request for groundbased support for ALEXIS this week

(vsnet-alert 380, 1996 Apr. 9)

This week for ALEXIS may be a very busy week. In the past, delays caused by validating ALEXIS transient detections before alerting groundbased and satellite observers have resulted in 3 EUVE target of opportunity (TOO) observations which did not detect anything within the ALEXIS error box (+/-0.25 degree). It is our belief that the transients are very short lived and had turned off by the time that EUVE was able to slew over to take a look. Therefore, in an attempt to get on target sooner for TOO observations, we have an agreement with EUVE that for certain pre-approved times, if a source is detected above a significance of 7 in the ALEXIS telescopes, EUVE will slew over for a quick look (2-3 orbits) while the validation process is taking place. We hope to cut down the response time by 6-12 hours. The first test of this new observing plan will occur this week.

What does this mean to you? We would encourage groundbased observers to watch the ALEXIS web site for potential transients and to observe them whenever possible during the TOO alert and then about a day later to determine whether there might be an optical counterpart. Good candidates for TOO will be designated with a bright red TOO on the individual contact pages.

We expect the data to be processed after the following times:

 April 8:      11:30AM UT      (7:30AM EDT   4:30AM PDT)
               20:15PM UT      (4:15PM EDT   1:15PM PDT)

 April 9:      11:00AM UT      (7:00AM EDT   4:00AM PDT)
               19:50PM UT      (3:50PM EDT   12:50PM PDT)

 April 10:     10:30AM UT      (6:30AM EDT   3:30PM PDT)
               19:15PM UT      (3:15PM EDT   12:15PM PDT)

 April 11:     10:00AM UT      (6:00AM EDT   3:00AM PDT)
               20:30PM UT      (4:30PM EDT   1:30PM PDT)

 April 12:      9:30AM UT      (5:30AM EDT   2:30AM PDT)
               20:00PM UT      (4:00PM EDT   3:00PM PDT)

The top ALEXIS web page is:

There is a listing of the upcoming contacts available from this page. In addition, on the latest contact page ( where it has "ALEXIS current status", we will post which of the ALEXIS TOO that EUVE slews to observe. There is general information about ALEXIS transients on the ALEXIS Primer page (

At the current time, we are detecting about 1-2 potential transient of significance greater than 7 per week within the central 20 degrees of the detectors.

This week will be a time of demonstration of the capabilities of both satellites and shake out of the procedures. We expect that in the future, there will be several more week long opportunities to repeat this type of quick response observing with EUVE. Therefore, it you are unable to participate in this weeks activities, there will be more opportunities yet to come.

ALEIXS contacts are:


Diane Roussel-Dupre

Diane Roussel-Dupre, NIS-2
Los Alamos National Laboratory
Telephone: (505) 667-8895
FAX: (505) 665-4414

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