Microvariability of line profiles in the spectra of OB stars: III. The supergiant ρ LEO

We observed the bright supergiant ρ Leo (B1 lab) in January–February 2004 using the 6-m telescope of the Special Astrophysical Observatory (Russia) and the 1.8-m telescope of the Bohyunsan Optical Astronomy Observatory (South Korea). 47 spectra with high time resolution (4–10 min), signal-to-noise ratios 300–1000, and spectral resolutions 45 000–60 000 were obtained. We detected variability in the HeI, SiII, SiIII, and NII line profiles, which may be due to rotational modulation of the profiles and photospheric pulsations of ρ Leo. The possible influence of the stellar magnetic field on the line-profile variations is discussed.     

Detection of circular polarization and low-amplitude photometric variability of the white dwarf WD1748+508

We report the results of a polarimetric and photometric study of the cool white dwarf WD1748+508. Observations were performed during four consecutive nights on the telescopes of the Crimean Astrophysical Observatory. As a result, polarization was detected in the V band at the level of ?0.36 ± 0.087% and the star was found to be photometrically variable with a period ranging from five hours to about two days. Throughout the entire observing set the variability amplitude was constant and equal to about 10 ± 1 mmag. Non-zero circular polarization directly indicates that the white dwarf has a global magnetic field with a strength of 10 MG or higher.We interpret the photometric variations found in this study in terms of rotationally modulated variability of magnetic properties of the star’s atmosphere.     

Exoplanet Studies. Photometric Analysis of the Transmission Spectra of Selected Exoplanets

We present the results of ground based observations and model analysis of transits of exoplanets WASP-33b, WASP-43b, WASP-104b, and HD 219134b. Broadband transmission spectra (dependence of the observed radii on wavelength) have been plotted for all exoplanets, ranging from the near-UV to the IR region. We show that the transmission spectrum of WASP-33b is, within errors, flat in the range of 3800 Å to 12 000 Å. The derived broadband spectrum of WASP-43b is also flat in the first approximation, although other authors have reported the presence of absorption lines of various chemical elements in the narrow bands. Model spectra of WASP-43b taken from the literature and based on IR data allowed us to obtain a direct estimate of its nighttime temperature. We present and analyze the results of ground based observations which confirm the discovery of a transiting super-Earth in the HD 219134 star system. Signs of this planet’s existence were discovered earlier during the radial velocity analysis of the star, as well as transit observations with the Spitzer space telescope in the IR.At the estimated time, we registered a transit in the near-UV range several times. The transit depth measured in the U-band of the Johnson photometric system amounts to 0.13% ± 0.027%, which is deeper than the one based on Spitzer measurements. We discuss the possible causes of this difference.     

Spectroscopic observations of the exoplanet WASP-32b transit

We present first results of spectroscopic observations of transiting exoplanets in the Special Astrophysical Observatory of the Russian Academy of Sciences with the Main Stellar Spectrograph of the 6-m BTA telescope. For the exoplanetWASP-32b, we detected a significant variation of intensity and equivalent width in the Hα spectral line of the parent star at the time of a transit. The equivalent width of the line during transit is by 8–10% larger than outside the planet passage. Residual intensity in the core of the line reveals the following tendency: the line is by 10–15% deeper inside transit than outside it. Observations with the long-slit spectrograph of the Crimean Astrophysical Observatory at the 2.6-m ZTSh telescope also showed a transit event in the Hα line, although, with a smaller amplitude and shape inverted in relation to the data from the 6-m telescope. While in the observations with the BTA the Hα line becomes deeper during the transit, in the ZTSh observations, the residual intensity of the Hα line decreases during the transit. Reducing and analysis of the archive data of WASP-32b observations with the HARPS spectrograph also confirm the Hα line modulation at the time of the transit. The observed data give evidence of the envelope in WASP-32b filling the Roche lobe and a comet-like tail of changing geometry and orientation relative to the observer. These changes determine different depths and shapes of the Hα spectral line at the time of transits.     

Circumstellar Properties of the Herbig Be Star HD 259431. I. Signatures of Magnetospheric Accretion

Astrophysics - Results are presented from a spectroscopic study of the Ae/Be Herbig star HD 259431 conducted from 2010 to 2019 using high-resolution spectrographs at: (a) the Crimean Astrophysical...     

Line profile variability of OB stars: Pulsation,rotation, clumps and magnetic fields

The variability of line profiles in spectra of bright OB stars has been studied.We obtain more than 1000 high quality spectra of δ Ori A, λ Ori A, α Cam, 19 Cep, ι Her, ρ Leo and other target stars. We revealed the line profile microvariability of small amplitude (0.5–3% in the adjacent continuum units) for all observed stars. For most stars only cyclic components of the line profile variability (LPV) at the time scales from hours to days were detected. These components seem to be connected with both the non-radial pulsations (NRP) and rotation line profile modulation. In the spectra of δ Ori A and λ Ori A we found the evidences of the stochastic LPV in spectra, probably connected with the small clumps in the stellar wind. On the basis of recent observations we discuss the origin of the magnetic field of early-type stars. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Moderate-resolution holographic spectrograph

We present a new scheme of a moderate-resolution spectrograph based on a cascade of serial holographic gratings each of which produces an individual spectrum with a resolution of about 6000 and a bandwidth of 80 nm. The gratings ensure centering of each part of the spectrum they produce so as to provide uniform coverage of the broadest possible wavelength interval. In this study we manage to simultaneously cover the 430–680 nm interval without gaps using three gratings. Efficiency of the spectrograph optical system itself from the entrance slit to the CCD detector is typically of about 60% with a maximum of 75%. We discuss the advantages and drawbacks of the new spectrograph scheme as well as the astrophysical tasks for which the instrument can be used.     

Magnetic fields and rotation of the white dwarfs 40 Eri B and WD 0009+501

We describe the results of our magnetometric monitoring of two white dwarfs: 40 Eri B and WD 0009+501. We found periodic variations in the longitudinal magnetic field of 40 Eri B. The field variability with an amplitude of ～4 kG and a zero mean is discussed in terms of an oblique rotator model. The rotation period is ～5 h 17 min, but there is another period of 2 h 25 min that may be related to nondipolar field components. The published projected rotational velocities of 40 Eri B measured from a narrow non-LTE Hα peak V sin i?8 km s^?1 are in good agreement with our measurements of the magnetic field and the rotation period. The combined effect of magnetic and rotational broadening of the central Hα component constrains the rotation period, P? 5.2 h. We discovered the rotation period (1.83 h) of the magnetic white dwarf WD 0009+501. The period was found from the periodically varying magnetic field of the star with a mean 〈B_e〉 = ?42.3±5.4 kG and a half-amplitude of 32.0±6.8 kG.