20 research outputs found
Environmental Dependence of Type Ia Supernovae in Low-Redshift Galaxy Clusters
We present an analysis of 102 type Ia supernovae (SNe Ia) in nearby (z <
0.1), x-ray selected galaxy clusters. This is the largest such sample to date
and is based on archival data primarily from ZTF and ATLAS. We divide our SNe
Ia into an inner cluster sample projected within of the cluster
center and an outer cluster sample projected between and
. We compare these to field samples of SNe Ia at similar redshifts
in both quiescent and star-forming host galaxies. Based on SALT3 fits to the
light curves, we find that the inner cluster SNe Ia have a higher fraction of
fast-evolving objects (SALT3 ) than the outer cluster or field
quiescent samples. This implies an intrinsically different population of SNe Ia
occurs in inner cluster environments, beyond known correlations based on host
galaxy alone. Our cluster samples show a strongly bimodal distribution
with a fast-evolving component that dominates the inner cluster objects
( 75%) but is just a small fraction of SNe Ia in field star-forming
galaxies ( 10%). We do not see strong evidence for variations in the
color (SALT3 ) distributions among the samples and find only minor
differences in SN Ia standardization parameters and Hubble residuals. We
suggest that the age of the stellar population drives the observed
distributions, with the oldest populations nearly exclusively producing
fast-evolving SNe Ia.Comment: Submitted to AAS journal
Over 500 Days in the Life of the Photosphere of the Type Iax Supernova SN 2014dt
Type Iax supernovae (SNe Iax) are the largest known class of peculiar white dwarf SNe, distinct from normal Type Ia supernovae (SNe Ia). The unique properties of SNe Iax, especially their strong photospheric lines out to extremely late times, allow us to model their optical spectra and derive the physical parameters of the long-lasting photosphere. We present an extensive spectral timeseries, including 21 new spectra, of SN Iax 2014dt from +11 to +562 days after maximum light. We are able to reproduce the entire timeseries with a self-consistent, nearly unaltered deflagration explosion model from Fink et al. using TARDIS, an open source radiative-transfer code. We find that the photospheric velocity of SN 2014dt slows its evolution between +64 and +148 days, which closely overlaps the phase when we see SN 2014dt diverge from the normal spectral evolution of SNe Ia (+90 to +150 days). The photospheric velocity at these epochs, ~400-1000 km s-1, may demarcate a boundary within the ejecta below which the physics of SNe Iax and normal SNe Ia differ. Our results suggest that SN 2014dt is consistent with a weak deflagration explosion model that leaves behind a bound remnant and drives an optically thick, quasi-steady-state wind creating the photospheric lines at late times. The data also suggest that this wind may weaken at epochs past +450 days, perhaps indicating a radioactive power source that has decayed away
Ultraviolet Spectroscopy and TARDIS Models of the Broad-lined Type-Ic Supernova 2014ad
Few published ultraviolet (UV) spectra exist for stripped-envelope
supernovae, and none to date for broad-lined Type Ic supernovae (SN Ic-bl).
These objects have extremely high ejecta velocities and are the only supernova
type directly linked to gamma-ray bursts (GRBs). Here we present two epochs of
HST/STIS spectra of the SN Ic-bl 2014ad, the first UV spectra for this class.
