The stellar wind velocity field of HD 77581|
2015-07-07 | INTEGRAL, HEAVENS, X-ray binary
The early acceleration of stellar winds in massive stars is poorly constrained. The comparison of X-ray observations of the high-mass X-ray binary Vela X-1 accumulated over 9 years, with hydodynamical simulations allows to constrain the stellar wind velocity field very close to the surface of the super-giant companion. The observed acceletration is more efficient than usually assumed.
The high energy spectrum of 3C 273|
2015-03-12 | AGN, INTEGRAL, Fermi
We studied the high energy spectral variability of the bright quasar 3C 273 from ~1 keV up to ~10 GeV using data collected with RXTE-PCA, INTEGRAL and Fermi/LAT and compared them with radio data at 37 GHz collected at the Metsähovi Radio Observatory. Quasi-simultaneous broad band high energy spectra have been built at the epoch of γ ray flares and X-ray flares. Both timing and spectral analysis suggest a two-component scenario, where the X-ray emission is likely dominated by a Seyfert-like component, while the γ ray emission is dominated by a blazar-like component originated in the relativistic jet.
Origin of the X-ray off-states in Vela X-1|
2014-12-22 | INTEGRAL, X-ray binary, HEAVENS
INTEGRAL discovered huge hard X-ray variability and off-sates in Vela X-1 and other high mass X-ray binaries. Hydrodynamic simulations allowed us to discover the likely source for such variations occuring on time scales of hours. These variations are related to oscillations of the accretion rate (with a typical period of ∼ 6800 sec) corresponding to the complex motion of a bow shock forming between the neutron star and the massive companion, moving either towards or away from the neutron star.
Extraordinary jet shot by a runaway pulsar|
2014-02-07 | INTEGRAL | Press Release
The source IGR J11014-6103, discovered with INTEGRAL, is powered by an isolated pulsar, which is running through our Galaxy at a speed of ~1000 km/s. Thanks to our observations with the Chandra X-ray satellite and with the Australia Radio Telescope Compact Array (ATCA), we found that this pulsar forms a ~15pc (i.e. 40 light-years) long, ballistic jet. This is the first case where a supersonic runaway pulsar is shown to produce a ballistic jet. This discovery opens up several new questions about the formation of pulsars and how do they produce jets.
Swings between rotation and accretion power in a millisecond binary pulsar |
2013-09-26 | INTEGRAL, X-ray binary | Press Release
A new transient source, identified as IGR J18245-2452, was first detected in X-rays on 28 March 2013 by INTEGRAL in the globular cluster M28, which lies in the constellation Sagittarius. Observations by XMM-Newton determined the pulsar's spin period to be 3.9 milliseconds clearly identifying it as an X-ray-bright millisecond pulsar powered by accretion of material from a nearby low-mass star companion. The spin period and other key characteristics was found to match perfectly those of a pulsar in M28 that had been observed in 2006, but only at radio wavelengths. This is then the first ever fast-spinning 'millisecond pulsar' caught in a crucial evolutionary phase, as it swings between emitting pulses of X-rays and radio waves.
Tidal disruption of a super-Jupiter by a massive black hole|
2013-04-02 | INTEGRAL | Press Release
A strong hard X-ray flare was discovered in the galaxy NGC 4845 by INTEGRAL in January 2011. This emission corresponds to the tidal disruption of a super-Jupiter close to the giant black hole at the center of the galaxy. The disrupted material heated up before falling in the black hole, emitting at high energies.
Measuring neutron star masses by gravitational deflection|
2012-09-13 | INTEGRAL, X-ray binary | Press Release
Neutron stars are fundamental to probe the physics of matter at the highest density, where even atom nuclei are broken into quarks. New stellar systems, discovered by INTEGRAL, including a neutron star orbiting a massive companion, allow to weight the neutron star in an original manner, by measuring the gravitational deflection of the wind stream generated by the companion star. The gas stream is so dense that it completely absorbs the emission of the neutron star, even X-rays. Only gamma-rays telescopes, such as INTEGRAL, can detect them.
Reflection in Seyfert galaxies and the unified model of AGN|
2011-08-02 | INTEGRAL, AGN, Diffuse emission | Press Release
From an extremely long hard X-ray look at AGN we found unexpected differences amongst different classes of objects. These differences could be explained by supermassive black holes living in different environments, and might help shading light on the origin of the peak of the cosmic X-ray background.
IGR J11014-6103: a newly discovered pulsar wind nebula?|
2011-07-19 | INTEGRAL
To study the unidentified source IGR J11014-6103, we analyzed archival data from X-rays to the radio energy range spanning 30 years of observation. The analysis in soft X-rays revealed a 4-arcmin cometary-like tail with two brighter objects at one end of the extended emission. Based on the results of our spectral and timing analysis, we suggest that the source might be a pulsar wind nebula produced by a spinning neutron star (pulsar) advancing at high-velocity through the interstellar medium. These system are rare, and if confirmed, this would be the first detected with INTEGRAL.
XMM-Newton observations of IGRJ18410-0535: The ingestion of a clump by a supergiant fast X-ray transient|
2011-06-28 | INTEGRAL, X-ray binary | Press Release
With a stroke of luck, we caught the supergiant fast X-ray transient IGRJ18410-0535 undergoing a bright X-ray flare by using ESA's XMM-Newton X-ray observatory. This outburst of X-rays, which lasted about four hours, was due to a sudden increase in the rate at which the neutron star was accreting matter from its companion, a blue supergiant star. By monitoring this phenomenon in unprecedented detail, the data provide the first, substantive evidence to explain such luminosity variations in this type of binary system; the flare appears to be due to the ingestion of a massive clump of matter by the neutron star.
