Delta Apodis

Delta Apodis (δ Aps, δ Apodis) is the Bayer designation for a double star in the southern constellation of Apus.

Delta Apodis
Location of δ Apodis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Apus
δ1 Aps
Right ascension 16h 20m 20.80462s[1]
Declination –78° 41′ 44.6889″[1]
Apparent magnitude (V) +4.76[2]
δ2 Aps
Right ascension 16h 20m 26.85843s[1]
Declination –78° 40′ 02.9901″[1]
Apparent magnitude (V) +5.27[2]
Characteristics
Spectral type M5 IIIb + K3 III[3]
U−B color index +1.68/+1.62[2]
B−V color index +1.69/+1.41[2]
Variable type irregular variable
Astrometry
δ1 Aps
Radial velocity (Rv)–12.0[4] km/s
Proper motion (μ) RA: –9.122 ± 0.390[5] mas/yr
Dec.: –36.968 ± 0.505[5] mas/yr
Parallax (π)5.1748 ± 0.2734[5] mas
Distance630 ± 30 ly
(190 ± 10 pc)
δ2 Aps
Radial velocity (Rv)–10.2[6] km/s
Proper motion (μ) RA: –1.321 ± 0.229[5] mas/yr
Dec.: –31.507 ± 0.259[5] mas/yr
Parallax (π)5.9845 ± 0.1353[5] mas
Distance550 ± 10 ly
(167 ± 4 pc)
Other designations
CP-78 1092, FK5 1424, HR 6020.[7][8]
δ1 Aps: HD 145366, HIP 80047, SAO 257380.[7]
δ2 Aps: HD 145388, HIP 80057, SAO 257381.[8]
Database references
SIMBADδ1 Aps
δ2 Aps

The brighter star, δ¹ Apodis, is a M-type red giant and has an apparent magnitude that varies from magnitude +4.66 to +4.87.[9] It is classified as a semiregular variable with pulsations of multiple periods of 68.0, 94.9 and 101.7 days.[10] At an angular separation of 102.9 arcseconds is δ² Apodis, an orange K-type giant with an apparent magnitude of +5.27.

Hipparcos data report the distance to δ¹ Apodis to be approximately 760 light years, while δ² Apodis is found to be around 610 light years from Earth. They may form a common proper motion pair.

Naming

In Chinese caused by adaptation of the European southern hemisphere constellations into the Chinese system, 異雀 (Yì Què), meaning Exotic Bird, refers to an asterism consisting of δ1 Apodis, ζ Apodis, ι Apodis, β Apodis, γ Apodis, δ Octantis, η Apodis, α Apodis and ε Apodis. Consequently, δ1 Apodis itself is known as 異雀六 (Yì Què liù, English: the Sixth Star of Exotic Bird.)[11]

References
  1. 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, S2CID 18759600.
  2. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J.
  3. Houk, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars, 1, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
  4. Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veroeffentlichungen des Astronomischen Rechen-Instituts Heidelberg, Astronomisches Rechen-Institut Heidelberg, 35 (35): 1, Bibcode:1999VeARI..35....1W.
  5. 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.
  6. Wilson, Ralph Elmer (1953), "General Catalogue of Stellar Radial Velocities", Carnegie Institute Washington D.C. Publication, Washington: Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W.
  7. "del01 Aps -- Pulsating variable Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-07-08.
  8. "HR 6021 -- Star in double system", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-07-08.
  9. Watson, Christopher (25 August 2009). "Delta1 Apodis". The International Variable Star Index. American Association of Variable Star Observers. Retrieved 30 March 2016.
  10. Tabur, V.; et al. (December 2009), "Long-term photometry and periods for 261 nearby pulsating M giants", Monthly Notices of the Royal Astronomical Society, 400 (4): 1945–1961, arXiv:0908.3228, Bibcode:2009MNRAS.400.1945T, doi:10.1111/j.1365-2966.2009.15588.x, S2CID 15358380.
  11. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 29 日
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