLT/X-shooter spectroscopy of the GRB counterpart.2012Rapport (Annet vitenskapelig)
    Abstract [en]

    Not Available

  • 276. Schulze, S.
    et al.
    Malesani, D.
    Cucchiara, A.
    Tanvir, N. R.
    Kruhler, T.
    de Ugarte Postigo, A.
    Leloudas, Georgios
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). University of Copenhagen, Denmark.
    Lyman, J.
    Bersier, D.
    Wiersema, K.
    Perley, D. A.
    Schady, P.
    Gorosabel, J.
    Anderson, J. P.
    Castro-Tirado, A. J.
    Cenko, S. B.
    De Cia, A.
    Ellerbroek, L. E.
    Fynbo, J. P. U.
    Greiner, J.
    Hjorth, J.
    Kann, D. A.
    Kaper, L.
    Klose, S.
    Levan, A. J.
    Martin, S.
    O'Brien, P. T.
    Page, K. L.
    Pignata, G.
    Rapaport, S.
    Sanchez-Ramirez, R.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Smith, I. A.
    Sparre, M.
    Thoene, C. C.
    Watson, D. J.
    Xu, D.
    Bauer, E. E.
    Bayliss, M.
    Björnsson, G.
    Bremer, M.
    Cano, Z.
    Covino, S.
    D'Elia, V.
    Frail, D. A.
    Geier, S.
    Goldoni, P.
    Hartoog, O. E.
    Jakobsson, P.
    Korhonen, H.
    Lee, Kai Yan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Milvang-Jensen, B.
    Nardini, M.
    Guelbenzu, A. Nicuesa
    Oguri, M.
    Pandey, S. B.
    Petitpas, G.
    Rossi, A.
    Sandberg, Andreas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Schmidl, S.
    Tagliaferri, G.
    Tilanus, R. P. J.
    Winters, J. M.
    Wright, D.
    Wuyts, E.
    GRB 120422A/SN 2012bz: Bridging the gap between low- and high-luminosity gamma-ray bursts2014Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 566, artikkel-id A102Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Context. At low redshift, a handful of gamma-ray bursts (GRBs) have been discovered with luminosities that are substantially lower (L-iso less than or similar to 10(48.5) erg s(-1)) than the average of more distant ones (L-iso greater than or similar to 10(49.5) erg s(-1)). It has been suggested that the properties of several low-luminosity (low-L) GRBs are due to shock break-out, as opposed to the emission from ultrarelativistic jets. This has led to much debate about how the populations are connected. Aims. The burst at redshift z = 0.283 from 2012 April 22 is one of the very few examples of intermediate-L GRBs with a gamma-ray luminosity of L-iso similar to 10(49.6-49.9) erg s(-1) that have been detected up to now. With the robust detection of its accompanying supernova SN 2012bz, it has the potential to answer important questions on the origin of low-and high-L GRBs and the GRB-SN connection. Methods. We carried out a spectroscopy campaign using medium-and low-resolution spectrographs with 6-10-m class telescopes, which covered a time span of 37.3 days, and a multi-wavelength imaging campaign, which ranged from radio to X-ray energies over a duration of similar to 270 days. Furthermore, we used a tuneable filter that is centred at H alpha to map star-formation in the host and the surrounding galaxies. We used these data to extract and model the properties of different radiation components and fitted the spectral energy distribution to extract the properties of the host galaxy. Results. Modelling the light curve and spectral energy distribution from the radio to the X-rays revealed that the blast wave expanded with an initial Lorentz factor of Gamma(0) similar to 50, which is a low value in comparison to high-L GRBs, and that the afterglow had an exceptionally low peak luminosity density of less than or similar to 2 x 10(30) erg s(-1) Hz(-1) in the sub-mm. Because of the weak afterglow component, we were able to recover the signature of a shock break-out in an event that was not a genuine low-L GRB for the first time. At 1.4 hr after the burst, the stellar envelope had a blackbody temperature of k(B)T similar to 16 eV and a radius of similar to 7 x 10(13) cm (both in the observer frame). The accompanying SN 2012bz reached a peak luminosity of M-V = -19.7 mag, which is 0.3 mag more luminous than SN 1998bw. The synthesised nickel mass of 0.58 M-circle dot, ejecta mass of 5.87 M-circle dot, and kinetic energy of 4.10x10(52) erg were among the highest for GRB-SNe, which makes it the most luminous spectroscopically confirmed SN to date. Nebular emission lines at the GRB location were visible, which extend from the galaxy nucleus to the explosion site. The host and the explosion site had close-to-solar metallicity. The burst occurred in an isolated star-forming region with an SFR that is 1/10 of that in the galaxy's nucleus. Conclusions. While the prompt gamma-ray emission points to a high-L GRB, the weak afterglow and the low Gamma(0) were very atypical for such a burst. Moreover, the detection of the shock break-out signature is a new quality for high-L GRBs. So far, shock break-outs were exclusively detected for low-L GRBs, while GRB 120422A had an intermediate L-iso of similar to 10(49.6-49.9) erg s(-1). Therefore, we conclude that GRB 120422A was a transition object between low-and high-L GRBs, which supports the failed-jet model that connects low-L GRBs that are driven by shock break-outs and high-L GRBs that are powered by ultra-relativistic jets.

