HV Vir: WZ Sge-type Superoutburst in January
Outburst detection and early outburst phase
Outburst Image taken by the Kyoto team
On 2002 January 4, P. Schmeer discovered an extremely rare outburst of WZ
Sge-type dwarf nova HV Vir at 12mag. The last recorded outburst occurred
in 1992 (vsnet-campaign
1262, vsnet-campaign-news
120, vsnet-campaign-hvvir
3, vsnet-campaign-dn
2026, vsnet-campaign
1263, vsnet-campaign-hvvir
6). Low-amplitude modulations were clearly seen in the S. Kiyota's run
(vsnet-campaign-hvvir
16, 19).
T. Kato reported the period of 0.05705(3) d, which clearly indicated that
the modulations were early superhumps. The amplitude of the variations
was 0.07 mag, and then weakened. In the late January 4, the modulation
was rather dominated by a single wave (vsnet-campaign-hvvir
21, 25,
26,
vsnet-campaign-dn
2030, 2031).
On January 5, the modulations had a low amplitude (0.06 mag) with a
complex profile. These modulations were diminishing early superhumps. On
January 6, the object suddenly started showing genuine superhumps, with
an amplitude of 0.15 mag and well-defined superhump-type profile. It
may be either that the outburst started a few nights before the initial
detection on January 4, or that the development of genuine superhumps was
more rapid than in 1992 (vsnet-campaign
1268, vsnet-campaign-hvvir
33, 37).
T. Kato reported on January 8 that their reduced data showed clear superhumps
with the amplitude of 0.2mag. The analysis of earlier data has also confirmed
that the final transition to early superhumps to genuine superhumps took
less than 5 hours, quite comparable to a sudden change observed in WZ Sge
(vsnet-campaign-dn
2037, 2040,
vsnet-campaign-hvvir
38, 41,
42,
45).
The period of superhumps were reported to be 0.058330(19) d (vsnet-campaign-hvvir
39, 43).
The light curve observed on January 6 showed super-QPOs with a period
of 8-10 m and the maximum amplitude of 0.1 mag (vsnet-campaign-hvvir
40). Morikawa-san's observation on Jan. 7 revealed the transient
presence of QPOs with a period of 5-6 min (vsnet-campaign-hvvir
44). On January 9, a possible bump-like structure appeared on the
superhumps (vsnet-campaign-hvvir
47). Clear superhumps were observed also on January 10 and 11 (vsnet-campaign-hvvir
49, 51).
The clear secondary superhumps appeared on January 11 and 12 (vsnet-campaign-hvvir
53, 55,
58).
The data showed that superhumps became less conspicuous on Jan. 13 (vsnet-campaign-hvvir
60).
Superhump profiles
Late phase of the superoutburst
T. Kato reported a negative superhump period change (around -2x10^-5),
significant at 4 sigma. This negative value makes a clear contrast to
the positive value (Kato et al. 2001, PASJ 53, 1191) observed during the
1992 superoutburst (vsnet-campaign-hvvir
52). Subsequent superhumps however showed that the superhump period
has started to lengthen. Such O-C behavior (variable period changes)
was seen in AL Com (vsnet-campaign-hvvir
56).
T. Krajci reported the gradual decline and the decreased amplitude of superhumps
on January 14 (vsnet-campaign-hvvir
61, 62).
Superhumps possibly regrowth on January 15 (vsnet-campaign-hvvir
63), and confirmed on January 16 with 0.2mag superhumps (vsnet-campaign-hvvir
65). The fading trend stopped on January 17 with even large superhumps
(vsnet-campaign-hvvir
67). And it again started somewhat rapid fading on January 18 (vsnet-campaign-hvvir
69). T. Kato analyzed these data and reported the humps were not late-superhumps,
but ordinary superhumps (vsnet-campaign-hvvir
70). The superhumps still appeared in January 19 (vsnet-campaign-hvvir
71).
On January 21, T. Krajci reported a rapid fading from the superoutburst
plateau (vsnet-campaign-hvvir
72, 73,
76).
The rapid fading stopped in the late January 21 when late superhumps
were clearly detected in the light curve taken by the Kyoto team (vsnet-campaign-hvvir
74, 75).
On January 24, the fading rate became more gradual and the late superhumps
were still seen (vsnet-campaign-hvvir
78). A slow brightening was seen in the light curve on January 25
(vsnet-campaign-hvvir
79). The object has remained at the faint state. Possible further fading
was reported on January 31 (vsnet-campaign-hvvir
81).
Other articles:
vsnet-campaign-dn
2008,vsnet-campaign
1264,vsnet-campaign
1267,vsnet-campaign-hvvir
7, 8,
12,
13,
10,
18,
24,
29,
11,
23,
19,
28,
31,
17,
22,
27,
30,
35,
46,
48,
50,
54,
59,
64,
66,
68,
77,
80
Links:
VSNET special page for the 2002 outburst:
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/DNe/hvvir.html
[vsnet-campaign-hvvir
36]
QSOs near the object, see [vsnet-campaign-hvvir
5]
Recommended comparison stars, see [vsnet-campaign-hvvir
4] [vsnet-campaign-dn
2026] [vsnet-campaign
1263] [vsnet-campaign-hvvir
6]
Outburst CCD image:
ftp://ftp.kusastro.kyoto-u.ac.jp/pub/vsnet/DNe/HV_Vir/hvvir.gif
[vsnet-campaign-hvvir
9]
Field photometry presented by A. Henden:
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/sequence/hvvir.dat
[vsnet-campaign-hvvir
32]
Charts provided by A. Price:
http://www.aavso.org/charts/standard/VIR/HV_VIR/
[vsnet-campaign-hvvir
34]
HV Vir Superhump profile:
ftp://ftp.kusastro.kyoto-u.ac.jp/pub/vsnet/DNe/HV_Vir/hv2.gif
[vsnet-campaign-hvvir
39]
ftp://ftp.kusastro.kyoto-u.ac.jp/pub/vsnet/DNe/HV_Vir/hv12.gif
[vsnet-campaign-hvvir
57]
Light curve taken by T. Vanmunster:
http://www.lunarpages.com/cbabelgium
[vsnet-campaign-dn
2040]