Confined dense circumstellar material surrounding a regular type II supernova

TLDR: In this article, the authors reported the discovery of the supernova iPTF 13dqy = SN 2013fs a mere 3'h after the explosion of a red supergiant.

Abstract: With the advent of new wide-field, high-cadence optical transient surveys, our understanding of the diversity of core-collapse supernovae has grown tremendously in the last decade. However, the pre-supernova evolution of massive stars, which sets the physical backdrop to these violent events, is theoretically not well understood and difficult to probe observationally. Here we report the discovery of the supernova iPTF 13dqy = SN 2013fs  a mere ~3 h after explosion. Our rapid follow-up observations, which include multiwavelength photometry and extremely early (beginning at ~6 h post-explosion) spectra, map the distribution of material in the immediate environment (≲10^(15) cm) of the exploding star and establish that it was surrounded by circumstellar material (CSM) that was ejected during the final ~1 yr prior to explosion at a high rate, around 10^(−3) solar masses per year. The complete disappearance of flash-ionized emission lines within the first several days requires that the dense CSM be confined to within ≲10^(15) cm, consistent with radio non-detections at 70–100 days. The observations indicate that iPTF 13dqy was a regular type II supernova; thus, the finding that the probable red supergiant progenitor of this common explosion ejected material at a highly elevated rate just prior to its demise suggests that pre-supernova instabilities may be common among exploding massive stars.

Figures

Figure 2 Early-time flash spectroscopy of iPTF 13dqy reveals flash-ionisation signatures during the first 2 d after explosion. High-ionisation oxygen emission lines (O VI λλ3811,

Figure 3 Spectra of iPTF 13dqy obtained between 8 and 57 days after explosion, showing P-Cygni profiles of the Balmer series and additional typical elements, confirm a regular Type II SN identification. The Balmer series, Ca II (the near-infrared triplet and the H&K lines), Fe II, and Mg I are marked for the specified expansion velocities. See the spectroscopic log (Table 1) for details of the spectra. All spectra presented in this study are publicly available via WISeREP32 (http://wiserep.weizmann.ac.il).

Figure 4 The best-fitting CMFGEN models to the observed early-time spectrum (6 hr post-explosion) of iPTF 13dqy reveal a temperature of the line forming region around

Figure 1 The early discovery of iPTF 13dqy and the prompt ensuing follow-up observations, multiband photometry and spectroscopy, enabled the direct probing and mapping of

Figure 6 The proposed CSM configuration surrounding the progenitor of iPTF 13dqy, resulting from our multiwavelength observations — a CSM density profile that is both nearby and confined. The figure summarises the CSM estimates we derive from analyses of the early-time spectra (at r ≈ 1014 cm) together with the region excluded by the later radio observations. The solid diagonal coloured lines denote constant mass-loss rates between 10−7 and 10−1 M yr−1 (following ρ = Ṁ/4πvwindr2, vwind = 100 km s−1) assuming an r−2 wind density profile. For an explanation of the lower limit on the mass-loss rate as obtained by measurement of the Hα luminosity, see Methods §5. The early-time

Figure 5 Radio non-detections rule out an extended dense wind structure around the progenitor of iPTF 13dqy. The plotted coloured curves display theoretical light curves of radio emission originating from the interaction of SN ejecta with an extended CSM. These extended CSM structures are assumed to be a result of a constant mass-loss rate through stellar winds. Our measured limits (triangles) on the late-time radio emission (at ∼ 70, 100d) rule out a wide range of mass-loss rates. In particular, our limits show that the mass-loss rate estimate required to explain the early optical data could not have been sustained over long periods. Otherwise, an extended CSM structure would have formed with sufficiently high density to be detected in the radio at late times (up to a

Full text

Confined Dense Circumstellar Material Surrounding a Regular Type II
Supernova
Yaron, O., Perley, D. A., Gal-Yam, A., Groh, J. H., Horesh, A., Ofek, E. O., Kulkarni, S. R., Sollerman, J.,
Fransson, C., Rubin, M. A., Szabo, P., Sapir, N., Taddia, F., Cenko, S. B., Arcavi, I., Howell, D. A., Kasliwal, M.
M., Vreeswijk, P. M., Khazov, D., ... Soumagnac, M. T. (2017). Confined Dense Circumstellar Material
Surrounding a Regular Type II Supernova.
Nature Physics
, 510-521. https://doi.org/10.1038/NPHYS4025
Published in:
Nature Physics
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Peer reviewed version
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Download date:09. Aug. 2022

Confined Dense Circumstellar Material Surrounding
a Regular Type II Supernova: The Unique Flash-
Spectroscopy Event - SN 2013fs
O. Yaron
1
, D. A. Perley
2,3
, A. Gal-Yam
1
, J. H. Groh
4
, A. Horesh
5,1
, E. O. Ofek
1
, S. R. Kulkarni
2
,
J. Sollerman
6
, C. Fransson
6
, A. Rubin
1
, P. Szabo
1
, N. Sapir
1,7
, F. Taddia
6
, S. B. Cenko
8,9
, S. Valenti
10
,
I. Arcavi
11,12
, D. A. Howell
11,12
, M. M. Kasliwal
2
, P. M. Vreeswijk
1
, D. Khazov
1
, O. D. Fox
13
,
Y. Cao
2
, O. Gnat
5
, P. L. Kelly
13
, P. E. Nugent
13,14
, A. V. Filippenko
13
, R. R. Laher
15
, P. R. Wozniak
16
,
W. H. Lee
17
, U. D. Rebbapragada
18
, K. Maguire
19
, M. Sullivan
20
, M. T. Soumagnac
1
1
Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100,
Israel.
2
Division of Physics, Math and Astronomy, California Institute of Technology, 1200 E. California
Boulevard, Pasadena, CA 91125, USA.
3
Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen Juliane Maries Vej 30,
2100 Copenhagen Ø, Denmark.
4
School of Physics, Trinity College Dublin, Dublin 2, Ireland.
5
Racah Institute of Physics, Hebrew University, Jerusalem 91904, Israel.
6
The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, 10691
Stockholm, Sweden.
7
Plasma Physics Department, Soreq Nuclear Research Center, Yavne 81800, Israel.
8
Astrophysics Science Division, NASA Goddard Space Flight Center, Mail Code 661, Greenbelt,
MD 20771, USA.
1
arXiv:1701.02596v2 [astro-ph.HE] 16 Feb 2017

