554 research outputs found
Radio Detection of 18 Rass BL Lac Objects
We present the radio detection of 18 BL Lac objects from our survey of over
575 square degrees of sky. These 18 objects are located within 20 arcsec of the
X-ray position, of which 11 have a measured red-shift. All candidates are radio
emitters above ~1 mJy and fall within the range of existing samples on the two
colour, alpha_ro vs alpha_ox, diagram with a transitional population of three
(3) evident. Two unusual sources have been identified, a candidate radio quiet
BL Lac, RX J0140.9-4130, and an extreme HBL, RX J0109.9-4020, with
Log(nu_peak)~19.2. The BL Lac Log(N)-Log(S) relation is consistent with other
samples and indicates the ROSAT All Sky Survey (RASS) could contain (2000+-400)
BL Lac objects.Comment: 14 pages, 6 figures, accepted for publication in Serbian Astronomical
Journa
Radio-Continuum Observations Of Small, Radially Polarised Supernova Remnant J0519-6902 In The Large Magellanic Cloud
We report on new Australian Telescope Compact Array (ATCA) observations of
SNR J0519-6902. The Supernova Remnant (SNR) is small in size (~8 pc) and
exhibits a typical SNR spectrum of alpha = -0.53 +- 0.07, with steeper spectral
indices found towards the northern limb of the remnant. SNR J0519-6902 contains
a low level of radially orientated polarisation at wavelengths of 3 & 6 cm,
which is characteristic of younger SNRs. A fairly strong magnetic field was
estimated of ~171 microG. The remnant appears to be the result of a typical
Type Ia supernovae, sharing many properties as another small and young Type Ia
LMC SNR, J0509-6731.Comment: 10 pages 7 figures, submitted to Serbian Astronomical Journa
Radio Continuum Study of Supernova Remnants in the Large Magellanic Cloud - SNR J0519-6926
We present the results of new high resolution ATCA observations of SNR
J0519-6926. We found that this SNR exhibits a typical "horseshoe" appearance
with alpha = -0.55 +- 0.08 and D=28+-1 pc. No polarization (or magnetic fields)
are detected to a level of 1%. This is probably due to a relatively poor
sampling of the uv plane caused be observing in "snap-shot" mode.Comment: 6 pages 4 figures, to be published in Serbian Astronomical Journa
Multifrequency Observations of One of the Largest Supernova Remnants in the Local Group of Galaxies, LMC - SNR J0450-709
We present the results of new Australia Telescope Compact Array (ATCA)
observations of one of the largest supernova remnants, SNR J0450-709, in the
Local Group of galaxies. We found that this Large Magellanic Cloud (LMC) ob
ject exhibits a typical morphology of an old supernova remnant (SNR) with
diameter D=102x75+-1 pc and radio spectral index alpha=-0.43+-0.06. Regions of
high polarisation were detected with peak value of ~40%.Comment: 7 pages, 4 figures, accepted for publication in Serbian Astronomical
Journa
Derivative pricing for a multi-curve extension of the Gaussian, exponentially quadratic short rate model
The recent financial crisis has led to so-called multi-curve models for the
term structure. Here we study a multi-curve extension of short rate models
where, in addition to the short rate itself, we introduce short rate spreads.
In particular, we consider a Gaussian factor model where the short rate and the
spreads are second order polynomials of Gaussian factor processes. This leads
to an exponentially quadratic model class that is less well known than the
exponentially affine class. In the latter class the factors enter linearly and
for positivity one considers square root factor processes. While the square
root factors in the affine class have more involved distributions, in the
quadratic class the factors remain Gaussian and this leads to various
advantages, in particular for derivative pricing. After some preliminaries on
martingale modeling in the multi-curve setup, we concentrate on pricing of
linear and optional derivatives. For linear derivatives, we exhibit an
adjustment factor that allows one to pass from pre-crisis single curve values
to the corresponding post-crisis multi-curve values
Multifrequency radio observations of SNR J0536-6735 (N 59B) with associated pulsar
We present a study of new Australian Telescope Compact Array (ATCA)
observations of supernova remnant, SNR J0536-6735. This remnant appears to
follow a shell morphology with a diameter of D=36x29 pc (with 1 pc uncertainty
in each direction). There is an embedded Hii region on the northern limb of the
remnant which made various analysis and measurements (such as flux density,
spectral index and polarisation) difficult. The radio-continuum emission
followed the same structure as the optical emission, allowing for extent and
flux density estimates at 20 cm. We estimate a surface brightness for the SNR
at 1 GHz of 2.55x10^-21 W m^-2 Hz^-1 sr^-1. Also, we detect a distinctive
radio-continuum point source which confirms the previous suggestion of this
remnant being associated with a pulsar wind nebulae (PWN). The tail of this
remnant isn't seen in the radio-continuum images and is only seen in the
optical and X-ray images.Comment: 10 pages 4 figures, accepted for publication in SA
On multicurve models for the term structure
In the context of multi-curve modeling we consider a two-curve setup, with
one curve for discounting (OIS swap curve) and one for generating future cash
flows (LIBOR for a give tenor). Within this context we present an approach for
the clean-valuation pricing of FRAs and CAPs (linear and nonlinear derivatives)
with one of the main goals being also that of exhibiting an "adjustment factor"
when passing from the one-curve to the two-curve setting. The model itself
corresponds to short rate modeling where the short rate and a short rate spread
are driven by affine factors; this allows for correlation between short rate
and short rate spread as well as to exploit the convenient affine structure
methodology. We briefly comment also on the calibration of the model
parameters, including the correlation factor.Comment: 16 page
Exponential ergodicity of the jump-diffusion CIR process
In this paper we study the jump-diffusion CIR process (shorted as JCIR),
which is an extension of the classical CIR model. The jumps of the JCIR are
introduced with the help of a pure-jump L\'evy process . Under
some suitable conditions on the L\'evy measure of , we derive a
lower bound for the transition densities of the JCIR process. We also find some
sufficient condition guaranteeing the existence of a Forster-Lyapunov function
for the JCIR process, which allows us to prove its exponential ergodicity.Comment: 14 page
Radio Detection of 18 RASS BL Lac Objects
We present the radio detection of 18 BL Lac objects from oursurvey of over 575 deg of sky. These 18 objects are located within of the X-ray position, of which 11 have a measuredred-shift. All candidates are radio emitters above 1 mJy and fall within the range of existing samples on the two colour, vs , diagram with a transitional population of three evident. Two unusual sources have been identified, a candidate radio quiet BL Lac, RX J0140.9-4130, and an extreme HBL, RX J0109.9-4020, with . The BL Lac relation is consistent with other samples and indicates the ROSAT All Sky Survey (RASS) could contain () BL Lac objects
- …