1,114 research outputs found
DK And: Reclassification as EW Binary from CCD Observations
This paper describes the reclassification of DK And, formerly classified as a
RRc type star, as EW binary. 1599 CCD unfiltered and filtered (V and R band)
observations between 1999 and 2005 show, that the star is actually an eclipsing
binary star with a period of P = 0.4892224 +/- 0.0000002 [d] with epoch E0 =
2451435.4353 +/- 0.0010 (if all historic data were taken into account). From
our new observations 12 timings of minimum light are given.Comment: PDF with reduced graph quality, 7 pages, 6 figures, 1 tabl
ASASSN-14cc: Likely Helium Analog of RZ Leonis Minoris
We identified that ASASSN-14cc is a very active dwarf nova spending
approximately 60% of the time in outburst. Our long-term photometry revealed
that the object shows long outbursts recurring with a period of 21-33 d and
very brief short outbursts lasting less than 1 d. The maximum decline rate
exceeds 2.8 mag/d. The duration of long outbursts is 9-18 d, comprising 50-60%
of the recurrence time of long outbursts. We detected 0.01560-0.01562 d (22.5
min) modulations during long outbursts, which we identified to be superhumps.
These features indicate that ASASSN-14cc has outburst parameters very similar
to the extreme dwarf nova RZ LMi but with a much shorter superhump period. All
the observations can be naturally understood considering that this object is a
helium analog (AM CVn-type object) of RZ LMi. The highest outburst activity
among AM CVn-type objects can be understood as the high-mass transfer rate
expected for the orbital period giving a condition close to the stability limit
of the accretion disk. In contrast to RZ LMi, this object shows little evidence
for premature quenching of the superoutburst, which has been proposed to
explain the unusual outburst parameters in RZ LMi.Comment: 5 pages, 5 figures, accepted for publication in PASJ (Letters
Photometric evolution of seven recent novae and the double component characterizing the lightcurve of those emitting in gamma rays
The BVI lightcurves of seven recent novae have been extensively mapped with
daily robotic observations from Atacama (Chile). They are V1534 Sco, V1535 Sco,
V2949 Oph, V3661 Oph, MASTER OT J010603.18-744715.8, TCP J1734475-240942 and
ASASSN-16ma. Five belong to the Bulge, one to SMC and another is a Galactic
disk object. The two program novae detected in gamma-rays by Fermi-LAT (TCP
J1734475-240942 and ASASSN-16ma) are Bulge objects with unevolved companions.
They distinguish themselves in showing a double-component optical lightcurve.
The first component to develop is the fireball from freely-expanding,
ballistic-launched ejecta with the time of passage through maximum which is
strongly dependent on wavelength (~1 day delay between B and I bands). The
second component, emerging simultaneously with the nova detection in
gamma-rays, evolves at a slower pace, its optical brightness being proportional
to the gamma-ray flux, and its passage through maximum not dependent on
wavelength. The fact that gamma-rays are detected at peak flux level differing
by 4x from novae at the distance of the Bulge seems to suggest that gamma-ray
emission is not a widespread property of normal novae. We discuss the
advantages offered by high-quality photometric observations collected with only
one telescope (as opposed to data provided by a number of different
instruments), and observe the effects of: wavelength dependence of a fireball
expansion, recombination in the flashed wind of a giant companion, subtle
presence of hiccups, super-soft X-ray emission on and off. Four program novae
(V2949 Oph, V3661 Oph, TCP J18102829-2729590, and ASASSN-16ma) are found to
have normal dwarf companions, while V1534 Sco contains an M3III giant, V1535
Sco a K-type giant, and MASTER OT J010603.18-744715.8 a sub-giant.Comment: MNRAS, 18 pages, 17 figures, 3 tables (1 electronic
The Eclipsing Cataclysmic Variables PHL 1445 and GALEX J003535.7+462353
PHL 1445 is found to be an eclipsing cataclysmic variable with an orbital
period of 76.3 minutes. GALEX J003535.7+462353 is a new eclipsing dwarf nova
with an orbital period of 4.13 hours. Both objects show deep eclipses with an
amplitude of more than two magnitudes.Comment: Published as IBVS 598
V0784 Ophiuchi: an RR Lyrae star with multiple Blazhko modulations
The results of an observation campaign of V0784 Ophiuchi over a time span of
two years have revealed a multi-periodic Blazhko effect. A Blazhko effect for
V0784 Ophiuchi has not been reported previously. From the observed light
curves, 60 pulsation maxima have been measured. The Fourier analyses of the
(O-C) values and of magnitudes at maximum light have revealed a main Blazhko
period of 24.51 days but also two other secondary Blazhko modulations with
periods of 34.29 and 31.07 days. A complete light curve Fourier analysis with
PERIOD04 has shown triplet structures based on main and secondary Blazhko
frequencies close to the reciprocal of Blazhko periods measured from the 60
pulsation maxima.Comment: 9 pages, accepted for publication in JAAVS
CC Sculptoris: Eclipsing SU UMa-Type Intermediate Polar
We observed the 2014 superoutburst of the SU UMa-type intermediate polar CC
Scl. We detected superhumps with a mean period of 0.05998(2) d during the
superoutburst plateau and during three nights after the fading. During the
post-superoutburst stage after three nights, a stable superhump period of
0.059523(6) d was detected. We found that this object is an eclipsing system
with an orbital period of 0.058567233(8) d. By assuming that the disk radius in
the post-superoutburst phase is similar to those in other SU UMa-type dwarf
novae, we obtained a mass ratio of q=0.072(3) from the dynamical precession
rate of the accretion disk. The eclipse profile during outbursts can be modeled
by an inclination of 80.6+/-0.5 deg. The 2014 superoutburst was preceded by a
precursor outburst and the overall appearance of the outburst was similar to
superoutbursts in ordinary SU UMa-type dwarf novae. We showed that the standard
thermal-tidal instability model can explain the outburst behavior in this
system and suggest that inner truncation of the disk by magnetism of the white
dwarf does not strongly affect the behavior in the outer part of the disk.Comment: 11 pages, 8 figures, accepted for publication in PAS
CX Lyrae 2008 Observing Campaign
The Blazhko effect in CX Lyr has been reported for the first time by Le
Borgne et al. (2007). The authors have pointed out that the Blazhko period was
not evaluated accurately due to dataset scarcity. The possible period values
announced were 128 or 227 days. A newly conducted four-month observing campaign
in 2008 (fifty-nine observation nights) has provided fourteen times of maximum.
