arXiv subjects

Yael Fuchs

Publications and source records attributed to Yael Fuchs.

13 recordsLinked to original sources

arXiv2005

SS 433 : a phenomenon imitating a Wolf-Rayet star

We present mid-infrared (2-12 micron) spectra of the microquasar SS 433 obtained with the Infrared Space Observatory (spectroscopic mode of ISOPHOT and ISOCAM). We compare them to the spectra of four Wolf-Rayet stars: WR78, WR134, WR136, and WR147 in the same wavelength range. The mid-infrared spectrum of SS 433 mainly shows HI and HeI emission lines and is very similar to the spectrum of WR147, a WN8(h)+B0.5V binary. The 2-12 micron continuum emission of SS 433 corresponds to optically thin and partially optically thick free-free emission, from which we calculate a mass loss rate of 2-3 x 10^{-4} Msun/yr if the wind is homogeneous and a third of these values if it is clumped. This is consistent with a strong stellar wind from a WN star. However, following recent studies concluding that the mass donor star of SS 433 is not a Wolf-Rayet star, we propose that this strong wind out flows from a geometrically thick envelope of material that surrounds the compact object like a stellar atmosphere, imitating the Wolf-Rayet phenomenon. This wind could also wrap the mass donor star, and at larger distances (~ 40 AU), it might form a dust envelope from which the thermal emission, detected with ISOPHOT at 25 micron and 60 micron, would originate. This wind also probably feeds the material that is ejected in the orbital plane of the binary system and that forms the equatorial outflow detected in radio at distances > 100 AU.

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arXiv2004

SS 433: a WR X-ray binary or a WR-type phenomenon ?

We present mid-infrared spectra of the microquasar SS 433 obtained with the Infrared Space Observatory (spectroscopic mode of ISOPHOT) and compare them to the spectra of four Wolf-Rayet stars. The mid-infrared spectrum of SS 433 shows mainly HI and HeI emission lines and is very similar to the spectrum of WR 147, a WN8(h)+B0.5V binary with a colliding wind. The 2-12 micron continuum emission corresponds to optically thin and partially optically thick free-free emission from which we calculate a mass loss rate of 1.4-2.2x10^{-4} M_sun/yr if the wind is homogeneous and a third of these values if it is clumped, which is consistent with a strong WN stellar wind. We propose that this strong wind outflows from a geometrically thick envelope of material surrounding the compact object like a stellar atmosphere, imitating the Wolf-Rayet phenomenon.

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arXiv2004

Multi-wavelength INTEGRAL NEtwork (MINE) observations of the microquasar GRS 1915+105

We present the international collaboration MINE (Multi-lambda Integral NEtwork) aimed at conducting multi-wavelength observations of X-ray binaries and microquasars simultaneously with the INTEGRAL gamma-ray satellite. We will focus on the 2003 March-April campaign of observations of the peculiar microquasar GRS 1915+105 gathering radio, IR and X-ray data. The source was observed 3 times in the plateau state, before and after a major radio and X-ray flare. It showed strong steady optically thick radio emission corresponding to powerful compact jets resolved in the radio images, bright near-infrared emission, a strong QPO at 2.5 Hz in the X-rays and a power law dominated spectrum without cutoff in the 3-300 keV range. We compare the different observations, their multi-wavelength light curves, including JEM-X, ISGRI and SPI, and the parameters deduced from fitting the spectra obtained with these instruments on board INTEGRAL.

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arXiv2003

Simultaneous multi-wavelength observations of microquasars (the MINE collaboration)

We present the international collaboration MINE (Multi-lambda INTEGRAL NEtwork) aimed at conducting multi-wavelength observations of microquasars simultaneously with the INTEGRAL satellite. The first results on GRS 1915+105 are encouraging and those to come should help us to understand the physics of the accretion and ejection phenomena around a compact object.

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arXiv2003

The MINE collaboration: multi-wavelength observations of microquasars with INTEGRAL, prospects with HESS and ANTARES

We present the international collaboration MINE (Multi-lambda Integral NEtwork) aimed at conducting multi-wavelength observations of X-ray binaries and microquasars simultaneously with INTEGRAL. The first results on GRS 1915+105 are encouraging and those to come should help us to understand the physics of the accretion and ejection phenomena around a compact object. A collaboration such as MINE could be very useful for observing quasars and microquasars simultaneously with HESS and later with ANTARES.

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arXiv2003

Simultaneous multi-wavelength observations of GRS 1915+105

We present the result of multi-wavelength observations of the microquasar GRS 1915+105 in a plateau state with a luminosity of ~7.5x10^{38) erg s-1 (~40% L_Edd), conducted simultaneously with the INTEGRAL and RXTE satellites, the ESO/NTT, the Ryle Telescope, the NRAO VLA and VLBA, in 2003 April 2-3. For the first time were observed concurrently in GRS 1915+105 all of the following properties: a strong steady optically thick radio emission corresponding to a powerful compact jet resolved with the VLBA, bright near-IR emission, a strong QPO at 2.5 Hz in the X-rays and a power law dominated spectrum without any cutoff in the 3-400 keV range.

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arXiv2003

Mid-Infrared observations of GRS 1915+105 during plateau and flaring states

We present mid-infrared (4-18 micron) observations of the microquasar GRS 1915+105 obtained with ISOCAM, the camera on board the Infrared Space Observatory (ISO), in 1996 April and 1997 October. The first observation probably occurred during a flaring event with oscillating synchrotron emission. The 1997 observation occurred a few days before a major relativistic ejection, during a plateau state of inverted-spectrum radio emission and hard quasi-stable X-ray emission. The K-M giant donor star in GRS 1915+105 cannot account for the mid-IR emission and we discuss the possible additional components depending on two absorption laws. Thermal emission from dust seems unlikely. The flat mid-IR spectrum obtained during the plateau state is likely to be synchrotron emission. It would be the first evidence of the infrared extension of the radio synchrotron emission from the compact jets, although optically thin free-free emission from an X-ray driven-wind from the accretion disc cannot be excluded.

