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Alert Notice 391: Rare Outburst of V358 Lyr

November 23, 2008
 

Event: Rare outburst of V358 Lyr

Discovered By: Jeremy Shears and Gary Poyner, BAAVSS, from a Bradford Robotic Telescope image.  Confirmed by Shawn Dvorak, Rolling Hills Observatory.

Discovery Magnitude: CV=16.11 +/- 0.04

Discovery Date: November 22.917 UT

Positions:
observer      RA (J2000) Dec
Antipin    18:59:32.95 +42:24:12.2  (+/- 0.5arcsec)
BRT:       18:59:32.99 +42:24:12.0  (+/- 0.2arcsec)
Dvorak:  18:59:32.97 +42:24:11.7  (+/- 0.2arcsec)
Krajci:    18:59:32.96 +42:24:12.0  (+/- 0.1arcsec)

Magnitudes:
Observer              date        magnitude
Shears/Poyner  Nov 22.917  16.11 CV +/- 0.04
Dvorak             Nov 22.98   16.14 CV +/- 0.04
Krajci               Nov 23.082  15.92 V  +/- 0.03

This is a likely WZ Sge variable.  The only known outburst was in 1965, as reported by Hoffmeister (1967, AN 289, 205). At that time, two photographic plates gave magnitudes of 16.42 and 17.31.  Antipin, Samus and Kroll (2004, IBVS 5544) looked at the original plate material and revised Hoffmeister's coordinates to the values listed above.

Antipin et al. checked 30 years of Moscow photographic plates and found no other outburst.  AAVSO reports over the past decade have had fainter-than limits around V=15, brighter than the known outburst, and so not a strong limit on subsequent outbursts.  Over the past year, however, the fainter-than limits have typically been around V=17.5, and no outburst has been seen.

Henden gives limiting magnitudes from USNO-Flagstaff observations:
2004 September 03  1.0m telescope  V < 22.2
2004 October 15    1.55m telescope V < 22.5

This gives a minimum outburst amplitude of 6.6 magnitudes.

Tom Krajci (Astrokolkhoz Observatory), using a C11 telescope, reports a 3-hour BVRI time series.  The magnitude listed above is an average of the 29 V-band images, and indicates no obvious brightening or fading over the interval.  The color is blue, as expected for a CV outburst.

All magnitudes listed above were obtained by Henden from images submitted to the AAVSO, along with the BV calibration sequence from VSP.  The coordinates for Shears/Poyner, Dvorak, and Krajci were obtained by Henden using a pre-release copy of UCAC3 as the reference catalog.

Time series photometry and visual monitoring of this rare outburst are requested from our observers.  Charts are available through our on-line chart-plotting tool, VSP:
http://www.aavso.org/vsp

Clear skies and good observing!

This Alert Notice prepared by A. Henden

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