Theta Apodis

θ Apodis
	Location of θ Apodis (circled)
Observation data; Epoch J2000 Equinox J2000
Constellation	Apus
Right ascension	14h 05m 19.881s
Declination	−76° 47′ 48.34″
Apparent magnitude (V)	4.65 - 6.20
Characteristics
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
Distance	390 ± 20 ly ; (119 ± 5 pc)
Absolute magnitude (MV)	0.7
Details
Mass	1.0±0.3 M☉
Radius	208 R☉
Luminosity	3,050±460 L☉
Surface gravity (log g)	+0.0 cgs
Temperature	2,850±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
SIMBAD	data

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,^[3] 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).^[10]

A light curve for Theta Apodis, adapted from Moon *et al.* (2008)^[11]

Benjamin Apthorp Gould announced that Theta Apodis is a variable star, in 1879.^[12] It is a semiregular pulsating variable and its brightness changes over a range of 0.56 magnitudes with a period of 119^[3] days. A longer period of around 1,000 days has also been detected.^[11]

This is an evolved red giant that is currently on the asymptotic giant branch,^[13] with a stellar classification of M7 III.^[3] It shines with a luminosity approximately 3879 times that of the Sun and has a surface temperature of 3,131 K.^[7] 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.^[13]

Theta Apodis has been identified as an astrometric binary, indicating that it has an orbiting companion that causes gravitational perturbation of the primary star.^[14]

References

^ ^a ^b ^c ^d ^e 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.
^ "VSX", AAVSO.org, retrieved 2018-10-29.
^ ^a ^b ^c ^d ^e ^f 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.
^ ^a ^b 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.
^ 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.
^ ^a ^b ^c ^d Ohnaka, K. (January 2014), "High spectral resolution spectroscopy of the SiO fundamental lines in red giants and red supergiants with VLT/VISIR" (PDF), Astronomy and Astrophysics, 561, arXiv:1310.7972, Bibcode:2014A&A...561A..47O, doi:10.1051/0004-6361/201321581
^ ^a ^b 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.
^ 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
^ "tet Aps -- Semi-regular pulsating Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-07-08.
^ 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
^ ^a ^b 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
^ 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, retrieved 19 December 2024
^ ^a ^b 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.
^ 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

[dr3-1] 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.

[vsx-2] "VSX", AAVSO.org, retrieved 2018-10-29.

[mnras355_2_601-3] ^ ^a ^b ^c ^d ^e ^f 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.

[aaass44_273-4] 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.

[mnras158_23-5] 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.

[aaa561_a47-6] Ohnaka, K. (January 2014), "High spectral resolution spectroscopy of the SiO fundamental lines in red giants and red supergiants with VLT/VISIR" (PDF), Astronomy and Astrophysics, 561, arXiv:1310.7972, Bibcode:2014A&A...561A..47O, doi:10.1051/0004-6361/201321581

[mcdonald2017-7] 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.

[starhorse-8] 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

[simbad-9] "tet Aps -- Semi-regular pulsating Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-07-08.

[Jiménez-Esteban-10] 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

[moon-11] 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

[Gould1879-12] 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, retrieved 19 December 2024

[aaa537_A35-13] 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.

[mnras389_2_869-14] 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

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Theta Apodis

References

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