Astronomy:HD 93521

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Short description: Star in the constellation Leo Minor
HD 93521
HD93521LightCurve.png
A light curve for HD 93521, plotted from TESS data[1]
Observation data
Equinox J2000.0]] (ICRS)
Constellation Leo Minor[2]
Right ascension  10h 48m 23.511s[3]
Declination 37° 34′ 13.08″[3]
Apparent magnitude (V) 7.03[2]
Characteristics
Spectral type O9.5IIInn[4] or O9.5Vp[5]
B−V color index −0.227±0.007[2]
Astrometry
Radial velocity (Rv)−14.1±3.2[6] km/s
Proper motion (μ) RA: −0.162[3] mas/yr
Dec.: −1.398[3] mas/yr
Parallax (π)0.6577 ± 0.0333[3] mas
Distance5,000 ± 300 ly
(1,520 ± 80 pc)
Details[7]
Mass17 M☉
RadiusPolar: 6.1±0.3 R☉
Equator: 7.4±0.4 R☉
Luminosity39,800+10,300
−8,200 L☉
Surface gravity (log g)Polar: 4.1±0.4 cgs
Equator: 3.7±0.4 cgs
TemperaturePolar: 34,600±1,200 K
Equator: 28,700±1,200 K
Rotational velocity (v sin i)435±20 km/s
Age<34[7] Myr
Other designations
BD+38°2179, GC 14866, HD 93521, HIP 52849, SAO 62257, PPM 75477[8]
Database references
SIMBADdata

HD 93521 is a single,[9] massive star in the northern constellation of Leo Minor. With an apparent visual magnitude of 7.03,[2] it is too faint to be seen with the naked eye. The star is located at a distance of approximately 5.0 kilolight-years (1.52 kpc) from the Sun based on parallax measurements.[3] It is positioned at a high galactic latitude of +62°[10] and is located about 4.6 kilolight-years (1.4 kpc) above the Galactic plane.[10]

The spectrum of this star matches an O-type main-sequence star with a stellar classification of O9.5V.[10] It is unusual for a star of this class to have formed so far away from the galaxy's star forming regions.[9] Absorption lines in its spectrum indicate a metallicity that is inconsistent with being a population II star,[10] which are typically found in the galaxy halo. Likewise, HD 93521 is unlikely to be a runaway star or a hot subdwarf, either of which could explain its remote location. It may instead be a blue straggler that was formed as a result of a merger.[9] The resulting star likely began as a close binary system of lower mass, longer-lived stars that were ejected from the galactic disk. The merger would then have reset the evolutionary clock, producing a hotter, shorter-lived star.[7]

HD 93521 is one of the most rapidly rotating stars known,[11] with estimates of its projected rotational velocity ranging from 390[10] up to 435 km/s.[7] This is at least 90% of the star's breakup velocity, assuming it is being viewed from along the equator.[10] The rapid spin is creating an equatorial bulge with the radius at the equator being an estimated 7.4 times the Sun's radius while the polar radius is 6.1 times that of the Sun. Due to gravity darkening, the surface temperature at the poles is 34,600 K while the temperature at the equator is only 28,700 K.[7]

The star may be undergoing mass loss from its stellar wind[12] and have an equatorial disk of orbiting gas. The star shows evidence of non-radial pulsations, which may be the result of a more rapidly rotating core.[10]

The brightness, position, and rapid rotation of this star makes it particularly suited to examining the interstellar gas in the Milky Way halo.[13]

