25 research outputs found
Time varying Na I D absorption in ILRTs as a probe of circumstellar material
Intermediate-Luminosity Red Transients (ILRTs) are a class of observed
transient posited to arise from the production of an electron-capture supernova
from a super-asymptotic giant branch star within a dusty cocoon. In this paper,
we present a systematic analysis of narrow Na I D absorption as a means of
probing the circumstellar environment of these events. We find a wide diversity
of evolution in ILRTs in terms of line strength, time-scale, and shape. We
present a simple toy model designed to predict this evolution as arising from
ejecta from a central supernova passing through a circumstellar environment
wherein Na II is recombining to Na I over time. We find that while our toy
model can qualitatively explain the evolution of a number of ILRTs, the
majority of our sample undergoes evolution more complex than predicted. The
success of using the Na I D doublet as a diagnostic tool for studying
circumstellar material will rely on the availability of regular high-resolution
spectral observations of multiple ILRTs, and more detailed spectral modelling
will be required to produce models capable of explaining the diverse range of
behaviours exhibited by ILRTs. In addition, the strength of the Na I D
absorption feature has been used as a means of estimating the extinction of
sources, and we suggest that the variability visible in ILRTs would prevent
such methods from being used for this class of transient, and any others
showing evidence of variabilityComment: 14 pages, 10 figures, submitted to MNRA
Signatures of an eruptive phase before the explosion of the peculiar core-collapse SN 2013gc
We present photometric and spectroscopic analysis of the peculiar
core-collapse SN 2013gc, spanning seven years of observations. The light curve
shows an early maximum followed by a fast decline and a phase of almost
constant luminosity. At +200 days from maximum, a brightening of 1 mag is
observed in all bands, followed by a steep linear luminosity decline after +300
d. In archival images taken between 1.5 and 2.5 years before the explosion, a
weak source is visible at the supernova location, with mag20. The
early supernova spectra show Balmer lines, with a narrow (560 km
s) P-Cygni absorption superimposed on a broad (3400 km s)
component, typical of type IIn events. Through a comparison of colour curves,
absolute light curves and spectra of SN 2013gc with a sample of supernovae IIn,
we conclude that SN 2013gc is a member of the so-called type IId subgroup. The
complex profile of the H line suggests a composite circumstellar medium
geometry, with a combination of lower velocity, spherically symmetric gas and a
more rapidly expanding bilobed feature. This circumstellar medium distribution
has been likely formed through major mass-loss events, that we directly
observed from 3 years before the explosion. The modest luminosity
( near maximum) of SN 2013gc at all phases, the very small amount
of ejected Ni (of the order of M), the major
pre-supernova stellar activity and the lack of prominent [O I] lines in
late-time spectra support a fall-back core-collapse scenario for the massive
progenitor of SN~2013gc.Comment: 20 pages, 11 figures, 8 tables, accepted by MNRA
Observations of Type Ia Supernova 2014J for Nearly 900 Days and Constraints on Its Progenitor System
We present extensive ground-based and ()
photometry of the highly reddened, very nearby type Ia supernova (SN Ia) 2014J
in M82, covering the phases from 9 days before to about 900 days after the
-band maximum. SN 2014J is similar to other normal SNe Ia near the maximum
light, but it shows flux excess in the band in the early nebular phase.
This excess flux emission can be due to light scattering by some structures of
circumstellar materials located at a few 10 cm, consistent with a single
degenerate progenitor system or a double degenerate progenitor system with mass
outflows in the final evolution or magnetically driven winds around the binary
system. At t+300 to +500 days past the -band maximum, the light
curve of SN 2014J shows a faster decline relative to the Ni decay. Such
a feature can be attributed to the significant weakening of the emission
features around [Fe III] 4700 and [Fe II] 5200 rather than
the positron escape as previously suggested. Analysis of the images taken
at t600 days confirms that the luminosity of SN 2014J maintains a flat
evolution at the very late phase. Fitting the late-time pseudo-bolometric light
curve with radioactive decay of Ni, Ni and Fe isotopes, we
obtain the mass ratio Ni/Ni as , which is
consistent with the corresponding value predicted from the 2D and 3D
delayed-detonation models. Combined with early-time analysis, we propose that
delayed-detonation through single degenerate scenario is most likely favored
for SN 2014J.Comment: 28 pages, 12 figures. Accepted for publication in Ap
Observations of the low-luminosity Type Iax supernova 2019gsc: a fainter clone of SN 2008ha?
