J/ApJ/927/78 Phot. & sp. follow-up of type Ia SN2020esm (Dimitriadis+, 2022)
A carbon/oxygen-dominated atmosphere days after explosion for the
"super-Chandrasekhar" type Ia SN 2020esm.
Dimitriadis G., Foley R.J., Arendse N., Coulter D.A., Jacobson-Galan W.V.,
Siebert M.R., Izzo L., Jones D.O., Kilpatrick C.D., Pan Y.-C., Taggart K.,
Auchettl K., Gall C., Hjorth J., Kasen D., Piro A.L., Raimundo S.I.,
Ramirez-Ruiz E., Rest A., Swift J.J., Woosley S.E.
<Astrophys. J., 927, 78 (2022)>
=2022ApJ...927...78D 2022ApJ...927...78D
ADC_Keywords: Supernovae; Spectra, optical; Photometry, ugriz; Ultraviolet
Keywords: Supernovae ; White dwarf stars
Abstract:
Seeing pristine material from the donor star in a type Ia supernova
(SN Ia) explosion can reveal the nature of the binary system. In this
paper, we present photometric and spectroscopic observations of
SN2020esm, one of the best-studied SNe of the class of
"super-Chandrasekhar" SNe Ia (SC SNe Ia), with data obtained -12 to
+360 days relative to peak brightness, obtained from a variety of
ground- and space-based telescopes. Initially misclassified as a
type II supernova, SN 2020esm peaked at MB=-19.9mag, declined slowly
(Δm15(B)=0.92mag), and had particularly blue UV and optical
colors at early times. Photometrically and spectroscopically,
SN2020esm evolved similarly to other SC SNe Ia, showing the usual low
ejecta velocities, weak intermediate-mass elements, and the enhanced
fading at late times, but its early spectra are unique. Our first few
spectra (corresponding to a phase of ≳10days before peak) reveal a
nearly pure carbon/oxygen atmosphere during the first days after
explosion. This composition can only be produced by pristine material,
relatively unaffected by nuclear burning. The lack of H and He may
further indicate that SN 2020esm is the outcome of the merger of
two carbon/oxygen white dwarfs. Modeling its bolometric light curve,
we find an 56Ni mass of 1.23-0.14+0.14M☉ and an ejecta
mass of 1.75-0.20+0.32M☉, in excess of the Chandrasekhar
mass. Finally, we discuss possible progenitor systems and explosion
mechanisms of SN 2020esm and, in general, the SC SNe Ia class.
Description:
We obtained optical photometric observations of SN 2020esm with
various telescopes/instruments.
Our main photometry was performed with the SINISTRO cameras of the Las
Cumbres Observatory Global Telescope Network (LCOGT) network of 1m
telescopes (NOAO2020A-012 and NOAO2020B-011, PI: Foley). Images were
obtained in ugri, from 2020 March 25 UT (approximately 3 days after
discovery and 11 days before peak brightness) until 2020 July 22 UT
(107 days after maximum).
Additional griz photometry was obtained through the Young Supernova
Experiment (YSE; Jones+ 2021ApJ...908..143J 2021ApJ...908..143J) with the Pan-STARRS1
telescope (PS1) between 2020 March 25 UT and 2020 July 24 UT, BVgri
photometry with the 1m telescope at the Lulin observatory in Taiwan,
and griz photometry with the 0.7m telescope of the Thacher
observatory in California (J. J. Swift et al. 2022, in preparation).
Late-time griz imaging (at 280 and 305 days from maximum brightness)
was performed with the Gemini Multi-Object Spectrograph (GMOS) on the
8.1m Gemini North telescope in Maunakea (GN-2020B-Q-324 and
GN-2021A-DD-102, PI: Foley) and F555W and F814W imaging with HST/WFC3
at 356 days from maximum brightness (SNAP-16239, PI: Foley).
UV photometric observations were performed with the Ultraviolet
Optical Telescope (UVOT) on board the Neil Gehrels Swift Observatory
from 2020 March 24 UT until 2020 March 30 UT, with template images
obtained on 2020 March 21 UT.
Spectroscopic coverage of SN 2020esm ranges from roughly -12 to +307d
relative to the B-band maximum. We obtained a total of seven
spectroscopic observations with the Folded Low Order whYte-pupil
Double-dispersed Spectrograph (FLOYDS) spectrograph on the Faulkes 2m
telescopes of the LCOGTN robotic network (NOAO2020A-012, PI: Foley),
one spectrum with the Kast spectrograph on the Lick Shane telescope
(2020A-S011, PI: Foley), two spectra with the Low-Resolution Imaging
Spectrometer (LRIS) on the Keck I telescope (2020A-U209, PI: Foley),
and one spectrum with GMOS on the Gemini North telescope
(GN-2021A-DD-102, PI: Foley).