References

  1. ↑ MAST: Barbara A. Mikulski Archive for Space Telescopes, Space Telescope Science Institute, https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html, retrieved 19 September 2022. 
  2. ↑ 2.0 2.1 2.2 2.3 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 Brown, A. G. A. (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics 649: A1. doi:10.1051/0004-6361/202039657. Bibcode: 2021A&A...649A...1G.  Gaia EDR3 record for this source at VizieR.
  4. ↑ Sota, A. et al. (April 2011), "The Galactic O-Star Spectroscopic Survey. I. Classification System and Bright Northern Stars in the Blue-violet at R ~ 2500", The Astrophysical Journal Supplement 193 (2): 50, doi:10.1088/0067-0049/193/2/24, 24, Bibcode: 2014MNRAS.441..910R. 
  5. ↑ Münch, Guido; Zirin, Harold (January 1961), "Interstellar Matter at Large Distances from the Galactic Plane", Astrophysical Journal 133: 11, doi:10.1086/146999, Bibcode: 1961ApJ...133...11M. 
  6. ↑ Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system", Astronomy Letters 32 (11): 759–771, doi:10.1134/S1063773706110065, Bibcode: 2006AstL...32..759G. 
  7. ↑ 7.0 7.1 7.2 7.3 7.4 Gies, Douglas R. et al. (February 2022), "The Transformative Journey of HD 93521", The Astronomical Journal 163 (2): 7, doi:10.3847/1538-3881/ac43be, 100, Bibcode: 2022AJ....163..100G. 
  8. ↑ "HD 93521". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+93521. 
  9. ↑ 9.0 9.1 9.2 Rauw, G.; Morel, T.; Palate, M. (October 2012), "The nature of the high Galactic latitude O-star HD 93521: new results from X-ray and optical spectroscopy", Astronomy & Astrophysics 546: 12, doi:10.1051/0004-6361/201219865, A77, Bibcode: 2012A&A...546A..77R. 
  10. ↑ 10.0 10.1 10.2 10.3 10.4 10.5 10.6 Rauw, G. et al. (August 2008), "Spectroscopic and photometric variability of the O9.5 Vp star HD 93521", Astronomy and Astrophysics 487 (2): 659–670, doi:10.1051/0004-6361:200810002, Bibcode: 2008A&A...487..659R. 
  11. ↑ Ramiaramanantsoa, Tahina et al. (June 2014), "MOST detects corotating bright spots on the mid-O-type giant ξ Persei", Monthly Notices of the Royal Astronomical Society 441 (1): 910–917, doi:10.1093/mnras/stu619, Bibcode: 2014MNRAS.441..910R. 
  12. ↑ Bjorkman, J. E.; Ignace, R.; Tripp, T. M.; Cassinelli, J. P. (May 1994), "Evidence for a Disk in the Wind of {HD93521}: UV Line Profiles from an Axisymmetric Model", Bulletin of the American Astronomical Society (American Astronomical Society, 184th AAS Meeting, id.31.07) 26: 909, Bibcode: 1994AAS...184.3107B. 
  13. ↑ Barnstedt, J.; Gringel, W.; Kappelmann, N.; Grewing, M. (April 2000), "The ORFEUS II Echelle spectrum of HD 93521: A reference for interstellar molecular hydrogen", Astronomy and Astrophysics Supplement 143 (2): 193–210, doi:10.1051/aas:2000176, Bibcode: 2000A&AS..143..193B. 

