Amatérská prohlídka oblohy - Chandra and VLA Satellite Observations of V4641 Sgr

Dr. Michael Rupen, National Radio Astronomy Observatory, has asked the AAVSO for CCD monitoring of V4641 Sgr during two observing windows coming up on July 30 and August 1. These observations will be coincident with Chandra and VLA observations of V4641 Sgr. The exact time for the observing windows are below:

30 July 2004: 1750-2400 UT – Chandra
01 Aug. 2004: 0231-0400 UT – VLA

Observations every half hour are requested. However, if you detect variability while observing please switch to time series observations with high time resolution. Also, if your schedule allows it, we recommend taking time series observations beginning an hour before each observing run and lasting until an hour after each run. This object can vary on timescales down to a few seconds so be prepared for anything. This also means that simultaneous observations from multiple observers can be combined to get a higher time resolution. So please make sure your computer clock is synced to an appropriate server (such as tick.usno.navy.mil) and that your FITS image records the time as the midpoint of the exposure. Dr. Rupen requests that a consistent photometric filter be used with these observations. Please use a V filter with your observations. A new AAVSO CCD chart with V magnitudes from A. Henden & B. Sumner has been posted at this URL:

aavso.org/cgi-bin/searchcharts3.pl?name=v4641%20sgr

Our latest visual observation of V4641 Sgr is:
JUL 22.4430 2453208.943 – 13.1 – Rod Stubbings (SRX)

Our latest CCD observation of V4641 Sgr is:
JUL 07.4704 2453193.9704 – 13.74 +/- 0.03 Unfiltered – Lew Cook (COO)

V4641 is an X-ray bright novalike variable star. Novalikes are CVs in a perpetual state of outburst. Information on novalikes can be found in the in our Spring, 2004 Variable Star of the Season article on UX Uma:

aavso.org/vstar/vsots/spring04.shtml

Zdroj: THE AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS
http://www.aavso.org