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		THE AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS 
			25 Birch Street, Cambridge, MA 02138 USA
		BITNET: aavso@cfa8 SPAN: nssdca::cfa8::aavso 
			INTERNET: aavso@cfa0.harvard.edu 
		Tel. 617-354-0484	FAX 617-354-0665


		AAVSO ALERT NOTICE 173 (July 7,1993)

REQUEST TO MONITOR CATACLYSMIC VARIABLES DURING ORFEUS MISSION

ORFEUS Mission: On July 17, 1993, the NASA's Space Shuttle Discovery is scheduled to 
launch a German-built, free-flying space platform equipped with an international cargo of 
science instruments. This first mission m the ASTRO-SPAS series of NASA and the 
German Space Agency (DARA) is called ORFEUS (Orbiting and Retrievable Far and 
Extreme Ultraviolet Spectrograph). The mission's primary goal during the planned 5-day 
science mission is to observe stars that emit most of their light m the ultraviolet band of the 
electromagnetic spectrum to help understand the evolution of these stars and their 
interaction with the interstellar medium. Once the instruments have completed their 
observations, the platform and the instruments will be retrieved and returned to Earth, 
where they will refurbished for later shuttle flights, at least three more over the next four 
years. NASA-Astrophysics Division is supplying us with a very informative pamphlet on 
ORFEUS mission which will be sent to you separately.

OBSERVATIONS OF CATACLYSMIC VARIABLES with the ORFEUS Mission: 
Astronomers at the Harvard-Smithsonian Center for Astrophysics and Lawrence 
Livermore National Laboratories at Livermore, California will be observing some 
cataclysmic variables - dwarf novae (DN) and magnetic novalike (NL) variables - during 
the ORFEUS Mission and have requested our assistance. Below is a list of their primary 
observing targets during this mission.

Designation	Star	Type	Magnitude Range
0058+40		RX And	DN	10.3-14.5
0409-71		VW Hyi	DN	8.4-14.4
0814+73		Z Cam	DN	10.2-13.8
1813+49		AM Her	NL	12.4-15.3
2138+43		SS Cyg	DN	8.1-12.4
2209+12		RU Peg	DN	9.4-13.1
The astronomers are particularly interested in monitoring outbursts of the dwarf novae and 
the different states ("down" or "up") of the novalike stars.

Please monitor these stars between now and the end of the mission or the end July (which 
ever is later - in case of change in the launch date), and call in your observations of the 
outbursts of the dwarf novae, and the brightness state of AM Her, to AAVSO 
Headquarters, using the charge free 800 number
				(800-642-3883)
that was established for the monitoring of cataclysmic variables for NASA's EUVE 
mission.

In addition to the stars above, if any of the brighter dwarf novae go into outburst (i.e, with 
outbursts brighter than 12.0 magnitude), please inform us at Headquarters, as these stars 
may also be observed during the ORFEUS Mission.

SPECIAL NOTES ON 2138+43 SS CYGNI and 0409-71 VW HYDRI

SS Cygni: This dwarf nova went into outburst on May 22, right before the ASCA mission 
(see AAVSO Alert Notice 171). This outburst was an anomalous one, in which the rise to 
maximum was slow, and the outburst was faint and short. Since then, SS Cyg has been 
particularly active during quiescence, with our observers reporting it brightening to 10.6 
and oscillating between 10.6 and 12.1 over the last few weeks. This behavior is rare for SS 
Cyg and has happened only few times since its discovery in 1896. It is particularly 
important to monitor SS Cyg closely at this time and to record the exact time of the 
observations. We have prepared a special information package to help observers 
determine the exact time of their observations, particularly in converting local time to 
Greenwich Mean Astronomical Time (GMAT). If you need this package, please let us 
know.

VW Hydri: This bright southern-hemisphere dwarf novae has been of interest to 
astronomers with observing programs with several satellites, such as the International 
Ultraviolet Explorer (IUE) and the Hubble Space Telescope (HST) and ORFEUS. HST is 
scheduled to observe VW Hyi in the coming months during quiescence in order to study 
the primary component (white dwarf) of this close binary system. Please monitor VW Hyi 
closely and inform us of its outbursts from now until December 1993. It is particularly 
important to know if the outburst is a superoutburst (predicted to occur in the coming 
months).

1908+01 NOVA AQUILAE 1993

Accompanying are b and d scale charts recently prepared by C. Scovil. Please use the d 
scale chart as this nova continues to fade. N Aql 93 was reported at magnitudes 12.5 and 
12.8 on July 6.1 UT by J. Bortle and C. Scovil, respectively.

FADING OF 1910-33 RY SAGITTARII

Our observers J. Bortle, P. Collins, L. Hiett, D. Overbeek, and D. York have reported that 
the R Coronae Borealis type variable RY Sgr has started to fade. From June 15 to July 7 it 
has faded from magnitude 6.5 to 9.1. Its last fading was in 1990. Please monitor RY Sgr 
closely as it continues to fade and call in your observations to AAVSO Headquarters.

REQUEST TO MONITOR 1834-23 V348 SAGITTARII

This interesting variable, whose light curve resembles that of an R CrB type variable, has 
been at its minimum state. Astronomers at Louisiana State University are interested to 
observe it with the IUE satellite when it starts to brighten. Please keep a close eye on it 
and call in your observations to Headquarters when it is brighter than magnitude 13.0.

As always, thank you very much for your efforts and for your valuable contributions to 
variable star research.

Clear skies and good observing,

Janet A. Mattel 
Director