HD 93521

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HD 93521
HD93521LightCurve.png
A light curve for HD 93521, plotted from TESS data [1]
Observation data
Epoch J2000.0       Equinox J2000.0
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  mas/yr [3]
Dec.: −1.398  mas/yr [3]
Parallax (π)0.6577 ± 0.0333  mas [3]
Distance 5,000 ± 300  ly
(1,520 ± 80  pc)
Details [7]
Mass 17  M☉
Radius Polar: 6.1±0.3 R☉
Equator: 7.4±0.4  R☉
Luminosity 39,800+10,300
−8,200  L☉
Surface gravity (log g)Polar: 4.1±0.4 cgs
Equator: 3.7±0.4  cgs
Temperature Polar: 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
SIMBAD data

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]

Related Research Articles

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<span class="mw-page-title-main">Extinction (astronomy)</span> Interstellar absorption and scattering of light

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<span class="mw-page-title-main">27 Aquilae</span> Star in the constellation Aquila

27 Aquilae is a star in the equatorial constellation of Aquila. 27 Aquilae is its Flamsteed designation though it also bears the Bayer designation d Aquilae. It has an apparent visual magnitude of 5.49, which is faintly visible to the naked eye. Based upon parallax measurements made during the Hipparcos mission, this star is at a distance of 440 light-years from Earth, give or take a 20 light-year margin of error. At this distance, the brightness of the star is diminished from extinction caused by interstellar gas and dust.

<span class="mw-page-title-main">Alpha Camelopardalis</span> Star in the constellation Camelopardalis

Alpha Camelopardalis, Latinized from α Camelopardalis, is a star in the northern constellation of Camelopardalis. With an apparent visual magnitude of 4.3, it is the third-brightest star in this not-very-prominent circumpolar constellation; the first and second-brightest stars being Beta Camelopardalis and CS Camelopardalis, respectively. It is the farthest constellational star, with a distance of approximately 6,000 light-years from Earth based on parallax measurements.

<span class="mw-page-title-main">Rho Leonis</span> Variable Star in the constellation Leo

Rho Leonis is a binary star in the zodiac constellation of Leo, and, like the prominent nearby star Regulus, is near the ecliptic. With an apparent visual magnitude of 3.9, this star can be readily seen with the naked eye. Parallax measurements give a distance estimate of about 5,400 light-years from the Earth. Rho Leonis is an Alpha Cygni-type variable star, showing 0.032 magnitude brightness variations with a period of 3.427 days, in Hipparcos data.

<span class="mw-page-title-main">Kappa Cassiopeiae</span> Star in the constellation Cassiopeia

Kappa Cassiopeiae is a star in the constellation Cassiopeia.

<span class="mw-page-title-main">19 Cephei</span> Star in the constellation Cepheus

19 Cephei is a supergiant star in the northern circumpolar constellation of Cepheus. It has a spectral class of O9 and is a member of Cep OB2, an OB association of massive stars located about 615 parsecs (2,010 ly) from the Sun.

<span class="mw-page-title-main">HD 34626</span> Star in the constellation Auriga

HD 34626, also known as MZ Aurigae, is an unusual variable star in the northern constellation of Auriga. It has an apparent magnitude of 8.2 and is about 3,300 light years away.

15 Sagittarii is a blue-hued binary star system in the southern zodiac constellation of Sagittarius. The estimated distance based upon photometry is around 4,200 ly (1,300 pc). It is faintly visible to the naked eye with an apparent visual magnitude of 5.37. The system is moving closer to the Sun with a heliocentric radial velocity of around −6 km/s.

<span class="mw-page-title-main">111 Tauri</span> Wide binary star system in the constellation Taurus

111 Tauri is a wide binary star system in the constellation Taurus. It is located at a distance of 48 light years from the Sun. Primary component A is a main sequence star with a stellar classification of F8V. The secondary component B is a K-type main sequence star. The primary is larger and more luminous than the Sun, with about 130% of the Sun's radius and 185% of the Sun's luminosity. The apparent magnitude of 5.0 indicates it is a faint star that can be viewed by the naked eye under good, dark-sky conditions.

Theta<sup>2</sup> Orionis Star in the constellation Orion

Theta2 Orionis is a multiple star system in the constellation Orion. It is a few arc minutes from its more famous neighbour the Trapezium Cluster, also known as θ1 Orionis.

<span class="mw-page-title-main">TU Muscae</span> Star in the constellation Musca

TU Muscae, also known as HD100213, is an eclipsing binary star in the constellation Musca. Its apparent magnitude ranges from 8.17 to 8.75 over around 1.4 days.

WR 135 is a variable Wolf-Rayet star located around 6,000 light years away from Earth in the constellation of Cygnus, surrounded by a faint bubble nebula blown by the intense radiation and fast wind from the star. It is just over four times the radius of the sun, but due to a temperature of 63,000 K it is 250,000 times as luminous as the sun.

