J/ApJ/921/L6 Opt. phot. & sp. for the type Iax SN 2021fcg (Karambelkar+, 2021)
Faintest of them all: ZTF 21aaoryiz/SN 2021fcg-Discovery of an extremely low
luminosity type Iax supernova.
Karambelkar V.R., Kasliwal M.M., Maguire K., Anand S.G., Andreoni I.,
De K., Drake A., Duev D.A., Graham M.J., Kool E.C., Laher R.R.,
Magee M.R., Mahabal A.A., Medford M.S., Perley D., Rigault M.,
Rusholme B., Schulze S., Sharma Y., Sollerman J., Tzanidakis A.,
Walters R., Yao Y.
<Astrophys. J., 921, L6 (2021)>
=2021ApJ...921L...6K 2021ApJ...921L...6K
ADC_Keywords: Supernovae; Photometry; Spectra, optical
Keywords: Type Ia supernovae ; White dwarf stars ; Time domain astronomy
Abstract:
We present the discovery of ZTF 21aaoryiz/SN 2021fcg-an extremely low
luminosity Type Iax supernova. SN 2021fcg was discovered by the Zwicky
Transient Facility in the star-forming galaxy IC0512 at a distance of
∼27Mpc. It reached a peak absolute magnitude of Mr=-12.66±0.20mag,
making it the least luminous thermonuclear supernova discovered to
date. The E(B-V) contribution from the underlying host galaxy is
unconstrained. However, even if it were as large as 0.5mag, the peak
absolute magnitude would be Mr=-13.78±0.20mag-still consistent
with being the lowest-luminosity SN. Optical spectra of SN 2021fcg
taken at 37 and 65 days post-maximum show strong [CaII], CaII, and
NaID emission and several weak [FeII] emission lines. The [CaII]
emission in the two spectra has extremely low velocities of ∼1300 and
1000km/s, respectively. The spectra very closely resemble those of the
very low luminosity Type Iax supernovae SN2008ha, SN2010ae, and
SN2019gsc taken at similar phases. The peak bolometric luminosity of
SN2021fcg is ∼2.5-0.3+1.5x1040erg/s, which is a factor of
3 lower than that for SN2008ha. The bolometric lightcurve of SN2021fcg
is consistent with a very low ejected nickel mass
(MNi∼0.8-0.5+0.4x10-3M☉). The low luminosity and nickel
mass of SN2021fcg pose a challenge to the picture that low-luminosity
SNe Iax originate from deflagrations of near-Mch hybrid
carbon-oxygen-neon white dwarfs. Instead, the merger of a
carbon-oxygen and oxygen-neon white dwarf is a promising model to
explain SN2021fcg.
Description:
SN 2021fcg was discovered by the Zwicky Transient Facility (ZTF),
which runs on the Palomar 48 inch (P48) Oschin Schmidt telescope.
The field containing SN 2021fcg was observed on several epochs by the
ZTF camera on P48 in the g, r, and i bands.
We obtained additional g, r, and i band photometric observations with
the Spectral Energy Distribution Machine (SEDM) mounted on the 60 inch
telescope at Palomar (P60) on MJD 59306 and 59318. We also observed
the field in the r band with the Alhambra Faint Object Spectrograph
and Camera (ALFOSC) at the 2.56m Nordic Optical Telescope (NOT; Spain)
on MJD 59367.
Finally, the field was also observed by the Asteroid
Terrestrial-impact Last Alert System (ATLAS) survey (e.g.
Tonry+ 2018, J/ApJ/867/105). We used the ATLAS forced photometry
service to query all photometric measurements at the location of
SN2021fcg.
Our spectroscopic follow-up comprises two optical spectra obtained
with the Low Resolution Imaging Spectrograph (LRIS) on the Keck I 10m
telescope. The spectra were obtained on MJD 59318 and 59344
corresponding to +37 days and +63 days after the r-band maximum of SN
2021fcg.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
09 04 32.36 +85 29 48.4 SN 2021fcg = ZTF21aaoryiz
----------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig2.dat 37 32 The g, r, i, o and c band light curve of SN 2021fcg
fig4.dat 26 10196 Late-time optical spectra of SN 2021fcg
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See also:
J/A+A/465/71 : 21cm observations of 452 galaxies (Theureau+, 2007)
J/MNRAS/383/1485 : BVRI light curves of SN 2003jd (Valenti+, 2008)
J/A+A/561/A146 : SN 2010ae optical spectra (Stritzinger+, 2014)
J/A+A/573/A2 : SN 2012Z spectra (Stritzinger+, 2015)
J/ApJ/843/16 : Galaxy groups within 3500km/s (Kourkchi+, 2017)
J/ApJ/867/105 : ATLAS all-sky stellar ref. cat., ATLAS-REFCAT2 (Tonry+, 2018)
J/ApJ/886/152 : ZTF early observations of Type Ia SNe. I. LCs (Yao+, 2019)
J/ApJ/905/58 : Local universe with ZTF. I. Ca-rich gap transients (De+, 2020)
http://fallingstar.com/ : ATLAS home page
Byte-by-byte Description of file: fig2.dat
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Bytes Format Units Label Explanations
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1- 8 F8.2 d MJD [59252.2/59366.9] Modified Julian Date of
observation
10- 15 F6.2 mag mag [19.6/22.9]?=-99 Apparent magnitude of 3-sigma
detections in Filter
17- 22 F6.2 mag e_mag [0.08/0.4]?=-99 Uncertainty in mag
24- 29 F6.2 mag Limmag [/21]?=-99 The 5-sigma limiting magnitude in
Filter
31- 37 A7 --- Filter Filter of observation
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Byte-by-byte Description of file: fig4.dat
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Bytes Format Units Label Explanations
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1- 2 I2 d Phase [37/63] Days since r-band peak (MJD59284.0)
4- 13 F10.4 0.1nm lamAir [3101/10301.5] Air Wavelength in Angstroms
15- 26 E12.5 mW/m2/Hz Flux [-9.2e-17/3.3e-16] Flux in erg/s/cm2/Hz
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 13-Mar-2023