| 1. |
- Jencson, Jacob E., et al.
(author)
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AT 2019qyl in NGC 300 : Internal Collisions in the Early Outflow from a Very Fast Nova in a Symbiotic Binary
- 2021
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In: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 920:2
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Journal article (peer-reviewed)abstract
- Nova eruptions, thermonuclear explosions on the surfaces of white dwarfs (WDs), are now recognized to be among the most common shock-powered astrophysical transients. We present the early discovery and rapid ultraviolet (UV), optical, and infrared (IR) temporal development of AT 2019qyl, a recent nova in the nearby Sculptor Group galaxy NGC 300. The light curve shows a rapid rise lasting ≲1 day, reaching a peak absolute magnitude of MV = −9.2 mag and a very fast decline, fading by 2 mag over 3.5 days. A steep dropoff in the light curves after 71 days and the rapid decline timescale suggest a low-mass ejection from a massive WD with MWD ≳ 1.2 M⊙. We present an unprecedented view of the early spectroscopic evolution of such an event. Three spectra prior to the peak reveal a complex, multicomponent outflow giving rise to internal collisions and shocks in the ejecta of an He/N-class nova. We identify a coincident IR-variable counterpart in the extensive preeruption coverage of the transient location and infer the presence of a symbiotic progenitor system with an O-rich asymptotic-giant-branch donor star, as well as evidence for an earlier UV-bright outburst in 2014. We suggest that AT 2019qyl is analogous to the subset of Galactic recurrent novae with red-giant companions such as RS Oph and other embedded nova systems like V407 Cyg. Our observations provide new evidence that internal shocks between multiple, distinct outflow components likely contribute to the generation of the shock-powered emission from such systems.
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| 2. |
- Jencson, Jacob E., et al.
(author)
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Discovery of an Intermediate-luminosity Red Transient in M51 and Its Likely Dust-obscured, Infrared-variable Progenitor
- 2019
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In: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 880:2
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Journal article (peer-reviewed)abstract
- We present the discovery of an optical transient (OT) in Messier. 51, designated M51 OT2019-1 (also ZTF 19aadyppr, AT 2019abn, ATLAS19bz1), by the Zwicky Transient Facility (ZTF). The OT rose over 15. days to an observed luminosity of M-r = -13 (nu L-nu = 9 x 10(6) L-circle dot), in the luminosity gap between novae and typical supernovae (SNe). Spectra during the outburst show a red continuum, Balmer emission with a velocity width of approximate to 400 km s(-1), Ca II and [Ca II] emission, and absorption features characteristic of an F-type supergiant. The spectra and multiband light curves are similar to the so-called SN impostors and intermediate-luminosity red transients (ILRTs). We directly identify the likely progenitor in archival Spitzer Space Telescope imaging with a 4.5 mu m luminosity of M-[4.5] approximate to -12.2 mag and a [3.6]-[4.5] color redder than 0.74 mag, similar to those of the prototype ILRTs SN 2008S and NGC 300 OT2008-1. Intensive monitoring of M51 with Spitzer further reveals evidence for variability of the progenitor candidate at [ 4.5] in the years before the OT. The progenitor is not detected in pre-outburst Hubble Space Telescope optical and near-IR images. The optical colors during outburst combined with spectroscopic temperature constraints imply a higher reddening of E(B - V) approximate to 0.7 mag and higher intrinsic luminosity of M-r approximate to -14.9 mag (nu L-nu = 5.3 x 10(7) L-circle dot) near peak than seen in previous ILRT candidates. Moreover, the extinction estimate is higher on the rise than on the plateau, suggestive of an extended phase of circumstellar dust destruction. These results, enabled by the early discovery of M51. OT2019-1 and extensive pre-outburst archival coverage, offer new clues about the debated origins of ILRTs and may challenge the hypothesis that they arise from the electron-capture induced collapse of extreme asymptotic giant branch stars.
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| 3. |
- Jencson, Jacob E., et al.
(author)
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The SPIRITS Sample of Luminous Infrared Transients : Uncovering Hidden Supernovae and Dusty Stellar Outbursts in Nearby Galaxies
- 2019
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In: Astrophysical Journal. - : IOP PUBLISHING LTD. - 0004-637X .- 1538-4357. ; 886:1
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Journal article (peer-reviewed)abstract
- We present a systematic study of the most luminous (M-IR [Vega magnitudes] brighter than ?14) infrared (IR) transients discovered by the SPitzer InfraRed Intensive Transients Survey (SPIRITS) between 2014 and 2018 in nearby galaxies (D < 35 Mpc). The sample consists of nine events that span peak IR luminosities of M-[4.5],M-peak between ?14 and ?18.2, show IR colors between 0.2;<;([3.6]?[4.5]);<;3.0, and fade on timescales between 55 days;t(fade);<;480 days. The two reddest events (A(V) > 12) show multiple, luminous IR outbursts over several years and have directly detected, massive progenitors in archival imaging. With analyses of extensive, multiwavelength follow-up, we suggest the following possible classifications: five obscured core-collapse supernovae (CCSNe), two erupting massive stars, one luminous red nova, and one intermediate-luminosity red transient. We define a control sample of all optically discovered transients recovered in SPIRITS galaxies and satisfying the same selection criteria. The control sample consists of eight CCSNe and one Type;Iax SN. We find that 7 of the 13 CCSNe in the SPIRITS sample have lower bounds on their extinction of 2;A(V);<;8. We estimate a nominal fraction of CCSNe in nearby galaxies that are missed by optical surveys as high as
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