HR 2024

Coordinates: Sky map 05h 50m 30s, +02° 01′ 28.9″
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HR 2024

Basic layout of the HR 2024 system.
Observation data
Epoch 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 Horizontal 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 companion
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)2.89 ± 0.83 mas[4]
Distance1128±323.4 ly
(346.02±99.38 pc)[4][b][c]
Absolute magnitude (MV)–2.53
(–2.3 (primary) + –0.75 (companion))[3]
Orbit
PrimaryCool primary
CompanionHot companion
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
Mass3.38+0.29
−0.2[2] M☉
Radius29.29+5.27
−7.65[2] R☉
Luminosity534.63[6] L☉
Surface gravity (log g)1.52[7] cgs
Temperature4,550[7] K
Metallicity [Fe/H]-0.34[7] dex
Rotational velocity (v sin i)4.19[8] km/s
Age263[2] Myr
B-type star
Temperature11,300[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
SIMBADdata

HR 2024 (HD 39118/19, BD+01 1148) is a spectroscopic binary star in the constellation Orion. It is made up from a cool primary (a K-type giant star) and a hot companion, which is a binary star formed from a B-type main-sequence star and an A-type main-sequence star. Based on a parallax measurement from Hipparcos, the system is located at 346 parsecs (1,130 ly) from Earth, with mild error margins. The apparent magnitude of the star is 5.976, making it visible to the naked eye only from locations not affected by light pollution.

Characteristics[edit]

HR 2024 is a spectroscopic binary (more precisely a single-lined spectroscopic binary)[10] made up of a cool primary and a hot companion.[3] The cool primary has a spectral type of K0II,[3] corresponding to a K-type star with a bright giant luminosity class. The hot companion is binary, made up by two stars with spectral types of B7V/B8V and A0V, corresponding to a B-type main-sequence star and an A-type main-sequence star respectively.[3]

The two components are separated by a distance of 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]

HR 2024 is in the constellation Orion, based on its astronomical coordinates.[a] It is located about 346 parsecs (1,130 light-years) away, based on a parallax of 2.89±0.83 milliarcseconds from the Hipparcos satellite.[4] This parallax has a considerable margin of error (about 30% of the parallax itself), which attributes an uncertainty of 99 parsecs (320 light-years) to the distance.[4][c] The star has an apparent magnitude of 5.976.[1] At this magnitude, it is very faint can be visible to the naked eye only in rural skies.[d] 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]

Primary star[edit]

The primary star of the system is an evolved K-type bright giant (spectral type K0 II)[3] that reached the horizontal branch stage of evolution.[2] It has expanded to 29 times the Sun's size and is emitting over 540 times the solar luminosity from its photosphere at an effective temperature of 4,550 K, which is 1,228 K cooler than the Sun.[2][6][7][e] It has a mass equivalent to 3.4 times the solar mass[2] and a subsolar metallicity, having an abundance of iron on its surface is equivalent to 46% that of the Sun.[7][f] The age of the primary is estimated at 263 million years and it rotates under its own axis at a velocity of 4.19 km/s.[2][8] It has a B-V index of 1.12,[3] giving a typical orange hue of a K-type star.[g]

Hot companion[edit]

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 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.[g]

Notes[edit]

  1. ^ a b Obtained with a right ascension of 05h 50m 30.03s and a declination of +02° 01′ 28.9″ on this website.
  2. ^ From D=P/1000, where D is the distance in parsecs and P the parallax in milliarcseconds.
  3. ^ a b The parallax error is calculated by dividing the error by the parallax, and then assigning this division to the distance.
    0.83/2.89 = 0.287.
    0.287*346.02 parsecs = 99.31 parsecs.
  4. ^ See the TheSkyLive page about 35 Leonis, which has a nearly identical apparent magnitude.
  5. ^ The Sun's effective temperature is 5778 K.
  6. ^ From a logarithm of -0.34
  7. ^ a b See the color index article

References[edit]

  1. ^ a b c d e f g h i j k "BD+01 1148". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved May 6, 2024.
  2. ^ a b c d e f g h 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. doi:10.1051/0004-6361/201833111. ISSN 0004-6361. Data about this star is avaliable here at VizieR.
  3. ^ a b c d e f g h i j k l m n o 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: 513–537. doi:10.1086/342942. ISSN 0067-0049.
  4. ^ a b c d van Leeuwen, Floor (13 August 2007). "Validation of the new Hipparcos reduction". Astronomy & Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. eISSN 1432-0746. ISSN 0004-6361. Hipparcos record for this source at VizieR.
  5. ^ 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. doi:10.1007/BF02709763. ISSN 0250-6335.
  6. ^ 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. doi:10.1111/j.1365-2966.2012.21873.x. ISSN 0035-8711. Data about this star is avaliable here at VizieR.
  7. ^ 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. doi:10.1051/0004-6361/201628497. ISSN 0004-6361. Data about this star is avaliable here at VizieR.
  8. ^ a b Hekker, S.; Meléndez, J. (2007-12-01). "Precise radial velocities of giant stars. III. Spectroscopic stellar parameters". Astronomy and Astrophysics. 475: 1003–1009. arXiv:0709.1145. doi:10.1051/0004-6361:20078233. ISSN 0004-6361. Data about this star is avaliable here at VizieR.
  9. ^ 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. ISSN 0004-6361. Data is avaliable here at VizieR.
  10. ^ 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: 433–460. doi:10.1051/aas:1999401. ISSN 0365-0138.
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