We supplement this with 26 new epochs of ground-based optical spectra,
augmenting a rich spectral time series. The UV spectra do not show strong
features, likely due to high opacity, and are consistent with broadened
versions of other SN Ic spectra observed in the UV. We measure Fe II 5169
Angstrom velocities and show that SN 2014ad has even higher ejecta velocities
than most SNe Ic both with and without observed GRBs. We construct models of
the SN 2014ad UV+optical spectra using TARDIS, a 1D Monte-Carlo
radiative-transfer spectral synthesis code. The models fit the data well at
multiple epochs in the optical but underestimate the flux in the UV. We find
that high densities at high velocities are needed to reproduce the spectra,
with 3 M of material at 22,000 km s, assuming
spherical symmetry. Our nebular line fits suggest a steep density profile at
low velocities. Together, these results imply a higher total ejecta mass than
estimated from previous light curve analysis and expected from theory. This may
be reconciled by a flattening of the density profile at low velocity and extra
emission near the center of the ejecta.Comment: 25 pages, 14 figures, submitted to AAS Journal
Over 500 Days in the Life of the Photosphere of the Type Iax Supernova SN 2014dt
Type Iax supernovae (SN Iax) are the largest known class of peculiar white
dwarf supernovae, distinct from normal Type Ia supernovae (SN Ia). The unique
properties of SN Iax, especially their strong photospheric lines out to
extremely late times, allow us to model their optical spectra and derive
physical parameters for the long-lasting photosphere. We present an extensive
spectral timeseries, including 21 new spectra, of SN Iax 2014dt from +11 to
+562 days after maximum light. We are able to reproduce the entire timeseries
with a self-consistent, nearly unaltered deflagration explosion model from Fink
et al. (2014) using TARDIS, an open-source radiative transfer code (Kerzendorf
& Sim 2014; Kerzendorf et al. 2023). We find that the photospheric velocity of
SN 2014dt slows its evolution between +64 and +148 days, which closely overlaps
the phase when we see SN 2014dt diverge from the normal spectral evolution of
SN Ia (+90 to +150 days). The photospheric velocity at these epochs,
~4001000 km s, may demarcate a boundary within the ejecta below which
the physics of SN Iax and normal SN Ia differ. Our results suggest that SN
2014dt is consistent with a weak deflagration explosion model that leaves
behind a bound remnant and drives an optically thick, quasi-steady-state wind
creating the photospheric lines at late times. The data also suggest that this
wind may weaken at epochs past +450 days, perhaps indicating a radioactive
power source that has decayed away.Comment: Accepted to ApJ, 22 pages, 8 figures, 3 table
SN 2019muj-a well-observed Type Iax supernova that bridges the luminosity gap of the class
We present early-time (t < +50 d) observations of SN 2019muj (=ASASSN-19tr), one of the best-observed members of the peculiar SN Iax class. Ultraviolet and optical photometric and optical and near-infrared spectroscopic follow-up started from similar to 5 d before maximum light [t(max)(B) on 58707.8 MJD] and covers the photospheric phase. The early observations allow us to estimate the physical properties of the ejecta and characterize the possible divergence from a uniform chemical abundance structure. The estimated bolometric light-curve peaks at 1.05 x 10(42) erg s(-1) and indicates that only 0.031 M-circle dot of Ni-56 was produced, making SN 2019muj a moderate luminosity object in the Iax class with peak absolute magnitude of M-V = -16.4 mag. The estimated date of explosion is t(0) = 58698.2 MJD and implies a short rise time of t(rise) = 9.6 d in B band. We fit of the spectroscopic data by synthetic spectra, calculated via the radiative transfer code TARDIS. Adopting the partially stratified abundance template based on brighter SNe Iax provides a good match with SN 2019muj. However, without earlier spectra, the need for stratification cannot be stated in most of the elements, except carbon, which is allowed to appear in the outer layers only. SN 2019muj provides a unique opportunity to link extremely low-luminosity SNe Iax to well-studied, brighter SNe Iax
SN 2021csp -- the explosion of a stripped envelope star within a H and He-poor circumstellar medium
We present observations of SN 2021csp, a unique supernova (SN) which displays evidence for interaction with H- and He- poor circumstellar material (CSM) at early times. Using high-cadence spectroscopy taken over the first week after explosion, we show that the spectra of SN 2021csp are dominated by C III lines with a velocity of 1800 km s. We associate this emission with CSM lost by the progenitor prior to explosion. Subsequently, the SN displays narrow He lines before metamorphosing into a broad-lined Type Ic SN. We model the bolometric light curve of SN 2021csp, and show that it is consistent with the energetic ( erg) explosion of a stripped star, producing 0.4 M of 56Ni within a 1 M shell of CSM extending out to 400 R...