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Improved model of the triple system V746 Cassiopeiae that has a bipolar magnetic field associated with the tertiary
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| Zeitschriftentitel: | Astronomy & Astrophysics |
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| Personen und Körperschaften: | , , , , , , , , , , , |
| In: | Astronomy & Astrophysics, 609, 2018, S. A5 |
| Format: | E-Article |
| Sprache: | Unbestimmt |
| veröffentlicht: |
EDP Sciences
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| Schlagwörter: |
| Zusammenfassung: | <jats:p>V746 Cas is known to be a triple system composed of a close binary with an alternatively reported period of either 25\hbox{$.\!\!^{\rm d}$}4 or 27\hbox{$.\!\!^{\rm d}$}8 and a distant third component in a 170 yr (62 000 d) orbit. The object was also reported to exhibit multiperiodic light variations with periods from 0\hbox{$.\!\!^{\rm d}$}83 to 2\hbox{$.\!\!^{\rm d}$}50, on the basis of which it was classified as a slowly pulsating B star. Interest in further investigation of this system was raised by the recent detection of a variable magnetic field. Analysing spectra from four instruments, earlier published radial velocities, and several sets of photometric observations, we arrived at the following conclusions: (1) The optical spectrum is dominated by the lines of the B-type primary (<jats:italic>T</jats:italic><jats:sub>eff 1</jats:sub> ~ 16 500(100) K), contributing 70% of the light in the optical region, and a slightly cooler B tertiary (<jats:italic>T</jats:italic><jats:sub>eff 3</jats:sub> ~ 13 620(150) K). The lines of the low-mass secondary are below our detection threshold; we estimate that it could be a normal A or F star. (2) We resolved the ambiguity in the value of the inner binary period and arrived at a linear ephemeris of \hbox{$T_{\rm super.\,conj.}={\rm HJD}~2\,443\,838.78(81)+25\fd41569(42)\times E$}. (3) The intensity of the magnetic field undergoes a sinusoidal variation in phase with one of the known photometric periods, namely 2\hbox{$.\!\!^{\rm d}$}503867(19), which we identify with the rotational period of the tertiary. (4) The second dominant photometric 1\hbox{$.\!\!^{\rm d}$}0649524(40) period is tentatively identified with the rotational period of the broad-lined B-type primary, but this interpretation is much less certain and needs further verification. (5) If our interpretation of photometric periods is confirmed, the classification of the object as a slowly pulsating B star should be revised. (6) Applying an <jats:italic>N</jats:italic>-body model to different types of available observational data, we can constrain the orbital inclination of the inner orbit to ~60°<<jats:italic>i</jats:italic><jats:sub>1</jats:sub>< 85° even in the absence of binary eclipses, and we estimate the probable properties of the triple system and its components.</jats:p> |
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| Umfang: | A5 |
| ISSN: |
0004-6361
1432-0746 |
| DOI: | 10.1051/0004-6361/201628363 |