HD 93250

Last updated
HD 93250
Carina Nebula by ESO.jpg
HD 93250 is the bright star just above and left of the centre of this image of the Carina Nebula, directly above the Keyhole Nebula.
Credit: ESO
Observation data
Epoch J2000       Equinox J2000
Constellation Carina
Right ascension 10h 44m 45.028s [1]
Declination −59° 33 54.68 [1]
Apparent magnitude  (V)7.41 [2]
Characteristics
Spectral type O4 IV(fc) [3]
U−B color index −0.85 [2]
B−V color index +0.17 [2]
Astrometry
Radial velocity (Rv)11.6 [4]  km/s
Proper motion (μ)RA: −7.116 [1]   mas/yr
Dec.: +3.081 [1]   mas/yr
Parallax (π)0.4115 ± 0.0199  mas [1]
Distance 7,900 ± 400  ly
(2,400 ± 100  pc)
Absolute magnitude  (MV)−6.14 [5]
Orbit [6]
Period (P)194.31±0.39  d
Semi-major axis (a)1.224±0.028  mas
Eccentricity (e)0.217±0.011
Inclination (i)22±41°
Longitude of the node (Ω)59±20°
Argument of periastron (ω)
(secondary)
171±24°
Details [5]
Radius 15.9  R
Luminosity 1,000,000  L
Surface gravity (log g)3.96  cgs
Temperature 46,000  K
Rotational velocity (v sin i)130 km/s
Age 1.3  Myr
A
Mass 49 [6]   M
Other designations
1E  104248-5918.0, XMMU  J104444.8-593354, ALS 1859, 2E  2317, HIP  52558, CD-58°3537, GC  14791, CGO  246, GCRV  25947, PPM  339400, Trumpler 16  180, SAO  238423, Trumpler 14  101, TYC  8626-2075-1, CPC  20°3140, GOS  G287.51-00.54 01, CPD 58°2661, GSC  08626-02075
Database references
SIMBAD data

HD 93250 is a highly luminous hot blue binary star in the Carina Nebula in the constellation Carina.

Contents

Location

HD 93250 is marked above centre in this mosaic of the Carina Nebula region. NGC 3372d.jpg
HD 93250 is marked above centre in this mosaic of the Carina Nebula region.

HD 93250 is one of the brightest stars in the region of the Carina Nebula. It is only 7.5 arc-minutes from the famous Eta Carinae2,350 [7] and HD 93250 is considered to be a member of the same loose open cluster Trumpler 16, although it appears closer to the more compact Trumpler 14. [8]

HD 93250 is in a region of the Carina Nebula with several bright stars, for example HD 93268 and HDE 303311, but relatively few faint stars. It has been proposed that these bright stars are the core of a separate cluster called Collinder 232, but the lack of any concentration of fainter stars in the area makes it more likely that Collinder 232 is not a real cluster and HD 93250 is just an outlying member of one of the more obvious clusters. [9]

Membership of Trumpler 16 constrains the distance and likely age of HD 93250. [5]

Spectrum

Although HD 93250 is known to be a binary star, individual spectra of the two components have never been observed, but they are thought to be very similar. The spectral type of HD 93250 has variously been given as O5, [10] O6/7, [11] O4, [12] and O3. [13] It has sometimes been classified as a main sequence star and sometimes as a giant star. [12] [13] The Galactic O-Star Spectroscopic Survey has used it as the standard star for the newly created O4 subgiant spectral type. [3]

Binary

HD 93250 is the brightest x-ray source in the Carina Nebula. [7] It has long been suspected that this is due to colliding winds in a close pair of hot luminous stars, but investigations have failed to show any significant radial velocity variations to support this. [4] One calculated orbit suggests that a small inclination means the radial velocity changes due to orbital motion will be too small to resolve given the type of spectrum of the two stars. [6]

In 2010, AMBER interferometry resolved HD 93250 into two separate stars. No relative motion or radial velocity variations could be detected and so the orbit and properties of the two stars is still uncertain. The projected separation of the stars is 1.5 mas, approximately 3.5 astronomical units. The two stars show no measurable colour difference and are both likely to be hot O stars with masses within 10% of each other. [7]

Properties

The physical properties of HD 93250 have only been calculated on the assumption that it is a single star. The temperature is around 50,000 K and its luminosity around 1,000,000 L Calculations of the mass have shown discrepancies between spectroscopic models and evolutionary models, which may be resolved by analysis of two separate stars in the system. [14]

See also

Related Research Articles

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<span class="mw-page-title-main">Trumpler 16</span> Massive open cluster in the constellation Carina

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<span class="mw-page-title-main">Trumpler 14</span> Open cluster in the constellation Carina

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c Ursae Majoris is the Bayer designation for a double-lined spectroscopic binary star system in the northern constellation of Ursa Major. It has an apparent visual magnitude of 5.18, which indicates that is visible to the naked eye. Parallax measurements yield an estimated distance of 66 light years from the Sun. The star is moving closer to the Earth with a heliocentric radial velocity of −14 km/s.

<span class="mw-page-title-main">HD 151932</span> Star in the constellation of Scorpius

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References

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