We present optical photometric and spectroscopic observations of the faint-and-fast evolving Type Iax supernova (SN) 2019gsc, extending from the time of g-band maximum until about 50 d post-maximum, when the object faded to an apparent r-band magnitude m(r )= 22.48 +/- 0.11 mag. SN 2019gsc reached a peak luminosity of only M-g = -13.58 +/- 0.15 mag, and is characterized with a post-maximum decline rate Delta m(15)(g) = 1.08 +/- 0.14 mag. These light curve parameters are comparable to those measured for SN 2008ha of M-g = -13.89 +/- 0.14 mag at peak and Delta m(15)(g) =1.80 +/- 0.03 mag. The spectral features of SN 2019gsc also resemble those of SN 2008ha at similar phases. This includes both the extremely low ejecta velocity at maximum, similar to 3000 km s(-1) and at late-time (phase +54 d) strong forbidden iron and cobalt lines as well as both forbidden and permitted calcium features. Furthermore, akin to SN 2008ha, the bolometric light curve of SN 2019gsc is consistent with the production of approximate to 0.003 +/- 0.001 M-circle dot of Ni-56. The explosion parameters, M-ej approximate to 0.13 M-circle dot and E-k approximate to 12 x 10(48) erg, are also similar to those inferred for SN 2008ha. We estimate a subsolar oxygen abundance for the host galaxy of SN 2019gsc (12 + log(10)(O/H) =8.10 +/- 0.18 dex), consistent with the equally metal-poor environment of SN 2008ha. Altogether, our data set for SN 2019gsc indicates that this is a member of a small but growing group of extreme SN Iax that includes SN 2008ha and SN 2010ae
Observations of A Fast-Expanding and UV-Bright Type Ia Supernova SN 2013gs
In this paper, we present extensive optical and ultraviolet (UV) observations
of the type Ia supernova (SN Ia) 2013gs discovered during the Tsinghua-NAOC
Transient Survey. The photometric observations in the optical show that the
light curves of SN 2013gs is similar to that of normal SNe Ia, with an absolute
peak magnitude of = 19.25 0.15 mag and a post-maximum decline
rate m(B) = 1.00 0.05 mag. \emph{Gehrels Swift} UVOT
observations indicate that SN 2013gs shows unusually strong UV emission
(especially in the band) at around the maximum light (M
18.9 mag). The SN is characterized by relatively weak Fe~{\sc ii} {\sc iii}
absorptions at 5000{\AA} in the early spectra and a larger expansion
velocity ( 13,000 km s around the maximum light) than the
normal-velocity SNe Ia. We discuss the relation between the color and
some observables, including Si~{\sc ii} velocity, line strength of Si~{\sc ii}
6355, Fe~{\sc ii}/{\sc iii} lines and (B). Compared to
other fast-expanding SNe Ia, SN 2013gs exhibits Si and Fe absorption lines with
similar strength and bluer color. We briefly discussed the origin of
the observed UV dispersion of SNe Ia.Comment: 31 pages, 10 figures, accepted to publish in Ap
SN 2022vqz: A Peculiar SN 2002es-like Type Ia Supernova with Prominent Early Excess Emission
We present extensive photometric and spectroscopic observations of a peculiar
type Ia supernova (SN Ia) 2022vqz. It shares many similarities with the SN
2002es-like SNe Ia, such as low luminosity (i.e.,
mag) and moderate post-peak decline rate (i.e.,
mag). The nickel mass synthesized in the explosion is estimated as
from the bolometric light curve, which is obviously
lower than normal SNe Ia. SN 2022vqz is also characterized by a slow expanding
ejecta, with Si II velocities persisting around 7000 km s since 16 days
before the peak, which is unique among all known SNe Ia. While all these
properties imply a less energetic thermonuclear explosion that should leave
considerable amount of unburnt materials, however, absent signature of unburnt
carbon in the spectra of SN 2022vqz is puzzling. A prominent early peak is
clearly detected in the - and -band light curves of ATLAS and in the
-band data of ZTF within days after the explosion. Possible mechanisms for
the early peak are discussed, including sub-Chandrasekhar mass double
detonation model and interaction of SN ejecta with circumstellar material
(CSM). We found both models face some difficulties in replicating all aspects
of the observed data. As an alternative, we propose a hybrid CONe white dwarf
as progenitor of SN 2022vqz which can simultaneously reconcile the tension
between low ejecta velocity and absence of carbon. We further discuss the
diversity of 02es-like objects and possible origins of different scenarios.Comment: 24 pages, 12 figures, submitted to MNRA
A Multi-Wavelength View on the Rapidly-Evolving Supernova 2018ivc: An Analog of SN IIb 1993J but Powered Primarily by Circumstellar Interaction
SN 2018ivc is an unusual type II supernova (SN II). It is a variant of SNe
IIL, which might represent a transitional case between SNe IIP with a massive
H-rich envelope, and IIb with only a small amount of the H-rich envelope.
