An accurate position for the black hole candidate XTE J1752−223: re-interpretation of the VLBI data

Abstract

Using high‐precision astrometric optical observations from the Walter Baade Magellan Telescope in conjunction with high‐resolution very long baseline interferometric (VLBI) radio imaging with the Very Long Baseline Array (VLBA), we have located the core of the X‐ray binary system XTE J1752−223. Compact radio emission from the core was detected following the state transition from the soft to the hard X‐ray state. Its position to the south‐east of all previously detected jet components mandated a re‐analysis of the existing VLBI data. Our analysis suggests that the outburst comprised at least two ejection events prior to 2010 February 26. No radio‐emitting components were detected to the south‐east of the core at any epoch, suggesting that the receding jets were Doppler‐deboosted below our sensitivity limit. From the ratio of the brightness of the detected components to the measured upper limits for the receding ejecta, we constrain the jet speed β > 0.66 and the inclination angle to the line of sight θ < 49°. Assuming that the initial ejection event occurred at the transition from the hard intermediate state to the soft intermediate state, an initial period of ballistic motion followed by a Sedov phase (i.e. self‐similar adiabatic expansion) appears to fit the motion of the ejecta better than a uniform deceleration model. The accurate core location can provide a long time baseline for a future proper motion determination should the system show a second outburst, providing insights into the formation mechanism of the compact object.

A late jet rebrightening revealed from multiwavelength monitoring of the black hole candidate XTE J1752−223★

“… Broad‐band, unabsorbed radio‐to‐optical SEDs at various stages of the outburst (see text for details). The radio data (ν < 10 10 Hz) were taken with the ATCA (black crosses; Brocksopp et al 2009), VLBA (grey open triangles and black open squares; Miller‐Jones et al 2011) and EVLA (red solid circles and blue solid triangles; Jonker et al, in preparation). …”

“…Radio, NIR and optical observations were taken within 5 days of each other, soon after the discovery of the outburst, when XTE J1752−223 was in a bright, hard state (Brocksopp et al 2009; Torres et al 2009b; C11; Miller‐Jones et al 2011). We plot these data in Fig.…”

“…The extrapolation of the flat spectrum seen at radio frequencies (α radio ∼ 0) is close to the K ‐band flux density, so the jet is unlikely to contribute much of the emission above this frequency. An optical SED from one date soon after, in the hard state (using data from C11; Miller‐Jones et al 2011), appears slightly bluer (SED [2]; purple open squares). An optical SED from the soft state (FT V , R , i ′ bands) is also blue; α OIR ∼ 0.5 (SED [3]; orange diamonds in Fig.…”

“…XTE J1752−223 is an X‐ray transient discovered by the Rossi X‐ray Timing Explorer ( RXTE ) and Swift satellites in 2009 October (Markwardt et al 2009). The outburst lasted ∼8 months and was observed by the Monitor of All‐sky X‐ray Image ( MAXI ) and RXTE satellites (Nakahira et al 2010; Shaposhnikov et al 2010) at X‐ray energies, Swift (Curran et al 2011, hereafter C11) at X‐ray and optical/ultraviolet (UV) (the optical counterpart was discovered by Torres et al 2009a), Faulkes Telescope and Small and Moderate Aperture Research Telescope System (SMARTS) at OIR (Russell et al 2010b; Kalemci et al 2011) and the Australia Telescope Compact Array (ATCA), the European VLBI Network (EVN), the Very Long Baseline Array (VLBA) and the Expanded Very Large Array (EVLA) at radio frequencies (Brocksopp et al 2009; Yang et al 2010; Miller‐Jones et al 2011; Jonker et al, in preparation). The source evolved from a hard X‐ray state to a soft state and back to a hard state at a lower luminosity before fading towards quiescence; overall showing a behaviour typical for a BHXB outburst (Fender et al 2004; Belloni 2010).…”

Disc-jet coupling in the 2009 outburst of the black hole candidate H1743−322

“…Although VLBI monitoring of XTE J1752−223 was carried out during its 2010 outburst, the observed one‐sided ejection event (Miller‐Jones et al 2011b) and the deceleration of the ejecta (Yang et al 2010) prevent us from accurately determining a zero‐separation time. However, the radio light curves and spectra show evidence for a quenching of the flat‐spectrum jet between MJD 55217 and 55220, with the peak of the initial radio flare occurring on MJD 55221.…”