B[e] Star CI Camelopardalis in the Optical Range

Barsukova E.A. Burenkov A.N. Goranskij V.P. Zharikov S.V. Iliev L. Manset N. Metlova N.V. Miroshnichenko A.S. Moiseeva A.V. Nedialkov P.L. Semenko E.A. Stoyanov K. Yakunin I.A.
March 2023 Pleiades Publishing

Astrophysical Bulletin
2023 #78 Issue 1 1 - 24 pp.

Abstract: We report the results of photometric and spectroscopic monitoring of CI Cam within 24 years since its outburst in 1998. Over this time, we found a system component emitting in the He II 4686 Å emission line, on an elliptical orbit with a period of (Formula presented.) days and an eccentricity of 0.44–0.49. The variations of the optical brightness are observed with the same period and with an average amplitude of (Formula presented.). The total amplitude of the He II radial velocity variations is about 380 km s (Formula presented.). The equivalent width of the line is variable on a time scale of tens of minutes as well as with the orbital period. Maximum equivalent widths of the He II line are observed when the component passes the descending node of the orbit. The intensity of the He II 4686 Å emission gradually increases with time. Slow radial velocity variations on a scale of decades were detected by means of high resolution spectroscopy in the iron emission lines and a forbidden nitrogen line formed in the circumstellar nebula. The B-type star turned out to be a pulsating variable. During the period between 2005 and 2009, pulsations were multiperiodic with the dominant periods (Formula presented.), (Formula presented.), and (Formula presented.) days. However, since 2012 it has pulsated in a single mode with a variable period in the (Formula presented.) day range depending on the star’s luminosity. We identify the 2005–2009 pulsations as a resonance of the radial modes, and the residual stable mode as the first overtone. The pulsations are coherent on a scale of several months, and their average amplitudes are (Formula presented.). The pulsation data constrain the spectral type of the main component to B0–B2 III, the distance to the system to 2.5–4.5 kpc, and the absolute visual magnitude M_V to the range of (Formula presented.). The classification of the CI Cam main component as a B[e] supergiant is completely ruled out due to the observed pulsation periods. CI Cam may be a system at the stage after the first mass exchange and may be attributed to the FS CMa-type group of objects with the B[e] phenomenon.

binaries: general , methods: observational , stars: emission-line, B[e] , stars: evolution , stars: individual: CI Cam , stars: oscillations , techniques: photometric , techniques: spectroscopic

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Special Astrophysical Observatory, Russian Academy of Sciences, Nizhnii Arkhyz, 369167, Russian Federation
Sternberg Astronomical Institute, Moscow State University, Moscow, 119234, Russian Federation
Institute of Astronomy, National Autonomous University of Mexico, Baja California, Ensenada, 22800, Mexico
Al-Farabi Kazakh National University, Almaty, 050040, Kazakhstan
Institute of Astronomy and National Astronomical Observatory Rozhen, Bulgarian Academy of Sciences, Sofia, 1784, Bulgaria
Canadian-French-Hawaiian Telescope Corporation (CFHT), Kamuela, 96743, HI, United States
University of North Carolina at Greensboro, Greensboro, 27402, United States
Central (Pulkovo) Astronomical Observatory, Russian Academy of Sciences, St. Petersburg, 196140, Russian Federation
Fesenkov Astronomical Institute, Almaty, 050020, Kazakhstan
Department of Astronomy, Sofia University, Sofia, 1504, Bulgaria
National Astronomical Research Institute of Thailand, Chiang Mai, Mae Rim, 50180, Thailand
St. Petersburg University, St. Petersburg, 199034, Russian Federation

Special Astrophysical Observatory
Sternberg Astronomical Institute
Institute of Astronomy
Al-Farabi Kazakh National University
Institute of Astronomy and National Astronomical Observatory Rozhen
Canadian-French-Hawaiian Telescope Corporation (CFHT)
University of North Carolina at Greensboro
Central (Pulkovo) Astronomical Observatory
Fesenkov Astronomical Institute
Department of Astronomy
National Astronomical Research Institute of Thailand
St. Petersburg University

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