67 research outputs found
Optical to Mid-Infrared observations revealing the most obscured high-energy sources of the Galaxy
A new type of sources has been discovered by INTEGRAL. These sources are in
the course of being unveiled by means of multi-wavelength optical, near- and
mid-infrared observations. Among the high-energy binary sources, two distinct
classes are appearing. The first class is constituted of intrinsically obscured
high-energy sources, of which IGR J16318-4848 seems to be the archetype. The
second class is populated by the so-called supergiant fast X-ray transients,
with IGR J17544-2619 being the archetype. We report here on multi-wavelength
observations of sources from these two classes, focusing on optical to
mid-infrared observations. We show that in the case of the obscured sources IGR
J16318-4848 and IGR J16195-4945, our observations suggest the presence of
absorbing material (dust and/or cold gas) enshrouding the whole binary system.
We then discuss the nature of these two different types of sources.Comment: Proceedings of The 6th INTEGRAL Workshop, The Obscured Universe,
Space Research Institute, Moscow, Russia, July 2-8, 2006, to be published by
ESA's Publications Division in December 2006 as Special Publication SP-622, 8
pages, 7 figure
Herschel observations of INTEGRAL supergiant High Mass X-ray Binaries
We present preliminary results on Herschel/PACS mid/far-infrared photometric
observations of INTEGRAL supergiant High Mass X-ray Binaries (HMXBs), with the
aim of detecting the presence and characterizing the nature of absorbing
material (dust and/or cold gas), either enshrouding the whole binary systems,
or surrounding the sources within their close environment. These unique
observations allow us to better characterize the nature of these HMXBs, to
constrain the link with their environment (impact and feedback), and finally to
get a better understanding of the formation and evolution of such rare and
short-living supergiant HMXBs in our Galaxy.Comment: Proceedings of the 9th INTEGRAL Workshop and celebration of the 10th
anniversary of the launch "An INTEGRAL view of the high-energy sky (the first
10 years)", accepted for publication in Proceedings of Science (editors: F.
Lebrun, A. Goldwurm and C. Winkler), 4 pages, 2 figure
Herschel observations of dust around the high-mass X-ray binary GX 301-2
We aim at characterising the structure of the gas and dust around the high
mass X-ray binary GX 301-2, a highly obscured X-ray binary hosting a hypergiant
star and a neutron star, in order to better constrain its evolution. We used
Herschel PACS to observe GX 301-2 in the far infrared and completed the
spectral energy distribution of the source using published data or catalogs,
from the optical to the radio range (0.4 to 4x10^4 micrometer). GX 301-2 is
detected for the first time at 70 and 100 micrometer. We fitted different
models of circumstellar environments to the data. All tested models are
statistically acceptable, and consistent with a hypergiant star at ~3 kpc. We
found that the addition of a free-free emission component from the strong
stellar wind is required and could dominate the far infrared flux. Through
comparisons with similar systems and discussion on the estimated model
parameters, we favour a disk-like circumstellar environment of ~8 AU that would
enshroud the binary system. The temperature goes down to ~200 K at the edge of
the disk, allowing for dust formation. This disk is probably a rimmed viscous
disk with an inner rim at the temperature of the dust sublimation temperature
(~1500 K). The similarities between the hypergiant GX 301-2, B[e] supergiants
and the highly obscured X-ray binaries (in particular IGR J16318-4848) are
strengthened. GX 301-2 might represent a transition stage in the evolution of
massive stars in binary systems, connecting supergiant B[e] systems to luminous
blue variables.Comment: accepted for publication in ApJ (tentatively scheduled for the
December 1, 2014, V796 - 2 issue), 15 pages with emulateapj styl
Infrared identification of high-mass X-ray binaries discovered by INTEGRAL
Since it started observing the sky, the INTEGRAL satellite has discovered new
categories of high mass X-ray binaries (HMXB) in our Galaxy. These observations
raise important questions on the formation and evolution of these rare and
short-lived objects. We present here new infrared observations from which to
reveal or constrain the nature of 15 INTEGRAL sources, which allow us to update
and discuss the Galactic HMXB population statistics. After previous photometric
and spectroscopic observing campaigns in the optical and near-infrared, new
