3,333 research outputs found
On the Spectrum and Nature of the Peculiar Type Ia Supernova 1991T
A parameterized supernova synthetic-spectrum code is used to study line
identifications in the photospheric-phase spectra of the peculiar Type Ia SN
1991T, and to extract some constraints on the composition structure of the
ejected matter. The inferred composition structure is not like that of any
hydrodynamical model for Type Ia supernovae. Evidence that SN 1991T was
overluminous for an SN Ia is presented, and it is suggested that this peculiar
event probably was a substantially super-Chandrasekhar explosion that resulted
from the merger of two white dwarfs.Comment: 1 text, 7 figures, submitted to MNRA
SN 2005hj: Evidence for Two Classes of Normal-Bright SNe Ia and Implications for Cosmology
HET Optical spectra covering the evolution from about 6 days before to about
5 weeks after maximum light and the ROTSE-IIIb unfiltered light curve of the
"Branch-normal" Type Ia Supernova SN 2005hj are presented. The host galaxy
shows HII region lines at redshift of z=0.0574, which puts the peak unfiltered
absolute magnitude at a somewhat over-luminous -19.6. The spectra show weak and
narrow SiII lines, and for a period of at least 10 days beginning around
maximum light these profiles do not change in width or depth and they indicate
a constant expansion velocity of ~10,600 km/s. We analyzed the observations
based on detailed radiation dynamical models in the literature. Whereas delayed
detonation and deflagration models have been used to explain the majority of
SNe Ia, they do not predict a long velocity plateau in the SiII minimum with an
unvarying line profile. Pulsating delayed detonations and merger scenarios form
shell-like density structures with properties mostly related to the mass of the
shell, M_shell, and we discuss how these models may explain the observed SiII
line evolution; however, these models are based on spherical calculations and
other possibilities may exist. SN 2005hj is consistent with respect to the
onset, duration, and velocity of the plateau, the peak luminosity and, within
the uncertainties, with the intrinsic colors for models with M_shell=0.2 M_sun.
Our analysis suggests a distinct class of events hidden within the
Branch-normal SNe Ia. If the predicted relations between observables are
confirmed, they may provide a way to separate these two groups. We discuss the
implications of two distinct progenitor classes on cosmological studies
employing SNe Ia, including possible differences in the peak luminosity to
light curve width relation.Comment: ApJ accepted, 31 page
Computer programs for reduction of microphotometer data
Five computer programs for analyzing magnetic tape recordings of digital data from microphotomete
Preliminary Spectral Analysis of SN 1994I
We present optical spectra of the Type Ic supernova 1994I in M51 and
preliminary non-LTE analysis of the spectra. Our models are not inconsistent
with the explosions of C+O cores of massive stars. While we find no direct
evidence for helium in the optical spectra, our models cannot rule out small
amounts of helium. More than 0.1~\msol\ of helium seems unlikely.Comment: LaTeX, MN style, psfig, and natbib substyles, 7 pages, 4 figures, to
appear in MNRAS. Postscript file available from
http://www.nhn.uoknor.edu/~baro
Reading the Spectra of the Most Peculiar Type Ia Supernova 2002cx
In spite of the apparent lack of Si II and S II features in its spectra, SN
2002cx was classified as a peculiar Type Ia supernova (SN Ia) on the basis of
its overall photometric and spectroscopic behavior. Spectra obtained near
maximum light contained Fe III features, as in SN 1991T-like events, but the
blueshifts of the Fe III absorptions were exceptionally low. The luminosity
also was low. We use the supernova synthetic--spectrum code SYNOW to study line
identifications in SN 2002cx. We find that the maximum-light spectra appear to
contain weak features of Si II, S II, Si III, and Ca II, which strengthens the
connection with SN 1991T-like events. We show that later spectra, obtained 12,
25, and 56 days after maximum, consist of P-Cygni resonance-scattering features
due to permitted Fe II and Co II lines. SN 2002cx had been thought to have made
the transition from a permitted-line to a forbidden-line spectrum between 25
and 56 days. Owing to the low expansion velocities the postmaximum spectral
features are narrower and easier to identify than they are in other SNe Ia. SN
2002cx will lead to improved line identifications in other SNe Ia and clarify
when the transition from a permitted-line to a forbidden-line spectrum occurs.
In the context of current SN Ia explosion models, we suggest that the
properties of SN 2002cx may be consistent with 3D deflagration models, which
are not favored for normal SNe Ia.Comment: 21 pages including 7 figures and 4 tables; accepted by PAS
Study of Envelope Velocity Evolution of Type Ib-c Core-Collapse Supernovae from Observations of XRF 080109 / SN 2008D and GRB 060218 / SN 2006aj with BTA
Results of modeling the spectra of two supernovae SN 2008D and SN 2006aj
related to the X-ray flash XRF 080109 and gamma-ray burst GRB / XRF 060218,
respectively, are studied. The spectra were obtained with the 6-meter BTA
telescope of the Special Astrophysical Observatory of the Russian Academy of
Sciences in 6.48 and 27.61 days after the explosion of SN 2008D, and in 2.55
and 3.55 days after the explosion of SN 2006aj. The spectra were interpreted in
the Sobolev approximation with the SYNOW code. An assumption about the presence
of envelopes around the progenitor stars is confirmed by an agreement between
the velocities of lines interpreted as hydrogen and helium, and the empiric
power-law velocity drop with time for the envelopes of classic core-collapse
supernovae. Detection of a P Cyg profile of the H-beta line in the spectra of
optical afterglows of GRBs can be a determinative argument in favor of this
hypothesis.Comment: 12 pages, 6 figures, accepted for publication in Astrophysical
Bulletin
A study to define meteorological uses and performance requirements for the Synchronous Earth Observatory Satellite
The potential meteorological uses of the Synchronous Earth Observatory Satellite (SEOS) were studied for detecting and predicting hazards to life, property, or the quality of the environment. Mesoscale meteorological phenonmena, and the observations requirements for SEOS are discussed along with the sensor parameters
Hydrogen issue in Core Collapse Supernovae
We discuss results of analyzing a time series of selected
photospheric-optical spectra of core collapse supernovae (CCSNe). This is
accomplished by means of the parameterized supernovae synthetic spectrum (SSp)
code
``SYNOW''.
Special attention is addressed to traces of hydrogen at early phases,
especially for the stripped-envelope SNe (i.e. SNe Ib-c). A thin low mass
hydrogen layer extending to very high ejection velocities above the helium
shell, is found to be the most likely scenario for Type Ib SNe.Comment: 8 pages. Proceedings of the conference ``The Multicoloured Landscape
of Compact Objects and their Explosive Origins'', 2006 June 11--24, Cefalu,
Sicily, to be published by AI
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