August 17, 2005: Our assistance has been requested by Dr. Stefanie Wachter, Spitzer Science Center, Caltech, in observing the low-mass x-ray binary V818 Sco (Sco X-1) in support of her upcoming Spitzer observations of this object.
Dr. Wachter has requested coverage for August 21, 22, and 23, and especially August 22, when her satellite observation is scheduled for 16:00 UT. Since this time falls during daylight hours in North and South America, observers in other parts of the world are urgently asked to try to observe V818 Sco at and around that particular time. Dr. Wachter has indicated that every observation will be helpful - B,V,R,I,J,H,K, Positive visual. All observers are asked to observe V818 Sco from now through the end of August, making at least one observation per night and several during the nights of August 21 - 23, with special concentration on August 22 at and around 16:00 UT. According to observations in the AAVSO International Database, V818 Sco varies between visual magnitudes approximately 11.6 and 13.2, and may change in brightness by a magnitude or more in 24 hours or less.
V818 Sco is at R.A. = 16:19:54.6 Dec. = -15:38:22 (2000).
The field has been measured by Arne Henden. An AAVSO 'e' scale chart with BVI photometry has been prepared by Aaron Price and is available at http://www.aavso.org/cgi-bin/searchcharts3.pl?name=v818%20sco [obsolete link; create charts using VSP at http://www.aavso.org/vsp ]
Please use this chart to observe 1614-15 V818 Sco, and report your observations to the AAVSO, being sure to indicate which comparison stars you used.
For interesting and dramatic information on the discovery of Sco X-1, please visit the following page on the Chandra website: http://chandra.harvard.edu/xray_sources/sco/sco.html
Many thanks for your valuable astronomical contributions and your efforts.
Senior Technical Assistant