8 research outputs found
SN 2018gj: A Short-plateau Type II Supernova with Persistent Blue-shifted H-alpha Emission
We present an extensive, panchromatic photometric (UV, Optical, and NIR) and
low-resolution optical spectroscopic coverage of a Type IIP supernova SN 2018gj
that occurred on the outskirts of the host galaxy NGC 6217. From the V-band
light curve, we estimate the plateau length to be ~ 70 +- 2 d, placing it among
the very few well-sampled short plateau supernovae (SNe). With V-band peak
absolute magnitude Mv < -17.0 +- 0.1 mag, it falls in the middle of the
luminosity distribution of the Type II SNe. The colour evolution is typical to
other Type II SNe except for an early elbow-like feature in the evolution of
V-R colour owing to its early transition from the plateau to the nebular phase.
Using the expanding photospheric method, we present an independent estimate of
the distance to SN 2018gj. We report the spectral evolution to be typical of a
Type II SNe. However, we see a persistent blue shift in emission lines until
the late nebular phase, not ordinarily observed in Type II SNe. The amount of
radioactive nickel (56Ni) yield in the explosion was estimated to be 0.026 +-
0.007 Msol. We infer from semi-analytical modelling, nebular spectrum, and 1-D
hydrodynamical modelling that the probable progenitor was a red supergiant with
a zero-age-main-sequence mass < 13 Msol. In the simulated hydrodynamical model
light curves, reproducing the early optical bolometric light curve required an
additional radiation source, which could be the interaction with the proximal
circumstellar matter (CSM).Comment: Accepted for publication in ApJ (31 pages, 23 figures and 7 tables
Far-Ultraviolet to Near-Infrared Observations of SN 2023ixf: A high energy explosion engulfed in complex circumstellar material
We present early-phase panchromatic photometric and spectroscopic coverage
spanning far-ultraviolet (FUV) to the near-infrared (NIR) regime of the nearest
hydrogen-rich core-collapse supernova in the last 25 years, SN~2023ixf. We
observe early `flash' features in the optical spectra due to a confined dense
circumstellar material (CSM). We observe high-ionization absorption lines Fe
II, Mg II in the ultraviolet spectra from very early on. We also observe a
multi-peaked emission profile of H-alpha in the spectrum beginning ~16 d, which
indicates ongoing interaction of the SN ejecta with a pre-existing shell-shaped
CSM having an inner radius of ~ 75 AU and an outer radius of ~140 AU. The
shell-shaped CSM is likely a result of enhanced mass loss ~ 35 - 65 years
before the explosion assuming a standard Red-Supergiant wind. Spectral modeling
of the FUV, NUV, and the optical spectra during 9-12 d, using the radiative
transfer spectrum synthesis code TARDIS indicates that the supernova ejecta
could be well represented by a progenitor elemental composition greater than
solar abundances. Based on early light curve models of Type II SNe, we infer
that the nearby dense CSM confined to ~7+-3e14~cm(~45 AU) is a result of
enhanced mass loss ~1e-(3.0+-0.5) Msol/yr two decades before the explosion.Comment: Submitted to AAS Journals, 4 figures, 2 table
SN 2020jfo: A short plateau Type II supernova from a low mass progenitor
We present spectroscopic and photometric observations of the Type IIP
supernova, SN 2020jfo, in ultraviolet and optical wavelengths. SN 2020jfo
occurred in the spiral galaxy M61 (NGC 4303), with eight observed supernovae in
the past 100 years. SN 2020jfo exhibited a short plateau lasting < 65 d, and
achieved a maximum brightness in V-band of = -17.4 0.4 mag at about
8.0 0.5 d since explosion. From the bolometric light curve, we have
estimated the mass of Ni synthesised in the explosion to be 0.033
0.006 . The observed spectral features are typical for a type IIP
supernova except for shallow H absorption throughout the evolution and
the presence of stable Ni feature at 7378 \r{A}, in the nebular phase.
Using hydrodynamical modelling in the MESA + STELLA framework, an ejecta mass
of ~ 5 is estimated. Models also indicate SN 2020jfo could be the
result of a Red Super Giant progenitor with ~ 12 .