  • 277.
    Schulze, Steve
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Fransson, Claes
    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).
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Omand, Conor M. B.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Sarin, Nikhil
    Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita). Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Lunnan, Ragnhild
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Gkini, Anamaria
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Pessi, Priscila J.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    1100 days in the life of the supernova 2018ibb The best pair-instability supernova candidate, to date2024Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 683, artikkel-id A223Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Stars with zero-age main sequence masses between 140 and 260 M are thought to explode as pair-instability supernovae (PISNe). During their thermonuclear runaway, PISNe can produce up to several tens of solar masses of radioactive nickel, resulting in luminous transients similar to some superluminous supernovae (SLSNe). Yet, no unambiguous PISN has been discovered so far. SN 2018ibb is a hydrogen-poor SLSN at z = 0.166 that evolves extremely slowly compared to the hundreds of known SLSNe. Between mid 2018 and early 2022, we monitored its photometric and spectroscopic evolution from the UV to the near-infrared (NIR) with 2–10 m class telescopes. SN 2018ibb radiated > 3 × 1051 erg during its evolution, and its bolometric light curve reached > 2 × 1044 erg s−1 at its peak. The long-lasting rise of > 93 rest-frame days implies a long diffusion time, which requires a very high total ejected mass. The PISN mechanism naturally provides both the energy source (56Ni) and the long diffusion time. Theoretical models of PISNe make clear predictions as to their photometric and spectroscopic properties. SN 2018ibb complies with most tests on the light curves, nebular spectra and host galaxy, and potentially all tests with the interpretation we propose. Both the light curve and the spectra require 25–44 M of freshly nucleosynthesised 56Ni, pointing to the explosion of a metal-poor star with a helium core mass of 120–130 M at the time of death. This interpretation is also supported by the tentative detection of [Co II] λ 1.025 μm, which has never been observed in any other PISN candidate or SLSN before. We observe a significant excess in the blue part of the optical spectrum during the nebular phase, which is in tension with predictions of existing PISN models. However, we have compelling observational evidence for an eruptive mass-loss episode of the progenitor of SN 2018ibb shortly before the explosion, and our dataset reveals that the interaction of the SN ejecta with this oxygen-rich circumstellar material contributed to the observed emission. That may explain this specific discrepancy with PISN models. Powering by a central engine, such as a magnetar or a black hole, can be excluded with high confidence. This makes SN 2018ibb by far the best candidate for being a PISN, to date.

  • 278.
    Schulze, Steve
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC). Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    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).
    Pearson Johansson, Joel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    The complex circumstellar environment of supernova 2023ixf2024Inngår i: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 627, nr 8005Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The early evolution of a supernova (SN) can reveal information about the environment and the progenitor star. When a star explodes in vacuum, the first photons to escape from its surface appear as a brief, hours-long shock-breakout flare1,2, followed by a cooling phase of emission. However, for stars exploding within a distribution of dense, optically thick circumstellar material (CSM), the first photons escape from the material beyond the stellar edge and the duration of the initial flare can extend to several days, during which the escaping emission indicates photospheric heating3. Early serendipitous observations2,4 that lacked ultraviolet (UV) data were unable to determine whether the early emission is heating or cooling and hence the nature of the early explosion event. Here we report UV spectra of the nearby SN 2023ixf in the galaxy Messier 101 (M101). Using the UV data as well as a comprehensive set of further multiwavelength observations, we temporally resolve the emergence of the explosion shock from a thick medium heated by the SN emission. We derive a reliable bolometric light curve that indicates that the shock breaks out from a dense layer with a radius substantially larger than typical supergiants.

