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Special Notice #185: Request for twilight observations of U Sco

AAVSO Special Notice #185

Request for twilight observations of U Sco
December 29, 2009

Dr. Brad Schaefer requests morning twilight observations of U Sco in continuation of the campaign to monitor this star for its next nova outburst (Alert Notice #367, January 22, 2008).  In particular, deep limits to V=16.5 or fainter are urgently needed to assess whether U Sco went into outburst between 2009 November 6 and early December. If U Sco is found fainter than this, then the intensive monitoring campaign will continue for 2010.

U Sco disappeared behind the Sun in mid-November 2009, and is now recoverable in morning twilight.  Visual observations by M. Linnolt on 2009 Dec 27 and 28 indicate that U Sco is fainter than 14.3.  This contrains any possible outburst to have occurred between 2009 November 6 and December 9. A short window of 2009 November 22 to November 30 is excluded with good probability due to estimates made by S. Dvorak using the SOHO LASCO instrument at solar conjunction.  In order to definitively confirm that U Sco did not erupt during this time, an observation finding the star fainter than approximately 16.5 is required.  Deep imaging during twilight may be able to confirm this, and CCD observations of this field are encouraged, particularly by southern hemisphere observers. 

U Sco is a very fast nova, taking about three days to decay by three magnitudes from its maximum of around 7.7.  Detection and confirmation of any nova event need to occur within just a few hours if possible. All observations including "fainter-than" estimates are valuable, and please report all observations as soon as possible.  Any indication of outburst should be emailed to matthewt@aavso.org immediately.

For more information about this campaign, please see the text of Alert Notice #367 at the following URL: http://www.aavso.org/publications/alerts/alert367.shtml

A page about the campaign has also been established here: http://www.aavso.org/news/usco.shtml

U Sco is located at RA 16:22:30.8 Dec -17:52:43 (J2000)

Custom charts and comparison star photometry tables for U Sco may be generated with VSP at the following URL:
http://www.aavso.org/observing/charts/vsp/index.html?pickname=u%20sco

Recent observations for U Sco are available at the following URL:
http://www.aavso.org/cgi-bin/newql.pl?name=u%20sco&output=html 

Please report all observations promptly to the AAVSO as "U SCO".

This AAVSO Special Notice was prepared by Matthew Templeton.

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