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Register a new userFaint Infrared Flares from the Microquasar GRS 1915+105
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Stephen S. Eikenberry
Publication date
2000
fields
Physics
and research's language is
English
Authors
S. Eikenberry
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We present simultaneous infrared and X-ray observations of the Galactic microquasar GRS 1915+105 using the Palomar 5-m telescope and Rossi X-ray Timing Explorer on July 10, 1998 UT. Over the course of 5 hours, we observed 6 faint infrared (IR) flares with peak amplitudes of $sim 0.3-0.6 $ mJy and durations of $sim 500-600 $ seconds. These flares are associated with X-ray soft-dip/soft-flare cycles, as opposed to the brighter IR flares associated with X-ray hard-dip/soft-flare cycles seen in August 1997 by Eikenberry et al. (1998). Interestingly, the IR flares begin {it before} the X-ray oscillations, implying an ``outside-in origin of the IR/X-ray cycle. We also show that the quasi-steady IR excess in August 1997 is due to the pile-up of similar faint flares. We discuss the implications of this flaring behavior for understanding jet formation in microquasars.
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We report infrared observations of the microquasar GRS 1915+105 using the NICMOS instrument of the Hubble Space Telescope during 9 visits in April-June 2003. During epochs of high X-ray/radio activity near the beginning and end of this period, we find that the $1.87 $um infrared flux is generally low ($sim 2$ mJy) and relatively steady. However, during the X-ray/radio ``plateau state between these epochs, we find that the infrared flux is significantly higher ($sim 4-6$ mJy), and strongly variable. In particular, we find events with amplitudes $sim 20-30$% occurring on timescales of $sim 10-20$s (e-folding timescales of $sim 30$s). These flickering timescales are several times faster than any previously-observed infrared variability in GRS 1915+105 and the IR variations exceed corresponding X-ray variations at the same ($sim 8s$) timescale. These results suggest an entirely new type of infrared variability from this object. Based on the properties of this flickering, we conclude that it arises in the plateau-state jet outflow itself, at a distance $<2.5$ AU from the accretion disk. We discuss the implications of this work and the potential of further flickering observations for understanding jet formation around black holes.
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.
We present the results of seven years of K-band monitoring of the low-mass X-ray binary GRS 1915+105. Positive correlations between the infrared flux and the X-ray flux and X-ray hardness are demonstrated. Analysis of the frequency spectrum shows that the orbital period of the system is $P_{orb}= 30.8 pm 0.2$ days. The phase and amplitude of the orbital modulation suggests that the modulation is due to the heating of the face of the secondary star. We also report another periodic signature between 31.2 and 31.6 days, most likely due to a superhump resonance. From the superhump period we then obtain a range on the mass ratio of the system, $0.05 < q < 0.12$.
We present the first detections of the black hole X-ray binary GRS 1915+105 at sub-millimetre wavelengths. We clearly detect the source at 350 GHz on two epochs, with significant variability over the 24 hr between epochs. Quasi-simultaneous radio monitoring indicates an approximately flat spectrum from 2 - 350 GHz, although there is marginal evidence for a minimum in the spectrum between 15 - 350 GHz. The flat spectrum and correlated variability imply that the sub-mm emission arises from the same synchrotron source as the radio emission. This source is likely to be a quasi-steady partially self-absorbed jet, in which case these sub-mm observations probe significantly closer to the base of the jet than do radio observations and may be used in future as a valuable diagnostic of the disc:jet connection in this source.
A scenario for a periodic filling and emptying of the accretion disc of the microquasar GRS 1915+105 is proposed, by computing the mass transfer rate from the evolving low mass red giant donor (Greiner at al. 2001) and comparing it with the observed accretion rate onto the primary black hole. We propose a duty-cycle with (5-10)(eta/0.1) per cent active ON-state where eta is the efficiency of converting accretion into radiation. The duration of the quiescent recurrent OFF-state is identified as the viscosity time scale at the circularization radius and equals 370(alpha/0.001)^(-4/5) years, where alpha is the viscosity parameter in the alpha-prescription of a classical disc. If the viscosity at the outer edge of the disc is small and eta is close to the maximum available potential energy (per rest mass energy) at the innermost stable orbit, the present active phase may last another 10 - 20 years.
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