  • 279. Schulze, Steve
    et al.
    Yaron, Ofer
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Leloudas, Giorgos
    Gal, Amit
    Wright, Angus H.
    Lunnan, Ragnhild
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Gal-Yam, Avishay
    Ofek, Eran O.
    Perley, Daniel A.
    Filippenko, Alexei
    Kasliwal, Mansi M.
    Kulkarni, Shrinivas R.
    Neill, James D.
    Nugent, Peter E.
    Quimby, Robert M.
    Sullivan, Mark
    Strotjohann, Nora Linn
    Arcavi, Iair
    Ben-Ami, Sagi
    Bianco, Federica
    Bloom, Joshua S.
    De, Kishalay
    Fraser, Morgan
    Fremling, Christoffer U.
    Horesh, Assaf
    Johansson, Joel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Kelly, Patrick L.
    Knezevic, Nikola
    Knezevic, Sladjana
    Maguire, Kate
    Nyholm, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Papadogiannakis, Seméli
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Petrushevska, Tanja
    Rubin, Adam
    Yan, Lin
    Yang, Yi
    Adams, Scott M.
    Bufano, Filomena
    Clubb, Kelsey
    Foley, Ryan J.
    Green, Yoav
    Harmanen, Jussi
    Ho, Anna Y. Q.
    Hook, Isobel M.
    Hosseinzadeh, Griffin
    Howell, D. Andrew
    Kong, Albert K. H.
    Kotak, Rubina
    Matheson, Thomas
    McCully, Curtis
    Milisavljevic, Dan
    Pan, Yen-Chen
    Poznanski, Dovi
    Shivvers, Isaac
    van Velzen, Sjoert
    Verbeek, Kars K.
    The Palomar Transient Factory Core-collapse Supernova Host-galaxy Sample. I. Host-galaxy Distribution Functions and Environment Dependence of Core-collapse Supernovae2021Inngår i: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 255, nr 2, artikkel-id 29Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Several thousand core-collapse supernovae (CCSNe) of different flavors have been discovered so far. However, identifying their progenitors has remained an outstanding open question in astrophysics. Studies of SN host galaxies have proven to be powerful in providing constraints on the progenitor populations. In this paper, we present all CCSNe detected between 2009 and 2017 by the Palomar Transient Factory. This sample includes 888 SNe of 12 distinct classes out to redshift z approximate to 1. We present the photometric properties of their host galaxies from the far-ultraviolet to the mid-infrared and model the host-galaxy spectral energy distributions to derive physical properties. The galaxy mass function of Type Ic, Ib, IIb, II, and IIn SNe ranges from 10(5) to 10(11.5) M (circle dot), probing the entire mass range of star-forming galaxies down to the least-massive star-forming galaxies known. Moreover, the galaxy mass distributions are consistent with models of star-formation-weighted mass functions. Regular CCSNe are hence direct tracers of star formation. Small but notable differences exist between some of the SN classes. Type Ib/c SNe prefer galaxies with slightly higher masses (i.e., higher metallicities) and star formation rates than Type IIb and II SNe. These differences are less pronounced than previously thought. H-poor superluminous supernovae (SLSNe) and SNe Ic-BL are scarce in galaxies above 10(10) M (circle dot). Their progenitors require environments with metallicities of < 0.4 and < 1 solar, respectively. In addition, the hosts of H-poor SLSNe are dominated by a younger stellar population than all other classes of CCSNe. Our findings corroborate the notion that low metallicity and young age play an important role in the formation of SLSN progenitors.