Bolometric light curve modelling revealed the presence of a secondary radiation
source for initial ~ 20 d, which has been attributed to interaction with a
circumstellar material of mass ~ 0.2 , which most likely was ejected
due to enhanced mass loss about 20 years prior to the supernova explosion.Comment: Accepted for publication in The Astrophysical Journal. 25 pages, 22
figures, and 7 table
Bridging between Type IIb and Ib Supernovae: SN IIb 2022crv with a Very Thin Hydrogen Envelope
We present optical, near-infrared, and radio observations of supernova (SN) SN IIb 2022crv. We show that it retained a very thin H envelope and transitioned from an SN IIb to an SN Ib; prominent H α seen in the pre-maximum phase diminishes toward the post-maximum phase, while He i lines show increasing strength. SYNAPPS modeling of the early spectra of SN 2022crv suggests that the absorption feature at 6200 Å is explained by a substantial contribution of H α together with Si ii , as is also supported by the velocity evolution of H α . The light-curve evolution is consistent with the canonical stripped-envelope SN subclass but among the slowest. The light curve lacks the initial cooling phase and shows a bright main peak (peak M _V = −17.82 ± 0.17 mag), mostly driven by radioactive decay of ^56 Ni. The light-curve analysis suggests a thin outer H envelope ( M _env ∼ 0.05 M _⊙ ) and a compact progenitor ( R _env ∼ 3 R _⊙ ). An interaction-powered synchrotron self-absorption model can reproduce the radio light curves with a mean shock velocity of 0.1 c . The mass-loss rate is estimated to be in the range of (1.9−2.8) × 10 ^−5 M _⊙ yr ^−1 for an assumed wind velocity of 1000 km s ^−1 , which is on the high end in comparison with other compact SNe IIb/Ib. SN 2022crv fills a previously unoccupied parameter space of a very compact progenitor, representing a beautiful continuity between the compact and extended progenitor scenario of SNe IIb/Ib
SN 2020udy: a new piece of the homogeneous bright group in the diverse Iax subclass
We present optical observations and analysis of the bright type Iax supernova SN 2020udy hosted by NGC 0812. The evolution of the light curve of SN 2020udy is similar to that of other bright type Iax SNe. Analytical modeling of the quasi-bolometric light curves of SN 2020udy suggests that 0.08 ± 0.01 M⊙ of 56Ni would have been synthesized during the explosion. The spectral features of SN 2020udy are similar to those of the bright members of type Iax class, showing a weak Si ii line. The late-time spectral sequence is mostly dominated by iron group elements with broad emission lines. Abundance tomography modeling of the spectral time series of SN 2020udy using TARDIS indicates stratification in the outer ejecta; however, to confirm this, spectral modeling at a very early phase is required. After maximum light, uniform mixing of chemical elements is sufficient to explain the spectral evolution. Unlike in the case of normal type Ia SNe, the photospheric approximation remains robust until +100 days, requiring an additional continuum source. Overall, the observational features of SN 2020udy are consistent with the deflagration of a carbon–oxygen white dwarf.<br/
Observational Properties of a Bright Type lax SN 2018cni and a Faint Type Iax SN 2020kyg
We present the optical photometric and spectroscopic analysis of two Type Iax supernovae (SNe), 2018cni and 2020kyg. SN 2018cni is a bright Type Iax SN ( M _V _,peak = −17.81 ± 0.21 mag), whereas SN 2020kyg ( M _V _,peak = −14.52 ± 0.21 mag) is a faint one. We derive ^56 Ni mass of 0.07 and 0.002 M _⊙ and ejecta mass of 0.48 and 0.14 M _⊙ for SNe 2018cni and 2020kyg, respectively. A combined study of the bright and faint Type Iax SNe in R / r -band reveals that the brighter objects tend to have a longer rise time. However, the correlation between the peak luminosity and decline rate shows that bright and faint Type Iax SNe exhibit distinct behavior. Comparison with standard deflagration models suggests that SN 2018cni is consistent with the deflagration of a CO white dwarf, whereas the properties of SN 2020kyg can be better explained by the deflagration of a hybrid CONe white dwarf. The spectral features of both the SNe point to the presence of similar chemical species but with different mass fractions. Our spectral modeling indicates stratification at the outer layers and mixed inner ejecta for both of the SNe
Characterizing the Ordinary Broad-lined Type Ic SN 2023pel from the Energetic GRB 230812B
International audienceWe report observations of the optical counterpart of the long gamma-ray burst (LGRB) GRB 230812B, and its associated supernova (SN) SN 2023pel. The proximity () and high energy ( erg) make it an important event to study as a probe of the connection between massive star core-collapse and relativistic jet formation. With a phenomenological power-law model for the optical afterglow, we find a late-time flattening consistent with the presence of an associated SN. SN 2023pel has an absolute peak -band magnitude of mag (about as bright as SN 1998bw) and evolves on quicker timescales. Using a radioactive heating model, we derive a nickel mass powering the SN of , and a peak bolometric luminosity of . We confirm SN 2023pel's classification as a broad-lined Type Ic SN with a spectrum taken 15.5 days after its peak in band, and derive a photospheric expansion velocity of at that phase. Extrapolating this velocity to the time of maximum light, we derive the ejecta mass and kinetic energy . We find that GRB 230812B/SN 2023pel has SN properties that are mostly consistent with the overall GRB-SN population. The lack of correlations found in the GRB-SN population between SN brightness and for their associated GRBs, across a broad range of 7 orders of magnitude, provides further evidence that the central engine powering the relativistic ejecta is not coupled to the SN powering mechanism in GRB-SN systems