25 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
SN~2012cg: Evidence for Interaction Between a Normal Type Ia Supernova and a Non-Degenerate Binary Companion
We report evidence for excess blue light from the Type Ia supernova SN 2012cg
at fifteen and sixteen days before maximum B-band brightness. The emission is
consistent with predictions for the impact of the supernova on a non-degenerate
binary companion. This is the first evidence for emission from a companion to a
SN Ia. Sixteen days before maximum light, the B-V color of SN 2012cg is 0.2 mag
bluer than for other normal SN~Ia. At later times, this supernova has a typical
SN Ia light curve, with extinction-corrected M_B = -19.62 +/- 0.02 mag and
Delta m_{15}(B) = 0.86 +/- 0.02. Our data set is extensive, with photometry in
7 filters from 5 independent sources. Early spectra also show the effects of
blue light, and high-velocity features are observed at early times. Near
maximum, the spectra are normal with a silicon velocity v_{Si} = -10,500$ km
s^{-1}. Comparing the early data with models by Kasen (2010) favors a
main-sequence companion of about 6 solar masses. It is possible that many other
SN Ia have main-sequence companions that have eluded detection because the
emission from the impact is fleeting and faint.Comment: accepted to Ap
Measuring nickel masses in Type Ia supernovae using cobalt emission in nebular phase spectra
The light curves of Type Ia supernovae (SNe Ia) are powered by the
radioactive decay of Ni to Co at early times, and the decay of
Co to Fe from ~60 days after explosion. We examine the evolution
of the [Co III] 5892 A emission complex during the nebular phase for SNe Ia
with multiple nebular spectra and show that the line flux follows the square of
the mass of Co as a function of time. This result indicates both
efficient local energy deposition from positrons produced in Co decay,
and long-term stability of the ionization state of the nebula. We compile 77
nebular spectra of 25 SN Ia from the literature and present 17 new nebular
spectra of 7 SNe Ia, including SN2014J. From these we measure the flux in the
[Co III] 5892 A line and remove its well-behaved time dependence to infer the
initial mass of Ni () produced in the explosion. We then examine
Ni yields for different SN Ia ejected masses ( - calculated
using the relation between light curve width and ejected mass) and find the
Ni masses of SNe Ia fall into two regimes: for narrow light curves (low
stretch s~0.7-0.9), is clustered near ~ 0.4 and
shows a shallow increase as increases from ~1-1.4; at high
stretch, clusters at the Chandrasekhar mass (1.4) while
spans a broad range from 0.6-1.2. This could constitute
evidence for two distinct SN Ia explosion mechanisms.Comment: 16 pages, 12 figures (main text), plus data tables in appendix.
Spectra released on WISeREP. Submitted to MNRAS, comments welcom
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 2012cg: Evidence for Interaction Between a Normal SN Ia and a Non-degenerate Binary Companion
We report evidence for excess blue light from the Type Ia supernova (Sn Ia) SN 2012cg at 15 and 16 days before maximum B-band brightness. The emission is consistent with predictions for the impact of the supernova on a non-degenerate binary companion. This is the first evidence for emission from a companion to a normal SN Ia. Sixteen days before maximum light, the color of SN 2012cg is 0.2 mag bluer than for other normal SN Ia. At later times, this supernova has a typical SN Ia light curve, with extinction-corrected mag and . Our data set is extensive, with photometry in seven filters from five independent sources. Early spectra also show the effects of blue light, and high-velocity features are observed at early times. Near maximum, the spectra are normal with a silicon velocity vSi = −10,500 km s−1. Comparing the early data with models by Kasen favors a main-sequence companion of about six solar masses. It is possible that many other SN Ia have main-sequence companions that have eluded detection because the emission from the impact is fleeting and faint
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