17 research outputs found
Young stellar objects from soft to hard X-rays
Magnetically active stars are the sites of efficient particle acceleration
and plasma heating, processes that have been studied in detail in the solar
corona. Investigation of such processes in young stellar objects is much more
challenging due to various absorption processes. There is, however, evidence
for violent magnetic energy release in very young stellar objects. The impact
on young stellar environments (e.g., circumstellar disk heating and ionization,
operation of chemical networks, photoevaporation) may be substantial. Hard
X-ray devices like those carried on Simbol-X will establish a basis for
detailed studies of these processes.Comment: Proc. "Simbol-X: Focusing on the Hard X-Ray Universe", Paris, 2-5
Dec. 2008, ed. J. Rodriguez and P. Ferrando, in press; 6 pages, 4 figure
Black-hole binaries: life begins at 40 keV
In the study of black-hole transients, an important problem that still needs
to be answered is how the high-energy part of the spectrum evolves from the
low-hard to the high-soft state, given that they have very different
properties. Recent results obtained with RXTE and INTEGRAL have given
inconsistent results. With RXTE, we have found that the high-energy cutoff in
GX 339-4 during the transition first decreases (during the low-hard state),
then increases again across the Hard-Intermediate state, to become unmeasurable
in the soft states (possibly because of statistical limitations). We show
Simbol-X will be able to determine the spectral shape with superb accuracy. As
the high-energy part of the spectrum is relatively less known than the one
below 20 keV, Simbol-X will provide important results that will help out
understanding of the extreme physical conditions in the vicinity of a
stellar-mass black hole.Comment: Proc. "Simbol-X: Focusing on the Hard X-Ray Universe", Paris, 2-5
Dec. 2008, ed. J. Rodriguez and P. Ferrando; 4 pages, 3 figure
Heavily obscured AGN with SIMBOL-X
By comparing an optically selected sample of narrow lines AGN with an X-ray
selected sample of AGN we have recently derived an estimate of the intrinsic
(i.e. before absorption) 2-10 keV luminosity function (XLF) of Compton Thick
AGNs. We will use this XLF to derive the number of Compton Thick AGN that will
be found in the SIMBOL-X survey(s).Comment: Talk at the Simbol-X symposium held in Paris, 2-5 December, 2008. 6
pages, 1 figure with three panel
The emerging population of pulsar wind nebulae in hard X-rays
The hard X-ray synchrotron emission from pulsar wind nebulae (PWNe) probes
energetic particles, closely related to the pulsar injection power at the
present time. INTEGRAL has disclosed the yet poorly known population of hard
X-ray pulsar/PWN systems. We summarize the properties of the class, with
emphasys on the first hard X-ray bow-shock (CTB 80 powered by PSR B1951+32),
and highlight some prospects for the study of Pulsar Wind Nebulae with the
Simbol-X mission.Comment: Proceedings of the 2nd Simbol-X Symposium, AIP Conf. Proc. Series,
Eds. P. Ferrando and J. Rodriguez (4 pages, 2 figures
The Galactic population of HMXBs as seen with INTEGRAL during its four first years of activity
We collected the parameters (position, absorption, spin, orbital period,
etc..), when known, of all Galactic sources detected by INTEGRAL during its
four first years of activity. We use these parameters to test theoretical
predictions. For example, it is clear that HMXBs tend to be found mostly in the
tangential direction of the Galactic arms, while LMXBs tend to be clustered in
the Galactic bulge. We then focus on HMXBs and present two possible new tools,
in addition to the well-known ``Corbet-diagram'', to distinguish between
Be-HMXBs and Sg-HMXBsComment: 5 pages, 3 figures proceedings of "A population explosion: the nature
and evolution of X-ray binaries in diverse environments", conference held in
St.Petersburg Beach, Florida; R.M.Bandyopadhyay, S.Wachter, D.Gelino,
C.R.Gelino, ed
What can Simbol-X do for gamma-ray binaries?
