HD 39118

Last updated
HD 39118 and HD 39119
Orion IAU.svg
Red circle.svg
Location of HD 39118 (circled in red)
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
PrimaryCool primary
CompanionHot 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.

Contents

Characteristics

Basic layout of the HR 2024 system Layout of the HR 2024 system.png
Basic layout of the HR 2024 system

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

  1. ↑ The Sun's effective temperature is 5772 K.
  2. ↑ 10−0.34
  3. 1 2 See the color index article

References

  1. 1 2 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.
  2. 1 2 3 4 5 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.
  3. ↑ 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.
  4. 1 2 3 4 5 6 7 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.
  5. 1 2 3 4 5 6 7 8 9 10 11 12 13 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.
  6. 1 2 3 4 5 6 7 8 "BD+01 1148". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved May 6, 2024.
  7. 1 2 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.
  8. 1 2 3 4 5 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.
  9. 1 2 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.
  10. 1 2 3 4 5 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.
  11. 1 2 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.
  12. 1 2 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.
  13. ↑ 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.
  14. ↑ "Determining the Limiting Magnitude – Saguaro Astronomy Club". www.saguaroastro.org. Retrieved 2024-05-21.
  15. ↑ 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.
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