Flickering amplitude of the cataclysmic variable star MV Lyrae in different states (original) (raw)
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The Astronomical Journal, 2007
Spectrophotometric observations of Hα and He I 6678 emission lines of the nova-like Cataclysmic Variable V3885 Sgr are presented and analyzed. The binary orbital period was determined as P = 0.20716071(22) days. Doppler Tomography was performed with both Hα and He I lines. Disc radial emissivity profiles were also computed. The tomography mapping of flickering sources was performed using the Hα line, from which we concluded that the flickering is not uniformly distributed on the disc. The observed tomogram of the flickering was compared with simulations, suggesting that the most intense flickering source in the Hα is not located in the accretion disc. It is proposed that the main line flickering source may be associated with the illuminated secondary star.
Monthly Notices of The Royal Astronomical Society, 2005
High-speed photometry is presented for 12 faint cataclysmic variable (CV) stars that have not previously been investigated. V433 Ari, a dwarf nova, has deep eclipses, an orbital period Porb= 4.698 h and evidence that it is a Z Cam star. OQ Car, another dwarf nova, shows flickering but no orbital modulation. The candidate for V591 Cen, a suspected dwarf nova, is found not to flicker in quiescence, nor does any other star in the vicinity. V1039 Cen (Nova Cen 2001) has characteristics of an intermediate polar, with a rotation period of 719 s and Porb= 5.92 h; there is also a strong brightness modulation at 8.98 h or its 1-d alias of 14.34 h. CAL 86, a dwarf nova, has a double-humped modulation at 1.587 h which is probably the orbital period, but has another modulation 4.5 per cent shorter in period that appears to be a rare example of a negative superhump observed in quiescence, and yet another periodicity at 4.74 h that is probably an example of the still unexplained GW Lib phenomenon. UY Mic, a suspected CV, has no flickering but has a periodic modulation at 4.856 h, which may be from a reflection effect. LB 9963, another suspected CV, is found to have strong flickering but no observable periodicity. V367 Peg, a dwarf nova, has a double-humped light curve with an eclipse at one of the minima and Porb= 3.89 h, strongly resembling BD Pav with an evolved secondary. Sgr, a possible nova type, discovered by the massive compact halo object survey, has a 2.808-h brightness modulation with occasional apparent secondary eclipses of unknown cause. RX J0403+044, a suspected CV, has low- and high-luminosity states, with a conspicuous 1012.7-s oscillation in the high state and an oscillation with a period near to twice that in the low state. V382 Vel (Nova Vel 1999) has a clear modulation with amplitude 0.12 mag and period 3.795 h, and also a quasi-periodic oscillation (QPO) at 2570 s and a longer period dwarf nova oscillation at 725 s. SY Vol, a dwarf nova, has no indication of any orbital modulation.
A Photometric and Spectroscopic Study of the Cataclysmic Variable ST LMi during 2005-2006
The Astronomical Journal, 2007
We present orbit-resolved spectroscopic and photometric observations of the polar ST LMi during its recent low and high states. In the low state spectra, we report the presence of blue and red satellites to the Hα emission line; the velocities and visibility of the satellites vary with phase. This behavior is similar to emission line profile variations recently reported in the low state of AM Her, which were interpreted as being due to magnetically-confined gas motions in large loops near the secondary. Our low-state spectroscopy of ST LMi is discussed in terms of extreme chromospheric activity on the secondary star. Concurrent photometry indicates that occasional low-level accretion may be present, as well as cool regions on the secondary near L 1 Furthermore, we report a new "extreme low-state" of the system at V∼18.5 mag.
New pulsational properties of eight 'anomalous' RR Lyrae variables
Monthly Notices of the Royal Astronomical Society, 1995
CCD photometry in the V band is presented for 7 eld RR Lyrae stars selected from a sample of eight v ariables which, according to data collected in the literature, are expected to be ab-type pulsators, to have short periods and hence high metallicity, and to be located at high z from the galactic plane. New periods and epochs are derived for them. The new periods are only slightly shorter than the values published on the last edition of the General Catalog of Variable Stars (GCVS4). Instead, in six cases our amplitude of the light v ariation is signicantly smaller than that published on the GCVS4, and in at least three cases the actual pulsation appears to be in the rst harmonic rather than in the fundamental mode. All the suggested c-type pulsators show v ariations in the amplitude and/or quite scattered light curves. Possible explanations are given. From a spectro-photometric analysis of the sample, only DL Com is conrmed to pulsate in the fundamental mode, to have short period, and to be located at relatively high z. A single object cannot be taken as evidence for a signicant metal rich population at large distance from the galactic plane.
CCD photometry of the cataclysmic variable star V425 Cas in 2006-2007
2009
We studied the photometric behavior of the cataclysmic variable V425 Cas using CCD observations with the telescopes at Rozhen NAO and Belogradchik AO. The changes of the star magnitude were determined during the period of observations from June 2006 to September 2007 in the bands B and V. Two respective light curves are presented. There were two nights with simultaneous observations in the bands B and I and the corresponding light curves are plotted too. We found correlation between the colours (B-I) and B and the corresponding fluxes.
