Robert P. Fender

The variable radio emission from grs 1915+105

We present data on the monitoring of the Galactic X-ray transient GRS 1915+105 at 15 GHz with the Ryle Telescope. We have found quasi-periodic oscillations with periods in the range 20-40 min which are tentatively associated with the soft-X-ray variations on the same time-scale. The overall behaviour of the radio emission is shown to vary in a strong association with the X-ray emission as recorded by the RXTE all-sky monitor.

Rapid infrared flares in GRS 1915+105: evidence for infrared synchrotron emission

We report imaging photometry of the radio-jet black hole candidate source GRS 1915+105 in the infrared K band. The observations reveal rapid infrared flare events on timescales of less than an hour. These events are strikingly similar to those regularly observed in radio monitoring at 15 GHz. Furthermore, when dereddened, the infrared events have comparable amplitudes to the radio oscillations, and observations at 15 GHz made approx. 8 hr after our infrared observations reveal that the source was indeed displaying radio oscillations at this time. We suggest that we have observed infrared synchrotron emission from this source. We estimate the equipartition magnetic field and power required to accelerate the particles for the repeated radio events, and find both to be orders of magnitude greater than those estimated for any other X-ray binary.

Discovery of extended radio emission in the young cluster Wd1

We present 10-mu m ISO-SWS and Australia Telescope Compact Array observations of the region in the cluster Wd1 in Ara centred on the B [e] star Ara C. An ISO-SWS spectrum reveals emission from highly ionized species in the vicinity of the star, suggesting a secondary source of excitation in the region. We find strong radio emission at both 3.5 and 6.3 cm, with a total spatial extent-of over 20 arcsec. The emission is found to be concentrated in two discrete structures, separated by similar to 14 arcsec, The westerly source is resolved, with a spectral index indicative of thermal emission. The easterly source is clearly extended and non-thermal (synchrotron) in nature. Positionally, the B le] star is found to coincide with the more compact radio source, while the southerly lobe of the extended source is coincident with Ara A, an M2 I star. Observation of the region at 10 mu m reveals strong emission with an almost identical spatial distribution to the radio emission. Ara C is found to have an extreme radio luminosity in comparison with prior radio observations of hot stars such as O and B supergiants and Wolf-Rayet stars, given the estimated distance to the cluster. An origin in a detatched shell of material around the central star is therefore suggested; however given the spatial extent of the emission, such a shell must be relatively young (tau similar to 10(3) yr), The extended non-thermal emission associated with the M star Ara A is unexpected; to the best of our knowledge this is a unique phenomenon. SAX (2-10 keV) observations show no evidence of X-ray emission, which might be expected if a compact companion were present.

The radio-jet X-ray binaries

Abstract We review the observational properties, from radio to X-rays, of the eight systems for which there is strong evidence for the formation of a radio jet in a X-ray binary system.

A radio survey of supersoft, persistent and transient X-ray sources in the Magellanic Clouds

We present a radio survey of X-ray sources in the Large and Small Magellanic Clouds with the Australia Telescope Compact Array at 6.3 and 3.5 cm. Specifically, we have observed the fields of five LMC and two SMC supersoft X-ray sources, the X-ray binaries LMC X-1, X-2, X-3 and X-4, the X-ray transient Nova SMC 1992, and the soft gamma-ray repeater SGR 0525-66. None of the targets are detected as point sources at their catalogued positions. In particular, the proposed supersoft jet source RXJ 0513-69 is not detected, placing constraints on its radio luminosity compared to Galactic jet sources. Limits on emission from the black hole candidate systems LMC X-1 and X-3 are consistent with the radio behaviour of persistent Galactic black hole X-ray binaries, and a previous possible radio detection of LMC X-1 is found to be almost certainly a result of nearby field sources. The SNR N49 in the field of SGR 0525-66 is mapped at higher resolution than it has been previously, but there is still no evidence for any enhanced emission or disruption of the SNR at the location of the X-ray source.

Modelling of infrared emission from Cyg X-3 and the UKIRT IRCAM3 point spread function

Abstract Modelling of the point spread function of the UKIRT IRCAM3 array was conducted in order to test for any extended emission around the X-ray binary Cyg X-3. We found that the point spread function cannot be represented by a simple Gaussian, but modelling of the stars required additional functions, namely Lorentzian and exponential components. After modelling for the PSF, we found that Cyg X-3 could be represented by two stellar-type profiles, 0.56″ apart.

A multiwavelength study of Cygnus X-3

We present a global comparison of long term observations of the hard X-ray (20–100 keV), soft X-ray (1.5–12 keV), infrared (1–2 μm) and radio (2.25, 8.3 and 15 GHz) bands for the unusual X-ray binary Cygnus X-3. Data were obtained in the hard X-ray band from CGRO/BATSE, in the soft X-ray band from RXTE/ASM, in the radio band from the Green Bank Interferometer and Ryle Telescope and in the infrared band from various ground based observatories. Radio flares, quenched radio states and quiescent radio emission can all be associated with changes in the hard and soft X-ray intensity. The injection of plasma into the radio jet is directly related to changes in the hard and soft X-ray emission. The infrared observations are examined in the context of these findings.

GRS 1915 +105: flares, QPOs and other events at 15 GHz

Monitoring with the Ryle Telescope at 15 GHz of the Galactic X-ray transient source GRS 1915+105 has revealed a remarkable range of rapid and extended flares which appear to be related to the X-ray emission as recorded by the RXTE all-sky monitor. Quasi-periodic oscillations in the range 20 - 40 min have been found and are probably related to oscillations in the soft X-ray flux.

Radio, Infrared and X-ray Observations of GRS 1915-105

We present multiwavelength observations of the superluminal jet source GRS 1915+105 in 1996 April–May, over which period a variety of phenomena, including radio QPO, strong infrared emission lines and rapid X-ray flickering and outbursts were observed.

An outburst of SS 433 observed on milliarcsecond scale

SS 433 is a high-mass X-ray binary system (XRB) and one of the most persistent sources of relativistic jets in the Milky Way. The object has been intensively studied in radio at arcsecond scales, however the high-resolution observations (i.e. VLBI) are relatively scarce. In 2008 November the system was in outburst. Using the e-VLBI capabilities of the European VLBI Network (EVN) we observed SS 433 for three epochs during the active phase. The data offered a detailed view of the system’s behaviour in outburst at milliarcsecond sca les. We used the “kinematic model” (which predicts the position along the jet of any knot ejecte d at some particular time in the past) to investigate the dynamic parameters of SS 433 and we examined the polarization properties of the ejected material. We report here the preliminary result s.