72 research outputs found
Photometry of the dwarf nova AW Sagittae during the 2006 November superoutburst
During 2006 November an outburst of the dwarf nova AW Sge was observed using
CCD photometry. This revealed 0.25 magnitude superhumps confirming it to be a
superoutburst, possibly only the second confirmed such outburst of this star.
The superhumps were observed for 4 days and had a stable period Psh =
0.0745(2)d, a value which is consistent with Psh measured during the 2000
superoutburst.Comment: 10 pages, 9 figures. Accepted for publication in the Journal of the
British Astronomical Associatio
The orbital period of the eclipsing dwarf nova CG Draconis
We have performed time resolved photometry on the dwarf nova CG Dra and have
established for the first time that it is an eclipsing system. By measuring the
times of the eclipses, we determined the orbital period as 0.18864(4) d, or 4h
31m 38 +/- 3s. This value is consistent with the shorter of two periods
proposed from earlier spectroscopic studies. The orbital period places CG Dra
above the period gap. The symmetrical eclipses are of short duration (FWHM
18+/-2 min, or 0.066(7) of the orbital period) and shallow (average 0.16+/-0.02
mag), suggesting a grazing eclipse which is consistent with an orbital
inclination just above the critical value. Flickering persists through the
eclipse which means that the flickering source is not occulted by the secondary
star.Comment: 12 pages, 8 figures, accepted for publication in the Journal of the
British Astronomical Associatio
Outburst characteristics of the dwarf nova V452 Cassiopeiae
V452 Cas was thought to have rare outbursts, but monitoring from 2005 to 2008
has shown that the outburst interval is about one month and is weakly periodic.
Observations of seven superoutbursts over the same period shows a very
repeatable superoutburst period of 146 +/-16 days. Time series photometry of
the 2007 September superoutburst shows that the outburst reached magnitude 15.3
at maximum and had an amplitude of 3.2 magnitudes. The outburst lasted for 12
days. Early superhumps with an amplitude of 0.3 magnitudes and period of Psh =
0.08943(7) days gave way to superhumps with decreasing amplitude and Psh =
0.08870(2) days later in the outburst, corresponding to a continuous period
change Pdot/P = -9(2)x10-4 d-1 . V452 Cas has one of the smallest outburst
amplitudes and shortest superoutburst periods of typical UGSU systems.Comment: 17 pages, 9 Figures. Accepted for publication in the Journal of the
British Astronomical Associatio
GSC2.3 N152008120 - a new SU UMa-type dwarf nova in Draco
We report observations during 2008 October of the first recorded
superoutburst of a previously unknown SU UMa-type dwarf nova in Draco located
at 19h 14m 43.52s +60d 52m 14.1s (J2000). Simbad lists a 21st magnitude star at
this position with identifiers GSC2.3 N152008120 and USNO-B1.0 1508-0249096.
The outburst reached magnitude 14.9, its amplitude was approximately 6
magnitudes and its duration at least 11 days. About 11 days after the end of
the main outburst there was a short-lived rebrightening by more than 2
magnitudes. Superhumps were observed with a mean period of 0.07117(1) d and
amplitude 0.12 mag. There was a distinct shortening in the superhump period
around cycle 80 with Psh = 0.07137(2) d before and Psh = 0.07091(2) d after. We
saw weak evidence of an increasing Psh before cycle 80 with dPsh/dt = 3.4(2.0)
* 10-5.Comment: Accepted for publication in Journal of the British Astronomical
Association, 9 pages, 6 figure
Superoutbursts and grazing eclipses in the dwarf nova V1227 Herculis
We present photometry obtained during the 2012 May and September outbursts of
the frequently outbursting dwarf nova, V1227 Her. Superhumps were present in
both cases with a peak-to peak amplitude of up to 0.28 mag, showing these
events to be superoutbursts. We show for the first time that the system
undergoes small eclipses with a depth of up to 0.08 mag, lasting 11 to 14 min,
which are likely to be grazing eclipses of the accretion disc. The September
outburst was the better observed of the two and lasted at least 14 days with an
outburst amplitude of approximately 4 magnitudes. The mean superhump period was
Psh = 0.065103(20) d. Analysis of eclipse times of minimum gave an orbital
