199 research outputs found
Optical and near infrared observations of SN 1998bu
Infrared and optical spectra of SN 1998bu at an age of one year after
explosion are presented. The data show evidence for the radioactive decay of
56Co to 56Fe, long assumed to be the powering source for the supernova light
curve past maximum light. The spectra provide direct evidence for at least 0.4
solar masses of iron being present in the ejecta of the supernova. The fits to
the data also show that the widths of the emission lines increase with time.
Photometric measurements in the H-band show that the supernova is not fading
during the observation period. This is consistent with theoretical
expectations.Comment: accepted A&A, 7 pages, 9 figure
SN~1991T: Reflections of Past Glory
We have obtained photometry and spectra of SN~1991T which extend more than
1000 days past maximum light, by far the longest a SN~Ia has been followed.
Although SN~1991T exhibited nearly normal photometric behavior in the first 400
days following maximum, by 600 days its decline had slowed, and by 950~days the
supernova brightness was consistent with a constant apparent magnitude of
. Spectra near maximum showed minor variations on the SN~Ia theme
which grew less conspicuous during the exponential decline. At 270 days the
nebular spectrum was composed of Fe and Co lines common to SNe~Ia. However, by
750 days past maximum light, these lines had shifted in wavelength, and were
superimposed on a strong blue continuum. The luminosity of SN~1991T at 950 days
is more than ~ergs~s with a rate of
decline of less than mags/100~days. We show that this emission is likely
to be light that was emitted by SN~1991T near maximum light which has reflected
from foreground dust, much like the light echos observed around SN~1987A.Comment: 15 pages (includes figures and tables) uuencoded compressed
postscript, CfA Preprint - To Appear in ApJ
Supernova search at intermediate z. I. Spectroscopic analysis
We study 8 supernovae discovered as part of the International Time Programme
(ITP) project ``Omega and Lambda from Supernovae and the Physics of Supernova
Explosions'' at the European Northern Observatory (ENO). The goal of the
project is to increase the sample of intermediate redshift (0.1<z<0.4) SNe Ia
for testing properties of SNe Ia along z and for enlarging the sample in the
Hubble diagram up to large z.Comment: 2 pages, 2 figures, 1 table, to appear in ``1604-2004: Supernovae as
Cosmological Lighthouses'', (extended text upon request
Scattering of scalar perturbations with cosmological constant in low-energy and high-energy regimes
We study the absorption and scattering of massless scalar waves propagating
in spherically symmetric spacetimes with dynamical cosmological constant both
in low-energy and high-energy zones. In the former low-energy regime, we solve
analytically the Regge-Wheeler wave equation and obtain an analytic absorption
probability expression which varies with , where is the
central mass and is cosmological constant. The low-energy absorption
probability, which is in the range of , increases monotonically
with increase in . In the latter high-energy regime, the scalar
particles adopt their geometric optics limit value. The trajectory equation
with effective potential emerges and the analytic high-energy greybody factor,
which is relevant with the area of classically accessible regime, also
increases monotonically with increase in , as long is less
than or of the order of . In this high-energy case, the null cosmological
constant result reduces to the Schwarzschild value .Comment: 12 pages, 6 figure
Late Light Curves of Normally-Luminous Type Ia Supernovae
The use of Type Ia supernovae as cosmological tools has reinforced the need
to better understand these objects and their light curves. The light curves of
Type Ia supernovae are powered by the nuclear decay of . The late time light curves can provide insight into the behavior of
the decay products and their effect of the shape of the curves. We present the
optical light curves of six "normal" Type Ia supernovae, obtained at late times
with template image subtraction, and the fits of these light curves to
supernova energy deposition models.Comment: Proceedings of Astronomy with Radioactivities V Conferenc
P 388 Diagnostic value of polymerase chain reaction of aqueous and vitreous humor for infectious uveitis in AIDS patients
Supernova search at intermediate z. II. Host galaxy morphology
We discuss the host galaxy morphology of the 8 SNe discovered as a part of
the International Time Programme (ITP) project ``Omega and Lambda from
Supernovae, and the Physics of Supernovae Explosions'' at the European Northern
Observatory (ENO). Identification of the SN host galaxy types was done
exploiting both imaging and spectroscopy. A peculiar SNIa at z= 0.033 is found
in a spiral galaxy, as most other SNeIa with z between 0.1 and 0.4. A complete
account of these studies will be given elsewhere.Comment: 2 pages, 2 figures, 1 table, to appear in ``1604-2004: Supernovae as
Cosmological Lighthouses'', (extended text upon request
Supernova search at intermediate z. III. Expansion velocities of the ejecta
We discuss the expansion velocities of different elements in the ejecta of
the intermediate-z SNe Ia discovered as a part of the International Time
Programme (ITP) project ``Omega and Lambda from Supernovae and the Physics of
Supernova Explosions'' at the European Northern Observatory (ENO). The
expansion velocities measured for each normal SNIa are found to be within the
typical velocity dispersion for their epoch. Meanwhile, the subluminous SN
2002lk SiII expansion velocity is significantly higher than that of SN 1991bg
shortly after maximum. The observed phase was younger in SN2002lk than in the
local subluminous SNIa SN1991bg.Comment: 2 pages, 1 figure, 1 table, to appear in ``1604-2004: Supernovae as
Cosmological Lighthouses'', (extended text upon request
Spectra of supernovae in the nebular phase
When supernovae enter the nebular phase after a few months, they reveal
spectral fingerprints of their deep interiors, glowing by radioactivity
produced in the explosion. We are given a unique opportunity to see what an
exploded star looks like inside. The line profiles and luminosities encode
information about physical conditions, explosive and hydrostatic
nucleosynthesis, and ejecta morphology, which link to the progenitor properties
and the explosion mechanism. Here, the fundamental properties of spectral
formation of supernovae in the nebular phase are reviewed. The formalism
between ejecta morphology and line profile shapes is derived, including effects
of scattering and absorption. Line luminosity expressions are derived in
various physical limits, with examples of applications from the literature. The
physical processes at work in the supernova ejecta, including gamma-ray
deposition, non-thermal electron degradation, ionization and excitation, and
radiative transfer are described and linked to the computation and application
of advanced spectral models. Some of the results derived so far from
nebular-phase supernova analysis are discussed.Comment: Book chapter for 'Handbook of Supernovae,' edited by Alsabti and
Murdin, Springer. 51 pages, 14 figure
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