The lowest of the low: discovery of SN 2019gsc and the nature of faint Iax supernovae. (arXiv:2001.09722v1 [astro-ph.HE])

The lowest of the low: discovery of SN 2019gsc and the nature of faint Iax supernovae. (arXiv:2001.09722v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Srivastav_S/0/1/0/all/0/1">Shubham Srivastav</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Smartt_S/0/1/0/all/0/1">Stephen J. Smartt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Leloudas_G/0/1/0/all/0/1">Giorgos Leloudas</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Huber_M/0/1/0/all/0/1">Mark E. Huber</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chambers_K/0/1/0/all/0/1">Ken Chambers</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Malesani_D/0/1/0/all/0/1">Daniele B. Malesani</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hjorth_J/0/1/0/all/0/1">Jens Hjorth</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gillanders_J/0/1/0/all/0/1">James H. Gillanders</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schultz_A/0/1/0/all/0/1">A. Schultz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sim_S/0/1/0/all/0/1">Stuart A. Sim</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Auchettl_K/0/1/0/all/0/1">Katie Auchettl</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fynbo_J/0/1/0/all/0/1">Johan P. U. Fynbo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gall_C/0/1/0/all/0/1">Christa Gall</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+McBrien_O/0/1/0/all/0/1">Owen R. McBrien</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rest_A/0/1/0/all/0/1">Armin Rest</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Smith_K/0/1/0/all/0/1">Ken W. Smith</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wojtak_R/0/1/0/all/0/1">Radoslaw Wojtak</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Young_D/0/1/0/all/0/1">David R. Young</a>

We present the discovery and optical follow-up of the faintest supernova-like
transient known. The event (SN 2019gsc) was discovered in a star-forming host
at 53 Mpc by ATLAS. A detailed multi-colour light curve was gathered with
Pan-STARRS1 and follow-up spectroscopy was obtained with the NOT and
Gemini-North. The spectra near maximum light show narrow features at low
velocities of 3000 to 4000 km s$^{-1}$, similar to the extremely low luminosity
SNe 2010ae and 2008ha, and the light curve displays a similar fast decline
(dmr $0.91 pm 0.1$ mag). SNe 2010ae and 2008ha have been classified as type
Iax supernovae, and together the three either make up a distinct physical class
of their own or are at the extreme low luminosity end of this diverse supernova
population. The bolometric light curve is consistent with a low kinetic energy
of explosion ($E_{rm k} sim 10^{49}$ erg s$^{-1}$), a modest ejected mass
($M_{rm ej} sim 0.2$ msol) and radioactive powering by $^{56}$Ni ($M_{rm
Ni} sim 3 times 10^{-3}$ msol). The spectra are quite well reproduced with
radiative transfer models (TARDIS) and a composition dominated by carbon,
oxygen, magnesium, silicon and sulphur. Remarkably, all three of these extreme
Iax events are in similar low-metallicity star-forming environments. The
combination of the observational constraints for all three may be best
explained by deflagrations of near $M_{rm Ch}$ hybrid carbon-oxygen-neon white
dwarfs which have short evolutionary pathways to formation.

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