January 22, 2008: Dr. Bradley E. Schaefer (Louisiana State University) requests increased monitoring of the recurrent nova U Scorpii (AAVSO 1616-17) over the next 24 months. Observers are asked to add U Sco to their regular observing program and to monitor the star in advance of an outburst predicted to occur around 2009.3 +/- 1.0 year. Schaefer predicts that because the nova outburst occurs after a certain amount of material collects on the white dwarf, and because the quiescent brightness of the star follows the mass accretion rate, we can predict when the accreted mass reaches the nova ignition point.
Schaefer requests that "... U Sco should be looked at frequently for the next year or more, starting [now]." Because U Sco is known to have short eruptions it is imperative that the field be observed as often as possible, particularly around the time of solar conjunction when observations are most difficult. Morning observations are therefore most urgently requested at this time.
If the star does go into outburst, observers are asked:
- to report observations immediately to the AAVSO via WebObs,
- to follow the outburst during the rise in order to provide an improved measure of the rise-time of this fast nova, and
- to obtain time-series photometry of eclipses during the tail of the eruption in order better to study the orbital properties of the system.
A confirmed outburst will trigger target-of-opportunity observations by the Hubble Space Telescope, Swift, and Spitzer, as well as intensive ground-based photometry by several observatories.
Both visual and photometric observations of U Sco are requested for this long-term campaign. All observers are asked to monitor the field regularly for outburst, making observations as deep as is realistically possible given the limits of your equipment. Both positive and "fainter-than" (negative) observations are useful for this campaign, and observers are asked to report the faintest comparison star they can reliably detect when making fainter-than estimates. In the event of an outburst, please report observations to the AAVSO immediately using the WebObs data submission tool on the AAVSO website. All observers are then asked to follow the entire outburst, and CCD observers are encouraged to begin time-series observations when eclipses become apparent (typically one month after the start of the eruption).
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:
Recent observations for U Sco may be found by going to the WebObs observation search page (replaces QuickLook):
http://www.aavso.org/apps/webobs/search
Please report all observations promptly to the AAVSO as "U Sco" -- please do not use "Nova Sco 200X" unless that alias is announced by the AAVSO.
A U Sco observing campaign page has been created for this monitoring request.
This AAVSO Alert Notice was prepared by Matthew Templeton.
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