56 research outputs found
Radio emission of the Galactic X-rays binaries with relativistic jets
Variable non-thermal radio emission from Galactic X-ray binaries is a trace
of relativistic jets, created near accretion disks. The spectral
characteristics of a lot of radio flares in the X-ray binaries with jets (RJXB)
is discussed in this report. We carried out several long daily monitoring
programs with the RATAN-600 radio telescope of the sources: SS433, Cyg X-3,
LSI+61o303, GRS 1915+10 and some others. We also reviewed some data from the
GBI monitoring program at two frequencies and hard X-ray BATSE (20-100 keV) and
soft X-ray RTXE (2-12 keV) ASM data. We confirmed that flaring radio emission
of Cyg X-3 correlated with hard and anti-correlated with soft X-ray emission
during the strong flare (>\tau$ depends upon frequency as tau \propto \nu^{-0.4} in the first
flare and does not depend upon frequency in the second flare, and is equal to
\tau=6+-1 days at frequencies from 0.96 to 21.7 GHz in the last flare in May
1999. Many flaring RJXB show two, exponential and power, laws of flare decay.
Moreover, these different laws could be present in one or several flares and
commonly flare decays are faster at a higher frequency. The decay law seems to
change because of geometric form of the conical hollow jets. The synchrotron
and inverse Compton losses could explain general frequency dependences in flare
evolution. In conclusion we summarized the general radio properties of RJXB.Comment: 10 pages, LaTeX, 14 Postscript figures, talk given at the Gamov
Memorial International Conference (GMIC'99) "Early Universe: Cosmological
Problems and Instrumental Technologies" in St.Petersburg, 23-27 August, 1999,
to appear in Astron. Astrophys. Trans., 200
A Massive Jet Ejection Event from the Microquasar SS 433 Accompanying Rapid X-Ray Variability
Microquasars occasionally exhibit massive jet ejections which are distinct
from the continuous or quasi-continuous weak jet ejections. Because those
massive jet ejections are rare and short events, they have hardly been observed
in X-ray so far. In this paper, the first X-ray observation of a massive jet
ejection from the microquasar SS 433 with the Rossi X-ray Timing Explorer
(RXTE) is reported. SS 433 undergoing a massive ejection event shows a variety
of new phenomena including a QPO-like feature near 0.1 Hz, rapid time
variability, and shot-like activities. The shot-like activity may be caused by
the formation of a small plasma bullet. A massive jet may be consist of
thousands of those plasma bullets ejected from the binary system. The size,
mass, internal energy, and kinetic energy of the bullets and the massive jet
are estimated.Comment: 21 pages including 5 figures, submitted to Ap
Fast optical variability of SS 433
We study the optical variability of the peculiar Galactic source SS 433 using
the observations made with the Russian Turkish 1.5-m telescope (RTT150). A
simple technique which allows to obtain high-quality photometric measurements
with 0.3-1 s time resolution using ordinary CCD is described in detail. Using
the test observations of nonvariable stars, we show that the atmospheric
turbulence introduces no significant distortions into the measured light
curves. Therefore, the data obtained in this way are well suited for studying
the aperiodic variability of various objects.
The large amount of SS 433 optical light curve measurements obtained in this
way allowed us to obtain the power spectra of its flux variability with a
record sensitivity up to frequencies of ~0.5 Hz and to detect its break at
frequency =~2.4e-3 Hz. We suggest that this break in the power spectrum results
from the smoothing of the optical flux variability due to a finite size of the
emitting region. Based on our measurement of the break frequency in the power
spectrum, we estimated the size of the accretion-disk photosphere as 2e12 cm.
We show that the amplitude of the variability in SS 433 decreases sharply
during accretion-disk eclipses, but it does not disappear completely. This
suggests that the size of the variable optical emission source is comparable to
that of the normal star whose size is therefore R_O \approx 2e12 cm \approx 30
R_sun. The decrease in flux variability amplitude during eclipses suggests the
presence of a nonvariable optical emission component with a magnitude
m_R=~13.2.Comment: 12 pages, 11 figures. Accepted for publication in Astronomy Letters.
The original version in Russian is available at
http://hea.iki.rssi.ru/rtt150/ru/ss433_pazh10/pss433_fast.pd
Multi-wavelength observations of afterglow of GRB 080319B and the modeling constraints
We present observations of the afterglow of GRB 080319B at optical, mm and
radio frequencies from a few hours to 67 days after the burst. Present
observations along with other published multi-wavelength data have been used to
study the light-curves and spectral energy distributions of the burst
afterglow. The nature of this brightest cosmic explosion has been explored
based on the observed properties and it's comparison with the afterglow models.
