Jacob E. Jencson

Illuminating gravitational waves: A concordant picture of photons from a neutron star merger

GROWTH observations of GW170817 The gravitational wave event GW170817 was caused by the merger of two neutron stars (see the Introduction by Smith). In three papers, teams associated with the GROWTH (Global Relay of Observatories Watching Transients Happen) project present their observations of the event at wavelengths from x-rays to radio waves. Evans et al. used space telescopes to detect GW170817 in the ultraviolet and place limits on its x-ray flux, showing that the merger generated a hot explosion known as a blue kilonova. Hallinan et al. describe radio emissions generated as the explosion slammed into the surrounding gas within the host galaxy. Kasliwal et al. present additional observations in the optical and infrared and formulate a model for the event involving a cocoon of material expanding at close to the speed of light, matching the data at all observed wavelengths. Science, this issue p. 1565, p. 1579, p. 1559; see also p. 1554 Observations of a binary neutron star merger at multiple wavelengths can be explained by an off-axis relativistic cocoon model. Merging neutron stars offer an excellent laboratory for simultaneously studying strong-field gravity and matter in extreme environments. We establish the physical association of an electromagnetic counterpart (EM170817) with gravitational waves (GW170817) detected from merging neutron stars. By synthesizing a panchromatic data set, we demonstrate that merging neutron stars are a long-sought production site forging heavy elements by r-process nucleosynthesis. The weak gamma rays seen in EM170817 are dissimilar to classical short gamma-ray bursts with ultrarelativistic jets. Instead, we suggest that breakout of a wide-angle, mildly relativistic cocoon engulfing the jet explains the low-luminosity gamma rays, the high-luminosity ultraviolet-optical-infrared, and the delayed radio and x-ray emission. We posit that all neutron star mergers may lead to a wide-angle cocoon breakout, sometimes accompanied by a successful jet and sometimes by a choked jet.

Massive star mergers and the recent transient in NGC 4490: a more massive cousin of V838 Mon and V1309 Sco

Some of the data reported here were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution. We thank the staffs at Lick and MMT Observatories for their assistance with the observations. We also appreciate the help of Jeff Silverman for some of the Lick observations. Data from Steward Observatory facilities were obtained as part of the observing programme AZTEC: Arizona Transient Exploration and Characterization. Lindsey Kabot assisted with early stages of the MMT spectral data reduction. The work presented here is based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. These are based in part on observations associated with programme #13364 (Legacy ExtraGalactic UV Survey, LEGUS). This paper has made use of the higher level data products provided by the LEGUS team.; NS and JEA received partial support from National Science Foundation (NSF) grants AST-1210599 and AST-1312221. MMK acknowledges support from the Carnegie-Princeton fellowship. Funding for this effort was provided in part by the Spitzer SPIRITS Cycles 10-12 exploration science programme. The supernova research of AVFs group at U.C. Berkeley presented here is supported by Gary & Cynthia Bengier, the Christopher R. Redlich Fund, the TABASGO Foundation, and NSF grant AST-1211916. KAIT and its ongoing operation were made possible by donations from Sun Microsystems, Inc., the Hewlett-Packard Company, AutoScope Corporation, Lick Observatory, the NSF, the University of California, the Sylvia & Jim Katzman Foundation, and the TABASGO Foundation. Research at Lick Observatory is partially supported by a generous gift from Google. JJ is supported by an NSF Graduate Research Fellowship under Grant No. DGE-1144469.

Common Envelope Ejection for a Luminous Red Nova in M101

We present the results of optical, near-infrared, and mid-infrared observations of M101 OT2015-1 (PSN J14021678+5426205), a luminous red transient in the Pinwheel galaxy (M101), spanning a total of 16 years. The light curve showed two distinct peaks with absolute magnitudes M_r ≤ -12.4 and M_r ≃ -12, on 2014 November 11 and 2015 February 17, respectively. The spectral energy distributions during the second maximum show a cool outburst temperature of ≈ 3700 K and low expansion velocities (≈-300 km s^(−1)) for the H i, Ca ii, Ba ii, and K i lines. From archival data spanning 15–8 years before the outburst, we find a single source consistent with the optically discovered transient, which we attribute to being the progenitor; it has properties consistent with being an F-type yellow supergiant with L ~ 8.7 x 10^4 L_⊙, T_(eff) ≈ 7000 K, and an estimated mass of M_1 = 18 ± 1 M_⊙. This star has likely just finished the H-burning phase in the core, started expanding, and is now crossing the Hertzsprung gap. Based on the combination of observed properties, we argue that the progenitor is a binary system, with the more evolved system overfilling the Roche lobe. Comparison with binary evolution models suggests that the outburst was an extremely rare phenomenon, likely associated with the ejection of the common envelope of a massive star. The initial mass of the primary fills the gap between the merger candidates V838 Mon (5−10 M_⊙) and NGC 4490-OT (30 M_⊙).

Spitzer observations of SN 2014J and properties of mid-IR emission in Type Ia Supernovae

SN 2014J in M 82 is the closest Type Ia supernova (SN Ia) in decades. The proximity allows for detailed studies of supernova physics and provides insights into the circumstellar and interstellar environment. In this work, we analyse Spitzer mid-infrared (mid-IR) data of SN 2014J in the 3.6 and 4.5 μm wavelength range, together with several other nearby and well-studied SNe Ia. We compile the first composite mid-IR light-curve templates from our sample of SNe Ia, spanning the range from before peak brightness well into the nebular phase. Our observations indicate that SNe Ia form a very homogeneous class of objects at these wavelengths. Using the low-reddening supernovae for comparison, we constrain possible thermal emission from circumstellar dust around the highly reddened SN 2014J. We also study SNe 2006X and 2007le, where the presence of matter in the circumstellar environment has been suggested. No significant mid-IR excess is detected, allowing us to place upper limits on the amount of pre-existing dust in the circumstellar environment. For SN 2014J, M_(dust) ≲ 10^(− 5) M⊙ within r_(dust) ∼ 10^(17) cm, which is insufficient to account for the observed extinction. Similar limits are obtained for SNe 2006X and 2007le.

A Systematic Study of Mid-Infrared Emission from Core-Collapse Supernovae with SPIRITS

We present a systematic study of mid-infrared (mid-IR) emission from 141 nearby supernovae (SNe) observed with the InfraRed Array Camera (IRAC) on Spitzer.These SNe reside in one of the 190 galaxies within 20 Mpc drawn from the ongoing SPIRITS program. We detect 8 Type Ia SNe and 36 core-collapse SNe. All Type I SNe become undetectable within 3 years of explosion. About 22

SPIRITS: Uncovering Unusual Infrared Transients with Spitzer

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A Tale of Two Transients: GW 170104 and GRB 170105A

11% of Type II SNe continue to be detected at late-times. Dust luminosity, temperature, and a lower liit on mass are obtained by fitting the SED using photometry with IRAC bands 1 and 2. The mass estimate does not distinguish between pre-existing and newly produced dust. We observe warm dust masses between

Optical observations of the luminous Type IIn Supernova 2010jl for over 900 d

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SPIRITS 15c and SPIRITS 14buu: Two Obscured Supernovae in the Nearby Star-forming Galaxy IC 2163

and

SPIRITS 16tn in NGC 3556: A Heavily Obscured and Low-luminosity Supernova at 8.8 Mpc

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