period Porb = 0.064419(26) d, although there is some ambiguity due to the
relatively short time over which the eclipses were observed. The fractional
superhump period excess, epsilon, was 0.0106(7).Comment: Accepted for publication in the Journal of the British Astronomical
Association. 17 pages, 6 figures. The target star of this paper, SDSS
J165359.06+201010.4, has now received the official name of V1227 Her in the
General Catalogue of Variable Stars. This version contains the new nam
The orbital and superhump periods of the deeply eclipsing dwarf nova PU UMa
We report unfiltered photometry during superoutbursts of PU UMa in 2009 and
2012. The amplitude was 4.5 magnitudes above mean quiescence and lasted at
least 9 to 10 days. Superhumps were present with a peak-to-peak amplitude of up
to ~0.3 mag, thereby confirming it to be a member of the SU UMa family of dwarf
novae. The mean superhump period during the later part of the 2012 outburst was
Psh = 0.08076(40) d. Analysis of the eclipse times of minimum, supplemented
with data from other researchers, revealed an orbital period of Porb =
0.077880551(17) d. The superhump period excess was epsilon = 0.037(5). During
the 2012 outburst, which was the better observed of the two, the FWHM eclipse
duration gradually declined from 9.5 to 5 min. The eclipse depth was up to 1.7
magnitudes.Comment: 16 pages, 5 figures. Accepted for publication in the Journal of the
British Astronomical Associatio
HW Bootis: an enigmatic cataclysmic variable star
We present the 13-year light curve of HW Boo between 2001 May and 2014 May.
We identified 12 outbursts, which typically lasted 2 to 5 days, with an
amplitude of 2.7 to 3.6 magnitudes. Time resolved photometry during two
outbursts revealed small hump-like structures which increased in size as the
outburst progressed, reaching a peak-to-peak amplitude of ~0.8 mag. They
occurred on timescales of 15 min to an hour, but did not exhibit a stable
period. Similar irregular hump-like variations of 0.1 to 0.8 magnitudes, at
intervals of 7 to 30 minutes, were also detected during quiescence. We discuss
whether HW Boo might be a dwarf nova of the SU UMa family or an Intermediate
Polar, but require further observations to support classification.Comment: 14 pages, 5 Figures. Accepted for publication in the Journal of the
British Astronomical Associatio
Measuring the period of the delta Scuti variable U1425-01208594 in Cassiopeia
The variability of U1425-01208594 was recently discovered by Schmidtobreick
et al, who suggested that it is a member of the delta Scuti family of pulsating
stars. Photometry conducted by the authors revealed a period of 0.06695(8) d
and a peak-to-peak amplitude of 0.014 mag.Comment: Accepted for publication in the Open European Journal on Variable
Stars. 4 pages, 4 figure
The 2008 February superoutburst of V452 Cas
Observations of the 2008 February outburst of V452 Cas show that the profile,
duration and magnitude at maximum were very similar to the previous
superoutburst in 2007 September. Low-amplitude variations consistent with
previously observed superhumps were also seen.Comment: 4 pages, 2 figure
The 2015 superoutburst of QZ Virginis: Detection of growing superhumps between the precursor and main superoutburst
We report on time-resolved photometry of the 2015 February-March
superoutburst of QZ Virginis. The superoutburst consisted of a separated
precursor, main superoutburst, and rebrightening. We detected superhumps with a
period of 0.061181(42) d between the precursor and main superoutburst. Based on
analyses of period changes and amplitudes of superhumps, the observed
superhumps were identified as growing superhumps (stage A superhumps). The
duration of stage A superhumps was about 5 d, unusually long for SU UMa-type
dwarf novae. Using the obtained stage A superhump period, we estimated the mass
ratio of QZ Vir to be 0.108(3). This value suggests that QZ Vir is an SU
UMa-type dwarf nova evolving toward the period minimum. Based on the present
and the previous observations regarding long-lasting stage A superhumps, a time
scale of stage A superhumps is likely to be determined by the mass ratio of the
system and the temperature of the accretion disk.Comment: 12 pages, 6 figures, published for PASJ, 69, 7
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