I. Arcavi

An outburst from a massive star 40 days before a supernova explosion

Some observations suggest that very massive stars experience extreme mass-loss episodes shortly before they explode as supernovae, as do several models. Establishing a causal connection between these mass-loss episodes and the final explosion would provide a novel way to study pre-supernova massive-star evolution. Here we report observations of a mass-loss event detected 40u2009days before the explosion of the typeu2009IIn supernova SNu20092010mc (also known as PTFu200910tel). Our photometric and spectroscopic data suggest that this event is a result of an energetic outburst, radiating at least 6u2009×u20091047u2009erg of energy and releasing about 10−2 solar masses of material at typical velocities of 2,000u2009kmu2009s−1. The temporal proximity of the mass-loss outburst and the supernova explosion implies a causal connection between them. Moreover, we find that the outburst luminosity and velocity are consistent with the predictions of the wave-driven pulsation model, and disfavour alternative suggestions.

THE RISE OF SN 2014J IN THE NEARBY GALAXY M82

We report on the discovery of SN2014J in the nearby galaxy M82. Given its proximity, it offers the best opportunity to date to study a thermonuclear supernova over a wide range of the electromagnetic spectrum. The first set of optical, near-IR and mid-IR observations of SN2014J, orchestrated by the intermediate Palomar Transient Factory (iPTF), show that SN2014J is a spectroscopically normal Type Ia supernova, albeit exhibiting high-velocity features in its spectrum and heavily reddened by dust in the host galaxy. Our earliest detections start just hours after the fitted time of explosion. We use high-resolution optical spectroscopy to analyze the dense intervening material and do not detect any evolution in the resolved absorption features during the lightcurve rise. Similarly to other highly reddened Type Ia supernovae, a low value of total-to-selective extinction, Rv<2, provides the best match to our observations. We also study pre-explosion optical and near-IR images from HST with special emphasis on the sources nearest to the SN location.We report on the discovery of SN 2014J in the nearby galaxy M82. Given its proximity, it offers the best opportunity to date to study a thermonuclear supernova (SN) over a wide range of the electromagnetic spectrum. Optical, near-IR, and mid-IR observations on the rising light curve, orchestrated by the intermediate Palomar Transient Factory, show that SN 2014J is a spectroscopically normal Type Ia supernova (SN Ia), albeit exhibiting high-velocity features in its spectrum and heavily reddened by dust in the host galaxy. Our earliest detections start just hours after the fitted time of explosion. We use high-resolution optical spectroscopy to analyze the dense intervening material and do not detect any evolution in the resolved absorption features during the light curve rise. Similar to other highly reddened SNe Ia, a low value of total-to-selective extinction, R_V ≲ 2, provides the best match to our observations. We also study pre-explosion optical and near-IR images from Hubble Space Telescope with special emphasis on the sources nearest to the SN location.

The diversity of Type II supernova versus the similarity in their progenitors

The authors acknowledge the ASASSN, La Silla Quest, and LOSS surveys for discovering new SNe that made this study possible. This material is based upon work supported by the National Science Foundation (NSF) under Grant No. 1313484. MDS gratefully acknowledges generous support provided by the Danish Agency for Science and Technology and Innovation realized through a Sapere Aude Level 2 grant. MF is supported by the European Union FP7 programme through ERC grant number 320360. SJS acknowledges funding from the European Research Council under the European Unions Seventh Framework Programme (FP7/2007-2013)/ERC Grant agreement No. [291222] and STFC grants ST/I001123/1 and ST/L000709/1. AVFs group at UC Berkeley is grateful for financial assistance from NSF grant AST-1211916, the TABASGO Foundation, Gary and Cynthia Bengier, and the Christopher R. Redlich Fund. This work was supported by the NSF under grants PHY-1125915 and AST-1109174. M.S. acknowledges support from EU/FP7-ERC grant no [615929]. This paper is based on observations made with the Swift, LCOGT, Gemini, and Keck Observatories; we thank their respective staffs for excellent assistance. The W. M. Keck Observatory is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA; the observatory was made possible by the generous financial support of the W. M. Keck Foundation. Based on observations collected at the European Organization for Astronomical Research in the Southern hemisphere, Chile as part of PESSTO, (the Public ESO Spectroscopic Survey for Transient Objects Survey) ESO program ID 188.D-3003.