  • 280. Selsing, J.
    et al.
    Malesani, D.
    Goldoni, P.
    Fynbo, J. P. U.
    Kruehler, T.
    Antonelli, L. A.
    Arabsalmani, M.
    Bolmer, J.
    Cano, Z.
    Christensen, L.
    Covino, S.
    D'Avanzo, P.
    D'Elia, V
    De Cia, A.
    de Ugarte Postigo, A.
    Flores, H.
    Fliis, M.
    Gomboc, A.
    Greiner, J.
    Groot, P.
    Hammer, F.
    Hartoog, O. E.
    Heintz, K. E.
    Hjorth, J.
    Jakobsson, P.
    Japelj, J.
    Kann, D. A.
    Kaper, L.
    Ledoux, C.
    Leloudas, G.
    Levan, A. J.
    Maiorano, E.
    Melandri, A.
    Milvang-Jensen, B.
    Palazzi, E.
    Palmerio, J. T.
    Perley, D. A.
    Pian, E.
    Piranomonte, S.
    Pugliese, G.
    Sanchez-Ramirez, R.
    Savaglio, S.
    Schady, P.
    Schulze, S.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Sparre, M.
    Tagliaferri, G.
    Tanvir, N. R.
    Thone, C. C.
    Vergani, S. D.
    Vreeswijk, P.
    Watson, D.
    Wiersema, K.
    Wijers, R.
    Xu, D.
    Zafar, T.
    The X-shooter GRB afterglow legacy sample (XS-GRB)2019Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 623, artikkel-id A92Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work we present spectra of all gamma-ray burst (GRB) afterglows that have been promptly observed with the X-shooter spectrograph until 31/03/2017. In total, we have obtained spectroscopic observations of 103 individual GRBs observed within 48 hours of the GRB trigger. Redshifts have been measured for 97 per cent of these, covering a redshift range from 0.059 to 7.84. Based on a set of observational selection criteria that minimise biases with regards to intrinsic properties of the GRBs, the follow-up effort has been focused on producing a homogeneously selected sample of 93 afterglow spectra for GRBs discovered by the Swift satellite. We here provide a public release of all the reduced spectra, including continuum estimates and telluric absorption corrections. For completeness, we also provide reductions for the 18 late-time observations of the underlying host galaxies. We provide an assessment of the degree of completeness with respect to the parent GRB population, in terms of the X-ray properties of the bursts in the sample and find that the sample presented here is representative of the full Swift sample. We have constrained the fraction of dark bursts to be <28 per cent and confirm previous results that higher optical darkness is correlated with increased X-ray absorption. For the 42 bursts for which it is possible, we have provided a measurement of the neutral hydrogen column density, increasing the total number of published HI column density measurements by similar to 33 per cent. This dataset provides a unique resource to study the ISM across cosmic time, from the local progenitor surroundings to the intervening Universe.

  • 281.
    Serafimovich, Natalia I.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Lundqvist, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Shibanov, Yu. A.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Optical observations of the young supernova remnant SNR 0540-69.3 and its pulsar2005Inngår i: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 35, nr 6, s. 1106-1111Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have used the ESO NTT/EMMI and VLT/FORS1 instruments to examine the LMC supernova remnant 0540-69.3 as well as its pulsar (PSR B0540-69) and pulsar-powered nebula in the optical range. Spectroscopic observations of the remnant covering the range of 3600 7350 Å centered on the pulsar produced results consistent with those of [Kirshner, R.P., Morse, J.A., Winkler, P.F., et al. The penultimate supernova in the Large Magellanic Cloud - SNR 0540-69.3. Astrophys.J. 342, 260 271, 1989.] but also revealed many new emission lines. The most important are [Ne III] λλ3869, 3967 and Balmer lines of hydrogen. In both the central part of the remnant, as well as in nearby H II regions, the [O III] temperature is higher than ˜2 × 104 K, but lower than previously estimated. For PSR B0540-69, previous optical data are mutually inconsistent: HST/FOS spectra indicate a significantly higher absolute flux and steeper spectral index than suggested by early time-resolved groundbased UBVRI photometry. We show that the HST and VLT spectroscopic data for the pulsar have ≳50% nebular contamination, and that this is the reason for the previous difference. Using HST/WFPC2 archival images obtained in various bands from the red part of the optical to the NUV range we have performed an accurate photometric study of the pulsar, and find that the spectral energy distribution of the pulsar emission has a negative slope with α=1.07-0.19+0.20. This is steeper than derived from previous UBVRI photometry, and also different from the almost flat spectrum of the Crab pulsar. We also estimate that the proper motion of the pulsar is 4.9 ± 2.3 mas year‑1, corresponding to a transverse velocity of 1190 ± 560 km s‑1, projected along the southern jet of the pulsar nebula.