From a period analysis of measured times of maximum, a Blazhko period of 62 +/-
2 days can be suggested. However, the present dataset is still not densely
sampled enough to exclude that the measured period is still a modulation of the
real Blazhko period. Indeed the shape of the (O-C) curve does not repeat itself
exactly during the campaign duration
SSS J122221.7-311523: Double Superoutburst in a Best Candidate Period Bouncer
We observed the 2012-2013 superoutburst of the newly identified transient SSS
J122221.7-311523 and found that this object showed successive two
superoutbursts. Superhumps grew in amplitude during the second superoutburst
and showed a characteristic pattern of period change reflecting the growth of
the superhump. Assuming that the periods of superhumps during the growing stage
[0.07721(1) d] and post-superoutburst stage [0.07673(3) d], represent the
dynamical precession rates at the radius of the 3:1 resonance and the radius
immediately after the superoutburst, respectively, we found that this object
has a very small mass ratio q=M2/M1 < 0.05. The possible orbital period from
quiescent data suggests q=0.045, one of the smallest among hydrogen-rich
cataclysmic variables. The long orbital period and low q make this object a
perfect candidate for a period bouncer. We suggest that the peculiar pattern of
double superoutburst is a result of a low q and may be characteristic to period
bouncers.Comment: 6 pages, 4 figures, accepted for publication in PASJ (Letters
V1820 Orionis : an RR Lyrae star with strong and irregular Blazhko effect
The Blazhko effect in V1820 Orionis and its period were reported for the
first time by Wils et al. (2006) from a data analysis of the Northern Sky
Variability Survey. The results of additional V1820 Orionis observations over a
time span of 4 years are presented herein. From the observed light curves, 73
pulsation maxima have been measured. The times of light maxima have been
compared to ephemerides to obtain the (O-C) values. The Blazhko period (27.917
+/- 0.002 d) has been derived from light curve Fourier analysis and from ANOVA
analyses of the (O-C) values and of magnitudes at maximum light (Mmax). During
one Blazhko cycle, a hump in the ascending branch of the light curve was
clearly identified and has also created a double maximum in the light curve.
The frequency spectrum of the light curve, from a Fourier analysis with
Period04, has revealed triplet, quintuplet structures, and a second Blazhko
weak modulation (period = 34.72 +/-0.01 d). V1820 Orionis can be ranked as a
strongly modulated star based on its observed amplitude and phase variations.
The amplitude ratio of the largest triplet component to main pulsation
component is quite large: 0.34.Comment: 13 pages, accepted for publication in JAAVS
Photometric long-term variations and superhump occurrence in the Classical Nova RR Pictoris
We present an analysis of all available time-resolved photometry from the
literature and new light curves obtained in 2013-2014 for the old nova RR
Pictoris. The well-known hump light curve phased with the orbital period
reveals significant variations over the last 42 years in shape, amplitude and
other details which apparently are caused by long-term variations in the disc
structure. In addition we found evidence for the presence of superhumps in
2007, with the same period (~9% longer than the orbital period), as reported
earlier by other authors from observations in 2005. Possibly, superhumps arise
quickly in RR Pic, but are sporadic events, because in all the other observing
runs analysed no significant superhump signal was detected. We also determined
an actual version of the Stolz--Schoembs relation between superhump period and
orbital period, analysing separately dwarf novae, classical novae and nova-like
stars, and conclude that this relation is of general validity for all
superhumpers among the cataclysmic variables (CVs), in spite of small but
significant differences among the sub-types mentioned above. We emphasize the
importance of such a study in context with the still open question of the
interrelation between the different sub-classes of CVs, crucial for our
understanding of the long-term CV evolution.Comment: 9 pages, 6 figures and 2 tables. Acepted by MNRAS, October 201
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