Time-resolved multicolour photometry of bright B-type variable stars in Scorpius

Abstract

Context. The first two of a total of six nano-satellites that will constitute the BRITE-Constellation space photometry mission have recently been launched successfully. Aims. In preparation for this project, we carried out time-resolved colour photometry in a field that is an excellent candidate for BRITE measurements from space. Methods. We acquired 117 h of Strömgren uvy data during 19 nights. Our targets comprised the β Cephei stars κ and λ Sco, the eclipsing binary μ 1 Sco, and the variable super/hypergiant ζ 1 Sco. Results. For κ Sco, a photometric mode identification in combination with results from the spectroscopic literature suggests a dominant (l, m) = (1, −1) β Cephei-type pulsation mode of the primary star. The longer period of the star may be a rotational variation or a g-mode pulsation. For λ Sco, we recover the known dominant β Cephei pulsation, a longer-period variation, and observed part of an eclipse. Lack of ultraviolet data precludes mode identification for this star. We noticed that the spectroscopic orbital ephemeris of the closer pair in this triple system is inconsistent with eclipse timings and propose a refined value for the orbital period of the closer pair of 5.95189 ± 0.00003 d. We also argue that the components of the λ Sco system are some 30% more massive than previously thought. The binary light curve solution of μ 1 Sco requires inclusion of the irradiation effect to explain the u light curve, and the system could show additional low amplitude variations on top of the orbital light changes. ζ 1 Sco shows long-term variability on a time scale of at least two weeks that we prefer to interpret in terms of a variable wind or strange mode pulsations.

Phase-locked polarization by photospheric reflection in the semidetached eclipsing binary μ1 Sco

“…Though gas flows in Algol-type binaries are expected to be faint, van Antwerpen & Moon (2010) suggest that it may be possible to detect the gas streams between the stars in µ 1 Sco spectroscopically using Doppler tomography. The most recent new data on µ 1 Sco was collected by Handler & Schwarzenberg-Czerny (2013), who made multi-band photometric observations, including the first such in u band. This ultraviolet data required inclusion of the reflection effect to fit the observations within the observational errors.…”

“…This ultraviolet data required inclusion of the reflection effect to fit the observations within the observational errors. Handler & Schwarzenberg-Czerny (2013) were interested in the system because the primary lies in the β Cep instability strip and the secondary in the domain of slowly pulsating B-type (SPB) stars. Which is pertinent to any polarimetric study in view of Odell (1979)'s prediction of polarization from non-radial pulsations.…”

“…Which is pertinent to any polarimetric study in view of Odell (1979)'s prediction of polarization from non-radial pulsations. After removing the binary light curve solution from their data Handler & Schwarzenberg-Czerny (2013) are left with two non-white frequencies at 0.123 and 8.07 c/d with an amplitude of around 3 mmag, but a S/N ratio less than is required for detection.…”

“…The most recent new data on µ 1 Sco was collected by Handler & Schwarzenberg-Czerny (2013), who made multi-band photometric observations, including the first such in u band. This ultraviolet data required inclusion of the reflection effect to fit the observations within the observational errors.…”