R-band Observations of 2S 1711-339 in 1998 During Outburst

ATel #244; John A. Tomsick (UC San Diego)
on 27 Feb 2004; 22:55 UT
Credential Certification: John A. Tomsick (jtomsick@ucsd.edu)

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In 1998 August, we obtained optical observations of the field containing the recurrent transient and type I X-ray burster 2S 1711-339 with the CTIO 0.9 meter telescope in an attempt to identify its optical counterpart. Our observations occurred during the only bright X-ray outburst of the past 8 years as determined by an inspection of the Rossi X-ray Timing Explorer All-Sky Monitor light curve. Prior to and at the time of our optical observations, the 1.5-12 keV flux was in the 25-55 mCrab range (Remillard et al. 1998, IAUC 6983 ). More recently, Wilson et al. (2003) reported a sub-arcsecond accuracy X-ray (Chandra) position, and Torres et al. (2004, ATEL#233) suggested a possible quiescent optical counterpart with R = 19.4 +/- 0.1. During UT 1998 August 5.99-6.05, we took six 10 minute R-band exposures. The CCD pixel size was 0".768, and the seeing was 1".5. We detect three blended sources within 4" of the Chandra position. Only one of these sources has a position consistent with the optical counterpart suggested by Torres et al., and we estimate that its R-band magnitude is 19.4 with a preliminary uncertainty of +/- 0.2 magnitudes. For the two nearby sources, one is similar in brightness, and one is about 0.5 magnitudes fainter. If the candidate counterpart suggested by Torres et al. is, in fact, 2S 1711-339, then our results indicate that the optical flux does not increase during X-ray outbursts, and such behavior could be indicative of a High Mass X-ray Binary (HMXB) system. However, type I X-ray bursts are not typical of HMXBs. Another possibility is that we and also Torres et al. did not detect the 2S 1711-339 counterpart due to the relatively high level of extinction for this source.