Our results show that the observed features of the afterglow fits equally good
with the Inter Stellar Matter and the Stellar Wind density profiles of the
circum-burst medium. In case of both density profiles, location of the maximum
synchrotron frequency is below optical and the value of cooling break
frequency is below rays, s after the burst. Also, the
derived value of the Lorentz factor at the time of naked eye brightness is
with the corresponding blast wave size of cm. The
numerical fit to the multi-wavelength afterglow data constraints the values of
physical parameters and the emission mechanism of the burst.Comment: 8 Pages, 3 Figures, Accepted for publication to Astronomy and
Astrophysics on 02/04/200
Broad band variability of SS433: Accretion disk at work?
We present broad band power spectra of variations of SS433 in radio, optical
and X-ray spectral bands. We show that at frequencies lower than 1e-5 Hz the
source demonstrates the same variability pattern in all these bands. The broad
band power spectrum can be fitted by one power law down to frequencies ~1e-7 Hz
with flattening afterwards. Such a flattening means that on time scales longer
than ~1e7 sec the source variability becomes uncorrelated. This naturally leads
to the appearance of quasi-poissonian flares in the source light curve, which
have been regularly observed in radio and optical spectral bands. The radio
flux power spectrum appears to have a second break at Fourier frequencies ~1e-5
Hz which can be caused by the smearing of the intrinsic radio variability on
timescale of the light-crossing time of the radio emitting region. We find a
correlation of the radio and optical fluxes of SS433 and the radio flux is
delayed by about ~2 days with respect to the optical one. Power spectra of
optical and X-ray variabilities continue with the same power law from 1e-7 Hz
up to ~0.01-0.05 Hz. The broad band power spectrum of SS433 can be interpreted
in terms of self-similar accretion rate modulations in the accretion disk
proposed by Lyubarskii (1997) and elaborated by Churazov et al. (2001). We
discuss a viscous time-scale in the accretion disk of SS433 in implication to
the observed broad band power spectrum.Comment: 8 pages, 2 figures. Submitted to A&
Catalog of Radio Galaxies with z>0.3. I:Construction of the Sample
The procedure of the construction of a sample of distant () radio
galaxies using NED, SDSS, and CATS databases for further application in
statistical tests is described. The sample is assumed to be cleaned from
objects with quasar properties. Primary statistical analysis of the list is
performed and the regression dependence of the spectral index on redshift is
found.Comment: 9 pages, 6 figures, 2 table
Discovery of extreme particle acceleration in the microquasar Cygnus X-3
The study of relativistic particle acceleration is a major topic of
high-energy astrophysics. It is well known that massive black holes in active
galaxies can release a substantial fraction of their accretion power into
energetic particles, producing gamma-rays and relativistic jets. Galactic
microquasars (hosting a compact star of 1-10 solar masses which accretes matter
from a binary companion) also produce relativistic jets. However, no direct
evidence of particle acceleration above GeV energies has ever been obtained in
microquasar ejections, leaving open the issue of the occurrence and timing of
extreme matter energization during jet formation. Here we report the detection
of transient gamma-ray emission above 100 MeV from the microquasar Cygnus X-3,
an exceptional X-ray binary which sporadically produces powerful radio jets.
Four gamma-ray flares (each lasting 1-2 days) were detected by the AGILE
satellite simultaneously with special spectral states of Cygnus X-3 during the
period mid-2007/mid-2009. Our observations show that very efficient particle
acceleration and gamma-ray propagation out of the inner disk of a microquasar
usually occur a few days before major relativistic jet ejections. Flaring
particle energies can be thousands of times larger than previously detected
maximum values (with Lorentz factors of 105 and 102 for electrons and protons,
respectively). We show that the transitional nature of gamma-ray flares and
particle acceleration above GeV energies in Cygnus X-3 is clearly linked to
special radio/X-ray states preceding strong radio flares. Thus gamma-rays
provide unique insight into the nature of physical processes in microquasars.Comment: 29 pages (including Supplementary Information), 8 figures, 2 tables
version submitted to Nature on August 7, 2009 (accepted version available at
http://www.nature.com/nature/journal/vaop/ncurrent/pdf/nature08578.pdf
The Radio Spectral Index of the Crab Nebula
We present the results of a new, comprehensive investigation of the radio
spectral index of the Crab Nebula supernova remnant. New data at 74 MHz are
combined with data at 327 MHz, 1.5 GHz and 5 GHz. In contrast to previous
claims, little spatial variation in the spectral index is seen. In particular,
between 327 MHz and 5 GHz we see no evidence of spectral steepening near the
edge of the nebula, the ``jet'' or the ionized filaments. The rms limits on any
spectral index variations in these regions amount to no more than 0.01. We
believe that earlier reports of large steepening were the result of correlator
bias and image registration problems. An elongated feature was detected
1\arcmin northwest of the pulsar which may be a continuation of the well-known
wisp-like structures seen closer to the center of the nebula. At 74 MHz, we see
for the first time evidence of free-free absorption by the thermal material in
the Crab Nebula's filaments. Apart from some possible renewed acceleration
occurring in the wisps, the dominant accelerator of relativistic electrons in
the Crab Nebula is the pulsar itself.Comment: 20 pages, Latex, requires aaspp4.st
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