Further reading

  • Rzaev, A. Kh.; Panchuk, V. E. (March 2008), "Variability of HeII and hydrogen line profiles in the spectrum of HD 93521", Astronomy Reports 52 (3): 237–246, doi:10.1134/S1063772908030062, Bibcode: 2008ARep...52..237R. 
  • Rzaev, A. Kh. (December 2007), "Some features of the radial-velocity variations of lines of different intensity in the spectrum of HD 93521. Variability of the stellar wind", Astrophysical Bulletin 62 (4): 331–338, doi:10.1134/S1990341307040049, Bibcode: 2007AstBu..62..331R. 
  • Danezis, A.; Antoniou, E.; Lyratzi, E.; Nikolaidis, D.; Popović, L. C.; Dimitrijević, M. S.; Theodossiou, E. (July 2007), Gómez de Castro, Ana I.; Barstow, Martin A., eds., "Long term variability of the coronal and post - coronal C IV region of the Oe star HD 93521", UV Astronomy: Stars from Birth to Death. Proceedings of the Joint Discussion n.4 during the IAU general Assembly of 2006: p. 113, ISBN 978-84-7491-852-6, Bibcode: 2007uasb.conf..113D, https://www.academia.edu/download/38205976/UVAstronomyJD04_113_2007.pdf, retrieved 2022-05-08. [|permanent dead link|dead link}}]
  • Kruk, J. W.; Oliveira, C.; Sembach, K. R.; Savage, B. D. (June 2006), Sonneborn, G.; Moos, H.; Andersson, B-G, eds., "Abundances of D, O, and other species towards the Halo Star HD 93521", Astrophysics in the Far Ultraviolet: Five Years of Discovery with FUSE. Proceedings of the Conference held 2-6 August, 2004 in Victoria, British Columbia, Canada, ASP Conference Series 348: p. 85, Bibcode: 2006ASPC..348...85K. 
  • Rzaev, A. Kh.; Panchuk, V. E. (January 2006), "Variability of the HeI line profiles in the spectrum of the hot O9.5V star HD 93521", Astronomy Reports 50 (1): 31–42, doi:10.1134/S1063772906010045, Bibcode: 2006ARep...50...31R. 
  • Kruk, J. W.; Oliveira, C.; Sembach, K. R.; Savage, B. D. (December 2003), "FUSE Observations of the Halo Star HD 93521", Bulletin of the American Astronomical Society 35: 1379, Bibcode: 2003AAS...20311008K. 
  • Hausen, N. R.; Reynolds, R. J.; Haffner, L. M.; Tufte, S. L. (February 2002), "Interstellar Hα Line Profiles toward HD 93521 and the Lockman Window", The Astrophysical Journal 565 (2): 1060–1068, doi:10.1086/324692, Bibcode: 2002ApJ...565.1060H. 
  • Gringel, W.; Barnstedt, J.; de Boer, K. S.; Grewing, M.; Kappelmann, N.; Richter, P. (June 2000), "ORFEUS II Echelle spectra: molecular hydrogen at high velocities toward HD 93521", Astronomy and Astrophysics 358: L37–L40, Bibcode: 2000A&A...358L..37G. 
  • Howarth, Ian D.; Townsend, R. H. D.; Clayton, M. J.; Fullerton, A. W.; Gies, D. R.; Massa, D.; Prinja, R. K.; Reid, A. H. N. (June 1998), "Time-dependent structure in ultraviolet absorption lines of the rapid rotators HD 64760 (B0Ib) and HD 93521 (O9.5V)", Monthly Notices of the Royal Astronomical Society 296 (4): 949–960, doi:10.1046/j.1365-8711.1998.01437.x, Bibcode: 1998MNRAS.296..949H. 
  • Massa, Derck (January 1995), "HD 93521, zeta Ophiuchi, and the Effects of Rapid Rotation on the Atmospheres and Winds of O9.5 V Stars", Astrophysical Journal 438: 376, doi:10.1086/175081, Bibcode: 1995ApJ...438..376M. 
  • Reid, A. H. N.; Bohlender, D.; Bolton, C. T.; Fullerton, A. W.; Howarth, I. D.; Manz, C.; Smith, K. C.; Townsend, R. H. D. (1995), Stobie, R. S.; Whitelock, P. A., eds., "Two Modes of Pulsation in the Rapidly Rotating O9.5 Dwarf, HD 93521", Astrophysical applications of stellar pulsation. Astronomical Society of the Pacific Conference Series; Proceedings of IAU Colloquium 155 held in Cape Town; South Africa; 6-10 February 1995 (San Francisco: Astronomical Society of the Pacific (ASP)) 83: p. 309, Bibcode: 1995ASPC...83..309R. 
  • Fullerton, A. W.; Gies, D. R.; Bolton, C. T. (1994), Balona, Luis A.; Henrichs, Huib F.; Le Contel, Jean Michel, eds., "Photospheric and circumsteliar variability of the rapidly rotating O star HD 93521", Pulsation; rotation; and mass loss in early-type stars: proceedings of the 162nd symposium of the International Astronomical Union held in Antibes; Juan-les-Pins; France; October 5-8; 1993 (Dordrecht: Kluwer Academic Publishers) 162: p. 114, Bibcode: 1994IAUS..162..114F. 
  • Howarth, Ian D.; Reid, Andy H. N. (November 1993), "UES and IUE observations of the O9.5V star HD 93521 : non-radial pulsatutions, wind and distance", Astronomy and Astrophysics 279: 148–162, Bibcode: 1993A&A...279..148H. 
  • Spitzer, Lyman, Jr.; Fitzpatrick, Edward L. (May 1993), "Composition of Interstellar Clouds in the Disk and Halo. I. HD 93521", Astrophysical Journal 409: 299, doi:10.1086/172664, Bibcode: 1993ApJ...409..299S. 
  • Spitzer, Lyman, Jr.; Fitzpatrick, Edward L. (May 1992), "Highly Ionized Atoms toward HD 93521", Astrophysical Journal Letters 391: L41, doi:10.1086/186394, Bibcode: 1992ApJ...391L..41S. 
  • Massa, D. (1992), "The Cylindrically Symmetric Wind of HD 93521 (Contributed Poster)", in Drissen, Laurent; Leitherer, Claus, Nonisotropic and Variable Outflows from Stars, ASP Conference Series, 22, p. 84, Bibcode: 1992ASPC...22...84M. 
  • Lennon, D. J.; Dufton, P. L.; Keenan, F. P.; Holmgren, D. E. (June 1991), "On the nature of HD 93521, a high galactic latitude O-star", Astronomy and Astrophysics 246: 175, Bibcode: 1991A&A...246..175L. 
  • Irvine, Nelson J. (February 1989), "HD 93521: A High-Latitude Shell Star", Astrophysical Journal Letters 337: L33, doi:10.1086/185372, Bibcode: 1989ApJ...337L..33I. 
  • Ramella, M.; Morossi, C.; Santin, P. (October 1980), "Ultraviolet observations of the blue halo star : HD 93521.", Astronomy and Astrophysics 90: 146–150, Bibcode: 1980A&A....90..146R. 
  • Bisiacchi, G. F.; Carrasco, L.; Costero, R.; Firmani, C. (April 1978), "Spectroscopic observations of HD 93521: an O-type star of population II.", Revista Mexicana de Astronomía y Astrofísica 2: 309–317, Bibcode: 1978RMxAA...2..309B. 
  • Hack, M.; Yilmaz, N. (May 1977), "The High-Galactic-Latitude O-Type Star HD 93521", Astrophysics and Space Science 48 (2): 483–489, doi:10.1007/BF00648132, Bibcode: 1977Ap&SS..48..483H. 
  • Munch, Guido (December 1952), "Interstellar Lines in the spectrum of the high-galactic-latitude star HD 93521", Publications of the Astronomical Society of the Pacific 64 (381): 312–315, doi:10.1086/126507, Bibcode: 1952PASP...64..312M. 




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