777 research outputs found
SAXJ1712.6-3739: a persistent hard X-ray source as monitored with INTEGRAL
The X-ray source SAXJ1712.6-3739 is a very weak Low Mass X-ray Binary
discovered in 1999 with BeppoSAX and located in the Galactic Center. This
region has been deeply investigated by the INTEGRAL satellite with an
unprecedented exposure time, giving us an unique opportunity to study the hard
X-ray behavior also for weak objects. The spectral results are based on the
systematic analysis of all INTEGRAL observations covering the source position
performed between February 2003 and October 2006. SAXJ1712.6-3739 did not shows
any flux variation along this period as well as compared to previous BeppoSAX
observation. Hence, to better constrain the physical parameters we combined
both instrument data. Long INTEGRAL monitoring reveals, for the first time,
that this X-ray burster is a weak persistent source, displaying a X-ray
spectrum extended to high energy and spending most of the time in a low
luminosity hard state. The broad-band spectrum is well modeled with a simple
Comptonized model with a seed photons temperature of ~0.5keV and an electron
temperature of ~24keV. The low mass accretion rate (~2x10^{-10} Msun/yr), the
long bursts recurrence time, the small sizes of the region emitting the seed
photons consisting with the inner disk radius and the high luminosity ratio in
the 40-100keV and 20-40keV band, are all features common to the Ultra Compact
source class.Comment: accepted A&
Six new candidate ultracompact X-ray binaries
Ultracompact X-ray binaries (UCXBs) appear able to sustain accretion onto the
compact accretor at rates lower than in wider X-ray binaries. This may be
understood by the smaller accretion disks in UCXBs: a lower X-ray luminosity
suffices to keep a disk completely ionized through irradiation and, thus, keep
the viscosity at a sufficiently high level to allow effective transport of
matter to the compact object. We employ this distinguishing factor on data from
RXTE and BeppoSAX to identify six new candidate UCXBs, thus increasing the
population by one quarter. The candidates are drawn from the population of
persistently accreting and type-I X-ray bursting low-mass X-ray binaries. The
X-ray bursts establish the low-mass X-ray binary nature and provide a handle on
the accretion rate. We find that the low accretion rates are supported by the
long burst recurrence times and the hard X-ray spectra of the persistent
emission as derived from the 2nd INTEGRAL catalog of soft gamma-ray sources. We
discuss the peculiar light curves of some new UCXB candidates.Comment: Section 2 corrected and improved thanks to comments by J.-P. Lasota.
Accepted for publication in Astronomy and Astrophysic
The nature of the infrared counterpart of IGR J19140+0951
The INTEGRAL observatory has been (re-)discovering new X-ray sources since
the beginning of nominal operations in early 2003. These sources include X-ray
binaries, Active Galactic Nuclei, cataclysmic variables, etc. Amongst the X-ray
binaries, the true nature of many of these sources has remained largely
elusive, though they seem to make up a population of highly absorbed high-mass
X-ray binaries. One of these new sources, IGR J19140+0951, was serendipitously
discovered on 2003 Mar 6 during an observation of the galactic microquasar GRS
1915+105. We observed IGR J19140+0951 with UKIRT in order to identify the
infrared counterpart. Here we present the H- and K-band spectra. We determined
that the companion is a B0.5-type bright supergiant in a wind-fed system, at a
distance \la 5 kpc.Comment: 5 pages, 2 figures, accepted for publication in MNRA
The supergiant fast X-ray transient IGRJ18483-0311 in quiescence: XMM-Newton, Swift, and Chandra observations
IGR J18483-0311 was discovered with INTEGRAL in 2003 and later classified as
a supergiant fast X-ray transient. It was observed in outburst many times, but
its quiescent state is still poorly known. Here we present the results of
XMM-Newton, Swift, and Chandra observations of IGRJ18483-0311. These data
improved the X-ray position of the source, and provided new information on the
timing and spectral properties of IGR J18483-0311 in quiescence. We report the
detection of pulsations in the quiescent X-ray emission of this source, and
give for the first time a measurement of the spin-period derivative of this
source. In IGRJ18483-0311 the measured spin-period derivative of
-(1.3+-0.3)x10^(-9) s/s likely results from light travel time effects in the
binary. We compare the most recent observational results of IGRJ18483-0311 and
SAXJ1818.6-1703, the two supergiant fast X-ray transients for which a similar
orbital period has been measured.Comment: Accepted for publication in MNRA
Orbital parameters of supergiant fast X-ray transients
Supergiant fast X-ray transient (SFXT) is a new class of the high mass X-ray
binary that shows short X-ray flares. The physical mechanism of SFXT short
flares is still open for discussion. The accretion process of dense clumps in
stellar wind onto neutron star (NS) has been proposed as the origin of such
short flares. In order to examine the applicability of the clumpy wind
scenario, we focus on the accretion mode that depends on orbital parameters.