However, SN 2018ivc shows an optical light curve evolution more complicated
than canonical SNe IIL. In this paper, we present the results of prompt
follow-up observations of SN 2018ivc with the Atacama Large
Millimeter/submillimeter Array (ALMA). Its synchrotron emission is similar to
that of SN IIb 1993J, suggesting that it is intrinsically an SN IIb-like
explosion of a He star with a modest (~0.5 - 1 Msun) extended H-rich envelope.
Its radio, optical, and X-ray light curves are explained primarily by the
interaction between the SN ejecta and the circumstellar material (CSM); we thus
suggest that it is a rare example (and the first involving the `canonical' SN
IIb ejecta) for which the multi-wavelength emission is powered mainly by the
SN-CSM interaction. The inner CSM density, reflecting the progenitor activity
in the final decade, is comparable to that of SN IIb 2013cu that showed a flash
spectral feature. The outer CSM density, and therefore the mass-loss rate in
the final ~200 years, is larger than that of SN 1993J by a factor of ~5. We
suggest that SN 2018ivc represents a missing link between SNe IIP and IIb/Ib/Ic
in the binary evolution scenario.Comment: 31 pages, 14 figures, 3 tables. Accepted for publication in Ap
Low luminosity Type II supernovae - IV. SN 2020cxd and SN 2021aai, at the edges of the sub-luminous supernovae class
Photometric and spectroscopic data for two Low Luminosity Type IIP Supernovae (LL SNe IIP) 2020cxd and 2021aai are presented. SN 2020cxd was discovered 2 d after explosion at an absolute magnitude of Mr = -14.02 ± 0.21 mag, subsequently settling on a plateau which lasts for ∼120 d. Through the luminosity of the late light curve tail, we infer a synthesized 56Ni mass of (1.8 ± 0.5) × 10-3 M⊙. During the early evolutionary phases, optical spectra show a blue continuum (8000 K) with broad Balmer lines displaying a P Cygni profile, while at later phases, Ca ii, Fe ii, Sc ii, and Ba ii lines dominate the spectra. Hydrodynamical modelling of the observables yields 575 R⊙ for the progenitor star, with Mej = 7.5 M⊙ and 0.097 foe emitted during the explosion. This low-energy event originating from a low-mass progenitor star is compatible with both the explosion of a red supergiant (RSG) star and with an Electron Capture Supernova arising from a super asymptotic giant branch star. SN 2021aai reaches a maximum luminosity of Mr = -16.57 ± 0.23 mag (correcting for AV = 1.92 mag), at the end of its remarkably long plateau (∼140 d). The estimated 56Ni mass is (1.4 ± 0.5) × 10-2 M⊙. The expansion velocities are compatible with those of other LL SNe IIP (few 103 km s-1). The physical parameters obtained through hydrodynamical modelling are 575 R⊙, Mej = 15.5 M⊙, and E = 0.4 foe. SN 2021aai is therefore interpreted as the explosion of an RSG, with properties that bridge the class of LL SNe IIP with standard SN IIP events.GV acknowledges INAF for funding his PhD fellowship within the PhD School in Astronomy at the University of Padova. MLP acknowledges support from the plan ‘programma ricerca di ateneo UNICT 2020-22 linea 2” of the University of Catania. AR acknowledges support from ANID BECAS/DOCTORADO NACIONAL 21202412. NER acknowledges partial support from MIUR, PRIN 2017 (grant 20179ZF5KS), from the Spanish MICINN grant PID2019-108709GB-I00 and FEDER funds, and from the programme Unidad de Excelencia María de Maeztu CEX2020-001058-M. LG acknowledges financial support from the Spanish Ministerio de Ciencia e Innovación (MCIN), the Agencia Estatal de Investigación (AEI) 10.13039/501100011033, and the European Social Fund (ESF) ‘Investing in your future’ under the 2019 Ramón y Cajal programme RYC2019-027683-I and the PID2020-115253GA-I00 HOSTFLOWS project, from Centro Superior de Investigaciones Científicas (CSIC) under the PIE project 20215AT016, and the programme Unidad de Excelencia María de Maeztu CEX2020-001058-M. TMB acknowledges financial support from the Spanish Ministerio de Ciencia e Innovación (MCIN), the Agencia Estatal de Investigación (AEI) 10.13039/501100011033 under the PID2020-115253GA-I00 HOSTFLOWS project, and from Centro Superior de Investigaciones Científicas (CSIC) under the PIE project 20215AT016, and the programme Unidad de Excelencia María de Maeztu CEX2020-001058-M. Y-ZC is funded by China Postdoctoral Science Foundation (grant no. 2021M691821