[vsnet-outburst 7932] SDSS J155644.24-000950.2 shortening of superhump period

[Taichi Kato]

SDSS J155644.24-000950.2 shortening of superhump period

   Nakajima-san has reported further set of observations on Aug. 4.
The data clearly show the change in the superhump profile.
The superhump period significantly decreased from 0.08378(4) d
(July 29-31) to 0.08301(1) d (July 31-Aug 4).  This explains
the apparent discrepancy between reported period analyses.
This change may have been a discontinuous period jump as observed
in a similar long-period system EG Aqr (cf. vsnet-alert 9126

http://ooruri.kusastro.kyoto-u.ac.jp/pipermail/vsnet-alert/2006-November/000748.html ), UV Gem (cf. vsnet-campaign-dn 3302, 3307)
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-campaign-dn/msg03302.html
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-campaign-dn/msg03307.html

    The following message might be helpful in planning further
observation of SDSS J155644.24-000950.2:

(excerpt from vsnet-campaign-dn 3302 on UV Gem)

   A preliminary period analysis has revealed an interesting period change.
Up to Jan. 7, the superhumps were well expressed by a single period of
0.0966 d.  After that, The period suddenly switched to 0.0932 d.
The difference between these periods are comparable to the differences
between superhump periods and orbital periods!  Such a dramatic change
(and a large change) in the superhump period is quite unexpected and
unprecedented in SU UMa-type superhumps.  Such a dramatic change may have
affected the past (seemingly contractding) interpretation of the UV Gem
superhumps.

  In order to fully describe and interpret this unexpected behavior,
we encourage further dense (hopefully full-night long) observations to
catch as many superhumps as possible!