N. A. Gorynya

A Search for Evolutionary Changes in the Periods of Cepheids Using Archival Data from the Harvard Observatory Plate Collection. III. GY Sagittae

A total of 1095 magnitude estimates for the long‐period classical Cepheid GY Sge (P = 51 days), derived from the photographic plate collections of Harvard College Observatory, Sonneberg Observatory, and Sternberg Astronomical Institute, were combined with 48 new radial velocity measures obtained using the correlation spectrometer on the 1 m reflector of the Crimean Astrophysical Observatory. The data, in combination with published photometry (including observations from the All Sky Automated Survey 3) and radial velocity measurements, cover a time baseline spanning 116 years. The resulting O - C data display evolutionary changes in the period of GY Sge amounting to + 203 ± 27 s yr−1, a value in good agreement with theoretical predictions for a star in the third crossing of the instability strip. Large cyclical drifts with durations of ~23,000 days superposed on the parabolic evolutionary trend in the O - C data exhibit the positive signature of random fluctuations in pulsation period, of magnitude similar to what is found in other pulsating stars of similar period.

Astrometric Study of the Relative Motion of Three Stars with Possible Invisible Companions Based on Homogeneous Series Obtained at Pulkovo with a 26-Inch Refractor

We investigate the relative motion of three stars, ADS 7446, 9346, and 9701, based on long-term observations with the Pulkovo 26-inch refractor. The relative motion of all three stars shows a perturbation that could be produced by the gravitational influence of an invisible companion. For ADS 7446, we have determined the orbit of the photocenter with a period of 7.9 yr; the mass of the companion is more than 0.4M⊙. For ADS 9346, we have determined the radial velocities of the components: −14.60 km s−1 for A and −13.94 km s−1 for B. For ADS 9346 and 9701, we have determined the dynamical parallaxes, 24 and 20 mas, respectively, which are larger than those in the Hipparcos catalog by 5 mas, and calculated the orbits by the apparent motion parameter (AMP) method. The new orbit of ADS 9346 is: a = 5″.2, P = 2035 yr, and e = 0.46 at the system’s mass M = 2.5M⊙. The new orbits of ADS 9701 are: (a = 2″.9, P = 829 yr, e = 0.54, M = 4.3M⊙) and (a = 3″.8, P = 1157 yr, e = 0.53, M = 5.0M⊙).

The Baade–Becker–Wesselink technique and the fundamental astrophysical parameters of Cepheids

The BBW method remains one of most demanded tool to derive full set of Cepheid astrophysical parameters. Surface brightness version of the BBW technique was preferentially used during last decades to calculate Cepheid radii and to improve PLC relations. Its implementation requires a priory knowledge of Cepheid reddening value. We propose a new version of the Baade--Becker--Wesselink technique, which allows one to independently determine the colour excess and the intrinsic colour of a radially pulsating star, in addition to its radius, luminosity, and distance. It is considered to be a generalization of the Balona light curve modelling approach. The method also allows the function F(CI_0) = BC + 10 log Teff for the class of pulsating stars considered to be calibrated. We apply this technique to a number of classical Cepheids with very accurate light and radial-velocity curves. The new technique can also be applied to other pulsating variables, e.g. RR Lyraes. We discuss also possible dependence of the projection factor on the pulsation phase.

The Mass of the Cepheid V350 Sgr

V350 Sgr is a classical Cepheid suitable for mass determination. It has a hot companion which is prominent in the ultraviolet and which is not itself a binary. We have obtained two high resolution echelle spectra of the companion at orbital velocity maximum and minimum with the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) in the 1320 to 1510 \AA\/ region. By cross-correlating these spectra we obtained the orbital velocity amplitude of the companion with an uncertainty in the companion amplitude of 1.9 km sec

Combined General Catalogue of Variable Stars

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Catalogue of suspected variable stars.

. This provides a mass ratio of the Cepheid to the companion of 2.1. The ultraviolet energy distribution of the companion provides the mass of the companion, yielding a Cepheid mass of 5.2

A catalog of Cepheid radial velocities measured in 1995-1998 with the correlation spectrometer

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The Orbit of the Cepheid V350 Sgr Revisited

0.3 M

The radii of 62 classical Cepheids

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A search for evolutionary changes in the period of classical Cepheid GY Sge

. This mass requires some combination of moderate main sequence core convective overshoot and rotation to match evolutionary tracks.