BD Camelopardalis

BD Camelopardalis is an S star and symbiotic star in the constellation Camelopardalis. It was recognized as a spectroscopic binary star in 1922, and its orbital solution published in 1984;[6] it has a 596-day orbital period. A spectroscopic composition analysis was done of the red giant primary star in 1986.[7]

BD Camelopardalis
Observation data
Epoch J2000      Equinox J2000
Constellation Camelopardalis
Right ascension  03h 42m 09.32470s[1]
Declination +63° 13′ 00.4977″[1]
Apparent magnitude (V) 5.11[2]
Characteristics
Spectral type S3.5/2 (M4III)[2]
U−B color index 1.82[3]
B−V color index 1.63[3]
R−I color index 1.39
Variable type Lb[4]
Astrometry
Radial velocity (Rv)-22.28[2] km/s
Proper motion (μ) RA: -17.27[1] mas/yr
Dec.: 18.94[1] mas/yr
Parallax (π)6.28 ± 0.34[1] mas
Distance520 ± 30 ly
(159 ± 9 pc)
Absolute magnitude (MV)-0.90
Orbit[5]
PrimaryBD Cam A
CompanionBD Cam B
Period (P)596.2 days
Eccentricity (e)0.088
Inclination (i)105.6°
Longitude of the node (Ω)162.1°
Periastron epoch (T)2442794.5
Argument of periastron (ω)
(secondary)		334.3°
Details
Red giant primary
Radius135 R☉
Luminosity185(v)/1600(bol) L☉
Surface gravity (log g)0.9 cgs
Temperature3250 K
Metallicity0.0
Other designations
BD Cam, SAO 12874, BD+62° 597, HD 22649, HIP 17296, FK5 129, HR 1105[2]
Database references
SIMBADdata

Description

Although the star's spectrum shows the spectral features of zirconium oxide which define spectral class S, BD Cam shows no technetium lines in its spectrum. It is believed to be an "extrinsic" S star, one whose s-process element excesses originate in a binary companion star. The system displays only minimal variations in the visible, but the presence of the companion and its interactions with the stellar wind of the visible red giant makes for easily observed time-variable spectral features in the ultraviolet and in the near infrared spectral line of helium.

At times BD Cam is the brightest S star in the visible sky, because other bright S stars are mira variables or other types of variable star with large changes in apparent brightness. Its own brightness variability in the visible part of the spectrum is modest.

On the basis of the measurement of radial velocities of the line components it is concluded that the helium emission originates in the vicinity of the inner Lagrangian point of the system, indicating a gas motion from the red giant primary, directed to the secondary, with a velocity of about 5 km/s. At the same time, there is a high-velocity, hot wind outwards from the primary red giant with a velocity of about 50 km/s.

— Shcherbakov, A. G. and Tuominen, I.

However, HR 1105 appears to have a highly variable UV companion. In 1982, no UV flux was discerned for this system, but by 1986 C IV was strong, increasing by a factor of 3 in 1987 with prominent lines of Si III, C III, O III, Si IV, and N V.

— Ake, Thomas B., III; Johnson, Hollis R. and Perry, Benjamin F., Jr.
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References
  1. Van Leeuwen, Floor (2007). "Validation of the new Hipparcos reduction". Astronomy & Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. Vizier catalog entry
  2. "BD Cam". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 27 December 2016.
  3. van Leeuwen, F. (1970). "Photometry of high-luminosity M-type stars". Astrophysical Journal. 162: 217. Bibcode:1970ApJ...162..217L. doi:10.1086/150648.
  4. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/gcvs. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  5. Pourbaix, D. (2000). "Re-processing the Hipparcos Transit Data and Intermediate Astrometric Data of spectroscopic binaries. I. Ba, CH and Tc-poor S stars". Astronomy and Astrophysics Supplement. 145: 161–183. arXiv:astro-ph/0006175. Bibcode:2000A&AS..145..161P. doi:10.1051/aas:2000346.
  6. Griffin, R.F. (1984). "Spectroscopic binary orbits from photoelectric radial velocities. Paper 58: HR 1105". Observatory. 104: 224–231. Bibcode:1984Obs...104..224G.
  7. Smith, V.V.; Lambert, D.L. (1986). "The chemical composition of red giants. II - Helium burning and the s-process in the MS and S stars". Astrophysical Journal. 311: 843–863. Bibcode:1986ApJ...311..843S. doi:10.1086/164823.
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