Astronomy:Theta Apodis

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Short description: Star in the constellation Apus
θ Apodis
Location of θ Apodis (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Apus
Right ascension  14h 05m 19.881s[1]
Declination −76° 47′ 48.34″[1]
Apparent magnitude (V) 4.65 - 6.20[2]
Characteristics
Evolutionary stage AGB[3]
Spectral type M7 III[4]
U−B color index +1.07[5]
B−V color index +1.48[5]
Variable type SRb[4]
Astrometry
Radial velocity (Rv)+9.0[6] km/s
Proper motion (μ) RA: −88.586[1] mas/yr
Dec.: −32.655[1] mas/yr
Parallax (π)8.3808 ± 0.3574[1] mas
Distance390 ± 20 ly
(119 ± 5 pc)
Absolute magnitude (MV)0.7[4]
Details
Mass1.0±0.3[7] M☉
Radius208[8] R☉
Luminosity3,050±460[7] L☉
Surface gravity (log g)+0.0[7] cgs
Temperature2,850±160[7] K
Metallicity [Fe/H]−0.20[9] dex
Other designations
θ Apodis, Theta Aps, CD−76°615, FK5 1363, HD 122250, HIP 68815, HR 5261, SAO 257112[10]
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,[4] 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.[1] It is unusual in that it is a red star with a high proper motion (greater than 50 milliarcseconds a year).[11]

A light curve for Theta Apodis, adapted from Moon et al. (2008)[12]

Benjamin Apthorp Gould announced that Theta Apodis is a variable star, in 1879.[13] It is a semiregular pulsating variable and its brightness changes over a range of 0.56 magnitudes with a period of 119[4] days. A longer period of around 1,000 days has also been detected.[12]

This is an evolved red giant that is currently on the asymptotic giant branch,[14] with a stellar classification of M7 III.[4] It shines with a luminosity approximately 3879 times that of the Sun and has a surface temperature of 3,131 K.[8] 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.[14]

Theta Apodis has been identified as an astrometric binary, indicating that it has an orbiting companion that causes gravitational perturbation of the primary star.[15]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  2. ↑ VSX, https://www.aavso.org/vsx/index.php?view=detail.top&oid=844, 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. et al. (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. doi:10.1051/0004-6361/202140952. Bibcode: 2021A&A...653A..53A. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 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, doi:10.1111/j.1365-2966.2004.08344.x, Bibcode: 2004MNRAS.355..601Y. 
  5. ↑ 5.0 5.1 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. 
  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, doi:10.1093/mnras/158.1.23, Bibcode: 1972MNRAS.158...23F. 
  7. ↑ 7.0 7.1 7.2 7.3 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, doi:10.1051/0004-6361/201321581, Bibcode: 2014A&A...561A..47O 
  8. ↑ 8.0 8.1 McDonald, I. et al. (2017), "Fundamental parameters and infrared excesses of Tycho-Gaia stars", Monthly Notices of the Royal Astronomical Society 471 (1): 770, doi:10.1093/mnras/stx1433, Bibcode: 2017MNRAS.471..770M. 
  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, doi:10.1051/0004-6361/201935765, Bibcode: 2019A&A...628A..94A 
  10. ↑ "tet Aps -- Semi-regular pulsating Star", SIMBAD (Centre de Données astronomiques de Strasbourg), http://simbad.u-strasbg.fr/simbad/sim-id?Ident=HD+122250, 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, doi:10.1051/0004-6361/201118375, Bibcode: 2012A&A...539A..86J 
  12. ↑ 12.0 12.1 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, 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. ↑ 14.0 14.1 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, doi:10.1051/0004-6361/201117910, Bibcode: 2012A&A...537A..35C.  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, doi:10.1111/j.1365-2966.2008.13596.x, Bibcode: 2008MNRAS.389..869E 



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