3,558 research outputs found
20 cm VLA Radio-Continuum Study of M31 - Images and Point Source Catalogues DR2: Extraction of a supernova remnant sample
We present Data Release 2 of the Point Source Catalogue created from a series
of previously constructed radio-continuum images of M31 at lambda=20 cm (nu=1.4
GHz) from archived VLA observations. In total, we identify a collection of 916
unique discrete radio sources across the field of M31. Comparing these detected
sources to those listed by Gelfand et al. (2004) at lambda=92 cm, the spectral
index of 98 sources has been derived. The majority (73%) of these sources
exhibit a spectral index of alpha <-0.6, indicating that their emission is
predominantly non-thermal in nature, which is typical for background objects
and Supernova Remnants (SNRs). Additionally, we investigate the presence of
radio counterparts for some 156 SNRs and SNR candidates, finding a total of
only 13 of these object in our images within a 5 arcsec search area. Auxiliary
optical, radio and X-ray catalogs were cross referenced highlighting a small
population of SNR and SNR candidates common to multi-frequency domains
Affine Processes and Application in Finance
We provide the definition and a complete characterization of regular affine processes. This type of process unifies the concepts of continuousstate branching processes with immigration and Ornstein-Uhlenbeck type processes. We show, and provide foundations for, a wide range of financial applications for regular affine processes.
Newly confirmed and high quality candidate Galactic SNRs uncovered from the AAO/UKST HAlpha survey
We present a catalogue of 18 new Galactic supernova remnants (SNRs) uncovered
in the optical regime as filamentary emissions and extended nebulosities on
images of the Anglo Australian Observatory/United Kingdom Schmidt Telescope
(AAO/UKST) HAlpha survey of the southern Galactic plane. Our follow-up spectral
observations confirmed classical optical SNR emission lines for these 18
structures via detection of very strong [SII] at 6717 and 6731A relative to
HAlpha ([SII]/HAlpha> 0.5). Morphologically, 10 of these remnants have
coherent, extended arc or shell structures, while the remaining objects are
more irregular in form but clearly filamentary in nature, typical of optically
detected SNRs.
In 11 cases there was a clear if not complete match between the optical and
radio structures with H filamentary structures registered inside and along the
presumed radio borders. Additionally, ROSAT X-ray sources were detected inside
the optical/radio borders of 11 of these new remnants and 3 may have an
associated pulsar.
The multi-wavelength imaging data and spectroscopy together present strong
evidence to confirm identification of 18 new, mostly senile Galactic SNRs. This
includes G288.7-6.3, G315.1+2.7 and G332.5-5.6, identified only as possible
remnants from preliminary radio observations. We also confirm existence of
radio quiet but optically active supernova remnants.Comment: In original form 21 pages, 29 figures Accepted for MNRA
SMC SMP 24: A newly radio-detected planetary nebula in the small magellanic cloud
In this paper we report new radio-continuum detection of an extragalactic PN:
SMC SMP 24. We show the radio-continuum image of this PN and present the
measured radio data. The newly reduced radio observations are consistent with
the multi-wavelength data and derived parameters found in the literature. SMC
SMP 24 appear to be a young and compact PN, optically thick at frequencies
below 2 GHz.Comment: accepted for publication in Serbian Astronomical Journa
A Study of Optical Observing Techniques for Extra-Galactic Supernova Remnants: Case of NGC 300
We present the results of a study of observational and identification
techniques used for surveys and spectroscopy of candidate supernova remnants
(SNRs) in the Sculptor Group galaxy NGC 300. The goal of this study was to
investigate the reliability of using [Sii]/Halpha > 0.4 in optical SNR surveys
and spectra as an identifying feature of extra-galactic SNRs (egSNRs) and also
to investigate the effectiveness of the observing techniques (which are
hampered by seeing conditions and telescope pointing errors) using this
criterion in egSNR surveys and spectrographs. This study is based on original
observations of these objects and archival data obtained from the Hubble Space
Telescope which contained images of some of the candidate SNRs in NGC 300. We
found that the reliability of spectral techniques may be questionable and very
high-resolution images may be needed to confirm a valid identification of some
egSNRs.Comment: 27 Figures, 10 table
A ROSAT PSPC X-Ray Survey of the Small Magellanic Cloud
We present the results of a systematic search for point-like and moderately
extended soft (0.1-2.4 keV) X-ray sources in a raster of nine pointings
covering a field of 8.95 deg^2 and performed with the ROSAT PSPC between
October 1991 and October 1993 in the direction of the Small Magellanic Cloud.
