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    THE AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS
           25 Birch Street, Cambridge, MA 02138 USA
                      aavso@aavso.org
         Tel. 617-354-0484       Fax 617-354-0665

AAVSO ALERT NOTICE 335  (February 13, 2006)

SUBJECTS:

1. RECURRENT NOVA 1744-06 RS OPHIUCHI IN OUTBURST
2. W VIR MONITORING WINDOW EXTENDED TO MID-APRIL

1. RECURRENT NOVA 1744-06 RS OPHIUCHI IN OUTBURST

Object: 1744-06 RS OPH

Coordinates: R.A. 17h 50m 13.202s Dec. -06o 42' 28.48" (2000.0)

The recurrent nova RS Oph is in outburst at visual magnitude 4.8, according to observations by Hiroaki Narumi, Ehime, Kita-gun, Japan, and Kiyotaka Kanai, Gunma, Isezaki-shi, Japan (IAU Circular 8671), and confirmed by Wolfgang Renz, Karlsruhe, Germany.

According to observations in the AAVSO International Database, the last outburst of RS Oph occurred in January 1985, when the star reached visual magnitude 5.2 and was brighter than 10.5 for about 80 days; RS Oph returned to its normal inter-outburst behavior approximately 570 days after outburst maximum. Previous outbursts have been recorded in 1898, 1933, 1958, and 1967, with a probable outburst in 1945. AAVSO observations confirm that no outburst occurred between the 1985 one and the current one.

While the length of the interoutburst interval in RS Oph varies greatly, the shape of the outburst and recovery to interoutburst is remarkably similar from outburst to outburst. For a very interesting analysis of the behavior of RS Oph, see B.D. Oppenheimer and J.A. Mattei, JAAVSO, 22, 2, 105 (1993), or Oppenheimer and Mattei in Compact Stars in Binaries, proceedings of IAU Symposium 165, ed. J. van Paradijs, Edward Peter Jacobus van den Heuvel, and Erik Kuulkers, Kluwer Acad. Publ., Dordrecht, 457 (1994).

Visual, CCDV, and PEPV observations are requested. CCD and PEP observers should use the 68 (V = 6.84, B-V = 0.99) star North of RS Oph on the 'a' and 'b' charts as a comparison star and the 63 (V = 6.30, B-V = 0.31) star West-Southwest of RS Oph on the same charts as a check star. For stars this bright, CCD observers may need to use some technique to reduce the brightness of the star. Please see the AAVSO CCD Manual, section 4.7 (http://www.aavso.org/observing/programs/ccd/manual/4.shtml#7). Time-series observations would be very interesting, as this outburst is the first one of RS Oph for which they are feasible for amateur astronomers to make.

Charts: AAVSO a, b, c, and d scale charts for RS Oph are available at:

http://www.aavso.org/cgi-bin/searchcharts3.pl?name=RS%20OPH

Ulisse Munari and Arne Henden are in the process of publishing all-sky UBVRI calibration for this field, and that .dat file will be posted (probably on February 14) to help CCD/PEP observers, especially as RS Oph fades.

Report Object to the AAVSO as: 1744-06 RS OPH

Observations Reported to the AAVSO:
FEB 08.2493 UT, 10.9, A. Gonzalez Herrera, Ferol, Spain; 10.2100, 11.0, B. Granslo, Fjellhamar, Norway; 12.829, 4.5, H. Narumi, Ehime, Kita-gun, Japan (via K. Hirosawa, Aichi, Inazawa-shi, Japan; IAU Circular 8671); 12.8426, 4.5 CCD, Y. Nakamura, Kameyama, Mie-ken, Japan (via S. Nakano, Sumoto, Japan; IAU Circular 8671); 12.847, 4.6, K. Kanai, Gunma, Isezaki-shi, Japan (via Hirosawa; IAU Circular 8671); 12.862, 4.4, Kanai (via Hirosawa; IAU Circular 8671); 13.27, 4.9, A. Pereira, Cabo da Roca, Portugal (IAU Circular 8671); 13.1631, 4.8, W. Renz, Karlsruhe, Germany; 13.1806, 4.8, Renz; 13.2139, 4.8, Renz; 13.2347, 4.8, Renz; 13.3965, 5.1, J. Bortle, Stormville, NY; 13.341, 5.4 V (saturated), ASAS via G. Pojmanski (IAU Circular 8671); 13.344, 5.3 V, ASAS via G. Pojmanski (IAU Circular 8671); 13.4826, 5.71 PEPB, D. West, Mulvane, KS; 13.4826, 4.88 PEPV, West; 13.4715, 2.36 PEPH, West; 13.4715, 2.71 PEPJ, West; 13.490, 5.65 CCDB, G. Sostero, Cavalicco, Italy; 13.491, 5.04 CCDV, Sostero; 13.493, 4.43 CCDR, Sostero.

Congratulations to Hiroaki Narumi and Kiyotaka Kanai on their discovery!

2. W VIR MONITORING WINDOW EXTENDED TO MID-APRIL

The monitoring interval of the Cepheid variable 1320-02 W Vir, requested in AAVSO Alert Notice 331 on behalf of Dr. George Wallerstein, University of Washington, has been extended to mid-April 2006.

Poor weather prevented Dr. Wallerstein from obtaining his observations of W Vir from minimum to well past maximum, and his telescope time has been extended. Thus, he has requested that AAVSO observers extend their monitoring to mid-April in order to provide good optical coverage for his observations.

Visual and CCD (with V filter) observations are requested. For PEP observers who can reach magnitude 10 or fainter, PEP-V observations are also requested. Nightly observations are needed; CCD observers in particular should see Alert Notice 331 for additional observing instructions.

Thank you very much for your astronomical contributions and efforts.

Good observing!

Elizabeth O. Waagen
Senior Technical Assistant

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Many thanks for your valuable astronomical contributions and your efforts.

Good observing!

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