J/ApJ/958/173 Kast and LRIS spectra of SNIa SN 2020hvf (Siebert+, 2023)
An asymmetric double-degenerate type Ia supernova explosion with a surviving
companion star.
Siebert M.R., Foley R.J., Zenati Y., Dimitriadis G., Schmidt E., Yang G.,
Davis K.W., Taggart K., Rojas-Bravo C.
<Astrophys. J., 958, 173 (2023)>
=2023ApJ...958..173S 2023ApJ...958..173S
ADC_Keywords: Supernovae; Spectra, optical
Keywords: Supernovae ; Observational astronomy ; White dwarf stars ;
Type Ia supernovae
Abstract:
We present nebular spectroscopy of SN 2020hvf, a Type Ia supernova
(SNIa) with an early bump in its light curve. SN 2020hvf shares many
spectroscopic and photometric similarities to the carbon-rich
high-luminosity "03fg-like" SNe Ia. At >240 days after peak
brightness, we detect unambiguous emission from [CaII]
λλ7291,7324, which is rarely observed in normal SNe Ia
and only seen in peculiar subclasses. SN 2020hvf displays "sawtooth"
emission profiles near 7300Å that cannot be explained with single
symmetric velocity components of [FeII], [NiII], and [CaII],
indicating an asymmetric explosion. The broad [CaII] emission is best
modeled by two velocity components offset by 1220km/s, which could be
caused by ejecta associated with each star in the progenitor system,
separated by their orbital velocity. For the first time in an SN Ia,
we identify narrow (FWHM=180±40km/s) [CaII] emission, which we
associate with a wind from a surviving, puffed-up companion star. Few
published spectra have sufficient resolution and the signal-to-noise
ratio necessary to detect similar narrow [CaII] emission; however, we
have detected similar line profiles in other 03fg-like SNe Ia. The
extremely narrow velocity width of [CaII] has only otherwise been
observed in SNe Iax at late times. Since this event likely had a
double-degenerate "super-Chandrasekhar" mass progenitor system, we
suggest that a single white dwarf (WD) was fully disrupted and a wind
from a surviving companion WD is producing the observed narrow
emission. It is unclear whether this unique progenitor and explosion
scenario can explain the diversity of 03fg-like SNe Ia, potentially
indicating that multiple progenitor channels contribute to this
subclass.
Description:
We obtained a total of four optical spectra of SN 2020hvf that range
from 240 to 332 days after maximum light. Two spectra were acquired
with the Kast spectrograph on the Lick Shane telescope and two spectra
were acquired with the Low-resolution Imaging Spectrometer (LRIS),
mounted on the 10m Keck I telescope at the W. M. Keck Observatory.
The Kast spectra were obtained on 2021 January 6 and 2021 February 6
UT and cover a wavelength range of 3255-10893Å.
The LRIS observations were obtained with two different setups.
On 2021 February 12 UT, we observed a low-resolution setting (1800 and
1430s blue channel exposures with the B600/4000 grism) and a
high-resolution red channel setting (two 825s exposures with the
R1200/7500 grating, with a pixel scale of 0.4Å/pixel). The blue
channel and red channel spectra cover 3141-5640Å and 6210-7800Å,
respectively.
On 2021 April 8 UT we observed an identical blue channel setup, but
obtained two 525s red channel exposures with the R400/8500 grating,
with pixel scales of 0.63 and 1.16Å/pixel, respectively). This
low-resolution spectrum covers 3162-10147Å.
See Section 2.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
11 21 26.44 +03 00 52.8 SN 2020hvf = SN 2020hvf
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File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 79 5 List of spectra presented in Data behind Figure 1;
table added by CDS
sp/* . 5 The nebular spectra (in ASCII format) of SN 2020hvf
ranging from +240-332 days after peak brightness
(Data behind Figure 1)
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See also:
J/ApJS/190/418 : Light curves for 165 SNe (Ganeshalingam+, 2010)
J/ApJ/742/89 : Relations between spectra & colors of SNe Ia (Foley+, 2011)
J/MNRAS/410/585 : SN 2009dc BVRI light curves (Silverman+, 2011)
J/MNRAS/425/1789 : Berkeley supernova Ia program. I. (Silverman+, 2012)
J/ApJ/826/56 : HST/WFC3 obs. of Cepheids in SN Ia host gal. (Riess+, 2016)
J/A+A/595/A118 : NIBLES. I. The Nancay HI survey (van Driel+, 2016)
J/ApJ/843/16 : Galaxy groups within 3500km/s (Kourkchi+, 2017)
J/ApJ/850/207 : Action dynamics of the Local Supercluster (Shaya+, 2017)
J/A+A/620/A141 : Physical properties of AM CVn stars (Ramsay+, 2018)
J/ApJ/870/L1 : K2 obs. of type Ia supernova SN 2018oh (Dimitriadis+, 2019)
J/A+A/630/A76 : SN2016hnk photometry and spectroscopy (Galbany+, 2019)
J/ApJS/244/24 : A z=0 Multiwavelength Gal. Synth. (z0MGS). I. (Leroy+, 2019)
J/ApJ/900/140 : CSP-II: sp. obs. of the SN Ia LSQ14fmg (Hsiao+, 2020)
J/ApJ/898/166 : UV to NIR obs. of SN 2019ehk (Jacobson-Galan+, 2020)
J/ApJ/898/56 : UVOT, ZTF gri LCs & sp. of the SN Ia 2019yvq (Miller+, 2020)
J/MNRAS/493/1044 : Nebular spectra of 111 Type Ia supernovae (Tucker+, 2020)
J/ApJ/923/L8 : Follow-up phot. & sp. of SNIa 2020hvf (Jiang+, 2021)
J/ApJ/914/50 : Opt. phot. and GMOS & NIRES sp. of SN2019yvq (Tucker+, 2021)
J/ApJ/927/78 : Phot. & sp. follow-up of SNIa SN2020esm (Dimitriadis+, 2022)
J/ApJ/943/L20 : Phot. obs. of SN 2022ilv and SN 2020hvf (Srivastav+, 2023)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 40 A40 --- File Name of the ASCII file in subdirectory "sp"
42- 44 I3 d Days [240/332] Days after peak brightness
46- 56 A11 --- Inst Instrument ("KAST"; "LRIS"; "LRIS (blue)"
or "LRIS (red)")
58- 79 A22 "datime" Date Observation date (UT)
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Byte-by-byte Description of file: sp/*
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 24 E24.19 0.1nm lambda [3140.5/10896] Wavelength, Angstroms
26- 50 E25.19 10-15cW/m2/nm Flux [-1.51/2.2] Flux, 10-15erg/s/cm2^/Å
52- 75 E24.19 10-15cW/m2/nm e_Flux [0.0007/1.4] Uncertainty in Flux
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 26-Jan-2026