Bibcode
Aungwerojwit, A.; Gänsicke, B. T.; Rodríguez-Gil, P.; Hagen, H.-J.; Araujo-Betancor, S.; Baernbantner, O.; Engels, D.; Fried, R. E.; Harlaftis, E. T.; Mislis, D.; Nogami, D.; Schmeer, P.; Schwarz, R.; Staude, A.; Torres, M. A. P.
Bibliographical reference
Astronomy and Astrophysics, Volume 455, Issue 2, August IV 2006, pp.659-672
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8
2006
Journal
Citations
35
Refereed citations
32
Description
Aims.We report the discovery of five new dwarf novae that were
spectroscopically identified in the Hamburg Quasar Survey (HQS), and
discuss the properties of the sample of new dwarf novae from the HQS.Methods.Follow-up time-resolved spectroscopy and photometry have been
obtained to characterise the new systems.Results.The orbital
periods determined from analyses of the radial velocity variations
and/or orbital photometric variability are P_orb≃105.1 min or
P_orb≃109.9 min for HS 0417+7445, P_orb=114.3±2.7 min for HS
1016+3412, P_orb=92.66±0.17 min for HS 1340+1524,
P_orb272.317±0.001 min for HS 1857+7127, and
P_orb=258.02±0.56 min for HS 2214+2845. HS 1857+7127 is found to
be partially eclipsing. In HS 2214+2845 the secondary star of spectral
type M3±1 is clearly detected, and we estimate the distance to
the system to be d=390±40 pc. We recorded one superoutburst of HS
0417+7445, identifying the system as a SU UMa-type dwarf nova. HS
1016+3412 and HS 1340+1524 have rare outbursts, and their subtype is yet
undetermined. HS 1857+7127 frequently varies in brightness and may be a
Z Cam-type dwarf nova. HS 2214+2845 is a U Gem-type dwarf nova with a
most likely cycle length of 71 d.Conclusions.To date, 14 new dwarf
novae have been identified in the HQS. The ratio of short-period (<3
h) to long-period (>3 h) systems of this sample is 1.3, much smaller
compared to the ratio of 2.7 found for all known dwarf novae. The HQS
dwarf novae display typically infrequent or low-amplitude outburst
activity, underlining the strength of spectroscopic selection in
identifying new CVs independently of their variability. The
spectroscopic properties of short-period CVs in the HQS, newly
identified and previously known, suggest that most, or possibly all of
them are still evolving towards the minimum period. Their total number
agrees with the predictions of population models within an order of
magnitude. However, the bulk of all CVs is predicted to have evolved
past the minimum period, and those systems remain unidentified. This
suggests that those post-bounce systems have markedly weaker Hβ
emission lines compared to the average known short-period CVs, and
undergo no or extremely rare outbursts.