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Rebrightening of MAXI J0556-332

ATel #3327; D. Maitra (U. of Michigan), M. T. Reynolds (U. of Michigan), P. A. Curran (CEA-Saclay), K. Gultekin (U. of Michigan), J. M. Miller (U. of Michigan), J. A. Kennea (PSU), D. M. Russell (U. of Amsterdam)
on 5 May 2011; 17:35 UT
Credential Certification: Dipankar Maitra (maitra@astro.yale.edu)

Subjects: Optical, X-ray, Binary, Transient

Referred to by ATel #: 3328, 3349, 4524

We report a rebrightening of the newly discovered transient MAXI J0556-332 (ATEL #3102, #3103, #3104, #3106, #3110, #3112, #3116, #3119) in optical through soft-X-ray wavelengths. The source is being monitored regularly in the I-band using the SMARTS 1.3m telescope in CTIO, and the I-band light curve has been showing a monotonically increasing trend since 55670.9748 (2011 April 19.97, when the I-band magnitude was 18.39 ± 0.15). During the most recent SMARTS observation made on MJD 55683.9916 the I-band magnitude was 17.25 ± 0.12, implying an ~2.8x increase in the I-band flux over this period.

Contemporaneous Swift observations made on MJD 55670.15 (hereafter obs1) and MJD 55682.52 (hereafter obs2) also confirm the ongoing rebrightening. The UVOT v magnitudes during obs1 and obs2 were 19.08 ±0.37 and 17.94 ± 0.19 respectively. The other UVOT bands support the rise. Note that the UVOT magnitudes are calculated in the UVOT photometric system (Poole et al. 2008,MNRAS, 383, 627). The absorbed XRT flux during obs1 and obs2 were (5.0 ± 0.2) x 10-10 erg s-1 cm-2 and (5.5 ± 0.2) x 10-10 erg s-1 cm-2 respectively (in 0.6-10 keV range, and assuming a thermal accretion disk plus a power law continuum model and a column density of NH = 1021 cm-2 for both observations).

Observations at other wavelengths are encouraged.

I-band light curve