Wikipedia

LU Delphini

LU Delphini
Location of LU Delphini (circled in red)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Delphinus
Right ascension 20h 41m 58.16454s[1]
Declination +17° 31′ 17.3644″[1]
Apparent magnitude (V) 6.24±0.01[2]
Characteristics
Spectral type G8 III[3]
U−B color index +0.57[4]
B−V color index +0.94[4]
Variable type CST:[5]
Astrometry
Radial velocity (Rv)1.6±0.4[6] km/s
Proper motion (μ) RA: +15.091 mas/yr[1]
Dec.: +43.740 mas/yr[1]
Parallax (π)7.4534±0.0249 mas[1]
Distance438 ± 1 ly
(134.2 ± 0.4 pc)
Absolute magnitude (MV)+0.39[7]
Details
Mass1.89[8] M☉
Radius13.13±0.27[1] R☉
Luminosity83.77+0.60
−0.63[1] L☉
Surface gravity (log g)2.48[9] cgs
Temperature4,773+4
−5[1] K
Metallicity [Fe/H]−0.30±0.06[10] dex
Rotational velocity (v sin i)<1[11] km/s
Age2.95[8] Gyr
Other designations
LU Del, AG+17°2244, BD+17°4382, GC 28843, HD 197249, HIP 102158, HR 7923, SAO 106396, TIC 341072887[12]
Database references
SIMBADdata

LU Delphini is a star located in the equatorial constellation Delphinus, the dolphin. It is also designated as HD 197249 and HR 7923. It has an apparent magnitude of 6.24,[2] placing it near the limit for naked eye visibility. Gaia DR3 parallax measurements imply a distance of 438 light years,[1] and it is currently receding with a heliocentric radial velocity of 1.6 km/s.[6] At its current distance, LU Delphini's brightness is diminished by an interstellar extinction of two-tenths of a magnitude, and it has an absolute visual magnitude of +0.39.[7]

LU Delphini was first observed to be a variable star by Diethard Böhme during the late 1980's.[13] He observed an amplitude of two-tenths of a magnitude over the course of 100 days, and believed it to either be a semiregular variable or a RS Canum Venaticorum variable.[13] However, no variations greater than two-hundredths of a magnitude were detected in Hipparcos data.[14] The object most likely has a constant brightness as opposed to being variable.[14][5]

The object has a stellar classification of G8 III,[3] indicating that it is an evolved G-type giant star that has ceased hydrogen fusion at its core and left the main sequence. It has 1.89 times the mass of the Sun but at the age of 2.95 billion years,[8] it has expanded to 13.13 times the radius of the Sun. It radiates 83.77 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,773 K,[1] giving it a yellow hue when it is viewed in the night sky. LU Delphini only has half of the Sun's iron abundance,[10] and it spins too slowly for its projected rotational velocity to be measured accurately.[11]

References

[edit]
  1. ^ a b c d e f g h i 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. ^ a b Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27 – L30. Bibcode:2000A&A...355L..27H. ISSN 0004-6361. S2CID 17128864.
  3. ^ a b Halliday, Ian (September 1955). "Luminosity Function and Space Motions of G8-K1 Stars Derived from Spectroscopic Parallaxes". The Astrophysical Journal. 122: 222. Bibcode:1955ApJ...122..222H. doi:10.1086/146080. ISSN 0004-637X. S2CID 119640884.
  4. ^ 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. ISSN 0365-0138.
  5. ^ a b Watson, C. L.; Henden, A. A.; Price, A. (May 2006). "The International Variable Star Index (VSX)". Society for Astronomical Sciences Annual Symposium. 25: 47. Bibcode:2006SASS...25...47W.
  6. ^ a b Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35,495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. eISSN 1562-6873. ISSN 1063-7737. S2CID 119231169.
  7. ^ a b Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. eISSN 1562-6873. ISSN 1063-7737. S2CID 119257644.
  8. ^ a b c Dotter, Aaron; Chaboyer, Brian; Jevremović, Darko; Kostov, Veselin; Baron, E.; Ferguson, Jason W. (September 2008). "The Dartmouth Stellar Evolution Database". The Astrophysical Journal Supplement Series. 178 (1): 89–101. arXiv:0804.4473. Bibcode:2008ApJS..178...89D. doi:10.1086/589654. eISSN 1538-4365. ISSN 0067-0049. S2CID 119290835.
  9. ^ Anders, F.; et al. (August 2019). "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18". Astronomy & Astrophysics. 628: A94. arXiv:1904.11302. Bibcode:2019A&A...628A..94A. doi:10.1051/0004-6361/201935765. eISSN 1432-0746. ISSN 0004-6361. S2CID 131780028.
  10. ^ a b Luck, R. Earle (25 August 2015). "Abundances in the Local Region. I. G and K Giants". The Astronomical Journal. 150 (3): 88. arXiv:1507.01466. Bibcode:2015AJ....150...88L. doi:10.1088/0004-6256/150/3/88. eISSN 1538-3881. ISSN 0004-6256. S2CID 118505114.
  11. ^ a b de Medeiros, J. R.; Mayor, M. (November 1999). "A catalog of rotational and radial velocities for evolved stars". Astronomy and Astrophysics Supplement Series. 139 (3): 433–460. Bibcode:1999A&AS..139..433D. doi:10.1051/aas:1999401. ISSN 0365-0138. S2CID 54046583.
  12. ^ "LU Delphini". SIMBAD. Centre de données astronomiques de Strasbourg.
  13. ^ a b Bohme, D. (May 1988). "HR 7923 is a Variable Star". Information Bulletin on Variable Stars. 3186: 1. Bibcode:1988IBVS.3186....1B. ISSN 0374-0676.
  14. ^ a b "The HIPPARCOS and TYCHO catalogues. Astrometric and photometric star catalogues derived from the ESA HIPPARCOS Space Astrometry Mission". ESA Special Publication. 1200. 1997. Bibcode:1997ESASP1200.....E. ISSN 1609-042X.