| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Orion[1] |
| Right ascension | 05h 50m 30.03s[2] |
| Declination | +02° 01′ 28.9″[2] |
| Apparent magnitude (V) | 5.976[3] |
| Characteristics | |
| Cool primary | |
| Evolutionary stage | Horizontal branch[4] |
| Spectral type | K0II[5] |
| Apparent magnitude (B) | 6.83±0.015[6] |
| Apparent magnitude (G) | 5.64[6] |
| Apparent magnitude (J) | 4.193±0.238[6] |
| Apparent magnitude (H) | 3.502±0.194[6] |
| Apparent magnitude (K) | 3.337±0.19[6] |
| B−V color index | 1.12[5] |
| Hot secondary | |
| Evolutionary stage | Main sequence + Main sequence |
| Spectral type | B7/B8V + A0:V[5] |
| B−V color index | −0.09[5] |
| Astrometry | |
| Radial velocity (Rv) | 4.24[5] km/s |
| Proper motion (μ) | RA: +1.097 mas/yr[2] Dec.: −5.161 mas/yr[2] |
| Parallax (π) | 1.4703±0.2299 mas[2] |
| Distance | 2300+350 −270 ly (707.6+107 −83.3 pc)[7] |
| Absolute magnitude (MV) | –2.53 (–2.3 (primary) + –0.75 (secondary))[5] |
| Orbit | |
| Primary | Cool primary |
| Companion | Hot secondary |
| Period (P) | 2570±13 d 7.04±0.04 year[8] |
| Semi-major axis (a) | 4.7×108 km 3.14 AU[8] |
| Eccentricity (e) | 0.3±0.007[8] |
| Details | |
| K-type giant | |
| Mass | 3.3+0.3 −0.27[4] M☉ |
| Radius | 23.5+3.7 −1.9[4] R☉ |
| Luminosity | 535[9] L☉ |
| Surface gravity (log g) | 1.52[10] cgs |
| Temperature | 4,550[10] K |
| Metallicity [Fe/H] | −0.34[10] dex |
| Rotational velocity (v sin i) | 4.19[11] km/s |
| Age | 257[4] Myr |
| B-type star | |
| Temperature | 11,300[12] K |
| Other designations | |
| BD+01 1148, Gaia DR2 3316078695157768448, Gaia DR3 3316078695157768448, HD 39118/39119, HIP 27588, HR 2024, SAO 113198, PPM 149543, TIC 158867386, TYC 120-877-1, GSC 00120-00877, IRAS 05478+0200, 2MASS J05503003+0201290[6] | |
| Database references | |
| SIMBAD | data |
HD 39118 (HD 39119, HR 2024) is a spectroscopic binary star in the constellation Orion, close to the celestial equator. It is made up from three stars: a cool primary (a K-type giant star) and a hot secondary, which is a binary star formed from a B-type main-sequence star and an A-type main-sequence star. A 2021 estimate derive a distance of 708 parsecs (2,310 ly) to HD 39118, and it is moving away from Earth at a speed of 4.24 km/s. The apparent magnitude is 5.976, making it visible to the naked eye only from dark skies.
Characteristics
HR 2024 is a spectroscopic binary (more precisely a single-lined spectroscopic binary)[13] made up of a cool primary and a hot secondary, which is also a binary star.[5] The designations “cool” and “hot” refer to the relative effective temperature of the components. They are separated by 4.7×108 kilometres (3.1 AU), and complete an orbit around each other every 2,570 days (7 years).[8] The orbital eccentricity is equivalent to 0.3.[8]
HD 39118 can be seen in the northern celestial hemisphere, close to the celestial equator, at a distance of 708 parsecs (2,310 light-years) in the constellation Orion.[6][7][1] It has an apparent magnitude of 5.976. At this magnitude, it is visible to the naked eye only in dark skies, being close to the limiting magnitude to naked-eye vision of 6.5.[14] The absolute magnitude, i.e. its brightness if it was seen at a distance or 10 parsecs (32.6 ly), is –2.53.[5] It is moving away from Earth at a velocity of 4.24 km/s.[6]
The Henry Draper Catalogue recognises that the spectrum is composite: the designation HD 39118 is applied to component A with spectral class G0; HD 39119 is applied to component B with spectral class A0, although both entries have the same position and magnitude.[15]
Primary star
The primary has a spectral classification of K0II,[5] meaning that it is a K-type star that has evolved away from the main sequence and is now a bright giant star. Currently, it is on the horizontal branch, fusing helium in its core.[4] It is 3.28 times more massive than the Sun and has expanded to 25 times the Sun's size.[4] It emits a luminosity 535 times the solar luminosity[9] from its photosphere at an effective temperature of 4,550 K, which is around 1,200 K cooler than the Sun.[10][a] It has a subsolar metallicity, having an abundance of iron on its surface equivalent to 46% that of the Sun.[10][b] The age of the primary is estimated at 263 million years,[4] much younger than the Sun (4.6 billion years) despite its advanced evolutionary stage. It rotates on its own axis at a projected velocity of 4.19 km/s.[11] The B-V index is of 1.12,[5] giving it the typical orange hue of a K-type star.[c]
Hot companion
The hot companion is made up of two other stars, one is a late B-type main-sequence star (spectral type B7V/B8V) and the other is an early A-type main-sequence star (spectral type A0V).[5] They have a combined brightness about 1.55 magnitudes fainter than the cooler primary star.[5] The B-type star has an effective temperature of 11,300 K.[12] Although stars cannot be resolved, it is calculated that the combined B-V index of the hot companions is –0.09,[5] meaning that it has a typical hue of a B-type star.[c]
Notes
- ^ The Sun's effective temperature is 5772 K.
