38 research outputs found
Point-source and diffuse high-energy neutrino emission from Type IIn supernovae
Type IIn supernovae (SNe), a rare subclass of core collapse SNe, explode in
dense circumstellar media that have been modified by the SNe progenitors at
their last evolutionary stages. The interaction of the freely expanding SN
ejecta with the circumstellar medium gives rise to a shock wave propagating in
the dense SN environment, which may accelerate protons to multi-PeV energies.
Inelastic proton-proton collisions between the shock-accelerated protons and
those of the circumstellar medium lead to multi-messenger signatures. Here, we
evaluate the possible neutrino signal of type IIn SNe and compare with IceCube
observations. We employ a Monte Carlo method for the calculation of the diffuse
neutrino emission from the SN IIn class to account for the spread in their
properties. The cumulative neutrino emission is found to be ~ 10 per cent of
the observed IceCube neutrino flux above 60 TeV. Type IIn SNe would be the
dominant component of the diffuse astrophysical flux, only if 4 per cent of all
core collapse SNe were of this type and 20 to 30 per cent of the shock energy
was channeled to accelerated protons. Lower values of the acceleration
efficiency are accessible by the observation of a single type IIn SN as a
neutrino point source with IceCube using up-going muon neutrinos. Such an
identification is possible in the first year following the SN shock breakout
for sources within 20 Mpc.Comment: 13 pages, 9 figures, MNRAS accepte
Observations of the Optical Afterglow of GRB 050319 : Wind to ISM transition in view
The collapse of a massive star is believed to be the most probable progenitor
of a long GRB. Such a star is expected to modify its environment by stellar
wind. The effect of such a circum-stellar wind medium is expected to be seen in
the evolution of a GRB afterglow, but has so far not been conclusively found.
We claim that a signature of wind to constant density medium transition of
circum-burst medium is visible in the afterglow of GRB 050319. Along with the
optical observations of the afterglow of GRB 050319 we present a model for the
multiband afterglow of GRB 050319. We show that the break seen in optical light
curve at 0.02 day could be explained as being due to wind to constant
density medium transition of circum-burst medium, in which case, to our
knowledge, this could be the first ever detection of such a transition at any
given frequency band. Detection of such a transition could also serve as a
confirmation of massive star collapse scenario for GRB progenitors, independent
of supernova signatures.Comment: 11 pages, 3 tables, 1 figure
A search for near-infrared counterparts of two faint neutron star X-ray transients : XMMU J174716.1-281048 and SAX J1806.5-2215
We present our near-infrared (NIR) imaging observations of two neutron star
low mass X-ray binaries XMMU J174716.1-281048 and SAX J1806.5-2215 obtained
using the PANIC instrument on the 6.5-meter Magellan telescope and the WHIRC
instrument on the 3.5-meter WIYN telescope respectively. Both sources are
members of the class of faint to very-faint X-ray binaries and undergo very
long X-ray outburst, hence classified as `quasi persistent X-ray binaries'.
While XMMU J174716.1-281048 was active for almost 12 years between 2003 and
2015, SAX J1806.5-2215 has been active for more than 5 years now since 2011.
From our observations, we identify two NIR stars consistent with the Chandra
X-ray error circle of XMMU J174716.1-281048. The comparison of our observations
with the UKIRT Galactic plane observations taken during the same outburst,
color-color diagram analysis and spectral energy distribution suggest that both
stars are probably a part of the field population and are likely high mass
stars. Hence possibly neither of the two stars is a true NIR counterpart. For
the faint X-ray binary SAX J1806.5-2215 during its current outburst, we
detected a NIR star in our K band WIYN observations consistent with its Chandra
error circle. The identified NIR star was not detected during the UKIRT
observations taken during its quiescent state. The comparison of two
observations suggest that there was an increase in flux by at least one
magnitude of the detected star during our observations, hence suggests the
detection of the likely counterpart of SAX J1806.5-2215.Comment: 9 pages, 4 figures, accepted for publication in MNRA
Multiband Optical Photometry and Bolometric Light Curve of the Type Ia Supernova 2004S
We present broad band CCD photometry of the Type Ia
supernova SN 2004S, which appeared in the galaxy MCG-05-16-021, obtained during
2004 February 12 to March 22. Multiband and bolometric light curves constructed
using our data as well as other available data are presented. The time of B
band maximum and the peak magnitudes in different bands are obtained using the
fits of light curve and colour templates. We clearly see a strong shoulder in
band and a second maximum in band. SN 2004S closely
resembles SN 1992al after maximum. From the peak bolometric luminosity we
estimate the ejected mass of to be 0.41 .Comment: 8 pages, 5 figures, accepted for publication in MNRA
A Deep Search for Prompt Radio Emission from Thermonuclear Supernovae with the Very Large Array
Searches for circumstellar material around Type Ia supernovae (SNe Ia) are
one of the most powerful tests of the nature of SN Ia progenitors, and radio
observations provide a particularly sensitive probe of this material. Here we
report radio observations for SNe Ia and their lower-luminosity thermonuclear
cousins. We present the largest, most sensitive, and spectroscopically diverse
study of prompt (delta t <~ 1 yr) radio observations of 85 thermonuclear SNe,
including 25 obtained by our team with the unprecedented depth of the Karl G.
Jansky Very Large Array. With these observations, SN 2012cg joins SN 2011fe and
SN 2014J as a SN Ia with remarkably deep radio limits and excellent temporal
coverage (six epochs, spanning 5--216 days after explosion, yielding Mdot/v_w
<~ 5 x 10^-9 M_sun/yr / (100 km/s), assuming epsilon_B = 0.1 and epsilon_e =
0.1).
All observations yield non-detections, placing strong constraints on the
presence of circumstellar material. We present analytical models for the
temporal and spectral evolution of prompt radio emission from thermonuclear SNe
as expected from interaction with either wind-stratified or uniform density
media. These models allow us to constrain the progenitor mass loss rates, with
limits ranging from Mdot <~ 10^-9--10^-4 M_sun/yr, assuming a wind velocity
v_w=100 km/s. We compare our radio constraints with measurements of Galactic
symbiotic binaries to conclude that <~10% of thermonuclear SNe have red giant
companions.Comment: Submitted to Ap
Interaction Between the Broad-Lined Type Ic Supernova 2012ap and Carriers of Diffuse Interstellar Bands
The diffuse interstellar bands (DIBs) are absorption features observed in optical and near-infrared spectra that are thought to be associated with carbon-rich polyatomic molecules in interstellar gas. However, because the central wavelengths of these bands do not correspond with electronic transitions of any known atomic or molecular species, their nature has remained uncertain since their discovery almost a century ago. Here we report on unusually strong DIBs in optical spectra of the broad- lined Type Ic supernova SN2012ap that exhibit changes in equivalent width over short (. 30 days) timescales. The 4428 A and 6283 A DIB features get weaker with time, whereas the 5780 A feature shows a marginal increase. These nonuniform changes suggest that the supernova is interacting with a nearby source of the DIBs and that the DIB carriers possess high ionization potentials, such as small cations or charged fullerenes. We conclude that moderate-resolution spectra of supernovae with DIB absorptions obtained within weeks of outburst could reveal unique information about the mass-loss environment of their progenitor systems and provide new constraints on the properties of DIB carriers