Astronomy:HD 39118

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Short description: Triple stellar system in the constellation Orion

Coordinates: Sky map 05h 50m 30s, +02° 01′ 28.9″

HD 39118 and HD 39119
Location of HD 39118 (circled in red)
Observation data
Equinox J2000.0]] (ICRS)
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[2] mas/yr
Dec.: −5.161[2] mas/yr
Parallax (π)1.4703 ± 0.2299[2] mas
Distance2300+350
−270 ly
(707.6+107
−83.3 pc)
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[7]
Semi-major axis (a)4.7×108 km
3.14 AU[7]
Eccentricity (e)0.3±0.007[7]
Details
K-type giant
Mass3.3+0.3
−0.27[4] M☉
Radius23.5+3.7
−1.9[4] R☉
Luminosity535[8] L☉
Surface gravity (log g)1.52[9] cgs
Temperature4,550[9] K
Metallicity [Fe/H]−0.34[9] dex
Rotational velocity (v sin i)4.19[10] km/s
Age257[4] Myr
B-type star
Temperature11,300[11] K
Other designations
BD+01 1148, Gaia DR2 3316078695157768448, HD 39118/39119, HIP 27588, HR 2024, SAO 113198, PPM 149543, TYC 120-877-1, GSC 00120-00877, IRAS 05478+0200, 2MASS J05503003+0201290[6]
Database references
SIMBADdata

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

Basic layout of the HR 2024 system

HR 2024 is a spectroscopic binary (more precisely a single-lined spectroscopic binary)[12] 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 astronomical unit|AU), and complete an orbit around each other every 2,570 days (7 years).[7] The orbital eccentricity is equivalent to 0.3.[7]

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][13][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[8] from its photosphere at an effective temperature of 4,550 K, which is around 1,200 K cooler than the Sun.[9][lower-alpha 1] It has a subsolar metallicity, having an abundance of iron on its surface equivalent to 46% that of the Sun.[9][lower-alpha 2] 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.[10] The B-V index is of 1.12,[5] giving it the typical orange hue of a K-type star.[lower-alpha 3]

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.[11] 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.[lower-alpha 3]

Notes

  1. ↑ The Sun's effective temperature is 5772 K.
  2. ↑ 10−0.34
  3. ↑ 3.0 3.1 See the color index article

References

  1. ↑ 1.0 1.1 Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific 99 (617): 695. doi:10.1086/132034. Bibcode: 1987PASP...99..695R  Constellation record for this object at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  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. et al. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics 355. Bibcode: 2000A&A...355L..27H. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 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. doi:10.1051/0004-6361/201833111. ISSN 0004-6361. Bibcode: 2018A&A...616A..33S.  HD 39118's database entry at VizieR.
  5. ↑ 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 5.11 5.12 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. doi:10.1086/342942. ISSN 0067-0049. Bibcode: 2002ApJS..143..513G. 
  6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 "BD+01 1148". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=BD%2B01+1148. 
  7. ↑ 7.0 7.1 7.2 7.3 7.4 Griffin, R. F. (1990-12-01). "Composite Spectra - Part 5 - Orbital Elements for 30 Systems". Journal of Astrophysics and Astronomy 11 (4): 491–505. doi:10.1007/BF02709763. ISSN 0250-6335. Bibcode: 1990JApA...11..491G. 
  8. ↑ 8.0 8.1 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. doi:10.1111/j.1365-2966.2012.21873.x. ISSN 0035-8711. Bibcode: 2012MNRAS.427..343M.  HD 39118's database entry at VizieR.
  9. ↑ 9.0 9.1 9.2 9.3 9.4 Soubiran, Caroline; Le Campion, Jean-François; Brouillet, Nathalie; Chemin, Laurent (2016-06-01). "The PASTEL catalogue: 2016 version". Astronomy and Astrophysics 591: A118. doi:10.1051/0004-6361/201628497. ISSN 0004-6361. Bibcode: 2016A&A...591A.118S.  HD 39118's database entry at VizieR.
  10. ↑ 10.0 10.1 Hekker, S.; Meléndez, J. (2007-12-01). "Precise radial velocities of giant stars. III. Spectroscopic stellar parameters". Astronomy and Astrophysics 475 (3): 1003–1009. doi:10.1051/0004-6361:20078233. ISSN 0004-6361. Bibcode: 2007A&A...475.1003H.  HD 39118's database entry at VizieR.
  11. ↑ 11.0 11.1 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. ISSN 0004-6361. Bibcode: 1993A&A...276..161H.  HD 39118's database entry at VizieR.
  12. ↑ 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. doi:10.1051/aas:1999401. ISSN 0365-0138. Bibcode: 1999A&AS..139..433D. 
  13. ↑ 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. doi:10.3847/1538-3881/abd806. ISSN 0004-6256. Bibcode: 2021AJ....161..147B.  Data about this star can be seen here.
  14. ↑ "Determining the Limiting Magnitude – Saguaro Astronomy Club". https://www.saguaroastro.org/determining-the-limiting-magnitude/. 
  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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