4 research outputs found
SDSS J0349-0059 is a GW Virginis star
High speed photometric observations of the spectroscopically-discovered PG
1159 star SDSS J034917.41-005917.9 in 2007 and 2009 reveal a suite of pulsation
frequencies in the range of 1038 - 3323 microHz with amplitudes between 3.5 and
18.6 mmag. SDSS J034917.41-005917.9 is therefore a member of the GW Vir class
of pulsating pre-white dwarfs. We have identified 10 independent pulsation
frequencies that can be fitted by an asymptotic model with a constant period
spacing of 23.61 +/- 0.21 s, presumably associated with a sequence of l = 1
modes. The highest amplitude peak in the suite of frequencies shows evidence
for a triplet structure, with a frequency separation of 14.4 microHz. Five of
the identified frequencies do not fit the l = 1 sequence, but are, however,
well-modeled by an independent asymptotic sequence with a constant period
spacing of 11.66 +/- 0.13 s. It is unclear to which l mode these frequencies
belong.Comment: Accepted for publication in MNRAS; 5 pages, 6 figures and 4 table
On the spin modulated circular polarization from the intermediate polars NY Lup and IGRJ1509-6649
We report on high time resolution, high signal/noise, photo-polarimetry of
the intermediate polars NY Lup and IGRJ1509-6649. Our observations confirm the
detection and colour dependence of circular polarization from NY Lup and
additionally show a clear white dwarf, spin modulated signal. From our new high
signal/noise photometry we have unambiguously detected wavelength dependent
spin and beat periods and harmonics thereof. IGRJ1509-6649 is discovered to
also have a particularly strong spin modulated circularly polarized signal. It
appears double peaked through the I filter and single peaked through the B
filter, consistent with cyclotron emission from a white dwarf with a relatively
strong magnetic field.
We discuss the implied accretion geometries in these two systems and any
bearing this may have on the possible relationship with the connection between
polars and soft X-ray-emitting IPs. The relatively strong magnetic fields is
also suggestive of them being polar progenitors.Comment: 8 pages, 6 figures and 1 table. Accepted for publication in MNRA
Possible detection of two giant extrasolar planets orbiting the eclipsing polar UZ Fornacis
We present new high-speed, multi-observatory, multi-instrument photometry of
the eclipsing polar UZ For in order to measure precise mid-eclipse times with
the aim of detecting any orbital period variations. When combined with
published eclipse times and archival data spanning ~27 years, we detect
departures from a linear and quadratic trend of ~60 s. The departures are
strongly suggestive of two cyclic variations of 16(3) and 5.25(25) years. The
two favoured mechanisms to drive the periodicities are either two giant
extrasolar planets as companions to the binary (with minimum masses of
6.3(1.5)M(Jupiter) and 7.7(1.2)M(Jupiter)) or a magnetic cycle mechanism (e.g.
Applegate's mechanism) of the secondary star. Applegate's mechanism would
require the entire radiant energy output of the secondary and would therefore
seem to be the least likely of the two, barring any further refinements in the
effect of magnetic fieilds (e.g. those of Lanza et al.). The two planet model
can provide realistic solutions but it does not quite capture all of the
eclipse times measurements. A highly eccentric orbit for the outer planet would
fit the data nicely, but we find that such a solution would be unstable. It is
also possible that the periodicities are driven by some combination of both
mechanisms. Further observations of this system are encouraged.Comment: 10 pages, 4 figures, 2 table
High speed photometry of faint Cataclysmic Variables - VII. Targets selected from the Sloan Digital Sky Survey and the Catalina Real-time Transient Survey
We present high speed photometric observations of 20 faint cataclysmic
variables, selected from the Sloan Digital Sky Survey and Catalina catalogues.
Measurements are given of 15 new directly measured orbital periods, including
four eclipsing dwarf novae (SDSS0904+03, CSS0826-00, CSS1404-10 and
CSS1626-12), two new polars (CSS0810+00 and CSS1503-22) and two dwarf novae
with superhumps in quiescence (CSS0322+02 and CSS0826-00). Whilst most of the
dwarf novae presented here have periods below 2 h, SDSS0805+07 and SSS0617-36
have relatively long orbital periods of 5.489 and 3.440 h, respectively. The
double humped orbital modulations observed in SSS0221-26, CSS0345-01,
CSS1300+11 and CSS1443-17 are typical of low mass transfer rate dwarf novae.
The white dwarf primary of SDSS0919+08 is confirmed to have non-radial
oscillations and quasi-periodic oscillations were observed in the short-period
dwarf nova CSS1028-08 during outburst. We further report the detection of a new
nova-like variable (SDSS1519+06). The frequency distribution of orbital periods
of CVs in the Catalina survey has a high peak near ~80 min orbital period,
independently confirming that found by Gaensicke et al (2009) from SDSS
sources. We also observe a marked correlation between the median in the orbital
period distribution and the outburst class, in the sense that dwarf novae with
a single observed outburst (over the 5-year baseline of the CRTS coverage)
occur predominantly at shortest orbital period.Comment: 17 pages, 38 figures, accepted for publication in MNRA