Triple stellar system in the constellation Orion
HD 39118
Basic layout of the HR 2024 system.
Observation dataEpoch J2000 Equinox J2000
Constellation
Orion [ a]
Right ascension
05h 50m 30.03s [ 1]
Declination
02° 01′ 28.93″[ 1]
Apparent magnitude (V)
5.976[ 1]
Characteristics
Cool primary
Evolutionary stage
Red giant branch [ 2]
Spectral type
K0II[ 3]
Apparent magnitude (B)
6.83± 0.015[ 1]
Apparent magnitude (G)
5.64[ 1]
Apparent magnitude (J)
4.193± 0.238[ 1]
Apparent magnitude (H)
3.502± 0.194[ 1]
Apparent magnitude (K)
3.337± 0.19[ 1]
B−V color index
1.12[ 3]
Hot secondary
Evolutionary stage
B-type main-sequence star + A-type main-sequence star
Spectral type
B7V/B8V + A0V[ 3]
B−V color index
-0.09[ 3]
Astrometry Radial velocity (Rv )4.24[ 3] km/s Proper motion (μ) RA: 1.097 mas /yr [ 1] Dec.: -5.161 mas /yr [ 1] Parallax (π)1.47 ± 0.23 mas [ 4] Distance 2300+350 −270 ly ( 707.6+107 −83.3 pc )[ 4] Absolute magnitude (MV )–2.53 (–2.3 (primary) + –0.75 (secondary))[ 3]
Orbit Primary Cool primary Companion Hot secondary Period (P) 2570± 13 d 7.04± 0.04 year[ 5] Semi-major axis (a) 4.7× 108 km 3.14 AU [ 5] Eccentricity (e) 0.3± 0.007[ 5]
Details K-type giant Mass 3.3+0.3 −0.27 [ 2] M ☉ Radius 23.5+3.7 −1.9 [ 2] R ☉ Luminosity 535[ 6] L ☉ Surface gravity (log g )1.52[ 7] cgs Temperature 4,550[ 7] K Metallicity [Fe/H]-0.34[ 7] dex Rotational velocity (v sin i )4.19[ 8] km/s Age 257[ 2] Myr B-type star Temperature 11,300[ 9] 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
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)[ 10] made up of a cool primary and a hot secondary, which is also a binary star .[ 3] The designations “cold” and “hot” refer to the 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).[ 5] The orbital eccentricity is equivalent to 0.3.[ 5]
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 .[ 1] [ 4] [ b] It has an apparent magnitude of 5.976.[ 1] 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.[ 11] The absolute magnitude , i.e. its brightness if it was seen at a distance or 10 parsecs (32.6 ly), is –2.53.[ 3] It is moving away from Earth at a velocity of 4.24 km/s.[ 1]
It was double cataloged in the Henry Draper Catalogue , receiving the designations HD 39118 and HD 39119.[ 1]
Primary star
The primary has an spectral classification of K0II,[ 3] meaning that it is a K-type star that has left the main sequence , being now a bright giant star. Currently, it is in the red giant branch of evolution.[ 2] It is 3.28 times more massive has expanded to 25 times the Sun's size.[ 2] It emitts a luminosity 535[ 6] times the solar luminosity from its photosphere at an effective temperature of 4,550 K , which is around 1,200 K cooler than the Sun .[ 7] [ c] It has a subsolar metallicity , having an abundance of iron on its surface equivalent to 46% that of the Sun.[ 7] [ d] The age of the primary is estimated at 263 million years,[ 2] much younger than the Sun (4.6 billion years) despite its advanced evolutionary stage. It rotates under its own axis at a velocity of 4.19 km/s.[ 8] The B-V index is of 1.12,[ 3] giving it the typical orange hue of a K-type star .[ e]
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).[ 3] It has an absolute magnitude about 1.55 magnitudes fainter than the primary companion.[ 3] The B-type star has an effective temperature of 11,300 K.[ 9] The B-V index of the hot companion is of –0.09,[ 3] meaning that it has a typical hue of a B-type star .[ e]
Notes
^ Obtained with a right ascension of 05h 50m 30.03s and a declination of +02° 01′ 28.9″ on this website .
^ Constellation obtained with SIMBAD's celestial coordinates placed on this website
^ The Sun's effective temperature is 5772 K.
^ From a logarithm of -0.34
^ a b See the color index article
References
^ a b c d e f g h i j k l m "BD+01 1148" . SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved May 6, 2024 .
^ 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 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 : 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 : 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 .