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arXiv2002

SS433: the second Wolf-Rayet X-ray binary ?

We present mid-infrared spectrophotometric observations of SS433 with ISOPHOT. The HeI+HeII lines in both spectra of SS433 and of the Wolf-Rayet star WR147, a wind-colliding WN8+BO5 binary system, closely match. The 2.5-12 micron continuum radiation is due to an expanding wind free-free emission in an intermediate case between optically thick and optically thin regimes. The inferred mass loss rate evaluation gives ~10^{-4} Msun/yr. Our results are consistent with a Wolf-Rayet-like companion to the compact object in SS433. A similar study for Cygnus X-3 confirms the Wolf-Rayet-like nature of its companion, although with a later WN type than previously suggested.

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arXiv2002

Multiwavelength Observation of SS433 Jet Interaction with the Interstellar Medium

SS433 is an X-ray binary emitting persistent relativistic double sided jets that expand into the surrounding W50 radio nebula. The SS433/W50 system is then an excellent laboratory for studying relativistic jet interaction with the surrounding interstellar medium. In this context, part of W50 nebula has been mapped with ISOCAM at 15 micron, where the large scale X-ray jets are observed. I will show the results, particularly on the W50 western lobe, on two emitting regions detected in IR with IRAS, and observed in millimeter wavelength (CO(1-0) transition). It is uncertain whether these regions are due to heated dust by either young stars or the relativistic jet, or to synchrotron emission from shock re-acceleration regions as in some extragalactic jets from AGN. In this latter case, INTEGRAL might detect soft gamma-ray emission.

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arXiv2001

A 2.4-80 micron spectrophotometric study of SS433 with ISO

We present ISOPHOT spectrophotometric observations of SS433 at four different orbital phases in 1996 and 1997. The HeI+HeII lines in both spectra of SS433 and the Wolf-Rayet star WR147, a WN8+BO5 binary system, closely match. The 2.5-12 micron continuum radiation is due to an expanding wind free-free emission in an intermediate case between optically thick and optically thin regime. A rough mass loss rate evaluation gives about 1.4 10^{-4} M_sun/yr. Results are consistent with a Wolf-Rayet-like companion to the compact object in SS433.

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arXiv2001

ISO's view of SS433 Jet Interactions with the Interstellar Medium

SS433 is a jet emitting X-ray binary surrounded by the W50 radio nebula. The SS433/W50 system is an excellent laboratory for studying relativistic jet interaction with the surrounding interstellar medium. In this context, part of the W50 nebula has been mapped with ISOCAM at 15 micron. I will show the results particularly on the W50 west lobe, and on 2 emitting zones detected with IRAS who have also been observed in millimetre wavelength (CO(1-0) transition), and for one of them by spectroscopy with ISOLWS and ISOSWS between 2 and 200 micron.

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arXiv1999

Soft Gamma-ray Repeaters in Clusters of Massive Stars

Infrared observations of the environment of the two Soft Gamma-ray Repeaters (SGRs) with the best known locations on the sky show that they are associated to clusters of massive stars. Observations with ISO revealed that SGR 1806-20 is in a cluster of giant massive stars, still enshrouded in a dense cloud of gas and dust. SGR 1900+14 is at the edge of a similar cluster that was recently found hidden in the glare of a pair of M5 supergiant stars. Since none of the stars of these clusters has shown in the last years significant flux variations in the infrared, these two SGRs do not form bound binary systems with massive stars. SGR 1806-20 is at only ~ 0.4 pc, and SGR 1900+14 at ~ 0.8 pc from the centers of their parental star clusters. If these SGRs were born with typical neutron star runaway velocities of ~ 300 km/s, they are not older than a few 10$^{3}$ years. We propose that SGR 1806-20 and SGR 1900+14 are ideal laboratories to study the evolution of supernovae explosions inside interstellar bubbles produced by the strong winds that prevail in clusters of massive stars.

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arXiv1999

ISO observations of the environment of the soft gamma-ray repeater SGR 1806-20

Observations at near and mid-infrared wavelengths (1-18 micron) of SGR 1806-20 suggest that it is associated with a cluster of giant massive stars which are enshrouded in a dense cloud of dust. The centre of the best sky position of the gamma-ray source (Hurley et al. 1999) lies on top of the dust cloud at only 7 arcsec (~0.5 pc at a distance of 14.5 kpc) from the star cluster, and 12 arcsec (~0.85 pc) from a Luminous Blue Variable Star (LBV) which had been proposed to be associated with the SGR (Kulkarni et al. 1995). The bright cloud of interstellar gas and dust observed with ISO (Infrared Space Observatory) is probably the birth site of the cluster of massive stars, the LBV star, and the progenitor of the soft gamma-ray repeater pulsar. The presence of such a young star formation region is compatible with the current interpretation of soft gamma-ray repeaters as young neutron stars. The SGR 1806-20 compact source is unlikely to form a bound binary system with any of the infrared luminous massive stars, since no flux variations in the near-infrared were detected from the latter in an interval of 4 years.The ISO observations were made over two epochs, 11 days before and 2 hours after a soft gamma-ray burst detected with the Interplanetary Network, and they show no enhanced mid-infrared emission associated to the high energy activity of the SGR.

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