Our goal is to impose restrictions on the orbital parameters of SFXT. Assuming
a simple analytic model of clumpy wind, we investigate the condition where the
size of accretion cylinder overcomes the clump size. The allowed parameter
region for SFXT is restricted in a relatively narrow window in diagram. Binary systems with large eccentricities (e \ga 0.4) and moderate
orbital periods ( d) are prone to show periodic X-ray
outbursts which are characteristic for SFXT. We confirm that systems with a
long orbital period of more than 100 days cannot produce bright X-ray flares in
the simple clumpy wind scenario.Comment: 6 pages, accepted for publication in A&
The INTEGRAL Galactic bulge monitoring program: the first 1.5 years
The Galactic bulge region is a rich host of variable high-energy point
sources. Since 2005, February 17 we are monitoring the source activity in this
region about every three days with INTEGRAL. Thanks to the large field of view,
the imaging capabilities and the sensitivity at hard X-rays, we are able to
present for the first time a detailed homogeneous (hard) X-ray view of a sample
of 76 sources in the Galactic bulge region. We describe the successful
monitoring program and show the first results for a period of about one and a
half year. We focus on the short (hour), medium (month) and long-term (year)
variability in the 20-60 keV and 60-150 keV bands. When available, we discuss
the simultaneous observations in the 3-10 keV and 10-25 keV bands. Per
visibility season we detect 32/33 sources in the 20-60 keV band and 8/9 sources
in the 60-150 keV band. On average, we find per visibility season one active
bright (>~100 mCrab, 20-60 keV) black-hole candidate X-ray transient and three
active weaker (<~25 mCrab, 20-60 keV) neutron star X-ray transients. Most of
the time a clear anti-correlation can be seen between the soft and hard X-ray
emission in some of the X-ray bursters. Hard X-ray flares or outbursts in X-ray
bursters, which have a duration of the order of weeks, are accompanied by soft
X-ray drops. On the other hand, hard X-ray drops can be accompanied by soft
X-ray flares/outbursts. We found a number of new sources, IGR J17354-3255, IGR
17453-2853, IGR J17454-2703, IGR J17456-2901b, IGR J17536-2339, and IGR
J17541-2252. We report here on some of the high-energy properties of these
sources. The high-energy light curves of all the sources in the field of view,
and the high-energy images of the region, are made available through the WWW at
http://isdc.unige.ch/Science/BULGE/.Comment: 27 pages, 42 figures, accepted for publication in A&A. Abstract
abridged. Tables 3,4,6,7 appear at the end. Images have been compressed and
are reduced in quality; original PostScript images can be retrieved from
http://isdc.unige.ch/~kuulkers/bulge
Multi-wavelength observations of Galactic hard X-ray sources discovered by INTEGRAL. I. The nature of the companion star
Context: The INTEGRAL hard X-ray observatory has revealed an emerging
population of highly obscured X-ray binary systems through multi-wavelength
observations. Previous studies have shown that many of these sources are
high-mass X-ray binaries hosting neutron stars orbiting around luminous and
evolved companion stars. Aims: To better understand this newly-discovered
population, we have selected a sample of sources for which an accurate
localisation is available to identify the stellar counterpart and reveal the
nature of the companion star and of the binary system. Methods: We performed an
intensive study of a sample of thirteen INTEGRAL sources, through
multi-wavelength optical to NIR photometric and spectroscopic observations,
using EMMI and SofI instruments at the ESO NTT telescope. We performed accurate
astrometry and identified candidate counterparts for which we give the optical
and NIR magnitudes. We detected many spectral lines allowing us to determine
the spectral type of the companion star. We fitted with stellar black bodies
the mid-infrared to optical spectral energy distributions of these sources.
From the spectral analysis and SED fitting we identified the nature of the
companion stars and of the binary systems. (abridged).Comment: A&A in press; The official date of acceptance is 15/12/2007; 25
pages, 6 figures, 8 tables. New version with language editing required by
edito
INTEGRAL/IBIS 7-year All-Sky Hard X-Ray Survey. Part II: Catalog of Sources
This paper is the second in a series devoted to the hard X-ray (17-60 keV)
whole sky survey performed by the INTEGRAL observatory over seven years. Here
we present a catalog of detected sources which includes 521 objects, 449 of
which exceed a 5 sigma detection threshold on the time-averaged map of the sky,
and 53 were detected in various subsamples of exposures. Among the identified
sources with known and suspected nature, 262 are Galactic (101 low-mass X-ray
binaries, 95 high-mass X-ray binaries, 36 cataclysmic variables, and 30 of
other types) and 219 are extragalactic, including 214 active galactic nuclei
(AGNs), 4 galaxy clusters, and galaxy ESO 389-G 002. The extragalactic (|b|>5
deg) and Galactic (|b|<5 deg) persistently detected source samples are of high
identification completeness (respectively ~96% and ~94%) and valuable for
population studies.Comment: 17 pages, 2 figures, accepted for publication in Astronomy and
Astrophysic
岩国徴古館所蔵『鳥類八百首』翻刻
The following is a reprint of 800 Bird Waka Poems preserved in Iwakuni Chouko-kan Library: Its postscript shows that this collection of poems is a transcript of a book which Masamoto Hosokawa ordered Tamehiro Reizei to transcribe in January 1943 (the third year of the Entoku Era). According to A Dictionary of Waka Poems, more than 250 poems in this collection come from A collection of Fuboku Waka Poems. However, not all of them are bird poems: they include poems of various topics such as animals, grass, trees, houses, weapons, cloth, and official duties. Therefore, the title of the collection does not represent its content precisely
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