Optical and Near-Infrared Monitoring of the Black Hole X-Ray Binary Gx 339-4 During 2002-2010

Abstract

We present the optical/infrared (O/IR) light curve of the black hole X-ray binary GX 339-4 collected at the SMARTS 1.3 m telescope from 2002 to 2010. During this time the source has undergone numerous state transitions including hard-to-soft state transitions when we see large changes in the near-IR flux accompanied by modest changes in optical flux, and three rebrightening events in 2003, 2005, and 2007 after GX 339-4 transitioned from the soft state to the hard. All but one outburst show similar behavior in the X-ray hardness-intensity diagram. We show that the O/IR colors follow two distinct tracks that reflect either the hard or soft X-ray state of the source. Thus, either of these two X-ray states can be inferred from O/IR observations alone. From these correlations we have constructed spectral energy distributions of the soft and hard states. During the hard state, the near-IR data have the same spectral slope as simultaneous radio data when GX 339-4 was in a bright optical state, implying that the near-IR is dominated by a non-thermal source, most likely originating from jets. Non-thermal emission dominates the near-IR bands during the hard state at all but the faintest optical states, and the fraction of non-thermal emission increases with increasing optical brightness. The spectral slope of the optical bands indicate that a heated thermal source is present during both the soft and hard X-ray states, even when GX 339-4 is at its faintest optical state. We have conducted a timing analysis of the light curve for the hard and soft states and find no evidence of a characteristic timescale within the range of 4-230 days.

The Reflares and Outburst Evolution in the Accreting Millisecond Pulsar Sax J1808.4–3658: A Disk Truncated Near Co-Rotation?

“…SAX J1808.4 −3658 was observed with a roughly daily cadence (weather permitting) between 2008 September 22 and November 11. The I-band data were analyzed with the standard IRAF optical data reduction pipelines (Buxton et al 2012) whereas for the NIR data multiple dithered frames were taken and then flatfielded, sky subtracted, aligned, and average-combined using an in-house IRAF script. Three stars nearby SAX J1808.4 −3658 and within the SMARTS field of view (FOV) were used as references and their average magnitudes were used as a basis for differential photometry with respect to SAX J1808.4−3658.…”

Wind, jet, hybrid corona and hard X-ray flares: multiwavelength evolution of GRO J1655−40 during the 2005 outburst rise

“…For calculating the OIR fluxes, we dereddened magnitudes using E(B-V) = 1.3±0.1 (Orosz & Bailyn 1997) and extinction laws given by Cardelli, Clayton & Mathis (1989) with corrections described in O'Donnell (1994). The procedure is outlined in detail in Buxton et al (2012). All measurements used in this work are provided in Table 2.…”

X-Ray, Optical, and Infrared Observations of Gx 339-4 During Its 2011 Decay

“…For this purpose, we used the optical extinction, A V = 3.7 ± 0.3 (Zdziarski et al 1998) together with the extinction laws given by Cardelli et al (1989) and O'Donnell (1994). The same A V was previously utilized in Corbel & Fender (2002), Coriat et al (2009), andBuxton et al (2012) for the SED creation. For the details of the selection of A V , dereddening, and the flux conversion procedures, we refer to Buxton et al (2012).…”

“…The same A V was previously utilized in Corbel & Fender (2002), Coriat et al (2009), andBuxton et al (2012) for the SED creation. For the details of the selection of A V , dereddening, and the flux conversion procedures, we refer to Buxton et al (2012).…”