38 Boötis

38 Boötis is a single[8] star in the northern constellation of Boötes,[1] located approximately 157 light years from the Sun.[1] It has the traditional name Merga[9] /ˈmɜːrɡə/ and the Bayer designation h Boötis; 38 Boötis is the star's Flamsteed designation. This object is visible to the naked eye as a dim, yellow-white hued star with an apparent visual magnitude of 5.76.[2] It is moving closer to the Earth with a heliocentric radial velocity of −4.5 km/s.[2]

38 Boötis
Observation data
Epoch J2000      Equinox J2000
Constellation Boötes
Right ascension 14h 49m 18.67062s[1]
Declination +46° 06′ 58.3369″[1]
Apparent magnitude (V) 5.76[2]
Characteristics
Evolutionary stage subgiant[3]
Spectral type F6 IVs[4]
B−V color index 0.482±0.002[2]
Astrometry
Radial velocity (Rv)−4.5±0.2[2] km/s
Proper motion (μ) RA: –6.404[1] mas/yr
Dec.: −78.073[1] mas/yr
Parallax (π)20.7166 ± 0.0638[1] mas
Distance157.4 ± 0.5 ly
(48.3 ± 0.1 pc)
Absolute magnitude (MV)2.31[2]
Details
Mass1.60±0.04[5] M☉
Radius2.51+0.04
−0.08[1] R☉
Luminosity9.511±0.039[1] L☉
Surface gravity (log g)3.92±0.02[5] cgs
Temperature6,591±63[5] K
Metallicity [Fe/H]0.11±0.05[5] dex
Rotational velocity (v sin i)9.8[6] km/s
Age1.74+0.19
−0.10[5] Gyr
Other designations
Merga, Marrha, El Mara el Musalsela, Falx Italica, h Boötis, 38 Boo, BD+46°1993, FK5 1383, GC 19959, HD 130945, HIP 72487, HR 5533, SAO 45226[7]
Database references
SIMBADdata

This is a sharp-lined ('s') subgiant[3] star with a stellar classification of F6 IVs,[4] which indicates it has consumed the hydrogen at its core and is evolving off the main sequence. It is about 1.7[5] billion years old and is spinning with a relatively low projected rotational velocity of 10 km/s,[6] as indicated by the sharp lines. The star has 1.6[5] times the mass of the Sun and 2.5[1] times the Sun's radius. It is radiating 9.5[1] times the luminosity of the Sun from its photosphere at an effective temperature of 6,591 K.[5]

Nomenclature

It has the traditional name Merga, occasionally spelled Marrha[10][11] or in full El Mara el Musalsela,[11] from the Arabic المرأة المسلسلة al-mar’ah al-musalsalah "the chained woman". Another occasional name was Falx Italica,[11] from the Latin falx ītalica "billhook". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[12] to catalogue and standardize proper names for stars. The WGSN approved the name Merga for this star on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.[9]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
  3. do Nascimento, J. D., Jr.; et al. (July 2003), "On the link between rotation, chromospheric activity and Li abundance in subgiant stars", Astronomy and Astrophysics, 405 (2): 723–731, arXiv:astro-ph/0307196, Bibcode:2003A&A...405..723D, doi:10.1051/0004-6361:20030633, S2CID 1106754.
  4. Gray, R. O.; et al. (2001), "The Physical Basis of Luminosity Classification in the Late A-, F-, and Early G-Type Stars. I. Precise Spectral Types for 372 Stars", The Astronomical Journal, 121 (4): 2148, Bibcode:2001AJ....121.2148G, doi:10.1086/319956.
  5. Aguilera-Gómez, Claudia; et al. (June 2018), "Lithium abundance patterns of late-F stars: an in-depth analysis of the lithium desert", Astronomy & Astrophysics, 614: 15, arXiv:1803.05922, Bibcode:2018A&A...614A..55A, doi:10.1051/0004-6361/201732209, S2CID 62799777, A55.
  6. Schröder, C.; et al. (January 2009), "Ca II HK emission in rapidly rotating stars. Evidence for an onset of the solar-type dynamo", Astronomy and Astrophysics, 493 (3): 1099–1107, Bibcode:2009A&A...493.1099S, doi:10.1051/0004-6361:200810377.
  7. "38 Boo". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved May 12, 2019.
  8. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
  9. Naming Stars, IAU.org, retrieved 16 December 2017.
  10. Bakich, Michael E. (1995), The Cambridge Guide to the Constellations, Cambridge University Press, ISBN 9780521449212.
  11. Dolan, Christopher J, Merga, retrieved 2016-06-24.
  12. IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.
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