146 research outputs found
A Search For Supernova Remnants in The Nearby Spiral Galaxy M74 (NGC 628)
We have identified nine new SNR candidates in M74 with [S II]/H
0.4 as the basic criterion. We obtain [S II]/H ratio in the
range from 0.40 to 0.91 and H intensities from 2.8
erg cm s to 1.7 erg cm s. We
also present spectral follow-up observations of the SNR candidates and can
confirm only three of them (SNR2, SNR3, and SNR5). The lack of confirmation for
the rest might be due to the contamination by the nearby H II emission regions
as well as due to the inaccurate positioning of the long slit on these objects.
In addition, we search the Observatory archival data for the X-ray
counterparts to the optically identified candidates. We find positional
coincidence with only three SNR candidates, SNR1, SNR2, and SNR8. The spectrum
of SNR2 yields a shock temperature of 10.8 keV with an ionization timescale of
1.6 10 s cm indicating a relatively young remnant in an
early Sedov phase which is not supported by our optical wavelength analysis.
Given the high luminosity of 10 erg s and the characteristics of
the X-ray spectrum, we favor an Ultra Luminous X-ray Source interpretation for
this source associated with an SNR. We calculate an X-ray flux upper limit of
9.0 erg cm s for the rest of the SNRs
including spectroscopically identified SNR3 and SNR5.Comment: 10 pages, 8 figures, accepted to be published in A&
X - Ray Flares and Their Connection With Prompt Emission in GRBs
We use a wavelet technique to investigate the time variations in the light
curves from a sample of GRBs detected by Fermi and Swift. We focus primarily on
the behavior of the flaring region of Swift-XRT light curves in order to
explore connections between variability time scales and pulse parameters (such
as rise and decay times, widths, strengths, and separation distributions) and
spectral lags. Tight correlations between some of these temporal features
suggest a common origin for the production of X-ray flares and the prompt
emission.Comment: 7th Huntsville Gamma-Ray Burst Symposium, GRB 2013: paper 15 in eConf
Proceedings C130414
A Proposal to Localize Fermi GBM GRBs Through Coordinated Scanning of the GBM Error Circle via Optical Telescopes
We investigate the feasibility of implementing a system that will coordinate
ground-based optical telescopes to cover the Fermi GBM Error Circle (EC). The
aim of the system is to localize GBM detected GRBs and facilitate
multi-wavelength follow-up from space and ground. This system will optimize the
observing locations in the GBM EC based on individual telescope location, Field
of View (FoV) and sensitivity. The proposed system will coordinate GBM EC
scanning by professional as well as amateur astronomers around the world. The
results of a Monte Carlo simulation to investigate the feasibility of the
project are presented.Comment: 2011 Fermi Symposium proceedings - eConf C11050
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