<span class="mw-page-title-main">WR 1</span> Star in the constellation Cassiopeia

WR 1 is a Wolf-Rayet star located around 10,300 light years away from Earth in the constellation of Cassiopeia. It is only slightly more than twice the size of the sun, but due to a temperature over 100,000 K it is over 758,000 times as luminous as the sun.

LoTr 5 is a large, faint planetary nebula in the constellation of Coma Berenices. In 2018, its parallax was measured by Gaia, giving a distance of about 1,650 light-years.

<span class="mw-page-title-main">HD 73882</span> Eclipsing binary system in constellation Vela

HD 73882 is a visual binary system with the components separated by 0.6″ and a combined spectral class of O8. One of stars is an eclipsing binary system. The period of variability is listed as both 2.9199 days and 20.6 days, possibly due to the secondary being a spectroscopic binary star.

<span class="mw-page-title-main">SZ Tauri</span> Variable star in Taurus

SZ Tauri is a variable star in the equatorial constellation of Taurus. The brightness of this star varies from an apparent visual magnitude of 6.39 down to 6.69 with a period of 3.149 days, which is near the lower limit of visibility to the naked eye. The distance to this star is approximately 2,070 light years based on parallax measurements. There is some indication this may be a binary system, but the evidence is inconclusive.

<span class="mw-page-title-main">SY Equulei</span> High galactic latitude β Cephei variable

SY Equulei, also known as HD 203664, is a single variable star located in the equatorial constellation Equuleus. It has an average apparent magnitude of about 8.5, varying by a few hundredths of a magnitude, making it readily visible in binoculars and small telescopes, but not to the naked eye. The star is relatively far away at a distance of 8,000 light years and is receding with a heliocentric radial velocity of 48 km/s. At that distance, SY Equulei is dimmed by 0.19 magnitudes due to interstellar dust.

<span class="mw-page-title-main">X Cygni</span> Variable star in the constellation Cygnus

X Cygni is a variable star in the northern constellation of Cygnus, abbreviated X Cyg. This is a Delta Cephei variable that ranges in brightness from an apparent visual magnitude of 5.85 down to 6.91 with a period of 16.386332 days. At it brightest, this star is dimly visible to the naked eye. The distance to this star is approximately 628 light years based on parallax measurements. It is drifting further away with a radial velocity of 8.1 km/s. This star is a likely member of the open cluster Ruprecht 173.

HD 116852, also known as HIP 65890, is a solitary, whitish-blue-hued star located in the southern circumpolar constellation Chamaeleon. It has an apparent magnitude of 8.47, making it readily visible in binoculars but not to the naked eye. The star is located relatively far at a distance of 6,310 parsecs but is drifting closer with a heliocentric radial velocity of −47 km/s. At its current distance, HD 116852's brightness is diminished by 0.67 magnitudes due to extinction from interstellar dust. It has an absolute bolometric magnitude of −9.0.

References

  1. ↑ MAST: Barbara A. Mikulski Archive for Space Telescopes, Space Telescope Science Institute, retrieved 19 September 2022.
  2. 1 2 3 4 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. 1 2 3 4 5 6 Brown, A. G. A.; et al. (Gaia collaboration) (2021), "Gaia Early Data Release 3: Summary of the contents and survey properties", Astronomy & Astrophysics , 649: A1, arXiv: 2012.01533 , Bibcode:2021A&A...649A...1G, doi: 10.1051/0004-6361/202039657 , S2CID   227254300 (Erratum:  doi:10.1051/0004-6361/202039657e). 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, arXiv: 1101.4002 , Bibcode:2014MNRAS.441..910R, doi:10.1088/0067-0049/193/2/24, S2CID   119248206, 24.
  5. ↑ Münch, Guido; Zirin, Harold (January 1961), "Interstellar Matter at Large Distances from the Galactic Plane", Astrophysical Journal, 133: 11, Bibcode:1961ApJ...133...11M, doi:10.1086/146999.
  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, arXiv: 1606.08053 , Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID   119231169.
  7. 1 2 3 4 5 Gies, Douglas R.; et al. (February 2022), "The Transformative Journey of HD 93521", The Astronomical Journal, 163 (2): 7, arXiv: 2112.08235 , Bibcode:2022AJ....163..100G, doi: 10.3847/1538-3881/ac43be , S2CID   245144736, 100.
  8. ↑ "HD 93521", SIMBAD , Centre de données astronomiques de Strasbourg , retrieved 2022-05-07.
  9. 1 2 3 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, arXiv: 1209.2606 , Bibcode:2012A&A...546A..77R, doi:10.1051/0004-6361/201219865, S2CID   54618518, A77.
  10. 1 2 3 4 5 6 7 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, arXiv: 0806.3640 , Bibcode:2008A&A...487..659R, doi:10.1051/0004-6361:200810002, S2CID   18164022.
  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, arXiv: 1403.7843 , Bibcode:2014MNRAS.441..910R, doi: 10.1093/mnras/stu619 .
  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, 26, American Astronomical Society, 184th AAS Meeting, id.31.07: 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, arXiv: astro-ph/0006294 , Bibcode:2000A&AS..143..193B, doi:10.1051/aas:2000176, S2CID   17500722.

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