HD 28780

HD 28780, also known as HR 1440, is a solitary white-hued star^[14] located in the northern circumpolar constellation Camelopardalis. It has an apparent magnitude of 5.91,^[2] making it faintly viisble to the naked eye under ideal conditions. Gaia DR3 parallax measurements imply a distance of 488 light-years,^[1] and it is currently drifting closer with a heliocentric radial velocity of −22.6 km/s.^[7] At its current distance, HD 28780's brightness is diminished by 0.33 magnitudes due to interstellar extinction^[15] and it has an absolute magnitude of +0.26.^[8]

HD 28780

Location of HD 28780 on the map (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Camelopardalis
Right ascension	04h 36m 24.19802s[1]
Declination	+64° 15′ 41.7609″[1]
Apparent magnitude (V)	5.91±0.01[2]
Characteristics
Evolutionary stage	main sequence star[3]
Spectral type	A1 V[4] or A1 III[5]
U−B color index	−0.02[6]
B−V color index	−0.03[6]
Astrometry
Radial velocity (Rv)	−22.6±1.8[7] km/s
Proper motion (μ)	RA: −25.398 mas/yr[1] Dec.: −8.119 mas/yr[1]
Parallax (π)	6.6785 ± 0.0412 mas[1]
Distance	488 ± 3 ly (149.7 ± 0.9 pc)
Absolute magnitude (MV)	+0.26[8]
Details
Mass	2.48±0.08[9] M☉
Radius	3.79+0.12 −0.13[10] R☉
Luminosity	101±2[1] L☉
Surface gravity (log g)	3.67+0.06 −0.08[10] cgs
Temperature	9,616+134 −132[3] K
Metallicity [Fe/H]	−0.21[11] dex
Rotational velocity (v sin i)	41.3±2.0[12] km/s
Age	300+21 −19[9] Myr
Other designations
AG+64°277, BD+63°515, FK5 2336, GC 5574, HD 28780, HIP 21452, HR 1440, SAO 13196[13]
Database references
SIMBAD	data

HD 28780 has a stellar classification of A1 V,^[4] indicating that it is an ordinary A-type main-sequence star that is generating energy via hydrogen fusion at its core. However, Abt & Morell (1995) gave a classification of A1 III,^[5] indicating that it is an evolved A-type giant star that has exhausted hydrogen fusion at its core. At the age of 300 million years,^[9] HD 28780 has completed 80.2% of its main sequence lifetime.^[3] It has 2.48 times the mass of the Sun^[9] and a slightly enlarged radius 3.79 times larger than the Sun's.^[10] The star radiates 101 times the luminosity of the Sun^[1] from its photosphere at an effective temperature of 9,616 K.^[3] HD 28780 is metal deficient with an iron abundance 61.7% that of the Sun's ([Fe/H] = −0.21)^[11] and unlike most hot stars, it spins modestly with a projected rotational velocity of 41.3 km/s.^[12]

References

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.
2. Oja, T. (August 1991). "UBV photometry of stars whose positions are accurately known. VI". Astronomy and Astrophysics Supplement Series. 89: 415. Bibcode:1991A&AS...89..415O. ISSN 0365-0138.
3. Zorec, J.; Royer, F. (January 2012). "Rotational velocities of A-type stars IV: Evolution of rotational velocities". Astronomy & Astrophysics. 537: A120. arXiv:1201.2052. Bibcode:2012A&A...537A.120Z. doi:10.1051/0004-6361/201117691. eISSN 1432-0746. ISSN 0004-6361. S2CID 55586789.
4. Cowley, A.; Cowley, C.; Jaschek, M.; Jaschek, C. (April 1969). "A study of the bright stars. I. A catalogue of spectral classifications". The Astronomical Journal. 74: 375. Bibcode:1969AJ.....74..375C. doi:10.1086/110819. ISSN 0004-6256. S2CID 121555804.
5. Abt, Helmut A.; Morrell, Nidia I. (July 1995). "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars". The Astrophysical Journal Supplement Series. 99: 135. Bibcode:1995ApJS...99..135A. doi:10.1086/192182. ISSN 0067-0049. S2CID 120495962.
6. Oja, T. (April 1983). "UVB photometry of FK4 and FK4 Supplement stars". Astronomy and Astrophysics Supplement Series. 52: 131–134. Bibcode:1983A&AS...52..131O. ISSN 0365-0138.
7. 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.
8. 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.
9. Grosbol, P. J. (June 1978). "Space velocities and ages of nearby early-type stars". Astronomy and Astrophysics Supplement Series. 32: 409–421. Bibcode:1978A&AS...32..409G. ISSN 0365-0138.
10. Stassun, Keivan G.; et al. (9 September 2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467. eISSN 1538-3881. hdl:1721.1/124721. S2CID 166227927.
11. 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.
12. Ramella, M.; Boehm, C.; Gerbaldi, M.; Faraggiana, R. (January 1989). ""Normal" main sequence A0 stars of low rotational velocity". Astronomy and Astrophysics. 209: 233–243. Bibcode:1989A&A...209..233R. ISSN 0004-6361.
13. "HD 28780". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved July 20, 2023.
14. Eggleton, P. P.; Tokovinin, A. A. (11 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. eISSN 1365-2966. ISSN 0035-8711. S2CID 14878976.
15. Gontcharov, George A.; Mosenkov, Aleksandr V. (28 September 2017). "Verifying reddening and extinction for Gaia DR1 TGAS main sequence stars". Monthly Notices of the Royal Astronomical Society. 472 (4): 3805–3820. arXiv:1709.01160. Bibcode:2017MNRAS.472.3805G. doi:10.1093/mnras/stx2219. eISSN 1365-2966. ISSN 0035-8711. S2CID 118879856.