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Star in the constellation Capricornus
Tau2 Capricorni
Observation data
Epoch
J2000.0
Equinox
J2000.0 (
ICRS )
Constellation
Capricornus
Right ascension
20h 39m 16.31779s
[1]
Declination
−14° 57′ 17.1352″
[1]
Apparent magnitude (V)
5.20 (5.77 + 9.5 + 6.19)
[2]
Characteristics
Spectral type
B6III + ? + B6IV
[2]
Astrometry
Radial velocity (Rv ) −4.1± 2.1
[3] km/s
Proper motion (μ)
RA: +2.62
[1]
mas /
yr
Dec.: −19.46
[1]
mas /
yr
Parallax (π) 2.87 ± 0.65
mas
[1]
Distance approx. 1,100
ly (approx. 350
pc )
Orbit
[4] Primary τ2 Cap A Companion τ2 Cap B
Period (P) 420
yr
Semi-major axis (a) 0.48″
Eccentricity (e) 0.73
Inclination (i) 75°
Longitude of the node (Ω) 93.0°
Periastron
epoch (T) 1915.0
Argument of periastron (ω) (secondary)270°
Details A
Mass 5.01± 0.35
[5]
M ☉ Luminosity (bolometric) 1,893
[5]
L ☉
Surface gravity (log g ) 3.90
[6]
cgs
Temperature 15,439
[6]
K
Metallicity [Fe/H]0.14
[6]
dex
Rotational velocity (v sin i ) 170
[7] km/s
Other designations
τ2 Cap ,
14 Capricorni ,
BD −15°5743 ,
GC 28748,
HD 196662,
HIP 101923,
HR 7889,
SAO 163771,
ADS 14099,
CCDM J20392-1457 ,
WDS J20393-1457
[8]
Database references
SIMBAD
data
Tau2 Capricorni ,
Latinized from τ2 Capricorni, is a
triple star
[2] system in the
constellation
Capricornus . It is approximately 1,100
light years from
Earth based on
parallax . The system has a blue-white hue and a combined
apparent visual magnitude of +5.20.
[2] Because it is positioned near the
ecliptic , τ2 Capricorni can be
occulted by the
Moon .
[9]
The primary, component A, is a
B-type
giant with a
stellar classification of B6III and an
apparent magnitude of +5.8.
[2] It has five
[5] times the
mass of the Sun and is spinning rapidly with a
projected rotational velocity of 170 km/s.
[7] The star is radiating 1,893
[5] times the
luminosity of the Sun from its
photosphere at an
effective temperature of 15,439 K.
[6]
At an angular separation of only 0.34
arcseconds is the companion, component B, a B-type
subgiant star with a class of B6IV
[2] and an
apparent magnitude of +6.3. These two stars orbit around their common centre of mass once every 420 years.
[4] A possible third component with an apparent magnitude of +9.5,
[2] detected by studying the star during
occultation , is located 0.052
arcseconds away from the A component.
[10]
References
^
a
b
c
d
e van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics , 474 (2): 653–664,
arXiv :
0708.1752 ,
Bibcode :
2007A&A...474..653V ,
doi :
10.1051/0004-6361:20078357 ,
S2CID
18759600 .
^
a
b
c
d
e
f
g Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems",
Monthly Notices of the Royal Astronomical Society , 389 (2): 869–879,
arXiv :
0806.2878 ,
Bibcode :
2008MNRAS.389..869E ,
doi :
10.1111/j.1365-2966.2008.13596.x ,
S2CID
14878976 .
^ Kharchenko, N. V.; et al. (2007), "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ˜55000 stars and mean radial velocities of 516 Galactic open clusters and associations", Astronomische Nachrichten , 328 (9): 889,
arXiv :
0705.0878 ,
Bibcode :
2007AN....328..889K ,
doi :
10.1002/asna.200710776 ,
S2CID
119323941 .
^
a
b Hartkopf, W. I.; et al. (June 30, 2006),
Sixth Catalog of Orbits of Visual Binary Stars , United States Naval Observatory, archived from
the original on 2017-04-30, retrieved 2017-06-02 .
^
a
b
c
d Hohle, M. M.; et al. (2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten , 331 (4): 349,
arXiv :
1003.2335 ,
Bibcode :
2010AN....331..349H ,
doi :
10.1002/asna.200911355 ,
S2CID
111387483 .
^
a
b
c
d Koleva, M.; Vazdekis, A. (February 2012), "Stellar population models in the UV. I. Characterisation of the New Generation Stellar Library", Astronomy & Astrophysics , 538 : A143,
arXiv :
1111.5449 ,
Bibcode :
2012A&A...538A.143K ,
doi :
10.1051/0004-6361/201118065 ,
S2CID
53999614 .
^
a
b Abt, Helmut A.; et al. (2002), "Rotational Velocities of B Stars", The Astrophysical Journal , 573 (1): 359–365,
Bibcode :
2002ApJ...573..359A ,
doi :
10.1086/340590 .
^
"tau Cap" .
SIMBAD .
Centre de données astronomiques de Strasbourg . Retrieved 2017-08-30 . {{
cite web }}
: CS1 maint: postscript (
link )
^ Radick, R.; Lien, D. (August 1980), "Illinois occultation summary. I. 1977-1978", Astronomical Journal , 85 : 1053–1061,
Bibcode :
1980AJ.....85.1053R ,
doi :
10.1086/112767 .
^ Hoffleit, Dorrit; Jaschek, Carlos (1991), "The Bright star catalogue", New Haven ,
Bibcode :
1991bsc..book.....H .