73 research outputs found
Leo5 Is a Z Cam Type Dwarf Nova
Photometry of Leo5 = 1H 1025+220 show that it is a dwarf nova of the Z Cam
subtype. Two long standstills have been observed in the last five years.Comment: Accepted for publication in JAAVS
New light curves and ephemeris for the close eclipsing binary V963 PER
We have obtained CCD photometry in 2010-11 of V963 Per (=GSC3355 0394), which
is a recently identified close binary star with unequal eclipse depths. The
seven new eclipse timings yield an improved ephemeris, but we caution that
secondary eclipse can be affected by variation of the light curve. This
variation seems to be on a monthly timescale at the few percent level.Comment: 6 pages, 3 figure
A Catalogue of RR Lyrae Stars from the Northern Sky Variability Survey
A search for RR Lyrae stars has been conducted in the publicly available data
of the Northern Sky Variability Survey (NSVS). Candidates have been selected by
the statistical properties of their variation; the standard deviation, skewness
and kurtosis with appropriate limits determined from a sample 314 known RRab
and RRc stars listed in the GCVS. From the period analysis and light curve
shape of over 3000 candidates 785 RR Lyrae have been identified of which 188
are previously unknown. The light curves were examined for the Blazhko effect
and several new stars showing this were found. Six double-mode RR Lyrae stars
were also found of which two are new discoveries. Some previously known
variables have been reclassified as RR Lyrae stars and similarly some RR Lyrae
stars have been found to be other types of variable, or not variable at all.Comment: Accepted for publication in MNRAS. Tables 1 and 2 are available here
in full, but not in the printed editio
The Unique Frequency Spectrum of the Blazhko RRc Star LS Her
The Blazhko effect in RR Lyrae stars is still poorly understood
theoretically. Stars with multiple Blazhko periods or in which the Blazhko
effect itself varies are particularly challenging. This study investigates the
Blazhko effect in the RRc star LS Her. Detailed VRI CCD photometry has been
performed on 63 nights during six months. LS Her is confirmed to have a Blazhko
period of 12.75+/-0.02 days. However, where normally the side frequencies of
the Blazhko triplet are expected, an equidistant group of three frequencies is
found on both sides of the main pulsation frequency. As a consequence the
period and amplitude of the Blazhko effect itself vary in a cycle of 109+/-4
days. LS Her is a unique object turning out to be very important in the
verification of the theories for the Blazhko effect.Comment: Accepted for publication in MNRA
Discovery of a Very Young Field L Dwarf, 2MASS J01415823-4633574
While following up L dwarf candidates selected photometrically from the Two
Micron All Sky Survey, we uncovered an unusual object designated 2MASS
J01415823-4633574. Its optical spectrum exhibits very strong bands of vanadium
oxide but abnormally weak absorptions by titanium oxide, potassium, and sodium.
Morphologically such spectroscopic characteristics fall intermediate between
old, field early-L dwarfs (log(g)~5) and very late M giants (log(g)~0), leading
us to favor low gravity as the explanation for the unique spectral signatures
of this L dwarf. Such a low gravity can be explained only if this L dwarf is
much lower in mass than a typical old field L dwarf of similar temperature and
is still contracting to its final radius. These conditions imply a very young
age. Further evidence of youth is found in the near-infrared spectrum,
including a triangular-shaped H-band continuum reminiscent of young brown dwarf
candidates discovered in the Orion Nebula Cluster. Using the above information
along with comparisons to brown dwarf atmospheric and interior models, our
current best estimate is that this L dwarf has an age of 1-50 Myr and a mass of
6-25 M_Jupiter. The location of 2MASS 0141-4633 on the sky coupled with a
distance estimate of ~35 pc and the above age estimate suggests that this
object may be a brown dwarf member of either the 30-Myr-old Tucana/Horologium
Association or the ~12-Myr-old beta Pic Moving Group.Comment: Accepted for publication in the 10 March 2006 issue (volume 639) of
the Astrophysical Journa
NSV 1907 - a new eclipsing, nova-like cataclysmic variable
NSV 1907, formerly listed as an irregular variable in variability catalogues, was classified as an Algol-type eclipsing binary in the Catalina Surveys Periodic Variable Star Catalogue. We have identified NSV 1907 as an ultraviolet (UV) bright source using measurements from the GALEX space telescope and detected obvious out-of-eclipse variability in archival photometric data from the Catalina Sky Survey, which instigated a closer examination of the object. A spectrum and extensive multicolour photometric observations were acquired, from which we deduce that NSV 1907 is a deeply eclipsing, nova-like cataclysmic variable. Apart from the orbital variations (deep eclipses with a period of P ≈ 6.63 hours), changes in mean brightness and irregular short-term variability (flickering) were observed. The presence of a secondary minimum at phase φ ≈ 0.5 was established, which indicates a significant contribution of the companion star to the optical flux of the system. We find possible evidence for sinusoidal variations with a period of P ≈ 4.2 d, which we interpret as the nodal precession period of the accretion disc. No outbursts or VY Scl-like drops in brightness were detected either by the CSS or during our photometric monitoring. Because of its spectral characteristics and the observed variability pattern, we propose NSV 1907 as a new moderately bright long-period SW Sextantis star. Further photometric and spectroscopic observations are encouraged
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