THE HYDROGEN-POOR SUPERLUMINOUS SUPERNOVA iPTF 13ajg AND ITS HOST GALAXY IN ABSORPTION AND EMISSION

We present imaging and spectroscopy of a hydrogen-poor superluminous supernova (SLSN) discovered by the intermediate Palomar Transient Factory, iPTF 13ajg. At a redshift of z = 0.7403, derived from narrow absorption lines, iPTF 13ajg peaked at an absolute magnitude of M_(u,AB) = –22.5, one of the most luminous supernovae to date. The observed bolometric peak luminosity of iPTF 13ajg is 3.2 × 10^(44) erg s^(–1), while the estimated total radiated energy is 1.3 × 10^(51) erg. We detect narrow absorption lines of Mg I, Mg II, and Fe II, associated with the cold interstellar medium in the host galaxy, at two different epochs with X-shooter at the Very Large Telescope. From Voigt profile fitting, we derive the column densities log N(Mg I) =11.94 ± 0.06, log N(Mg II) =14.7 ± 0.3, and log N(Fe II) =14.25 ± 0.10. These column densities, as well as the Mg I and Mg II equivalent widths of a sample of hydrogen-poor SLSNe taken from the literature, are at the low end of those derived for gamma-ray bursts (GRBs) whose progenitors are also thought to be massive stars. This suggests that the environments of hydrogen-poor SLSNe and GRBs are different. From the nondetection of Fe II fine-structure absorption lines, we derive a lower limit on the distance between the supernova and the narrow-line absorbing gas of 50 pc. The neutral gas responsible for the absorption in iPTF 13ajg exhibits a single narrow component with a low velocity width, ΔV = 76 km s^(–1), indicating a low-mass host galaxy. No host galaxy emission lines are detected, leading to an upper limit on the unobscured star formation rate (SFR) of SFR_([OII]) < 0.07 M_☉ yr^(-1). Late-time imaging shows the iPTF 13ajg host galaxy to be faint, with g_(AB) ≈ 27.0 and R_(AB) ≥ 26.0 mag, corresponding to M_(B,Vega) ≳ –17.7 mag.

Optical emission from a kilonova following a gravitational-wave-detected neutron-star merger

The merger of two neutron stars has been predicted to produce an optical–infrared transient (lasting a few days) known as a ‘kilonova’, powered by the radioactive decay of neutron-rich species synthesized in the merger. Evidence that short γ-ray bursts also arise from neutron-star mergers has been accumulating. In models of such mergers, a small amount of mass (10−4–10−2 solar masses) with a low electron fraction is ejected at high velocities (0.1–0.3 times light speed) or carried out by winds from an accretion disk formed around the newly merged object. This mass is expected to undergo rapid neutron capture (r-process) nucleosynthesis, leading to the formation of radioactive elements that release energy as they decay, powering an electromagnetic transient. A large uncertainty in the composition of the newly synthesized material leads to various expected colours, durations and luminosities for such transients. Observational evidence for kilonovae has so far been inconclusive because it was based on cases of moderate excess emission detected in the afterglows of γ-ray bursts. Here we report optical to near-infrared observations of a transient coincident with the detection of the gravitational-wave signature of a binary neutron-star merger and with a low-luminosity short-duration γ-ray burst. Our observations, taken roughly every eight hours over a few days following the gravitational-wave trigger, reveal an initial blue excess, with fast optical fading and reddening. Using numerical models, we conclude that our data are broadly consistent with a light curve powered by a few hundredths of a solar mass of low-opacity material corresponding to lanthanide-poor (a fraction of 10−4.5 by mass) ejecta.

The Rise and Fall of the Type Ib Supernova iPTF13bvn Not a Massive Wolf-Rayet Star

Context. We investigate iPTF13bvn, a core-collapse (CC) supernova (SN) in the nearby spiral galaxy NGC 5806. This object was discovered by the intermediate Palomar Transient Factory (iPTF) very close to the estimated explosion date and was classified as a stripped-envelope CC SN, likely of Type Ib. Furthermore, a possible progenitor detection in pre-explosion Hubble Space Telescope (HST) images was reported, making this the only SN Ib with such an identification. Based on the luminosity and color of the progen itor candidate, as well as on early-time spectra and photometry of the SN, it was argued that the progenitor candidate is consistent with a single, massive Wolf-Rayet (WR) star. Aims. We aim to confirm the progenitor detection, to robustly class ify the SN using additional spectroscopy, and to investigate if our follow-up photometric and spectroscopic data on iPTF13bvn are consistent with a single-star WR progenitor scenario.

The superluminous transient ASASSN-15lh as a tidal disruption event from a Kerr black hole

When a star passes within the tidal radius of a supermassive black hole, it will be torn apart1. For a star with the mass of the Sun (M ⊙) and a non-spinning black hole with a mass 108 M ⊙ 12,13, a star with the same mass as the Sun could be disrupted outside the event horizon if the black hole were spinning rapidly14. The rapid spin and high black hole mass can explain the high luminosity of this event.

SN 2015bn: A DETAILED MULTI-WAVELENGTH VIEW OF A NEARBY SUPERLUMINOUS SUPERNOVA

We present observations of SN 2015bn (= PS15ae = CSS141223-113342+004332 = MLS150211-113342+004333), a Type I superluminous supernova (SLSN) at redshift

Type II supernova energetics and comparison of light curves to shock-cooling models

z=0.1136

Rapidly Rising Transients in the Supernova - Superluminous Supernova Gap

. As well as being one of the closest SLSNe I yet discovered, it is intrinsically brighter (