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
14 07 18.27 -05 07 37.3 SN 2020esm = ASASSN -20dl
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 20 57 UVOIR bolometric light curve of SN 2020esm
tablea1.dat 58 335 Observed photometry of SN 2020esm
tablea2.dat 120 11 Observing details of the optical spectra of SN 2020esm
sp/* . 11 Individual spectra in ASCII format
(Data behind Figure 3)
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See also:
VII/259 : 6dF galaxy survey final redshift release (Jones+, 2009)
J/AJ/137/4517 : UVOT light curves of supernovae (Brown+, 2009)
J/ApJ/700/331 : Light curves of type Ia supernovae (CfA3) (Hicken+, 2009)
J/MNRAS/410/585 : SN 2009dc BVRI light curves (Silverman+, 2011)
J/ApJ/753/22 : Swift/UVOT observations of SN 2011fe (Brown+, 2012)
J/MNRAS/425/1789 : Berkeley supernova Ia program. I. (Silverman+, 2012)
J/A+A/554/A27 : 2011fe spectrophotometric time series (Pereira+, 2013)
J/ApJ/795/44 : PS1 SNe Ia (0.02<z<0.7) griz light curves (Rest+, 2014)
J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)
J/ApJS/220/9 : CfAIR2: NIR light curves of Type Ia SNe (Friedman+, 2015)
J/ApJ/826/56 : HST/WFC3 obs. of Cepheids in SN Ia host gal. (Riess+, 2016)
J/ApJ/841/48 : UBVR and IR photometry of SN 2011fe (Ia) (Shappee+, 2017)
J/ApJ/859/101 : The supernovae Ia Pantheon sample (Scolnic+, 2018)
J/ApJ/900/140 : CSP-II: sp. of the 03fg-like SN Ia LSQ14fmg (Hsiao+, 2020)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 F6.2 d Phase [-12/307] Phase, days (1)
8- 13 F6.4 10+36W Lum [0.0019/2.6] Luminosity, 10+43erg/s
15- 20 F6.4 10+36W e_Lum [0.0003/0.4] Uncertainty in Lum
--------------------------------------------------------------------------------
Note (1): Relative to B-band maximum (MJD=58944.58)
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Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 F8.2 d MJD [58932.26/59313.42] Modified Julian Date
of Observation (JD-2400000.5)
10- 15 F6.2 d Phase [-11.9/356.02] Phase, Rest-frame Days (1)
17- 21 A5 --- Filt Filter observed
23- 30 A8 --- Inst Instrument or facility used (2)
32- 37 F6.3 mag omag [16/25] Observed AB magnitude in Filt
39- 43 F5.3 mag e_omag [0.006/0.4] Uncertainty in omag
45- 51 F7.4 10-16cW/m2/nm Flux [0.003/27] Flux, 10-16erg/s/cm2/Å
53- 58 F6.4 10-16cW/m2/nm e_Flux [0.0003/1.5] Uncertainty in Flux
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Note (1): Relative to B-band maximum (MJD=58944.58)
Note (2): Facility as follows:
Thatcher = the 0.7m telescope of the Thacher observatory in California
(94 occurrences)
Swift = the Neil Gehrels Swift Observatory / UVOT (86 occurrences)
LCOGT = the SINISTRO cameras of the Las Cumbres Observatory Global Telescope
Network network of 1m telescopes (80 occurrences)
PS1 = the Pan-STARRS1 telescope (36 occurrences)
Lulin = the 1m telescope at the Lulin observatory in Taiwan (30 occurrences)
GMOS = the Gemini Multi-Object Spectrograph (GMOS) on the 8.1m Gemini
North telescope in Maunakea (7 occurrences)
WFC3 = HST/WFC3 (2 occurrences)
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Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 "Y/M/D" Date Date of observation (UT)
12- 16 F5.1 d Phase [-11.8/306.9] Rest-frame days relative to
B-band maximum (MJD58944.58)
18- 39 A22 --- Tel Telescope+Instrument
41- 43 F3.1 arcsec Slit [1/2] Slit width
45- 63 A19 --- Grism Grism/Grating
65- 90 A26 s Exp Exposure time(s)
92-120 A29 --- File Name of the ASCII file in subdirectory "sp";
column added by CDS
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Byte-by-byte Description of file: sp/*
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 F10.4 0.1nm lambda [3626.4/10097] Wavelength, in Angstrom units
12- 25 E14.9 cW/m2/nm Flux [-6.1e-16/3.1e-15] Flux, erg/cm2/s/Å
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 14-Nov-2023