  • 282.
    Serafimovich, Natalia I.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Shibanov, Yu. A.
    Lundqvist, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    The young pulsar PSR B0540-69.3 and its synchrotron nebula in the optical and X-rays2004Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 425, nr 3, s. 1041-1060Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The young PSR B0540-69.3 in the LMC is the only pulsar (except the Crab pulsar) for which a near-UV spectrum has been obtained. However, the absolute flux and spectral index of the HST/FOS spectrum are significantly higher than suggested by previous broad-band time-resolved groundbased UBVRI photometry. To investigate this difference, observations with ESO/VLT/FORS1 and analysis of HST/WFPC2 archival data were done. We show that the HST and VLT spectral data for the pulsar have ⪆50% nebular contamination and that this is the reason for the above-mentioned difference. The broadband HST spectrum for the range 3300-8000 Å is clearly nonthermal and has a negative spectral index, Fν ∝ ν-α with αν = 1.07+0.20-0.19. This is different from the almost flat spectrum of the Crab pulsar, and also steeper than for the previously published broadband photometry of PSR B0540-69.3. We have also studied the spatial variations of the brightness and spectral index of the Pulsar Wind Nebula (PWN) around the pulsar, and find no significant spectral index variation over the PWN. The HST data show a clear asymmetry of the surface brightness distribution along the major axis of the torus-like structure of the PWN with respect to the pulsar position, also seen in Chandra/HRC X-ray images. This is different from the Crab PWN and likely linked to the asymmetry of the surrounding SN ejecta. The HST/WFPC2 archival data have an epoch separation of 4 years, and this allows us to estimate the proper motion of the pulsar. We find a motion of 4.9±2.3 mas yr-1 (corresponding to a transverse velocity of 1190±560 km s-1) along the southern jet of the PWN. If this is confirmed at a higher significance level by future observations, this makes PSR B0540-69.3 the third pulsar with a proper motion aligned with the jet axis of its PWN, which poses constraints on pulsar kick models. To establish the multiwavelength spectrum of the pulsar and its PWN, we have included recent Chandra X-ray data, and discuss the soft pulsar X-ray spectrum based on spectral fits including absorption by interstellar gas in the Milky Way, LMC as well as the supernova ejecta. We have compared the multiwavelength spectra of PSR B0540-69.3 and the Crab pulsar, and find that both PSR B0540-69.3 and the Crab pulsar have a weaker flux in the optical than suggested by a low-energy power-law extension of the X-ray spectrum. This optical depression is more severe for PSR B0540-69.3 than for the Crab pulsar. The same trend is seen for the PWNe of the two pulsars, and continues for low energies also out in the radio band. We discuss possible interpretations of this behavior. Based on observations performed at the European Southern Observatory, Paranal, Chile (ESO Program 67.D-0519).

  • 283. Sharma, Yashvi
    et al.
    Sollerman, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Fremling, Christoffer
    Kulkarni, Shrinivas R.
    De Kishalay, Kishalay
    Irani, Ido
    Schulze, Steve
    Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Strotjohann, Nora Linn
    Gal-Yam, Avishay
    Maguire, Kate
    Perley, Daniel A.
    Bellm, Eric C.
    Kool, Erik C.
    Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Brink, Thomas G.
    Bruch, Rachel
    Deckers, Maxime
    Dekany, Richard
    Dugas, Alison
    Filippenko, Alexei V.
    Goldwasser, Samantha
    Graham, Matthew J.
    Graham, Melissa L.
    Groom, Steven L.
    Hankins, Matt
    Jencson, Jacob
    Pearson Johansson, Joel
    Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Karambelkar, Viraj
    Kasliwal, Mansi M.
    Masci, Frank J.
    Medford, Michael S.
    Neill, James D.
    Nir, Guy
    Riddle, Reed L.
    Rigault, Mickael
    Schweyer, Tassilo
    Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Terwel, Jacco H.
    Yan, Lin
    Yang, Yi
    Yao, Yuhan
    A Systematic Study of Ia-CSM Supernovae from the ZTF Bright Transient Survey2023Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 948, nr 1, artikkel-id 52Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Among the supernovae (SNe) that show strong interaction with a circumstellar medium (CSM), there is a rare subclass of Type Ia supernovae, SNe Ia-CSM, which show strong narrow hydrogen emission lines much like SNe IIn but on top of a diluted Type Ia spectrum. The only previous systematic study of this class identified 16 SNe Ia-CSM, eight historic and eight from the Palomar Transient Factory (PTF). Now using the successor survey to PTF, the Zwicky Transient Facility (ZTF), we have classified 12 additional SNe Ia-CSM through the systematic Bright Transient Survey (BTS). Consistent with previous studies, we find these SNe to have slowly evolving optical light curves with peak absolute magnitudes between -19.1 and -21, spectra having weak H ss and large Balmer ldecrements of similar to 7. Out of the 10 SNe from our sample observed by NEOWISE, nine have 3 sigma detections, with some SNe showing a reduction in the red wing of Ha, indicative of newly formed dust. We do not find our SN Ia-CSM sample to have a significantly different distribution of equivalent widths of He I.5876 than SNe IIn as observed in Silverman et al. The hosts tend to be late-type galaxies with recent star formation. We derive a rate estimate of 29+(27)(21) Gpc(-3) yr(-1) for SNe Ia-CSM, which is similar to 0.02%-0.2% of the SN Ia rate. We also identify six ambiguous SNe IIn/Ia-CSM in the BTS sample and including them gives an upper limit rate of 0.07%-0.8%. This work nearly doubles the sample of well-studied Ia-CSM objects in Silverman et al., increasing the total number to 28.

  • 284. Sharma, Yashvi