[vsnet-alert 2962] Aql X-1 (=V1333 Aql) brightening

[Mike Garcia <garcia@head-cfa.harvard.edu>]

Dear Colleagues - We have submitted the following for inclusion
in the next IAUC.


R. Jain and C. Bailyn (Yale); M. Garcia and K. Rines(CfA); A. Levine (MIT);
J. Espinoza and D. Gonzalez (CTIO) report YALO consortium observations
 using the Yale 1-m telescope at CTIO and observations with the 48"
 telescope at the Whipple Observatory: "Aql X-1 = V1333 Aql appears to
be beginning a new outburst. This x-ray binary outbursts approximately
once per year, and based in its recent outbursts was due to erupt.  We
have monitored the optical counterpart of the soft X-ray transient
Aquila X-1 since early March in Johnson R using
 the YALO 1-m telescope.  Compared to the average quiescent level,
 which has a fluctuation of less than 0.1 magnitudes, the source had
 brightened in R by approximately 0.2 magnitudes on MJD 51306.4 (May
 08.3 UT).  During the night of May 10.2 -- 10.38 UT, we obtained 5
 data points spanning nine hours and found that the brightness
 increased from 0.4 to 0.55 magnitudes brighter than the quiescent average.
 V-band data from the 48" telescope at the Whipple Observatory show
 similar increases. We find that by MJD 51307.5 (May 09.5 UT) the
  source had brightened by approximately 0.4 magnitudes in V, compared to
 the average quiescent level.  Subsequently we obtained 3 YALO V images
 on May 10.2 -- 10.38 UT and found an increase in brightness
 of approximately 0.45 to 0.6 magnitudes, again compared to the
 quiescent average.  We will continue monitoring this source both 
 in the optical and in the X-ray using RXTE. Observations at all
 wavelengths are encouraged."

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