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We report an anticorrelation between continuum luminosity and the equivalent width (EW) of the H-alpha emission line in X-ray binary systems. The effect is evident both in a universal monotonic increase in H-alpha EW with time following outbursts, as systems fade, and in a comparison between measured EWs and contemporaneous X-ray measurements. The effect is most clear for black hole binaries in the low/hard X-ray state, which is prevalent at X-ray luminosities below ~1% Eddington. We do not find strong evidence for significant changes in line profiles across accretion state changes, but this is hampered by a lack of good data at such times. The observed anti-correlation, highly significant for black hole binaries, is only marginally so for neutron star systems, for which there are far less data. Comparison with previously established correlations between optical and X-ray luminosity suggest that the line luminosity is falling as the X-ray and optical luminosities drop, but not as fast (approximately as L_{H-alpha} propto L_X^{~0.4} propto L_{opt}^{~0.7}). We briefly discuss possible origins for such an effect, including the optical depth, form of the irradiating spectrum and geometry of the accetion flow. Further refinement of the relation in the future may allow measurements of H-alpha EW to be used to estimate the luminosity of, and hence the distance to, X-ray binary systems. Beyond this, further progress will require a better sample of spectro-photometric data.
The impact of ram pressure stripping (RPS) on galaxy evolution has been studied for over forty years. Recent multi-wavelength data have revealed many examples of galaxies undergoing RPS, often accompanied with multi-phase tails. As energy transfer in
We present results from an H-alpha monitoring campaign of the Be X-ray binary systems HDE 245770 = A 0535+26 and X Per. We use the H-alpha equivalent widths together with adopted values of the Be star effective temperature, disk inclination, and disk
We present spectroscopic observations of the Be/X-ray binary X Per obtained during the period 1999 - 2018. Using new and published data, we found that during disc-rise the expansion velocity of the circumstellar disc is 0.4 - 0.7 km/s. Our results su
We study the X-ray properties of LINER sources with definite detection of a broad H(alpha) emission line in their optical spectra, LINER 1s from Ho et al. sample. These objects preferentially harbor a low luminosity active nucleus at the center and s
We summarise all the reported detections of, and upper limits to, the radio emission from persistent (i.e. non-transient) X-ray binaries. A striking result is a common mean observed radio luminosity from the black hole candidates (BHCs) in the Low/Ha