Infrared study of H 1743-322 in outburst: a radio-quiet and NIR-dim microquasar

Abstract

Context. Microquasars are accreting Galactic sources that are commonly observed to launch relativistic jets. One of the most important issues regarding these sources is the energy budget of ejections relative to the accretion of matter. Aims. The X-ray binary, black hole candidate, and microquasar H 1743-322 exhibited a series of X-ray outbursts between 2003 and 2008. We took optical and near-infrared (OIR) observations with the ESO/NTT telescope during three of these outbursts (2003, 2004, and 2008). The goals of these observations were to investigate the presence of a jet, and to disentangle the various contributions constituting the spectral energy distribution (SED): accretion, ejection, and stellar emission. Methods. Photometric and spectroscopic OIR observations allowed us to produce a high time-resolution lightcurve in K s -band, to analyze emission lines present in the IR spectra, to construct a multiwavelength SED including radio, IR, and X-ray data, and to complete the OIR vs. X-ray correlation of black hole binaries with H 1743-322 data points. Results. We detect rapid flares of duration ∼5 min in the high time-resolution IR lightcurve. We identify hydrogen and helium emission lines in the IR spectra, coming from the accretion disk. The IR SED exhibits the spectral index typically associated with the X-ray high, soft state in our observations taken during the 2003 and 2004 outbursts, while the index changes to one that is typical of the X-ray low, hard state during the 2008 outburst. During this last outburst, we detected a change of slope in the NIR spectrum between the J and K s bands, where the JH part is characteristic of an optically thick disk emission, while the HK s part is typical of optically thin synchrotron emission. Furthermore, the comparison of our IR data with radio and X-ray data shows that H 1743-322 exhibits a faint jet both in radio and NIR domains. Finally, we suggest that the companion star is a late-type main sequence star located in the Galactic bulge. Conclusions. These OIR photometric and spectroscopic observations of the microquasar H 1743-322, which are the first of this source to be published in a broad multiwavelength context, allow us to unambiguously identify two spectra of different origins in the OIR domain, evolving from optically thick thermal emission to optically thin synchrotron emission toward longer wavelengths. Comparing these OIR observations with other black hole candidates suggests that H 1743-322 behaves like a radio-quiet and NIR-dim black hole in the low, hard state. This study will be useful when quantitatively comparing the overall contribution of the compact jet and accretion flow in the energy budget of microquasars.

Spectral and accretion evolution of H1743−322 during outbursts in RXTE era

“…Similarly, the orbital period of the system can be calculated as P = 15.07 h (Frank et al 1992). The secondary is a late-type main-sequence star (Chaty et al 2015) and the mass of the secondary can be estimated as 0.11 P = 1.65 (Frank et al 1992) and hence the mass ratio of the system is q = 0.13. Also, we estimated the disc temperature and hence the sound speed at R 0 usingṁ dc , M and assumed the viscosity parameter α h = 0.1 in the hot state as c s = 1.2 × 10 6 cm s −1 .…”

“…The spin of the black hole is constrained in the range of −0.3 < a < 0.7 (Steiner et al 2012) from X-ray spectral modelling. Even though not much information is available about the nature of the companion star, Chaty et al (2015) propose that the companion star is a late-type mainsequence star. The mass of the primary has not been dynamically confirmed; however, both timing as well as spectral studies reveal the black hole as a primary.…”

Lorentz Factors of Compact Jets in Black Hole X-Ray Binaries

“…A direct measurement of the IR excess from the light curve is not available for this source, because its outbursts were only partly sampled in the IR. However, Chaty et al (2015) published IR magnitudes of the source from several outbursts. We find that there is a strong correlation between the J and K S -band magnitudes in the soft state (see Fig.…”

“…IR observation of H1743 during soft (red) and hard (blue) states from(Chaty et al 2015) (see text for explanation).…”

Dark jets in the soft X-ray state of black hole binaries?

“…The OIR observations have been published by Chaty et al (2015). We refer the reader to these articles for further details.…”