Theta Apodis

Theta Apodis
Diagram showing star positions and boundaries of the Apus constellation and its surroundings


Location of θ Apodis (circled)

Observation data
Epoch J2000      Equinox J2000
Constellation Apus
Right ascension 14h 05m 19.87784s[1]
Declination –76° 47′ 48.3204″[1]
Apparent magnitude (V) 5.7[2]
Characteristics
Spectral type M7 III[2]
U−B color index +1.07[3]
B−V color index +1.48[3]
Variable type Semiregular[2] pulsating
Astrometry
Radial velocity (Rv)+9.0[4] km/s
Proper motion (μ) RA: –87.54[1] mas/yr
Dec.: –32.54[1] mas/yr
Parallax (π)8.84 ± 0.49[1] mas
Distance370 ± 20 ly
(113 ± 6 pc)
Absolute magnitude (MV)0.7[2]
Other designations
CD–76 615, FK5 1363, HD 122250, HIP 68815, HR 5261, SAO 257112.[5]

Theta Apodis (θ Aps, θ Apodis) is the Bayer designation for a star in the southern circumpolar constellation of Apus. It is a variable star with a mean apparent visual magnitude of 5.7,[2] which, according to the Bortle Dark-Sky Scale, means it is a faint star but visible to the naked eye from dark suburban skies. The distance to Theta Apodis is approximately 370 light-years (110 parsecs), based upon parallax measurements made from the Hipparcos spacecraft.[1]

This is an evolved red giant that is currently on the asymptotic giant branch,[6] with a stellar classification of M7 III.[2] It is a semiregular pulsating variable and its brightness changes over a range of 0.56 magnitudes with a period of 119[2] days. It is losing mass at the rate of 1.1 × 10−7 times the mass of the Sun per year through its stellar wind. Dusty material ejected from this star is interacting with the surrounding interstellar medium, forming a bow shock as the star moves through the galaxy. The stand-off distance for this front is located at about 0.134 ly (0.041 pc) from Theta Apodis.[6]

Theta Apodis has been identified as an astrometric binary, indicating that it has an orbiting companion that causes gravitational perturbation of the primary star.[7]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (November 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.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Yeşilyaprak, C.; Aslan, Z. (December 2004), "Period-luminosity relation for M-type semiregular variables from Hipparcos parallaxes", Monthly Notices of the Royal Astronomical Society 355 (2): 601–607, Bibcode:2004MNRAS.355..601Y, doi:10.1111/j.1365-2966.2004.08344.x.
  3. ↑ 3.0 3.1 Wisse, P. N. J. (May 1981), "Three colour observations of southern red variable giant stars", Astronomy and Astrophysics Supplement Series 44: 273–303, Bibcode:1981A&AS...44..273W.
  4. ↑ Feast, M. W.; Woolley, R.; Yilmaz, N. (1972), "The kinematics of semi-regular red variables in the solar neighbourhood", Monthly Notices of the Royal Astronomical Society 158: 23–46, Bibcode:1972MNRAS.158...23F.
  5. ↑ "tet Aps -- Semi-regular pulsating Star", SIMBAD (Centre de Données astronomiques de Strasbourg), retrieved 2012-07-08.
  6. ↑ 6.0 6.1 Cox, N. L. J. et al. (January 2012), "A far-infrared survey of bow shocks and detached shells around AGB stars and red supergiants", Astronomy & Astrophysics 537: A35, arXiv:1110.5486, Bibcode:2012A&A...537A..35C, doi:10.1051/0004-6361/201117910. See table 1, IRAS 14003-7633.
  7. ↑ 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.

External links