Gamma-ray binaries have been uncovered as a new class of Galactic objects in
the very high energy sky (> 100 GeV). The three systems known today have hard
X-ray spectra (photon index ~ 1.5), extended radio emission and a high
luminosity in gamma-rays. Recent monitoring campaigns of LSI +61 303 in X-rays
have confirmed variability in these systems and revealed a spectral hardening
with increasing flux. In a generic one-zone leptonic model, the cooling of
relativistic electrons accounts for the main spectral and temporal features
observed at high energy. Persistent hard X-ray emission is expected to extend
well beyond 10 keV. We explain how Simbol-X will constrain the existing models
in connection with Fermi Space Telescope measurements. Because of its
unprecedented sensitivity in hard X-rays, Simbol-X will also play a role in the
discovery of new gamma-ray binaries, giving new insights into the evolution of
compact binaries.Comment: 4 pages, 1 figure, Proceedings of the 2nd International Simbol-X
symposium held in Paris, 2-5 December 200
Pulsed thermal emission from the accreting pulsar XMMU J054134.7-682550
Aims. Soft X-ray excesses have been detected in several Be/X-ray binaries and
interpreted as the signature of hard X-ray reprocessing in the inner accretion
disk. The system XMMU J054134.7-682550, located in the LMC, featured a giant
Type II outburst in August 2007. The geometry of this system can be understood
by studying the response of the soft excess emission to the hard X-ray pulses.
Methods. We have analyzed series of simultaneous observations obtained with
XMM-Newton/EPIC-MOS and RXTE/PCA in order to derive spectral and temporal
characteristics of the system, before, during and after the giant outburst.
Spectral fits were performed and a timing analysis has been carried out.
Spectral variability, spin period evolution and energy dependent pulse shapes
are analysed.
Results. The outburst (L_X = 3* 10^38 erg/s \approx L_EDD) spectrum could be
modeled successfully using a cutoff powerlaw, a cold disk emission, a hot
blackbody, and a cyclotron absorption line. The magnetic field and
magnetospheric radius could be constrained. The thickness of the inner
accretion disk is broadened to a width of 75 km. The hot blackbody component
features sinusoidal modulations indicating that the bulk of the hard X-ray
emission is emitted preferentially along the magnetic equator. The spin period
of the pulsar decreased very significantly during the outburst. This is
consistent with a variety of neutron star equations of state and indicates a
very high accretion rate.Comment: 6 pages. Accepted for publication in A&
Simbol-X Background Minimization: Mirror Spacecraft Passive Shielding Trade-Off Study
The present work shows a quantitative trade-off analysis of the Simbol-X
Mirror Spacecraft (MSC) passive shielding, in the phase space of the various
parameters: mass budget, dimension, geometry, and composition. A simplified
physical (and geometrical) model of the sky screen, implemented by means of a
GEANT4 simulation, has been developed to perform a performance-driven mass
optimization and evaluate the residual background level on Simbol-X focal
plane.Comment: 3 pages, 6 figures, to appear in the proceedings of the second
Simbol-X International Symposium "Simbol-X - Focusing on the Hard X-ray
Universe", AIP Conf. Proc. Series, P. Ferrando and J. Rodriguez ed
Compton reflection in AGN with Simbol-X
AGN exhibit complex hard X-ray spectra. Our current understanding is that the
emission is dominated by inverse Compton processes which take place in the
corona above the accretion disk, and that absorption and reflection in a
distant absorber play a major role. These processes can be directly observed
through the shape of the continuum, the Compton reflection hump around 30 keV,
and the iron fluorescence line at 6.4 keV. We demonstrate the capabilities of
Simbol-X to constrain complex models for cases like MCG-05-23-016, NGC 4151,
NGC 2110, and NGC 4051 in short (10 ksec) observations. We compare the
simulations with recent observations on these sources by INTEGRAL, Swift and
Suzaku. Constraining reflection models for AGN with Simbol-X will help us to
get a clear view of the processes and geometry near to the central engine in
AGN, and will give insight to which sources are responsible for the Cosmic
X-ray background at energies above 20 keV.Comment: 4 pages, 1 figure, to appear in the proceedings of the second
Simbol-X Symposium "Simbol-X - Focusing on the Hard X-ray Universe", AIP
Conf. Proc. Series, P. Ferrando and J. Rodriguez ed