118 research outputs found
A two-component model for fitting light-curves of core-collapse supernovae
We present an improved version of a light curve model, which is able to
estimate the physical properties of different types of core-collapse supernovae
having double-peaked light curves, in a quick and efficient way. The model is
based on a two-component configuration consisting of a dense, inner region and
an extended, low-mass envelope. Using this configuration, we estimate the
initial parameters of the progenitor via fitting the shape of the
quasi-bolometric light curves of 10 SNe, including Type IIP and IIb events,
with model light curves. In each case we compare the fitting results with
available hydrodynamic calculations, and also match the derived expansion
velocities with the observed ones. Furthermore, we also compare our
calculations with hydrodynamic models derived by the SNEC code, and examine the
uncertainties of the estimated physical parameters caused by the assumption of
constant opacity and the inaccurate knowledge of the moment of explosion
Photospheric Velocity Gradients and Ejecta Masses of Hydrogen-poor Superluminous Supernovae -- Proxies for Distinguishing between Fast and Slow Events
We present a study of 28 Type I superluminous supernovae (SLSNe) in the
context of the ejecta mass and photospheric velocity. We combine photometry and
spectroscopy to infer ejecta masses via the formalism of radiation diffusion
equations. We show an improved method to determine the photospheric velocity by
combining spectrum modeling and cross correlation techniques. We find that Type
I SLSNe can be divided into two groups by their pre-maximum spectra. Members of
the first group have the W-shaped absorption trough in their pre-maximum
spectrum, usually identified as due to O II. This feature is absent in the
spectra of supernovae in the second group, whose spectra are similar to
SN~2015bn. We confirm that the pre- or near-maximum photospheric velocities
correlate with the velocity gradients: faster evolving SLSNe have larger
photosheric velocities around maximum. We classify the studied SLSNe into the
Fast or the Slow evolving group by their estimated photosheric velocities, and
find that all those objects that resemble to SN~2015bn belong to the Slow
evolving class, while SLSNe showing the W-like absorption are represented in
both Fast and Slow evolving groups. We estimate the ejecta masses of all
objects in our sample, and obtain values in the range of 2.9 (0.8) - 208
(61) , with a mean of . We conclude that
Slow evolving SLSNe tend to have higher ejecta masses compared to the Fast
ones. Our ejecta mass calculations suggests that SLSNe are caused by energetic
explosions of very massive stars, irrespectively of the powering mechanism of
the light curve.Comment: 21 pages, Submitted to Ap
Fitting optical light curves of Tidal Disruption Events with TiDE
A Tidal Disruption Event (TDE) occurs when a supermassive black hole tidally
disrupt a nearby passing star. The fallback accretion rate of the disrupted
star may exceed the Eddington limit, which induces a supersonic outflow and a
burst of luminosity, similar to an explosive event. Thus, TDEs can be detected
as very luminous transients, and the number of observations for such events is
increasing rapidly. In this paper we fit 20 TDE light curves with TiDE, a new
public, object-oriented code designed to model optical TDE light curves. We
compare our results with those obtained by the popular MOSFiT and the recently
developed TDEmass codes, and discuss the possible sources of differences.Comment: 14 pages, 4 figures, 4 tables, accepted in PAS
Comparison of different Tidal Disruption Event light curve models with TiDE, a new modular open source code
A tidal disruption event (TDE) occurs when a supermassive black hole disrupts
a nearby passing star by tidal forces. The subsequent fallback accretion of the
stellar debris results in a luminous transient outburst. Modeling the light
curve of such an event may reveal important information, for example the mass
of the central black hole. This paper presents the TiDE software based on
semi-analytic modeling of TDEs. This object-oriented code contains different
models for the accretion rate and the fallback timescale . We
compare the resulting accretion rates to each other and with hydrodynamically
simulated ones and find convincing agreement for full disruptions. We present a
set of parameters estimated with TiDE for the well-observed TDE candidate
AT2019qiz, and compare our results with those given by the MOSFiT code. Most of
the parameters are in reasonable agreement, except for the mass and the
radiative efficiency of the black hole, both of which depend heavily on the
adopted fallback accretion rate.Comment: 17 pages, 12 figures, 2 tables, accepted in PAS
Double neutron star formation via consecutive type II supernova explosions
Since the discovery of the first double neutron star (DNS) system, the number
of these exotic binaries has reached fifteen. Here we investigate a channel of
DNS formation in binary systems with components above the mass limit of type II
supernova explosion (SN II), i.e. 8 MSun. We apply a spherically symmetric
homologous envelope expansion model to account for mass loss, and follow the
dynamical evolution of the system numerically with a high-precision integrator.
