Variable H$alpha$ Emission in the Nebular Spectra of the Low-Luminosity Type Ia SN2018cqj/ATLAS18qtd. (arXiv:1909.05267v1 [astro-ph.HE])

Variable H$alpha$ Emission in the Nebular Spectra of the Low-Luminosity Type Ia SN2018cqj/ATLAS18qtd. (arXiv:1909.05267v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Prieto_J/0/1/0/all/0/1">Jose L. Prieto</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chen_P/0/1/0/all/0/1">Ping Chen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dong_S/0/1/0/all/0/1">Subo Dong</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bose_S/0/1/0/all/0/1">S. Bose</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gal_Yam_A/0/1/0/all/0/1">A. Gal-Yam</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Holoien_T/0/1/0/all/0/1">T. W.-S. Holoien</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kollmeier_J/0/1/0/all/0/1">J. A. Kollmeier</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Phillips_M/0/1/0/all/0/1">M. M. Phillips</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shappee_B/0/1/0/all/0/1">B. J. Shappee</a>

We present optical photometry and spectroscopy of the Type Ia supernova
SN2018cqj/ATLAS18qtd. The supernova exploded in an isolated region at $sim 65$
kpc from the S0 galaxy IC 550 at $z=0.0165$ ($Dapprox 74$ Mpc) and has a
redshift consistent with a physical association to this galaxy. Multicolor
photometry show that SN2018cqj/ATLAS18qtd is a low-luminosity
($M_{B_{max}}approx -17.9$ mag), fast-declining Type Ia with color stretch
$s_{BV} approx 0.6$ and $B$-band decline rate $Delta m_{15}(B) approx 1.77$
mag. Two nebular-phase spectra obtained as part of the 100IAS survey at +193
and +307 days after peak show the clear detection of a narrow H$alpha$ line in
emission that is resolved in the first spectrum with $rm FWHM approx 1200$ km
s$^{-1}$ and $L_{Halpha} approx 3.8times 10^{37}$ erg s$^{-1}$. The
detection of a resolved H$alpha$ line with a declining luminosity is broadly
consistent with recent models where hydrogen is stripped from the
non-degenerate companion in a single-degenerate progenitor system. The amount
of hydrogen consistent with the luminosities of the H$alpha$ line would be
$sim 10^{-3}$ M$_{odot}$, significantly less than theoretical model
predictions in the classical single-degenerate progenitor systems.
SN2018cqj/ATLAS18qtd is the second low-luminosity, fast-declining Type Ia SN in
the 100IAS survey after SN2018fhw/ASASSN-18tb that shows narrow H$alpha$ in
emission in its nebular-phase spectra.

We present optical photometry and spectroscopy of the Type Ia supernova
SN2018cqj/ATLAS18qtd. The supernova exploded in an isolated region at $sim 65$
kpc from the S0 galaxy IC 550 at $z=0.0165$ ($Dapprox 74$ Mpc) and has a
redshift consistent with a physical association to this galaxy. Multicolor
photometry show that SN2018cqj/ATLAS18qtd is a low-luminosity
($M_{B_{max}}approx -17.9$ mag), fast-declining Type Ia with color stretch
$s_{BV} approx 0.6$ and $B$-band decline rate $Delta m_{15}(B) approx 1.77$
mag. Two nebular-phase spectra obtained as part of the 100IAS survey at +193
and +307 days after peak show the clear detection of a narrow H$alpha$ line in
emission that is resolved in the first spectrum with $rm FWHM approx 1200$ km
s$^{-1}$ and $L_{Halpha} approx 3.8times 10^{37}$ erg s$^{-1}$. The
detection of a resolved H$alpha$ line with a declining luminosity is broadly
consistent with recent models where hydrogen is stripped from the
non-degenerate companion in a single-degenerate progenitor system. The amount
of hydrogen consistent with the luminosities of the H$alpha$ line would be
$sim 10^{-3}$ M$_{odot}$, significantly less than theoretical model
predictions in the classical single-degenerate progenitor systems.
SN2018cqj/ATLAS18qtd is the second low-luminosity, fast-declining Type Ia SN in
the 100IAS survey after SN2018fhw/ASASSN-18tb that shows narrow H$alpha$ in
emission in its nebular-phase spectra.

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