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Aquila X-1 still bright optically

ATel #1232; S. A.Ilovaisky, C. Chevalier (Observatoire de Haute-Provence, France)
on 10 Oct 2007; 12:22 UT
Credential Certification: Sergio A. Ilovaisky (ilovaisky@obs-hp.fr)

Subjects: Optical, X-ray, Binary, Neutron Star, Transient

Referred to by ATel #: 1553, 1557, 1970

CCD observations of V1333 Aql, the optical counterpart of the Aquila X-1 transient, obtained with the Haute-Provence 1.2-m telescope on UT 2007 October 2.7 and 9.7 by R.Giraud and S.Favard show the object to be relatively bright. The combined V magnitude of stars 'a' and 'e' (Chevalier et al. 1999, A&A 347, L1) is ~18.3 (once corrected for the 19-h modulation), nearly 1 magnitude above quiescence. Publicly available real-time data from the RXTE/Rossi Explorer show a low counting rate of ~1 ASM c/s (13 mCrab) at the time of our observations. Similar states of continued optical emission accompanied by a weak 2-10 keV flux have been seen in this source previously (1996, 1999, 2001, 2004, 2005) and are linked to X-ray spectral changes. Our data confirm the reported transition to a hard state reported by Rodriguez et al. (ATel #1229).