2,894 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
A JWST Near- and Mid-Infrared Nebular Spectrum of the Type Ia Supernova 2021aefx
We present JWST near- and mid-infrared spectroscopic observations of the nearby normal Type Ia supernova SN 2021aefx in the nebular phase at days past maximum light. Our Near Infrared Spectrograph (NIRSpec) and Mid Infrared Instrument (MIRI) observations, combined with ground-based optical data from the South African Large Telescope (SALT), constitute the first complete optical NIR MIR nebular SN Ia spectrum covering 0.314 m. This spectrum unveils the previously unobserved 2.55 m region, revealing strong nebular iron and stable nickel emission, indicative of high-density burning that can constrain the progenitor mass. The data show a significant improvement in sensitivity and resolution compared to previous Spitzer MIR data. We identify numerous NIR and MIR nebular emission lines from iron-group elements and as well as lines from the intermediate-mass element argon. The argon lines extend to higher velocities than the iron-group elements, suggesting stratified ejecta that are a hallmark of delayed-detonation or double-detonation SN Ia models. We present fits to simple geometric line profiles to features beyond 1.2 m and find that most lines are consistent with Gaussian or spherical emission distributions, while the [Ar III] 8.99 m line has a distinctively flat-topped profile indicating a thick spherical shell of emission. Using our line profile fits, we investigate the emissivity structure of SN 2021aefx and measure kinematic properties. Continued observations of SN 2021aefx and other SNe Ia with JWST will be transformative to the study of SN Ia composition, ionization structure, density, and temperature, and will provide important constraints on SN Ia progenitor and explosion models
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 2019ewu: A Peculiar Supernova with Early Strong Carbon and Weak Oxygen Features from a New Sample of Young SN Ic Spectra
With the advent of high cadence, all-sky automated surveys, supernovae (SNe)
are now discovered closer than ever to their dates of explosion. However, young
pre-maximum light follow-up spectra of Type Ic supernovae (SNe Ic), probably
arising from the most stripped massive stars, remain rare despite their
importance. In this paper we present a set of 49 optical spectra observed with
the Las Cumbres Observatory through the Global Supernova Project for 6 SNe Ic,
including a total of 17 pre-maximum spectra, of which 8 are observed more than
a week before V-band maximum light. This dataset increases the total number of
publicly available pre-maximum light SN Ic spectra by 25% and we provide
publicly available SNID templates that will significantly aid in the fast
identification of young SNe Ic in the future. We present detailed analysis of
these spectra, including Fe II 5169 velocity measurements, O I 7774 line
strengths, and continuum shapes. We compare our results to published samples of
stripped supernovae in the literature and find one SN in our sample that stands
out. SN 2019ewu has a unique combination of features for a SN Ic: an extremely
blue continuum, high absorption velocities, a P-cygni shaped feature almost 2
weeks before maximum light that TARDIS radiative transfer modeling attributes
to C II rather than H, and weak or non-existent O I 7774 absorption
feature until maximum light.Comment: Submitted to the Astrophysical Journal. 15 pages, 6 figure
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
Serendipitous Nebular-phase JWST Imaging of SN Ia 2021aefx: Testing the Confinement of 56-Co Decay Energy
We present new 0.3-21 micron photometry of SN 2021aefx in the spiral galaxy
NGC 1566 at +357 days after B-band maximum, including the first detection of
any SN Ia at >15 micron. These observations follow earlier JWST observations of
SN 2021aefx at +255 days after the time of maximum brightness, allowing us to
probe the temporal evolution of the emission properties. We measure the
fraction of flux emerging at different wavelengths and its temporal evolution.
Additionally, the integrated 0.3-14 micron decay rate of mag/100 days is higher than the decline rate from the
radioactive decay of Co of mag/100 days. The most plausible
explanation for this discrepancy is that flux is shifting to >14 micron, and
future JWST observations of SNe Ia will be able to directly test this
hypothesis. However, models predicting non-radiative energy loss cannot be
excluded with the present data.Comment: Accepted for publication in ApJL; 11 pages, 4 figures, 2 tables in
two-column AASTEX63 forma
Constraints on the χ_(c1) versus χ_(c2) polarizations in proton-proton collisions at √s = 8 TeV
The polarizations of promptly produced χ_(c1) and χ_(c2) mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at √s=8 TeV. The χ_c states are reconstructed via their radiative decays χ_c → J/ψγ, with the photons being measured through conversions to e⁺e⁻, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χ_(c2) to χ_(c1) yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ → μ⁺μ⁻ decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum
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