Results of a long-term monitoring of the multiple system SZ Cam

Abstract

We present the results of the reduction of our photometric and spectroscopic observations for the eclipsing binary SZ Cam performed with the telescopes at the Astronomical Observatory of the Ural Federal University and the Special Astrophysical Observatory of the Russian Academy of Sciences in 1996-2014. Based on an 11-year-long photometric monitoring of SZ Cam, we have obtained new elements of its photometric orbit and parameters of its components. We have detected low-amplitude periodic light variations in SZ Cam that are possibly related to the ellipsoidal shape of the components of the spectroscopic binary third body. Based on published data and our new spectroscopy, we have found new values for the mass ratio, q = 0.72 ± 0.01, and parameters of the radial velocity curves of the components, V 0 = −3.6 ± 1.7 km s −1 , K 1 = 190.2 ± 1.9 km s −1 , and K 2 = 263.0 ± 2.4 km s −1 . The component masses have been estimated to be M 1 = 16.1 M and M 2 = 11.6 M . We have obtained new light elements and parameters of the radial velocity curves for the third body, V 3b 0 = 4.2 ± 0.6 km s −1 and K 3b 1 = 26.6 ± 0.8 km s −1 . We have improved the period of the relative orbit of SZ Cam and the third body, P orb = 55.6 ± 1.5 yr.

Pulsations in close binaries from the BRITE point of view

“…We did not detect this periodicity despite the detection threshold in our data being three times smaller than the amplitude derived by Tamajo et al (2012). In his recent study of SZ Cam, Gorda (2015) did not detect this periodicity either. Since the frequency of this term, f = P −1 = 3.006 d −1 is almost exactly equal to 3 (sidereal days) −1 , we conclude that this term is almost certainly of instrumental origin.…”

Interstellar polarization and extinction towards the young open cluster NGC 1502

“…The light contribution of the third body in the ADS 2984B system has been estimated as 30% by speckle interferometry (Mason et al 1998, Balega et al 2007). The most recent estimate of the mass ratio of the SZ Cam proper components, 0.72 ± 0.01, is in agreement with the majority of the previous estimates (Gorda 2015). Budding (1975) first classified the primary as O9.5nk (V) and obtained a distance of 600 ± 150 pc.…”

“…In the case of W1, the uvbyβ-based M V = −4.55 mag seems the most reliable estimate and we accept this value to obtain the distance, as listed in Table 8. W1 was recently studied by Gorda (2015) who obtained 0.4 for the mass ratio of the components. This mass ratio justifies a correction of about 0.3 mag to the visual magnitude (assuming equal surface temperatures and a mass-radius relation in the form R ∼ M 0.555 , Demircan & Kahraman 1991).…”

“…The TGAS Gaia-based distance is uncertain (1263 +1477 −443 pc). ADS 2984B (W2, SZ Cam, HD 25638) is a quadruple system consisting of two close binaries in a relative orbit with a period of approximately 50 yr (Gorda 2015). The MK classification existing in the literature, has not been entirely consistent, especially regarding the luminosity class, varying from III to V: O9V, O9.5Vn, B0V (Murphy 1969, Lutz & Lutz 1977, B1III (Harris 1976).…”

How unique is Plaskett’s star? A search for organized magnetic fields in short period, interacting or post-interaction massive binary systems

“…• HD25638=SZ Cam (O9.5V-9IV+B0-0.5V) comprises an eclipsing, circular SB2 system with a period of 2.7 d (Gorda 2015, and references therein). The derived radius of the primary is too large for a main sequence star while the mass of the secondary is too small for its spectral type (Lorenz et al 1998).…”