BF Ara: "Missing Link" between ER UMa stars and ordinary SU UMa stars
BF Ara had been proposed to possibly related to ER UMa stars. Before August
2002, several outbursts were frequently reported by R. Stubbings: 14.3-14.4mag
on April 8 (vsnet-campaign-dn
2285), 14.4mag on May 4 (vsnet-campaign-dn
2355, 2360),
14.1mag on May 15 (vsnet-campaign-dn
2413, 2425),
14.4mag on July 30 (vsnet-campaign-dn
2679, 2688,
2690).
On August 14, an outburst to 14.4mag was detected by R. Stubbings. The object
further brightened to 14.0mag on August 16 and 13.9mag on August 17 (vsnet-campaign-dn
2726). The light curve obtained by G. Bolt clearly showed fully grown
superhumps with amplitudes of 0.25 mag and a period of 0.086 d. This observation
has established the SU UMa-type nature of BF Ara. BF Ara has the shortest
supercycle lengths except ER UMa stars (Kato et al. 2001, IBVS 5119).
T. Kato commented that BF Ara thus could be a "missing link" between classical
SU UMa-type dwarf novae and ER UMa stars (vsnet-campaign-dn
2732).
T. Kato reported that combined light curves obtained by G. Bolt and P. Nelson
yielded a longer superhump period of 0.0881 d. It may be possible that
BF Ara was in a stage of rapid period evolution (vsnet-campaign-dn
2736, 2738).
With a new data set on August 21 by G. Bolt, T. Kato reported a revised
superhump period of 0.08805(2) d. The mean fading rate during the present
superoutburst plateau is 0.08 mag/d, which is relatively small among SU
UMa-type dwarf novae (vsnet-campaign-dn
2739). The profile of superhumps on August 23 has become more symmetric
than before (vsnet-campaign-dn
2747). The data from P. Nelson showed superhumps decreased in amplitude
from 0.1mag on August 23 to 0.05mag on August 25 (vsnet-campaign-dn
2752). The superhumps detected by P. Nelson were rather narrow (sharp),
which are unlike many of other SU UMa stars (vsnet-campaign-dn
2753). The superoutburst continued until August 27, when it entered
a rapid fading phase (vsnet-campaign-dn
2733, 2735,
2745,
2748,
2754,
2765).
During the fading phase, the light curve obtained by P. Nelson showed double-wave
superhumps (vsnet-campaign-dn
2759). R. Stubbings detected a rebrightening to 14.9mag on September
1 (vsnet-campaign-dn
2779).
A new outburst to 15.0mag was reported by R. Stubbings on September 7.
t_n (cycle of normal outburst) = 6 d is the shortest cycle length among SU
UMa stars, except ER UMa stars (vsnet-campaign-dn
2810, 2824).