Recent Swift Ultra-violet/Optical Observations of GRO J1655-40
ATel #614; Albert K. H. Kong, Jeroen Homan, Walter H. G. Lewin (MIT)
on 26 Sep 2005; 21:15 UT
Credential Certification: Albert Kong (akong@cfa.harvard.edu)
Subjects: Optical, Ultra-Violet, X-ray, Binary, Black Hole, Transient
We report Swift-UVOT observations of GRO J1655-40 during the recent hard
X-ray state (ATEL #607). GRO J1655-40 was observed with Swift on 2005
Sept 23,
two days after the radio detection (ATEL #612). The Ultra-Violet/Optical
telescope (UVOT) obtained images through the U, B, V, UVW1, and UVW2
filters; GRO J1655-40 was clearly detected in the B and V filters,
and was marginally detected in the U filter. The V magnitude is
16.94+/-0.14 which is consistent with the ongoing trend
monitored with the SMARTS telescope (ATEL #608). In the U and B bands,
GRO J1655-40 is fading more rapidly. The U and B magnitude is
19.16+/-0.37 and 18.57+/-0.20, respectively. Swift observations taken
on 2005 June 6 when GRO J1655-40 ended a period of strong flaring in the
X-rays (ATEL #487) show that the U, B, and V magnitude is
18.43+/-0.20, 18.18+/-0.11, and 16.60+/-0.11, respectively.
From the SMARTS lightcurves, there is no obvious
change in optical colors after the period of X-ray flaring and before
the radio detection on 2005 Sept 21
(ATEL #608). These indicate that GRO J1655-40 becomes redder after that
time.
