HD 130144

HD 130144 is a variable star in the northern constellation of Boötes. It has the variable star designation EK Boötis (or EK Boo), while HD 130144 is the designation from the Henry Draper Catalogue. The star is faintly visible to the naked eye with an apparent visual magnitude that ranges from 5.33 down to 5.71.[4] Parallax measurements provide a distance estimate of approximately 810 light years from the Sun. It is drifting closer with a radial velocity of −23 km/s.[7]

HD 130144

The visual band light curve of EK Boötes, from AAVSO data[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Boötes
Right ascension 14h 46m 05.94566s[2]
Declination +15° 07′ 54.4332″[2]
Apparent magnitude (V) 5.78[3] (5.33 to 5.71)[4]
Characteristics
Spectral type M5III[5]
U−B color index +1.26[6]
B−V color index 1.335±0.021[3]
Variable type Lb?[4]
Astrometry
Radial velocity (Rv)−22.52±0.65[7] km/s
Proper motion (μ) RA: −85.49[2] mas/yr
Dec.: +18.86[2] mas/yr
Parallax (π)4.04 ± 0.38 mas[2]
Distance810 ± 80 ly
(250 ± 20 pc)
Absolute magnitude (MV)−1.17[3]
Details
Mass3.1±0.5[5] M☉
Radius210±21[5] R☉
Luminosity521.51[3] L☉
Temperature3,400[5] K
Rotational velocity (v sin i)8.5 or 11[5] km/s
Other designations
EK Boo, BD+15° 2758, FK5 3168, HD 130144, HIP 72208, HR 5512, SAO 101200[8]
Database references
SIMBADdata

This is an aging red giant star with a stellar classification of M5III.[5] It has an estimated 3.1 times the mass of the Sun and has expanded to around 210 times the Sun's radius.[5] EK Boo is classified as a slow irregular variable that ranges in luminosity with an amplitude of 0.38 in magnitude and no apparent periodicity. This is an X-ray source, and was possibly the first M-type giant star to have a magnetic field directly detected.[9] The strength of the field ranges from –0.1 to 8 G.[10]

HD 130144 has a high rotation rate for a star of this class, which may be the result of dredge-up of angular momentum from the interior, or else a merger with an orbiting companion.[10] A long-term trend in the radial velocity data suggests this star has an orbiting companion. Most likely this is an active red dwarf that is responsible for most of the X-ray emission from the system.[9] There is nearby visual companion at an angular separation of 0.20″ along a position angle of 82.2° (as of 2010).[11]

References
  1. "Download Data". aavso.org. AAVSO. Retrieved 1 October 2021.
  2. van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
  3. 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.
  4. Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  5. Konstantinova-Antova, R.; et al. (December 2010), "Direct detection of a magnetic field in the photosphere of the single M giant EK Bootis. How common is magnetic activity among M giants?", Astronomy and Astrophysics, 524: 9, arXiv:1009.2001, Bibcode:2010A&A...524A..57K, doi:10.1051/0004-6361/201014503, S2CID 119184105, A57.
  6. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data. SIMBAD, Bibcode:1986EgUBV........0M.
  7. Famaey, B.; et al. (2009), "Spectroscopic binaries among Hipparcos M giants,. I. Data, orbits, and intrinsic variations", Astronomy and Astrophysics, 498 (2): 627–640, arXiv:0901.0934, Bibcode:2009A&A...498..627F, doi:10.1051/0004-6361/200810698, S2CID 18739721.
  8. "EK Boo", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2021-04-30.
  9. Georgiev, S.; et al. (July 2020), "Magnetism in Cool Evolved Stars: the M giants EK Bootis and β Pegasi", Bulgarian Astronomical Journal, 33: 87, Bibcode:2020BlgAJ..33...87G.
  10. Konstantinova-Antova, Renada; Aurière, Michel; Schröder, Klaus-Peter; Petit, Pascal (April 2009), "Dynamo-generated magnetic fields in fast rotating single giants", Cosmic Magnetic Fields: From Planets, to Stars and Galaxies, Proceedings of the International Astronomical Union, IAU Symposium, vol. 259, pp. 433–434, arXiv:0901.1537, Bibcode:2009IAUS..259..433K, doi:10.1017/S1743921309031020, S2CID 119199670
  11. Horch, Elliott P.; et al. (February 2011), "Observations of Binary Stars with the Differential Speckle Survey Instrument. II. Hipparcos Stars Observed in 2010 January and June" (PDF), The Astronomical Journal, 141 (2): 13, Bibcode:2011AJ....141...45H, doi:10.1088/0004-6256/141/2/45, S2CID 27904496, 45.
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