photometry and spectroscopy was performed in the near-infrared with the SofI
instrument on the ESO/NTT telescope in 2008 and 2010 on a sample of INTEGRAL
sources. These observations, and specifically the detection of certain features
in the spectra, allow the identification of these high-energy objects by
comparison with published nIR spectral atlases of O and B stars. We present
photometric data of nine sources (IGR J10101-5654, IGR J11187-5438, IGR
J11435-6109, IGR J14331-6112, IGR J16328-4726, IGR J17200-3116, IGR
J17354-3255, IGR J17404-3655, and IGR J17586-2129) and spectroscopic
observations of 13 sources (IGR J10101-5654, IGR J11435-6109, IGR J13020-6359,
IGR J14331-6112, IGR J14488-5942, IGR J16195-4945, IGR J16318-4848, IGR
J16320-4751, IGR J16328-4726, IGR J16418-4532, IGR J17354-3255, IGR
J17404-3655, and IGR J17586-2129). Our spectroscopic measurements indicate
that: five of these objects are Oe/Be high-mass X-ray binaries (BeHMXB), six
are supergiant high-mass X-ray binaries (sgHMXB), and two are sgB[e]. From a
statistical point of view, we estimate the proportion of confirmed sgHMXB to be
42% and that of the confirmed BeHMXB to be 49%. The remaining 9% are peculiar
HMXB.Comment: Accepted for publication in A&A (in press
Multi-wavelength observations of Galactic hard X-ray sources discovered by INTEGRAL. II. The environment of the companion star
Context: The INTEGRAL mission has led to the discovery of a new type of
supergiant X-ray binaries (SGXBs), whose physical properties differ from those
of previously known SGXBs. Those sources are in the course of being unveiled by
means of multi-wavelength X-rays, optical, near- and mid-infrared observations,
and two classes are appearing. The first class consists of obscured persistent
SGXBs and the second is populated by the so-called supergiant fast X-ray
transients (SFXTs). Aims: We report here mid-infrared (MIR) observations of the
companion stars of twelve SGXBs from these two classes in order to assess the
contribution of the star and the material enshrouding the system to the total
emission.} Methods: We used data from observations we carried out at ESO/VLT
with VISIR, as well as archival and published data, to perform broad-band
spectral energy distributions of the companion stars and fitted them with a
combination of two black bodies representing the star and a MIR excess due to
the absorbing material enshrouding the star, if there was any. Results: We
detect a MIR excess in the emission of IGR J16318-4848, IGR J16358-4726, and
perhaps IGR J16195-4945. The other sources do not exhibit any MIR excess even
when the intrinsic absorption is very high. (abridged)Comment: A&A in press, The official date of acceptance is 25/01/2008, 17
pages, 4 figures, 9 tables. New version with english language editing
required by editor, note added in proo
Investigating the Optical Counterpart Candidates of Four INTEGRAL Sources localized with Chandra
We report on the optical spectroscopic follow up observations of the
candidate counterparts to four INTEGRAL sources: IGR J04069+5042, IGR
J06552-1146, IGR J21188+4901 and IGR J22014+6034. The candidate counterparts
were determined with Chandra, and the optical observations were performed with
1.5-m RTT-150 telescope (T\"{U}B\.{I}TAK National Observatory, Antalya, Turkey)
and 2.4-m Hiltner Telescope (MDM Observatory, Kitt Peak, Arizona). Our
spectroscopic results show that one of the two candidates of IGR J04069+5042
and the one observed for IGR J06552-1146 could be active late-type stars in RS
CVn systems. However, according to the likelihood analysis based on Chandra and
INTEGRAL, two optically weaker sources in the INTEGRAL error circle of IGR
J06552-1146 have higher probabilities to be the actual counterpart. The
candidate counterparts of IGR J21188+4901 are classified as an active M-type
star and a late-type star. Among the optical spectra of four candidates of IGR
J22014+6034, two show H\alpha emission lines, one is a late-type star and the
other is a M type. The likelihood analysis favors a candidate with no
distinguishing features in the optical spectrum. Two of the candidates
classified as M type dwarfs are similar to some IGR candidates claimed to be
symbiotic stars. However, some of the prominent features of symbiotic systems
are missing in our spectra, and their NIR colors are not consistent with those
expected for giants. We consider the IR colors of all IGR candidates claimed to
be symbiotic systems and find that low resolution optical spectrum may not be
enough for conclusive identification.Comment: 24 pages, 12 figures; accepted for publication in Ap
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