J/A+A/706/A183 SN 2021efd, SN 2019tsf photometry and spectra (Pyykkinen+, 2026)
The hydrogen-free circumstellar interaction in the Type Ib supernova 2021efd:
A clue to the mechanism of the helium-layer stripping.
Pyykkinen N., Nagao T., Kuncarayakti H., Stritzinger M.D., Kangas T.,
Maeda K., Chen P., Sollerman J., Burns C., Bose S., Folatelli G.,
Ferrari L., Morrell N., Reguitti A., Salmaso I., Mattila S., Gal-Yam A.,
Fremling C., Anand S., Kasliwal M., Gutierrez C.P., Galbany L.,
Hoogendam W., Schulze S., Ashall C., Medler K., Pfeffer C.M., Lundqvist P.,
Rusholme B., Adler J.
<Astron. Astrophys. 706, A183 (2026)>
=2026A&A...706A.183P 2026A&A...706A.183P (SIMBAD/NED BibCode)
ADC_Keywords: Supernovae ; Photometry ; Optical ; Spectroscopy
Keywords: circumstellar matter - stars: mass-loss - supernovae: general -
supernovae: individual: SN 2021efd -
supernovae: individual: SN 2019tsf
Abstract:
Stripped-envelope supernovae (SESNe), including Type IIb, Ib, and Ic
supernovae (SNe), originate from the explosions of massive stars whose
outer envelopes have been largely removed during their lifetimes. The
main stripping mechanism for the hydrogen (H) envelope in the
progenitors of SESNe is often considered to be interaction with a
binary companion, while that for the helium (He) layer is unclear.
We study the process of the He-layer stripping in the
progenitors of SESNe, which is closely related to the origin of their
diverse observational properties.
We conducted photometric and spectroscopic observations of the Type Ib
SN 2021efd, which shows signs of interaction with H-free circumstellar
material (CSM). At early phases, its photometric and spectroscopic
properties resemble those of typical Type Ib SNe. Around 30 days after
the r-band light curve (LC) peak, until at least ∼770 days, the
multi-band LCs display excessive luminosity compared to regular SESNe
and at least three distinct peaks. The light curve evolution is
similar to that of SN 2019tsf, whose previously unpublished spectrum
at 400 days is also presented here. The nebular spectrum of SN 2021efd
shows narrow emission lines (∼1000km/s) in various species, such as
OI, CaII, MgII, HeI, [OI], [CaII], and [SII]. Based on the
observations, we studied the properties of the ejecta and CSM of SN
2021efd.
Our observations suggest that SN 2021efd is a Type Ib SN interacting
with CSM with the following parameters: The estimated ejecta mass,
explosion energy, and 56Ni-56 mass are 2.2M☉, 9.1*10^50 erg, of
0.14M☉, respectively, while the estimated CSM mass, composition,
and distribution are at least a few times 0.1M☉, H-free, and
clumpy, respectively. Based on the estimated ejecta properties, we
conclude that this event is a transitional SN whose progenitor was
experiencing He-layer stripping at the epoch of the explosion, and was
on the way to becoming a carbon-oxygen star (as the progenitors of
Type Ic SNe) from a He star (as the progenitors of Type Ib SNe).
The estimated CSM properties suggest that the progenitor had some
episodic mass ejections with the rate of ∼0.005-0.01M☉/yr for
the last decade and slightly smaller before this final phase at least
from ∼200 years before the explosion, for the assumed CSM velocity of
100km/s. For the case of ∼1000km/s, the necessary mass-loss rate would
be increased by a factor of ten, and the timescales decreased by a
factor of ten.
Description:
This data release includes the photometric and spectroscopic data of
SN 2021efd presented in the accompanying article, as well as the
results of the bolometric fitting. Some of the data were observed as
part of the NUTS, POISE, and ZTF programs. Survey data from ATLAS is
also included in the photometric table. A previously unpublished
spectrum of SN 2019tsf is also included.
The photometric data here are presented in the observer frame and are
uncorrected for Milky Way and host galaxy extinction. The bolometric
fit results are in the object rest frame. In the log of spectroscopic
data, the dates in UT and MJD are also in the observer frame, but the
listed phases are corrected to the rest frame of SN 2021efd.
Objects:
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RA (2000) DE Designation(s)
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11 24 24.73 +23 38 58.3 SN 2021efd = ZTF21aanvncv
11 08 32.79 -10 28 54.4 SN 2019tsf = ZTF19ackjszs
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
photom.dat 69 478 SN 2021efd photometric observations
bol-fit.dat 150 132 Results of bolometric fitting for SN 2021efd
logsp.dat 116 14 Log of spectroscopy of SN 2021efd and SN2019tsf
sp/* . 14 SN2021efd and SN2019tsf individual spectra
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Byte-by-byte Description of file: photom.dat
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Bytes Format Units Label Explanations
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1- 18 F18.12 d MJD Modified Julian Date of observation
20- 37 F18.15 mag mag Apparent magnitude in Filter
39- 58 F20.18 mag e_mag Magnitude error
60 A1 --- Filt Filter
62- 69 A8 --- Source Data source
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Byte-by-byte Description of file: bol-fit.dat
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Bytes Format Units Label Explanations
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1- 3 I3 d Phase Object rest frame phase
5- 22 F18.15 [10-7W] logLum Log10 of luminosity
24- 41 F18.15 [10-7W] b_logLum Lower limit of luminosity
43- 60 F18.15 [10-7W] B_logLum Upper limit of luminosity
62- 65 I4 K Temp Temperature
67- 70 I4 K b_Temp Lower limit of temperature
72- 75 I4 K B_Temp Upper limit of temperature
77- 92 I16 cm Rad Radius
94-109 I16 cm b_Rad Lower limit of radius
111-126 I16 cm B_Rad Upper limit of radius
128-150 E23.15 --- Chi2 Goodness of fit value
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Byte-by-byte Description of file: logsp.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name SN name
11- 13 I3 d Phase Phase in object rest frame
15- 25 A11 "date" DateUT UT date of observation (1)
27- 34 F8.2 d DateMJD Modified Julian date of observation
36- 40 A5 --- Tel Telescope
42- 49 A8 --- Inst Instrument
51- 68 A18 --- Grism Grism identifier
70- 79 A10 0.1nm Range Wavelength range
81- 84 I4 --- Res ?=- Resolving power
86-116 A31 --- FileName Name of the spectrum file in subdirectory sp
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Note (1): for SN2021efd, the earliest epoch of observations was originally
published by Reguitti et al. (2021TNSCR.682....1R 2021TNSCR.682....1R) in the Transient name
server classification of SN 2021efd.
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Byte-by-byte Description of file: sp/*
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Bytes Format Units Label Explanations
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1- 22 F22.16 0.1nm lambda Wavelength
24- 48 E25.20 --- Flux ?=- Flux in arbitrary unit
49- 73 E25.20 --- e_Flux ? Flux error
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Acknowledgements:
Niko Pyykkinen, niko.pyykkinen(at)gmail.com
(End) Patricia Vannier [CDS] 18-Dec-2025