9
Joint Space-Science Institute, University of Maryland, College Park, MD 20742, USA.
10
Department of Physics, University of California, 1 Shields Ave, Davis, CA 95616-5270, USA
11
Las Cumbres Observatory, 6740 Cortona Drive, Suite 102,Goleta, CA 93117, USA.
12
Department of Physics, University of California, Santa Barbara, CA 93106-9530, USA.
13
Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA.
14
Computational Research Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road
MS 50B-4206, Berkeley, CA 94720, USA.
15
Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125, USA.
16
Los Alamos National Laboratory, Mail Stop B244, Los Alamos, NM 87545, USA.
17
Instituto de Astronom
´
ıa, Universidad Nacional Auton
´
oma de M
´
exico, Apdo. Postal 70-264,
04510 M
´
exico DF, M
´
exico.
18
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.
19
Astrophysics Research Centre, School of Mathematics and Physics, Queens University Belfast,
Belfast BT7 1NN, UK.
20
School of Physics and Astronomy, University of Southampton, Southampton, SO17 1BJ, UK.
2

With the advent of new wide-field, high-cadence optical transient surveys, our understand-
ing of the diversity of core-collapse supernovae has grown tremendously in the last decade.
However, the pre-supernova evolution of massive stars, that sets the physical backdrop to
these violent events, is theoretically not well understood and difficult to probe observation-
ally. Here we report the discovery of the supernova iPTF 13dqy = SN 2013fs a mere ∼ 3 hr
after explosion. Our rapid follow-up observations, which include multiwavelength photome-
try and extremely early (beginning at ∼ 6 hr post-explosion) spectra, map the distribution of
material in the immediate environment (
<
∼
10
15
cm) of the exploding star and establish that
it was surrounded by circumstellar material (CSM) that was ejected during the final ∼ 1 yr
prior to explosion at a high rate, around 10
−3
solar masses per year. The complete disap-
pearance of flash-ionised emission lines within the first several days requires that the dense
CSM be confined to within
<
∼
10
15
cm, consistent with radio non-detections at 70–100 days.
The observations indicate that iPTF 13dqy was a regular Type II SN; thus, the finding that
the probable red supergiant (RSG) progenitor of this common explosion ejected material at
a highly elevated rate just prior to its demise suggests that pre-supernova instabilities may
be common among exploding massive stars.
Why and how massive stars explode as supernovae is one of the outstanding open questions
in astrophysics. Massive stars fuse light elements into heavier ones in their core. During the
final years of their (relatively short, a few 10
6
–10
7
yr) lifetime, these stars burn heavy fuel, the
fusion products of hydrogen and helium, until an iron core grows and ultimately collapses. Stellar
evolution in these final years, which sets the initial conditions for the final collapse and explosion
3

of such stars as supernovae (SNe), is poorly understood
1
. Direct observations of these processes is
challenging, as stars in these brief final stages are rare. Statistically, it is very likely that not even
a single star that is within 1 yr of explosion currently exists in our Galaxy.
Recently, growing observational evidence has suggested the existence of pre-explosion el-
evated mass loss and eruptions
2, 3, 4, 5
. Accommodating these findings, a handful of theoretical
studies
6, 7, 8, 9
were carried out exploring possible pathways by which massive stars may become
unstable during their terminal years, leading to the observable signatures of increased mass loss,
variability, and eruptive episodes prior to the terminal explosion. Material ejected by the star in the
year prior to its demise may imprint unique signatures on the emission observed from the young
SN event, but as this material will be quickly swept away by the expanding explosion debris, such
detections require rapid observations to be secured within a few days of explosion
2, 10
. A handful
of recent observations provide evidence for enhanced mass loss and eruptive episodes during the
terminal years prior to explosion, but mainly for rare subclasses of SNe which comprise at most
a few percent of the population. The observations presented here of iPTF 13dqy indicate that it
was a fairly regular Type II SN, similar to ∼ 50%
11
of exploding massive stars, and thus may
strengthen the hypothesis that the ultimate collapse of the core and the preceding vigorous ejection
of mass from the outer envelope are causally coupled. In addition, the structure of the outer enve-
lope of massive stars during the very late stages of evolution may significantly differ from what is
predicted by stellar evolution models
12, 13
.
On 2013 Oct. 6.245 (UTC dates are used throughout this paper), a new transient source with
4

Frequently asked questions

Q1. What contributions have the authors mentioned in the paper "Confined dense circumstellar material surrounding a regular type ii supernova" ?

Yaron, O., Perley, D. this paper, Gal-Yam, A., Groh, J. H., Horesh, A, Ofek, E. O., Kulkarni, S. A., Kasliwal, M. M., Khazov, D., ... Soumagnac, M., Szabo, P., Sapir, N., Taddia, F., Cenko, S.,