T. Diamond

Goddard Space Flight Center

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E. Y. Hsiao

Florida State University

David J. Sand

University of Arizona

D. A. Howell

Las Cumbres Observatory Global Telescope Network

M. M. Phillips

Las Campanas Observatory

I. Arcavi

Tel Aviv University

L. Galbany

Institut d'Estudis Espacials de Catalunya

C. McCully

Las Cumbres Observatory Global Telescope Network

N. Morrell

Las Campanas Observatory

N. M. Ashok

Physical Research Laboratory

C. Contreras

Universidad Mayor

Cooperative Institutions

Cerro Tololo Inter-American Observatory

Astronomical Observatory

Queen's University Belfast

California Institute of Technology

Center for Astrophysics Harvard & Smithsonian

South African Radio Astronomy Observatory

University of California, Berkeley

Las Cumbres Observatory Global Telescope Network

ARC Centre of Excellence for All-sky Astrophysics

European Southern Observatory

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WiFeS+FIRE classification of ASASSN-14lw as a young SN Ia

The astronomer's telegram (2014)

M. Childress T. Diamond R. Scalzo C. Contreras B. Tucker

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Spectrocopic Classifcations of AT 2017gqd and AT 2017gqe by Baade/IMACS

ATel (2017)

Lingzhi Wang N. Morrell E. Y. Hsiao J. P. Anderson T. Diamond

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LSQ13ddu: a rapidly evolving stripped-envelope supernova with early circumstellar interaction signatures

Monthly Notices of the Royal Astronomical Society (2020)

P. Clark K. Maguire C. Inserra S. Prentice S. J. Smartt

This paper describes the rapidly evolving and unusual supernova LSQ13ddu, discovered by the La Silla-QUEST survey. LSQ13ddu displayed a rapid rise of just 4.8$\pm$0.9 d to reach a peak brightness of $-$19.70$\pm$0.02 mag in the $\mathit{LSQgr}$ band. Early spectra of LSQ13ddu showed the presence of weak and narrow He I features arising from interaction with circumstellar material (CSM). These interaction signatures weakened quickly, with broad features consistent with those seen in stripped-envelope SNe becoming dominant around two weeks after maximum. The narrow He I velocities are consistent with the wind velocities of luminous blue variables but its spectra lack the typically seen hydrogen features. The fast and bright early light curve is inconsistent with radioactive $^{56}$Ni powering but can be explained through a combination of CSM interaction and an underlying $^{56}$Ni decay component that dominates the later time behaviour of LSQ13ddu. Based on the strength of the underlying broad features, LSQ13ddu appears deficient in He compared to standard SNe Ib.

Envelope (radar)

Circumstellar envelope

10.1093/mnras/stz3598

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Nebular-phase spectra of Type Ia supernovae from the Las Cumbres Observatory Global Supernova Project

Monthly Notices of the Royal Astronomical Society (2022)

M. L. Graham Tina Kennedy S. Kumar R. Amaro David J. Sand

ABSTRACT The observed diversity in Type Ia supernovae (SNe Ia) – the thermonuclear explosions of carbon–oxygen white dwarf stars used as cosmological standard candles – is currently met with a variety of explosion models and progenitor scenarios. To help improve our understanding of whether and how often different models contribute to the occurrence of SNe Ia and their assorted properties, we present a comprehensive analysis of seven nearby SNe Ia. We obtained one to two epochs of optical spectra with Gemini Observatory during the nebular phase (>200 d past peak) for each of these events, all of which had time series of photometry and spectroscopy at early times (the first ∼8 weeks after explosion). We use the combination of early- and late-time observations to assess the predictions of various models for the explosion (e.g. double-detonation, off-centre detonation, stellar collisions), progenitor star (e.g. ejecta mass, metallicity), and binary companion (e.g. another white dwarf or a non-degenerate star). Overall, we find general consistency in our observations with spherically symmetric models for SN Ia explosions, and with scenarios in which the binary companion is another degenerate star. We also present an in-depth analysis of SN 2017fzw, a member of the subgroup of SNe Ia which appear to be transitional between the subluminous ‘91bg-like’ events and normal SNe Ia, and for which nebular-phase spectra are rare.

10.1093/mnras/stac192

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Near-infrared studies of V2944 Ophiuchi (Nova Ophiuchi 2015)

Monthly Notices of the Royal Astronomical Society (2016)

Mudit Srivastava D. Banerjee N. M. Ashok V. Venkataraman David J. Sand

We present multi-epoch near-infrared observations of Nova Ophiuchi 2015 which was discovered during outburst in March 2015. This nova showed a few special properties viz. (i) it displayed an unusual prolonged flat-top light curve which does not easily fit into known classes of nova light curves, (ii) it showed evidence for possessing an evolved secondary in the outbursting binary system, and (iii) it made a rare reverse hybrid transition from the He/N class to Fe ii class early during its outburst. The present studies focus on the spectroscopic evolution of the object around maximum light and early decline. We show that there was a unique, rapid strengthening and decline in the He 1.0831, 2.0581 μm line strengths during this stage, wherein the nova combined the traits of both the He/N and Fe ii classes. Possible causes for this behaviour are discussed. The relative strengths of the Lyβ fluoresced O i 0.8446, 1.1287 μm lines are used to estimate the reddening to the nova. A recombination Case B analysis of the early spectra is used to set constraints on the electron density and emission measure, and a later time spectrum when the ejecta were optically thin is used to estimate the ejecta mass to be (0.95–1.9) × 10−4 M⊙. Power-law fits made to study the evolution of the continuum, show a fairly constant slope which differs from the trend generally expected during a nova's evolution viz. beginning with a blackbody and evolving to a free–free distribution at later stages.

Nova (rocket)

Black-body radiation

10.1093/mnras/stw1807

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Rise and fall of the dust shell of the classical nova V339 Delphini

Monthly Notices of the Royal Astronomical Society (2016)

A. Evans D. P. K. Banerjee R. D. Gehrz Vishal Joshi N. M. Ashok

We present infrared spectroscopy of the classical nova V339 Del, obtained over an ∼2-yr period. The infrared emission lines were initially symmetrical, with half width half-maximum velocities of 525 km s−1. In later (t ≳ 77 d, where t is the time from outburst) spectra, however, the lines displayed a distinct asymmetry, with a much stronger blue wing, possibly due to obscuration of the receding component by dust. Dust formation commenced at approximately day 34.75 at a condensation temperature of 1480 ± 20 K, consistent with graphitic carbon. Thereafter, the dust temperature declined with time as Td ∝ t−0.346, also consistent with graphitic carbon. The mass of dust initially rose, as a result of an increase in grain size and/or number, peaked at approximately day 100, and then declined precipitously. This decline was most likely caused by grain shattering due to electrostatic stress after the dust was exposed to X-radiation. The appendix summarizes Planck means for carbon and the determination of grain mass and radius for a carbon dust shell.

Carbon fibers

Nova (rocket)

Circumstellar dust

10.1093/mnras/stw3334

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A new class of flares from accreting supermassive black holes

Nature Astronomy (2019)

Benny Trakhtenbrot I. Arcavi Cláudio Ricci Sandro Tacchella Daniel Stern

Flare

10.1038/s41550-018-0661-3

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Citations (69)