The 2008 outburst of the cataclysmic variable V358 Lyrae
2009
We report photometry of V358 Lyr during its 2008 November outburst, the first confirmed outburst since 1965. At its brightest the star was V=15.9 and the outburst amplitude was at least 7.3 magnitudes. The outburst lasted at least 23 days. The first 4 days of the outburst corresponded to the plateau phase and the star then faded at 0.13 mag/d over the next 7 days. There was then a drop in brightness to a temporary minimum at mag 19.5, which lasted less than 4 days, after which the star recovered to its previous brightness. The final stages of the outburst were poorly covered. Time resolved photometry during the outburst revealed no obvious large-scale modulations such as superhumps. Although some small apparently periodic signals were detected, their significance is uncertain. Our observations, and those of previous researchers, support V358 Lyr being a dwarf nova and are consistent with its being a member of the WZ Sge family.
Acta Astronomica, 2004
We report extensive photometry of frequently outbursting dwarf nova IX Draconis. During five months of observations the star went into three superoutbursts and seven ordinary outbursts. This allowed us to determine its supercycle and cycle lengths as equal to 54 +/- 1 and 3.1 +/- 0.1 days, respectively. During the Sep 2003 superoutburst, which had the best observational coverage, IX Dra displayed clear superhumps with a period of Psh=0.066968(17) days. This period was constant during the whole superoutburst. Another period, which was clearly present in the light curve of IX Dra in superoutburst, had a value of 0.06646(6) days and we interpret it as the orbital period of the binary. Thus IX Dra is the first SU UMa star showing orbital modulation during the entire superoutburst. The beat between these two periods is the main cause of an unusual phase reversal of superhumps - a phenomenon which was previously observed in ER UMa. If our interpretation of the second periodicity is correct, IX Dra has an extremely low period excess epsilon\epsilonepsilon equal to only 0.76% +/- 0.03%. This implies very low mass ratio q=0.035 +/- 0.003, which strongly suggests that the system contains a brown dwarf-like degenerate secondary of mass ~0.03 Mo and that IX Dra is the most evolved dwarf nova known. Such a very low mass ratio results in the outer edge of the accretion disk reaching 80% of the distance between the components of the system. In turn, this allows the disk particles to enter a 2:1 resonance and leads to the appearance of the orbital period in the light curve of the entire superoutburst.The high level of activity and brightness of IX Dra indicate that very old cataclysmic variables go through episodes of increased activity leading to loss of angular momentum through mass loss from the system.
Astronomical Journal, 1999
We present the results of a photometric study of RR Lyrae variables in the Ðeld of the globular cluster M55. We have discovered nine new RR Lyrae stars, increasing the number of known RR Lyrae variables in this cluster to 15 stars. Five of the newly discovered variables are Bailey type RRc, and two are type RRab. Two background RRab stars are probable members of the Sagittarius dwarf galaxy. Fourier decomposition of the light curves was used to derive basic properties of the present sample of RR Lyrae variables. From an analysis of the RRc variables we obtain a mean mass of M \ 0.53^0.03
GSC 4560–02157: a new long-period eclipsing cataclysmic variable star
Research in Astronomy and Astrophysics, 2015
We study the newly discovered variable star GSC 4560-02157. CCD photometry was performed in 2013-2014, and a spectrum was obtained with the 6-m telescope in June, 2014. GSC 4560-02157 is demonstrated to be a short-period (P = 0.265359 d) eclipsing variable star. All its flat-bottom primary minima are approximately at the same brightness level, while the star's out-of-eclipse brightness and brightness at secondary minimum varies considerably (by up to 0.6 m) from cycle to cycle. Besides, there are short-term (time scale of 0.03-0.04 days) small-amplitude brightness variations out of eclipse. This behavior suggests cataclysmic nature of the star, confirmed with a spectrum taken on June 5, 2014. The spectrum shows numerous emissions of the hydrogen Balmer series, HeI, HeII.
Cyclic variations inO−Cdiagrams of field RR Lyrae stars as a result of LiTE
Monthly Notices of the Royal Astronomical Society, 2016
This paper presents an extensive overview of known and proposed RR Lyrae stars in binaries. The aim is to revise and extend the list with new Galactic field systems. We utilized maxima timings for 11 RRab type stars with suspicious behaviour from the GEOS data base, and determined maxima timings from data of sky surveys and our own observations. This significantly extended the number of suitable maxima timings. We modelled the proposed Light Time Effect (LiTE) in O−C diagrams to determine orbital parameters for these systems. In contrast to recent studies, our analysis focused on decades-long periods instead of periods in the order of years. Secondary components were found to be predominantly low-mass objects. However, for RZ Cet and AT Ser the mass of the suspected companion of more than one solar mass suggests that it is a massive white dwarf, a neutron star or even a black hole. We found that the semimajor axes of the proposed orbits are between 1 and 20 au. Because the studied stars belong to the closest RR Lyraes, maximal angular distances between components during orbit should at least be between 1 and 13 mas and this improves the chance to detect both stars using current telescopes. However, our interpretation of the O−C diagrams as a consequence of the LiTE should be considered as preliminary without reliable spectroscopic measurements. On the other hand, our models give a prediction of the period and radial velocity evolution which should be sufficient for plausible proof of binarity.