DM Lyrae

From Wikipedia, the free encyclopedia

**DM Lyrae A/B**
Observation data Epoch J2000.0
Constellation (pronunciation)	Lyra
Right ascension	18^h 58^m 44.43^s
Declination	+30° 15′ 33.0″
Apparent magnitude (V)	+18 (quiet), +13.6 (burst)
Characteristics
Spectral type	? / White dwarf
U-B color index	?
B-V color index	?
Variable type	SU UMa
Other designations
DM Lyr, AN 250.1929, 1RXS J185845.1+301548, AAVSO 1854+30

DM Lyrae (DM Lyr for short) is a dwarf nova in the constellation Lyra. This binary system is composed of a primary star of unknown type, and a white dwarf companion. It erupted in 1928 and 1996 and reached about magnitude 13. Due to its position, coverage of the star by major northern hemisphere observatories is difficult during the winter months and very difficult by major southern hemisphere observatories all year round; it is quite possible that several outbursts have been missed.

The July 1996 outburst—unlike the others—proved to be a long, bright one, which caused several observers to wonder if it could possibly be a supermaximum which is indicative of a SU Ursae Majoris star. Observers at Kyoto University carried out V band CCD photometry with the 60cm reflector and detected superhumps of 0.1 mag amplitude, thus reclassifying DM Lyrae as an SU UMa star. Their preliminary period analysis gave 0.066 ± 0.002 days as the best estimated superhump period.