We detect 248 objects which we include in the first version of our SMC
catalogue of soft X-ray sources. We set up seven source classes defined by
selections in the count rate, hardness ratio and source extent. We find five
high luminosity super-soft sources (1E 0035.4-7230, 1E 0056.8-7146, RX
J0048.4-7332, RX J0058.6-7146 and RX J0103-7254), one low-luminosity super-soft
source RX J0059.6-7138 correlating with the planetary nebula L357, 51 candidate
hard X-ray binaries including eight bright hard X-ray binary candidates, 19
supernova remnants, 19 candidate foreground stars and 53 candidate background
active galactic nuclei (and quasars). We give a likely classification for ~60%
of the catalogued sources. The total count rate of the detected point-like and
moderately extended sources in our catalogue is 6.9+/-0.3 s^-1, comparable to
the background subtracted total rate from the integrated field of ~6.1+/-0.1
s^-1.Comment: Accepted by A&AS, 13 pages, 2 Postscript figure
Radio Planetary Nebulae in the Large Magellanic Cloud
We present 21 new radio-continuum detections at catalogued planetary nebula
(PN) positions in the Large Magellanic Cloud (LMC) using all presently
available data from the Australia Telescope Online Archive at 3, 6, 13 and 20
cm. Additionally, 11 previously detected LMC radio PNe are re-examined with detections confirmed and reported here. An additional three PNe from our
previous surveys are also studied. The last of the 11 previous detections is
now classified as a compact \HII\ region which makes for a total sample of 31
radio PNe in the LMC. The radio-surface brightness to diameter (-D)
relation is parametrised as . With the
available 6~cm - data we construct - samples from 28 LMC
PNe and 9 Small Magellanic Cloud (SMC) radio detected PNe. The results of our
sampled PNe in the Magellanic Clouds (MCs) are comparable to previous
measurements of the Galactic PNe. We obtain for the MC PNe
compared to for the Galaxy. For a better insight into
sample completeness and evolutionary features we reconstruct the -
data probability density function (PDF). The PDF analysis implies that PNe are
not likely to follow linear evolutionary paths. To estimate the significance of
sensitivity selection effects we perform a Monte Carlo sensitivity simulation
on the - data. The results suggest that selection effects are
significant for values larger than and that a measured slope
of should correspond to a sensitivity-free value of .Comment: 19 pages, 9 figures, 6 table
Radio-continuum detections of Galactic Planetary Nebulae I. MASH PNe detected in large-scale radio surveys
We present an updated and newly compiled radio-continuum data-base for MASH
PNe detected in the extant large scale "blind" radio-continuum surveys (NVSS,
SUMSS/MGPS-2 and PMN) and, for a small number of MASH PNe, observed and
detected in targeted radio-continuum observations. We found radio counterparts
for approximately 250 MASH PNe. In comparison with the percentage of previously
known Galactic PNe detected in the NVSS and MGPS-2 radio-continuum surveys and
according to their position on the flux density-angular diameter and the radio
brightness temperature evolutionary diagrams we conclude, unsurprisingly, that
the MASH sample presents the radio-faint end of the known Galactic PNe
population. Also, we present radio-continuum spectral properties of a small
sub-sample of MASH PNe located in the strip between declinations -30arcdeg and
-40arcdeg, that are detected in both the NVSS and MGPS-2 radio surveys.Comment: 13 figures and 7 tables, accepted for publication in MNRA
Radio-continuum study of Large Magellanic Cloud Supernova Remnant J0509-6731
We present a detailed study of Australia Telescope Compact Array (ATCA)
observations ( = 20, 13, 6 & 3~cm) of supernova remnant (SNR)
J0509--6731 in the Large Magellanic Cloud (LMC). The remnant has a ring
morphology with brightened regions towards the south-western limb. We also find
a second brightened inner ring which is only seen in the radio-continuum. The
SNR is almost circular, with a diameter ranging from 7 to 8~pc, and a steep
radio spectral index between 36 and 3~cm of , which is
characteristic of younger SNRs. We also report detection of radially orientated
polarisation across the remnant at 6~cm, with a mean fractional polarisation
level of ~(26~~13)%. We find the magnetic field (168~G)
and ( ~W
m~Hz~sr , 7.35~pc) to be consistent with other young
remnants
Emission Measures and Emission-measure-weighted Temperatures of Shocked ISM and Ejecta in Supernova Remnants
A goal of supernova remnant (SNR) evolution models is to relate fundamental
parameters of a supernova (SN) explosion and progenitor star to the current
state of its SNR. The SNR hot plasma is characterized by its observed X-ray
spectrum, which yields electron temperature, emission measure and abundances.
Depending on their brightness, the properties of the plasmas heated by the SNR
forward shock, reverse shock or both can be measured. The current work utilizes
models which are spherically symmetric. One dimensional hydrodynamic
simulations are carried out for SNR evolution prior to onset of radiative
losses. From these, we derive dimensionless emission measures and
emission-measure-weighted temperatures, and we present fitting formulae for
these quantities as functions of scaled SNR time. These models allow one to
infer SNR explosion energy, circumstellar medium density, age, ejecta mass and
ejecta density profile from SNR observations. The new results are incorporated
into the SNR modelling code SNRPy. The code is demonstrated with application to
three historical SNRs: Kepler, Tycho and SN1006.Comment: 50 pages, 10 figures, 5 table
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