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Aql X-1 optical/IR outburst

ATel #279; D. Maitra, C. Bailyn, R. Winnick (Yale), J. Espinoza, D. Gonzalez (CTIO/SMARTS)
on 17 May 2004; 21:46 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Dipankar Maitra (maitra@astro.yale.edu)

Subjects: Infra-Red, Optical, Binary, Neutron Star, Transient

Referred to by ATel #: 280, 286

SMARTS consortium observations of the transient neutron star X-ray binary system Aql X-1 suggest that it is coming out of a prolonged Low-intensity state (LIS). In a LIS the optical/IR flux is higher than quiescence level but lower than typical outburst maximum, but there is no detectable flux increase in 2-12 keV RXTE ASM bands. For the past two months, Aql X-1 was hovering in a LIS with an R band flux 1.2 magnitude brighter than quiescence (18.8 mag at quiescence) and J band flux about a magnitude brighter than quiescence (16.4 mag at quiscence; also see ATEL #259, #260). Observations since 10th May 2004 show a steady increase in flux in both J (15.0 mag on 16th May 2004) and R (16.5 mag on 16th May 2004) bands which we interpret as the end of the LIS and begining of a new outburst of the source. We note that these measurements include light from the near neighbor star V1333 Aql (Chevalier et al., 1999, A&A, 347,L51). Most recent publicly available ASM data shows no activity in the 2-12keV ASM bands. Multiwavelength observations of the source are encouraged.

Lightcurve of Aql X-1