The first SN occurs in a binary system whose orbital parameters are
pre-defined, then, the homologous expansion model is applied again in the newly
formed system. Analysing 1 658 880 models we find that DNS formation via
subsequent SN II explosions requires a fine-tuning of the initial parameters.
Our model can explain DNS systems with a separation greater than 2.95 au. The
eccentricity of the DNS systems spans a wide range thanks to the orbital
circularisation effect due to the second SN II explosion. The eccentricity of
the DNS is sensitive to the initial eccentricity of the binary progenitor and
the orbital position of the system preceding the second explosion. In agreement
with the majority of the observations of DNS systems, we find the system
centre-of mass velocities to be less than 60 km/s. Neutron stars that become
unbound in either explosion gain a peculiar velocity in the range of 0.02 - 240
km/s. In our model, the formation of tight DNS systems requires a
post-explosion orbit-shrinking mechanism, possibly driven by the ejected
envelopes.Comment: Accepted for publication in MNRA
Initial 56Ni Masses in Type Ia Supernovae
We infer initial masses of the synthesized radioactive nickel-56 in a sample
of recent Type Ia supernovae applying a new formalism introduced recently by
Khatami & Kasen (2019). It is shown that the nickel masses we derive do not
differ significantly from previous estimates based on the traditional
Arnett-model. We derive the parameter for our sample SNe and show that
these are consistent with the fiducial value of given by Khatami &
Kasen (2019) from SN Ia hydrodynamical simulations.Comment: 7 pages, 6 figures, published in PAS
Detection and Classification of Supernovae Beyond Z ∼ 2 Redshift with the James Webb Space Telescope
Future time-domain surveys for transient events in the near- and midinfrared bands will significantly extend our understanding about the physics of the early universe. In this paper we study the implications of a deep (˜27 mag), long-term (˜3 yr), observationally inexpensive survey with the James Webb Space Telescope (JWST) within its Continuous Viewing Zone, aimed at discovering luminous supernovae beyond z ˜ 2 redshift. We explore the possibilities for detecting superluminous supernovae (SLSNe) as well as SNe Ia at such high redshifts and estimate their expected numbers within a relatively small (˜0.1 deg2) survey area. It is found that we can expect ˜10 new SLSNe and ˜50 SNe Ia discovered in the 1 < z < 4 redshift range. We show that it is possible to get relatively accurate (σ z ≲ 0.25) photometric redshifts for SNe Ia by fitting their Spectral Energy Distributions, redshifted into the observed near-IR bands, with SN templates. We propose that SNe Ia occupy a relatively narrow range on the JWST F220W-F440W versus F150W-F356W color-color diagram between ±7 rest-frame days around maximum light, which could be a useful classification tool for such types of transients. We also study the possibility of extending the Hubble-diagram of SNe Ia beyond redshift 2 up to z ˜ 4. Such high-z SNe Ia may provide new observational constraints for their progenitor scenario
Detecting Pair-instability Supernovae at z ≲ 5 with the James Webb Space Telescope
Pair-instability supernovae (PISNe) are the ultimate cosmic lighthouses, capable of being observed at z ≳ 25 and revealing the properties of primordial stars at cosmic dawn. But it is now understood that the spectra and light curves of these events evolved with redshift as the universe became polluted with heavy elements because chemically enriched stars in this mass range typically lose most of their hydrogen envelopes and explode as bare helium cores. The light curves of such transients can be considerably dimmer in the near-infrared today than those of primordial PISNe of equal energy and progenitor mass. Here, we calculate detection rates for PISNe whose progenitors lost their outer layers to either line-driven winds or rotation at z ≲ 10, their detection limit in redshift for the James Webb Space Telescope (JWST). We find that JWST may be able to detect only Population II (metal-poor) PISNe over the redshift range of z ≲ 4, but not their Population III (metal-free) counterparts
The Purport of Space Telescopes in Supernova Research
The violent stellar explosions known as supernovae have received especially strong attention in both the research community and the general public recently. With the advent of space telescopes, the study of these extraordinary events has switched gears and it has become one of the leading fields in modern astrophysics. In this paper, we review some of the recent developments, focusing mainly on studies related to space-based observations
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