arXiv subjects

Theodor Pribulla

Publications and source records attributed to Theodor Pribulla.

24 records · Page 2Linked to original sources

arXiv2008

Radial velocity mapping of Paczyński's star AW UMa: Not a contact binary

We present two-dimensional (radial velocity, orbital phase) spectroscopic results for the very low mass-ratio close binary AW UMa which strongly indicate that the spectroscopic mass ratio (q_sp = 0.10) does not agree with the photometrically derived one and that the widely adopted contact binary model appears to experience serious inconsistencies and limitations for this object. AW UMa is compared with V566 Oph (q_sp = 0.26) which we found to behave according to the contact model. Observed broadening functions of AW UMa can be interpreted by a very strong limb darkening and/or non-solid body rotation of the dominant primary component; the former assumption is unphysical while the differential rotation is not supported by an apparent stability of localized, dark features on the outer side of the primary. There are indications of the existence of an equatorial belt encompassing the whole system. All deficiencies in the interpretation and the discrepancy between the photometric and spectroscopic mass ratio of AW UMa can be solved within a new model of AW UMa where both components are detached and the system is submerged in a stream of hot, optically thick matter which mimics the stellar contact. While the masses and their ratio are correctly given by spectroscopy, the photometric picture is heavily modified by the matter engulfing both stars in the equatorial plane.

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arXiv2007

Discovery of the strongly eccentric, short-period binary nature of the B-type system HD 313926 by the MOST satellite

The MOST photometric space mission discovered an eclipsing binary among its guide stars in June 2006 which combines a relatively large eccentricity e = 0.20 with an orbital period of only 2.27 days. HD 313926 appears to consist of two early-type stars of spectral type B3 - B7. It has a largest eccentricity among known early-type binaries with periods less than 3.5 d. Despite the large components indicated by its spectral type and light curve model, and its short period, the orbit of HD 313926 has not yet circularised so it is probably very young, even compared to other young B stars.

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arXiv2007

Contact binaries with additional components. III. The adaptive optics detections

We present results of the CFHT adaptive optics search for companions of a homogeneous group of contact binary stars, as a contribution to our attempts to prove a hypothesis that these binaries require a third star to become so close as observed. In addition to companions directly discovered at separations of >=1", we introduced a new method of AO image analysis utilizing distortions of the AO diffraction ring pattern at separations of 0.07"-1". Very close companions, with separations in the latter range were discovered in systems HV Aqr, OO Aql, CK Boo, XY Leo, BE Scl, and RZ Tau. More distant companions were detected in V402 Aur, AO Cam, V2082 Cyg. Our results provide a contribution to the mounting evidence that the presence of close companions is a very common phenomenon for very close binaries with orbital periods <1 day.

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arXiv2007

Radial Velocity Studies of Close Binary Stars. XII

Radial-velocity measurements and sine-curve fits to the orbital radial velocity variations are presented for ten close binary systems: OO Aql, CC Com, V345 Gem, XY Leo, AM Leo, V1010 Oph, V2612 Oph, XX Sex, W UMa, and XY UMa. Most of these binaries have been observed spectroscopically before, but our data are of higher quality and consistency than in the previous studies. While most of the studied eclipsing pairs are contact binaries, V1010 Oph is probably a detached or semi-detached double-lined binary and XY UMa is a detached, chromospherically active system whose broadening functions clearly show well defined and localized dark spots on the primary component. A particularly interesting case is XY Leo, which is a member of visually unresolved quadruple system composed of a contact binary and a detached, non-eclipsing, active binary with 0.805 days orbital period. V345 Gem and AM Leo are known members of visual binaries. We found faint visual companions at about 2-3 arcsec from XX Sex and XY UMa.

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arXiv2006

Radial Velocity Studies of Close Binary Stars. XI

Radial-velocity measurements and sine-curve fits to the orbital radial velocity variations are presented for ten close binary systems: DU Boo, ET Boo, TX Cnc, V1073 Cyg, HL Dra, AK Her, VW LMi, V566 Oph, TV UMi and AG Vir. By this contribution, the DDO program has reached the point of 100 published radial velocity orbits. The radial velocities have been determined using an improved fitting technique which uses rotational profiles to approximate individual peaks in broadening functions. Three systems, ET Boo, VW LMi and TV UMi, were found to be quadruple while AG Vir appears to be a spectroscopic triple. ET Boo, a member of a close visual binary with $P_{vis} = 113$ years, was previously known to be a multiple system, but we show that the second component is actually a close, non-eclipsing binary. The new observations enabled us to determine the spectroscopic orbits of the companion, non-eclipsing pairs in ET Boo and VW LMi. The particularly interesting case is VW LMi, where the period of the mutual revolution of the two spectroscopic binaries is only 355 days. While most of the studied eclipsing pairs are contact binaries, ET Boo is composed of two double-lined detached binaries and HL Dra is single-lined detached or semi-detached system. Five systems of this group were observed spectroscopically before: TX Cnc, V1073 Cyg, AK Her (as a single-lined binary), V566 Oph, AG Vir, but our new data are of much higher quality than the previous studies.

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arXiv2006

Contact Binaries with Additional Components.I. The Extant Data

We have attempted to establish an observational evidence for presence of distant companions which may have acquired and/or absorbed the angular momentum during evolution of multiple systems thus facilitating or enabling formation of contact binaries. In this preliminary investigation we use several techniques (some of them distance-independent) and mostly disregard detection biases of individual techniques in an attempt to establish a lower limit to the frequency of triple systems. While the whole sample of 151 contact binary stars brighter than Vmax = 10 mag. gives a firm lower limit of 42+/-5%, the corresponding number for the much better observed Northern-sky sub-sample is 59+/-8%. These estimates indicate that most contact binary stars exist in multiple systems.

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