- ^ 10−0.34
- ^ a b See the color index article
References
- ^ a b Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific. 99 (617): 695. Bibcode:1987PASP...99..695R. doi:10.1086/132034. Constellation record for this object at VizieR.
- ^ a b c d 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.
- ^ Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355. Bibcode:2000A&A...355L..27H.
- ^ a b c d e f g Stock, Stephan; Reffert, Sabine; Quirrenbach, Andreas (2018-08-01). "Precise radial velocities of giant stars. X. Bayesian stellar parameters and evolutionary stages for 372 giant stars from the Lick planet search". Astronomy and Astrophysics. 616: A33. arXiv:1805.04094. Bibcode:2018A&A...616A..33S. doi:10.1051/0004-6361/201833111. ISSN 0004-6361. HD 39118's database entry at VizieR.
- ^ a b c d e f g h i j k l m Ginestet, N.; Carquillat, J. M. (2002-12-01). "Spectral Classification of the Hot Components of a Large Sample of Stars with Composite Spectra, and Implication for the Absolute Magnitudes of the Cool Supergiant Components". The Astrophysical Journal Supplement Series. 143 (2): 513–537. Bibcode:2002ApJS..143..513G. doi:10.1086/342942. ISSN 0067-0049.
- ^ a b c d e f g h "BD+01 1148". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved May 6, 2024.
- ^ a b Bailer-Jones, C. A. L.; Rybizki, J.; Fouesneau, M.; Demleitner, M.; Andrae, R. (2021-03-01). "Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3". The Astronomical Journal. 161 (3): 147. arXiv:2012.05220. Bibcode:2021AJ....161..147B. doi:10.3847/1538-3881/abd806. ISSN 0004-6256. Data about this star can be seen here.
- ^ a b c d e Griffin, R. F. (1990-12-01). "Composite Spectra - Part 5 - Orbital Elements for 30 Systems". Journal of Astrophysics and Astronomy. 11 (4): 491–505. Bibcode:1990JApA...11..491G. doi:10.1007/BF02709763. ISSN 0250-6335.
- ^ a b McDonald, I.; Zijlstra, A. A.; Boyer, M. L. (2012-11-01). "Fundamental parameters and infrared excesses of Hipparcos stars". Monthly Notices of the Royal Astronomical Society. 427 (1): 343–357. arXiv:1208.2037. Bibcode:2012MNRAS.427..343M. doi:10.1111/j.1365-2966.2012.21873.x. ISSN 0035-8711. HD 39118's database entry at VizieR.
- ^ a b c d e Soubiran, Caroline; Le Campion, Jean-François; Brouillet, Nathalie; Chemin, Laurent (2016-06-01). "The PASTEL catalogue: 2016 version". Astronomy and Astrophysics. 591: A118. arXiv:1605.07384. Bibcode:2016A&A...591A.118S. doi:10.1051/0004-6361/201628497. ISSN 0004-6361. HD 39118's database entry at VizieR.
- ^ a b Hekker, S.; Meléndez, J. (2007-12-01). "Precise radial velocities of giant stars. III. Spectroscopic stellar parameters". Astronomy and Astrophysics. 475 (3): 1003–1009. arXiv:0709.1145. Bibcode:2007A&A...475.1003H. doi:10.1051/0004-6361:20078233. ISSN 0004-6361. HD 39118's database entry at VizieR.
- ^ a b Hunsch, M.; Reimers, D. (1993-09-01). "Circumstellar MG II absorption in UV spectra of hot companions of red giants and the meaning of the MG II asymmetry dividing line". Astronomy and Astrophysics. 276: 161–170. Bibcode:1993A&A...276..161H. ISSN 0004-6361. HD 39118's database entry at VizieR.
- ^ de Medeiros, J. R.; Mayor, M. (1999-11-01). "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.
- ^ "Determining the Limiting Magnitude – Saguaro Astronomy Club". www.saguaroastro.org. Retrieved 2024-05-21.
- ^ Cannon, Annie Jump; Pickering, Edward Charles (1918). "The Henry Draper catalogue : 4h, 5h and 6h". Annals of Harvard College Observatory. 92: 1. Bibcode:1918AnHar..92....1C.
