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Mount Suhora High Cadence Photometric Survey of T Tauri-Type Stars

Siwak M., Dróżdż M., Gut K., Winiarski M., Ogłoza W., Stachowski G.

Acta Astronomica

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2019

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Vol. 69, No. 3

227--260

EN

Results of high-cadence multi-color observations of 121 pre-main sequence stars available from the northern hemisphere are presented. The aim of this survey was to detect transit-like signatures caused by occultation of these young stars and their accretion-induced hot spots by close-in planets and/or dusty clumps. Although none planetary transits were detected, our data allow the determination of rotational periods for some T Tau stars and characterization of the accretion processes operating in classical T Tau-type stars in time scales ranging from a few minutes to days, as well as characterization of the large-scale dips caused by dusty warped disks.

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Eclipsing Binaries in the Open Cluster NGC 2243 - I. Photometry

Kaluzny J., Krzeminski W., Thompson I. B., Stachowski G.

Acta Astronomica

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2006

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Vol. 56, No. 1

51--63

EN

We obtained BV time series photometry for 12 variable stars from the field of the old open cluster NGC 2243. The sample includes 3 newly identified detached/semi-detached binaries. There are now four detached eclipsing binaries which are likely members of the cluster. Determination of the absolute parameters of the components would provide a valuable check on evolutionary models of low-mass stars. An accurate ephemeris and orbital period analysis are presented for the previously-known detached binary NV CMa. We also provide ephemerides for seven other periodic variables. We show that three contact binaries are likely members of the cluster.

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Physical Parameters of Components in Close Binary Systems: III

Zola S., Rucinski S. M., Baran A., Ogloza W., Pych W., Kreiner J. M., Stachowski G., Gazeas K., Niarchos P., Siwak M.

Acta Astronomica

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2004

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Vol. 54, No. 3

299--312

EN

The paper presents combined spectroscopic and photometric orbital solutions for five close binary systems: V402 Aur, SX Crv, V829 Her, VZ Lib and V753 Mon. The photometric data consist of new complete, multicolor light curves, while the spectroscopy has been recently obtained within the radial velocity program at the David Dunlap Observatory. For one target, SX Crv, new spectroscopic data were obtained using the 6.5 m Magellan telescope. A contact configuration was found through light curve modeling for all targets except V753 Mon. Our solution for V753 Mon resulted in a semidetached configuration with the slightly less massive component filling its Roche lobe.

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Curious Variables Experiment (CURVE). IX Dra - a Clue for Understanding Evolution of Cataclysmic Variable Stars

Olech A., Złoczewski K., Mularczyk K., Kędzierski P., Wiśniewski M., Stachowski G.

Acta Astronomica

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2004

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Vol. 54, No. 1

57--85

EN

We report extensive photometry of frequently outbursting dwarf nova IX Dra. 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 September 2003 superoutburst, which had the best observational coverage, IX Dra displayed clear superhumps with a period of Psh=0.066968(17) days (96.43±0.02 min). 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 (95.70±0.09 min) 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 ε 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 Msolar 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. Modulations with the orbital period are also detectable during normal outbursts and in quiescence.