Theta Apodis

θ Apodis
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) 4.65 - 6.20[2]
Characteristics
Spectral type M7 III[3]
U−B color index +1.07[4]
B−V color index +1.48[4]
Variable type SRb[3]
Astrometry
Radial velocity (Rv)+9.0[5] km/s
Proper motion (μ) RA: −83.823[6] mas/yr
Dec.: −34.694[6] mas/yr
Parallax (π)9.2261 ± 0.6873 mas[6]
Distance350 ± 30 ly
(108 ± 8 pc)
Absolute magnitude (MV)0.7[3]
Details
Mass2.9[7] M☉
Radius208[8] R☉
Luminosity3,748[8] L☉
Surface gravity (log g)−0.086[8] cgs
Temperature3,131[8] K
Metallicity [Fe/H]−0.20[7] dex
Other designations
CD–76 615, FK5 1363, HD 122250, HIP 68815, HR 5261, SAO 257112[9]
Database references
SIMBADdata

Theta Apodis (θ Apodis, θ Aps) is a variable star in the southern circumpolar constellation of Apus. It 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 350 light-years (110 parsecs), based upon parallax measurements made from the Gaia telescope.[6] 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]

This is an evolved red giant that is currently on the asymptotic giant branch,[12] 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.[8] 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] 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.[12]

Theta Apodis has been identified as an astrometric binary, indicating that it has an orbiting companion that causes gravitational perturbation of the primary star.[13]

  1. ^ a b Cite error: The named reference aaa474_2_653 was invoked but never defined (see the help page).
  2. ^ Cite error: The named reference vsx was invoked but never defined (see the help page).
  3. ^ a b c d e f Cite error: The named reference mnras355_2_601 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference aaass44_273 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference mnras158_23 was invoked but never defined (see the help page).
  6. ^ a b c d Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  7. ^ a b Cite error: The named reference starhorse was invoked but never defined (see the help page).
  8. ^ a b c d e Cite error: The named reference mcdonald2017 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference simbad was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Jiménez-Esteban was invoked but never defined (see the help page).
  11. ^ a b Cite error: The named reference moon was invoked but never defined (see the help page).
  12. ^ a b Cite error: The named reference aaa537_A35 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference mnras389_2_869 was invoked but never defined (see the help page).