Theta Apodis

θ Apodis
Location of θ Apodis (circled)
Observation data
Epoch J2000      Equinox ICRS
Constellation Apus
Right ascension 14h 05m 19.881s
Declination −76° 47′ 48.34″
Apparent magnitude (V) 4.65 - 6.20
Characteristics
Evolutionary stage AGB
Spectral type M7 III
U−B color index +1.07
B−V color index +1.48
Variable type SRb
Astrometry
Radial velocity (Rv)+9.0 km/s
Proper motion (μ) RA: −88.586 mas/yr
Dec.: −32.655 mas/yr
Parallax (π)8.3808±0.3574 mas
Distance390 ± 20 ly
(119 ± 5 pc)
Absolute magnitude (MV)0.7
Details
Mass1.0±0.3 M☉
Radius208 R☉
Luminosity3,050±460 L☉
Surface gravity (log g)+0.0 cgs
Temperature2,850±160 K
Metallicity [Fe/H]−0.20 dex
Other designations
θ Apodis, Theta Aps, AAVSO 1355-76, CD−76°615, FK5 1363, HD 122250, HIP 68815, HR 5261, SAO 257112
Database references
SIMBADdata

Theta Apodis is a variable star in the southern circumpolar constellation of Apus. Its identifier is a Bayer designation that is Latinized from θ Apodis, and abbreviated Tet Aps or θ Aps, respectively. This is a variable star with an apparent visual magnitude range of 4.65 to 6.20, 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 390 light-years (120 parsecs), based upon parallax measurements made from the Gaia telescope. It is unusual in that it is a red star with a high proper motion (greater than 50 milliarcseconds a year).

A light curve for Theta Apodis, adapted from Moon et al. (2008)

Benjamin Apthorp Gould announced that Theta Apodis is a variable star, in 1879. It is a semiregular pulsating variable and its brightness changes over a range of 0.56 magnitudes with a period of 119 days. A longer period of around 1,000 days has also been detected.

This is an evolved red giant that is currently on the asymptotic giant branch, with a stellar classification of M7 III. It shines with a luminosity approximately 3879 times that of the Sun and has a surface temperature of 3,131 K. 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.

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

References

  1. 1 2 3 4 5 6 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. ↑ "VSX", AAVSO.org, retrieved 2018-10-29.
  3. ↑ Andriantsaralaza, M.; Ramstedt, S.; Vlemmings, W. H. T.; Danilovich, T.; De Beck, E.; Groenewegen, M. A. T.; Höfner, S.; Kerschbaum, F.; Khouri, T.; Lindqvist, M.; Maercker, M.; Olofsson, H.; Quintana-Lacaci, G.; Saberi, M.; Sahai, R.; Zijlstra, A. (2021). "DEATHSTAR: Nearby AGB stars with the Atacama Compact Array. II. CO envelope sizes and asymmetries: The S-type stars". Astronomy and Astrophysics. 653: A53. arXiv:2108.10742. Bibcode:2021A&A...653A..53A. doi:10.1051/0004-6361/202140952.
  4. 1 2 3 4 5 6 Yeşilyaprak, C.; et al. (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.
  5. 1 2 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.
  6. ↑ Feast, M. W.; et al. (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, doi:10.1093/mnras/158.1.23.
  7. 1 2 3 4 Ohnaka, K. (January 2014), "High spectral resolution spectroscopy of the SiO fundamental lines in red giants and red supergiants with VLT/VISIR", Astronomy and Astrophysics, 561: A47, arXiv:1310.7972, Bibcode:2014A&A...561A..47O, doi:10.1051/0004-6361/201321581
  8. 1 2 McDonald, I.; et al. (2017), "Fundamental parameters and infrared excesses of Tycho-Gaia stars", Monthly Notices of the Royal Astronomical Society, 471 (1): 770, arXiv:1706.02208, Bibcode:2017MNRAS.471..770M, doi:10.1093/mnras/stx1433, S2CID 73594365.
  9. ↑ Anders, F.; et al. (2019), "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18", Astronomy and Astrophysics, 628: A94, arXiv:1904.11302, Bibcode:2019A&A...628A..94A, doi:10.1051/0004-6361/201935765, S2CID 131780028
  10. ↑ "tet Aps -- Semi-regular pulsating Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-07-08.
  11. ↑ Jiménez-Esteban, F. M.; et al. (2012), "Identification of red high proper-motion objects in Tycho-2 and 2MASS catalogues using Virtual Observatory tools", Astronomy & Astrophysics, 539: 12, arXiv:1201.5315, Bibcode:2012A&A...539A..86J, doi:10.1051/0004-6361/201118375, S2CID 53404166
  12. 1 2 Moon, T. T. (2008), "Combining Visual and Photoelectric Observations of Semiregular Red Variables", Journal of the American Association of Variable Star Observers, 36 (1): 77, arXiv:0711.4873, Bibcode:2008JAVSO..36...77M
  13. ↑ Gould, Benjamin Apthorp (1879), "Uranometria Argentina: Brightness and position of every fixed star, down to the seventh magnitude, within one hundred degrees of the South Pole; with atlas", Resultados del Observatorio Nacional Argentino, 1: I-387, Bibcode:1879RNAO....1....1G
  14. 1 2 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, S2CID 56041336. See table 1, IRAS 14003-7633.
  15. ↑ 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