10 research outputs found
A Parameter Study of Type II Supernova Light Curves Using 6 M_odot He Cores
Results of numerical calculations of Type II supernova light curves are
presented. The model progenitor stars have 6 cores and various
envelopes, originating from a numerically evolved 20 star. Five
parameters that affect the light curves are examined: the ejected mass, the
progenitor radius, the explosion energy, the Ni mass, and the extent of
Ni mixing. The following affects have been found: 1) the larger the
progenitor radius the brighter the early--time light curve, with little affect
on the late--time light curve, 2) the larger the envelope mass the fainter the
early light curve and the flatter the slope of the late light curve, 3) the
larger the explosion energy the brighter the early light curve and the steeper
the slope of the late light curve, 4) the larger the Ni mass the
brighter the overall light curve after 20 to 50 days, with no affect on the
early light curve, 5) the more extensive the Ni mixing the brighter the
early light curve and the steeper the late light curve. The primary parameters
affecting the light curve shape are the progenitor radius and the ejected mass.
The secondary parameters are the explosion energy, Ni mass and Ni
mixing. I find that while in principle the general shape and absolute magnitude
of a light curve indicate a unique set of parameters, in practice it is
difficult to avoid some ambiguity in the parameters. I find that the
nickel--powered diffusion wave and the recombination of helium produce a
prominent secondary peak in all our calculations. The feature is less prominent
when compositional mixing, both Ni mixing and mixing between the
hydrogen and helium layers, occurs. The model photospheric temperatures and
velocities are presented, for comparison to observation.Comment: 39 pages, 15 figures. Astrophysical Journal (Accepted, Dec. 20, 2004
Hydrogen-poor superluminous stellar explosions
Supernovae (SNe) are stellar explosions driven by gravitational or
thermonuclear energy, observed as electromagnetic radiation emitted over weeks
or more. In all known SNe, this radiation comes from internal energy deposited
in the outflowing ejecta by either radioactive decay of freshly-synthesized
elements (typically 56Ni), stored heat deposited by the explosion shock in the
envelope of a supergiant star, or interaction between the SN debris and
slowly-moving, hydrogen-rich circumstellar material. Here we report on a new
class of luminous SNe whose observed properties cannot be explained by any of
these known processes. These include four new SNe we have discovered, and two
previously unexplained events (SN 2005ap; SCP 06F6) that we can now identify as
members. These SNe are all ~10 times brighter than SNe Ia, do not show any
trace of hydrogen, emit significant ultra-violet (UV) flux for extended periods
of time, and have late-time decay rates which are inconsistent with
radioactivity. Our data require that the observed radiation is emitted by
hydrogen-free material distributed over a large radius (~10^15 cm) and
expanding at high velocities (>10^4 km s^-1). These long-lived, UV-luminous
events can be observed out to redshifts z>4 and offer an excellent opportunity
to study star formation in, and the interstellar medium of, primitive distant
galaxies.Comment: Accepted to Nature. Press embargoed until 2011 June 8, 18:00 U
Supernova 2013fc in a circumnuclear ring of a luminous infrared galaxy: the big brother of SN 1998S
We present photometric and spectroscopic observations of SN 2013fc, a bright type II supernova (SN) in a circumnuclear star-forming ring in the luminous infrared galaxy ESO 154-G010, observed as part of the Public ESO Spectroscopic Survey of Transient Objects. SN 2013fc is both photometrically and spectroscopically similar to the well-studied type IIn SN 1998S and to the bright type II-L SN 1979C. It exhibits an initial linear decline, followed by a short plateau phase and a tail phase with a decline too fast for 56Co decay with full γ-ray trapping. Initially, the spectrum was blue and featureless. Later on, a strong broad (∼8000 km s−1) H α emission profile became prominent. We apply a starlight stellar population model fit to the SN location (observed when the SN had faded) to estimate a high extinction of AV = 2.9 ± 0.2 mag and an age of
10 +3 −2
10−2+3
Myr for the underlying cluster. We compare the SN to SNe 1998S and 1979C and discuss its possible progenitor star considering the similarities to these events. With a peak brightness of B = −20.46 ± 0.21 mag, SN 2013fc is 0.9 mag brighter than SN 1998S and of comparable brightness to SN 1979C. We suggest that SN 2013fc was consistent with a massive red supergiant (RSG) progenitor. Recent mass loss probably due to a strong RSG wind created the circumstellar matter illuminated through its interaction with the SN ejecta. We also observe a near-infrared excess, possibly due to newly condensed dust
Astronomical Distance Determination in the Space Age: Secondary Distance Indicators
The formal division of the distance indicators into primary and secondary leads to difficulties in description of methods which can actually be used in two ways: with, and without the support of the other methods for scaling. Thus instead of concentrating on the scaling requirement we concentrate on all methods of distance determination to extragalactic sources which are designated, at least formally, to use for individual sources. Among those, the Supernovae Ia is clearly the leader due to its enormous success in determination of the expansion rate of the Universe. However, new methods are rapidly developing, and there is also a progress in more traditional methods. We give a general overview of the methods but we mostly concentrate on the most recent developments in each field, and future expectations. © 2018, The Author(s)
Disparity between Hα and Hβ in SN 2008 in: Inhomogeneous external layers of type IIP supernovae?
MASTER OT J004207.99+405501.1/M31LRN 2015 luminous red nova in M31: discovery, light curve, hydrodynamics and evolution
Concepts of disease and their relationship to health-seeking behaviour in Chuquisaca department, south Bolivia
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