AX J1910.7+0917 and three newly discovered INTEGRAL sources|
2011-01-11 | INTEGRAL, X-ray binary
We investigated the nature of the still poorly known X-ray source AX J1910.7+0917 and searched for closeby previously undetected objects, making use of the high sensitivity of the IBIS/ISGRI telescope and the improvements in the data analysis software. We analyzed all publicly available data from INTEGRAL, XMM-Newton, Chandra and ASCA and we discussed the different possibilities for the nature of AX J1910.7+0917. In the IBIS/ISGRI field-of-view around AX J1910.7+0917, we discovered three new sources: IGR J19173+0747, IGR J19294+1327 and IGR J19149+1036. For two of them we report the results of follow-up observations carried out with Swift/XRT.
12 hours spikes from the Crab Pevatron|
2010-12-15 | INTEGRAL, Fermi, VHE | Press Release
The Crab nebula featured 3 gamma-ray spikes in the GeV band in September 2010. These γ-ray flares are due to synchrotron emission from a very compact Pevatron located closer to the pulsar than the equatorial termination shock between the supersonic wind and the surrounding nebula. The spectral and timing properties of the flare are interpreted in the framework of a relativistically moving emitter. The flare duration is of the order of the synchrotron cooling time scale for electrons at an energy larger than 1015 eV, the highest electron energy ever measured in a cosmic accelerator.
Eta Carinae: a very large hadron collider|
2010-12-13 | Fermi, INTEGRAL | Press Release
Eta Carinae system consists of two massive stars with dense supersonic winds. Observation with Fermi/LAT suggests that collisions of high energetic hadrons take place in the colliding winds region.
X-ray wind tomography of the highly absorbed HMXB IGR J17252-3616|
2010-12-08 | X-ray binary, INTEGRAL
We observed the highly absorbed HMXB IGR J17252-3616 along the orbit with XMM-Newton. Our analysis suggests highly asymmetric (and extended) structures trailing the neutron star and slower wind terminal velocities (~400 km/s) than observed in classical systems. If confirmed, it may turn out that half of the persistent sgHMXB have low stellar wind speeds.
Seyfert 2 galaxies in the GeV band: jets and starburst|
2010-10-18 | Fermi, AGN, INTEGRAL
We present Fermi/LAT data analysis of two unusual suspects in the GeV band, NGC 1068 and NGC 4945, which are both composite starburst/active galactic nuclei objects. We show that the GeV emission of NGC 4945 could be interpreted in terms of starburst activity, while the one of NGC 1068 should account for a dominant contribution from the central AGN.
INTEGRAL discovery of a new transient source: IGR J16374-5043|
2010-08-24 | INTEGRAL, X-ray binary
A new transient hard X-ray source was discovered by INTEGRAL in the large field of view of IBIS/ISGRI during observations of another source, RX J1713.7-3946. The new source called IGR J16374-5043 produced a bright flare on 22 August 2010 lasting about a day.
INTEGRAL and RXTE observations of XTE J1946+274 in outburst|
2010-06-23 | INTEGRAL, X-ray binary
During the observations of Cyg X-1 in satellite Rev. 0938 (PI Wilms), INTEGRAL caught the Be/X-ray binary transient XTE J1946+274 in outburst (flux of ~135 mCrab, 20-40 keV range). This is the first outburst of the source since 2001 after a long quiescence period.
Multi-zone warm and cold clumpy absorbers in 3 Seyfert galaxies|
2010-05-10 | AGN, INTEGRAL
We performed the spectral analysis of 3 Seyfert galaxies presenting evidence of a strong soft excess below 2 keV. We showed how this soft excess can be related only to a clumpy structure of the absorbers, and does not need any additional emission component.
An exceptionally bright outburst from the HMXB XTE J1855-026|
2010-03-16 | INTEGRAL, X-ray binary
On 14 March 2010, INTEGRAL observed three exceptionally bright flares from the high-Mass X-ray Binary XTE J1855-026. The first flare lasted only about 2 minutes and reached a peak intensity of almost that of the Crab nebula.
INTEGRAL spectra of the cosmic X-ray background and Galactic ridge emission|
2010-01-14 | INTEGRAL, Diffuse emission, AGN, X-ray binary
We reanalyzed the INTEGRAL Earth occultation observations of early 2006 to derive IBIS spectra of the cosmic X-ray background (CXB) and of the Galactic ridge X-ray emission (GRXE) in the ~20-200 keV range. The potential of such observations is demonstrated by the state-of-the-art hard X-ray spectra we derived for three fundamental components: the CXB, the GRXE and the Earth emission.
GRB 090817: INTEGRAL/OMC's unlucky gamma-ray burst|
2009-08-18 | INTEGRAL, GRB
On 17 August 2009, INTEGRAL caught another long Gamma-Ray Burst (GRB) in the field of view of IBIS/ISGRI. This one was special as it was also in the smaller field of view of the X-ray monitor JEM-X 1 and (almost) of the optical camera OMC.
Discovery of IGR J17497-2821 : a new X-ray nova|
2006-11-27 | INTEGRAL, X-ray binary | Press Release
INTEGRAL discovered a hard X-ray transient on 17 Sep. 2006 near the Galactic Centre. Infrared and X-ray follow-up observations pin-point the source location and show that it is a new X-ray nova and likely a black-hole candidate.
Public INTEGRAL TOO observation of V 0332+53 in outburst|
2005-01-12 | INTEGRAL, X-ray binary
The High-Mass X-ray Binary V 0332+53 (EXO 0331+530), underwent a dramatic outburst at the end of 2004, and was a Target of Opportunity (TOO) for a public INTEGRAL observation conducted on 6-10 January 2005. Three cyclotron lines are clearly detected in the spectrum.