Optical observations of SAX J1808.4-3658
ATel #511; J. Greenhill (U of Tasmania), C. Coutures, R. Corrales (IAP, Paris)
on 6 Jun 2005; 12:21 UT
Distributed as an Instant Email Notice Transients
Credential Certification: John Greenhill (John.Greenhill@utas.edu.au)
Subjects: Radio, Infra-Red, Optical, X-ray, Binary, Neutron Star, Transient, Pulsar
We report BVRI photometry of the accreting millisecond pulsar SAX J1808.4-3658 with the Mt Canopus 1m telescope on 3 nights June 2, 3 &5 (JD 3524.1, 3525.2, 3527.2). The intensity in I increased by ~0.25 mags between June 3 and 5 whereas the other colours changed very little with V~17.2.
The increase in I is suggestive of an "outside-in" transition in the disc or perhaps of synchrotron processes. We note that a similar transient increase in I was reported for this object in April 1998 (Wang et al, ApJ 563, L61-64).
Further photometry is planned.
