R145

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R145
Grand star-forming region R136 in NGC 2070 (captured by the Hubble Space Telescope).jpg
R145 is the isolated bright star to the left of the image, near R136 (annotated at Commons)
Credit: NASA, ESA, F. Paresce (INAF-IASF, Bologna, Italy), R. O'Connell (University of Virginia, Charlottesville), and the Wide Field Camera 3 Science Oversight Committee
Observation data
Epoch J2000       Equinox J2000
Constellation Dorado
Right ascension 05h 38m 57.059s [1]
Declination −69° 06′ 05.70″ [1]
Apparent magnitude  (V)12.04 [2]
Characteristics
Spectral type WN6h + O3.5If*/WN7 [3]
U−B color index −0.79 [4]
B−V color index −0.01 [2]
Astrometry
Radial velocity (Rv)270 ± 5 [3]  km/s
Distance 163,000  ly
(49,970 [5]   pc)
Absolute magnitude  (MV)−7.21 + −7.43 [3]
Orbit [3]
Period (P)158.760
Semi-major axis (a)955 R☉
Eccentricity (e)0.788 ± 0.007
Inclination (i)39 ± 6°
Semi-amplitude (K1)
(primary)		96 ± 3 km/s
Semi-amplitude (K2)
(secondary)		95 ± 4 km/s
Details [3]
Primary
Mass 53+40
−20  M☉
Radius 20+6
−5  R☉
Luminosity 2,240,000+924,000
−654,000  L☉
Temperature 50,000 ± 3,000  K
Rotational velocity (v sin i)< 200 km/s
Secondary
Mass 54+40
−20  M☉
Radius 26+9
−7  R☉
Luminosity2,140,000+882,000
−624,000  L☉
Temperature 43,000 ± 3,000  K
Rotational velocity (v sin i)< 150 km/s
Age 2.2  Myr
Other designations
RMC 145, Brey  90, BAT99  119, VFTS  695, HD  269928, 2MASS  J05385706-6906055
Database references
SIMBAD data

R145 (HD 269928) is a spectroscopic binary star in the Tarantula Nebula in the Large Magellanic Cloud located in the constellation Dorado. Both components are amongst the most luminous known.

Contents

Observations

Zooming in to the NGC 2070 region. R145 is the bright isolated star to the left of the box in the middle panel. ESO - Eso1030a (by).jpg
Zooming in to the NGC 2070 region. R145 is the bright isolated star to the left of the box in the middle panel.

R145 is listed in the Henry Draper Catalogue with photographic magnitude 11.8. The spectral type is given as O which then included all types of hot stars showing emission lines. It is included in the first Henry Draper Extension volume published in 1925. [6]

In 1960 R145 was included in the Radcliffe Magellanic Catalogue of the brightest stars in the Magellanic Clouds with a somewhat uncertain WN6-7 spectral type. Stars in the catalogue are referred to by the acronym RMC and their catalogue entry number, or just R with the number. [7]

In the first catalogue of LMC Wolf-Rayet stars, R145 is listed as number 90 with spectral type WN7. Stars in this catalogue are referred to with the abbreviation Brey after the author Breysacher. [8] In the fourth catalogue published in 1999, it is listed as BAT99-119. [9]

In the Very Large Telescope FLAMES survey published in 2011, R145 was given the designation VFTS 695. It was given the spectral type WN6h to recognise that it retained a significant amount of hydrogen in its atmosphere. It was also recognised that there was a second luminous star in the system but a spectral type could not be determined for it. [10]

In 2016, the orbit and physical parameters of the two stars were calculated from FLAMES survey data. [3]

System

R145 is a double-lined spectroscopic binary system with an orbital period of 159 days. The two stars have an eccentric orbit with a separation varying from less than one AU to nearly eight AU. They have almost identical orbital velocities and hence very similar masses. The exact values depend on the inclination of the orbital plane. The inclination of the R145 orbit calculated using polarimetry is 39°. At this small inclination the formal error of 6° translates into considerable margins of error in the masses. Estimates of the masses of the two stars by other methods give larger values, suggesting that the inclination may be smaller than 39°. [3]

Components

The primary component of R145 is designated as the star which dominates the spectrum with its strong broad emission lines. It is a WN6h Wolf-Rayet star with a temperature of around 50,000 K. Although it has a WR spectral type, it is a relatively young star which still has about 40% hydrogen in its atmosphere. The atmospheric enhancement of helium and nitrogen is caused by strong convection and heavy mass loss produced by the high luminosity and probably by rapid rotation. [3]

The secondary component is actually marginally more massive and visually brighter than the primary. It has a lower temperature of about 43,000 K and a larger size at 26 R☉. Its bolometric. Its spectral type is given as O3.5If*/WN7. The bolometric luminosity of each star is over two million times greater than the sun. [3]

The masses of the primary and secondary determined from the calculated orbit are 53 M☉ and 54 M☉ respectively, but these depend strongly on the precise orbital inclination and both the masses are likely to be somewhere between 23 M☉ and 94 M☉. Calculation of spectral and evolutionary masses suggest that the two masses are both near 80 M☉. Then the ages of the stars are about 2.2 million years and their initial masses were 105 M☉ and 90 M☉. [3]

Related Research Articles

<span class="mw-page-title-main">Wolf–Rayet star</span> Heterogeneous stars with unusual spectra

Wolf–Rayet stars, often abbreviated as WR stars, are a rare heterogeneous set of stars with unusual spectra showing prominent broad emission lines of ionised helium and highly ionised nitrogen or carbon. The spectra indicate very high surface enhancement of heavy elements, depletion of hydrogen, and strong stellar winds. The surface temperatures of known Wolf–Rayet stars range from 20,000 K to around 210,000 K, hotter than almost all other kinds of stars. They were previously called W-type stars referring to their spectral classification.

<span class="mw-page-title-main">R136b</span> Star in the constellation Dorado

R136b is a Wolf–Rayet star in the R136 cluster in the Large Magellanic Cloud. It is one of the most massive and most luminous stars known. It is found in the dense R136 open cluster at the centre of NGC 2070 in the Tarantula Nebula.

<span class="mw-page-title-main">R136a1</span> Wolf–Rayet star with one of the highest mass and luminosity of any known star

R136a1 is one of the most massive and luminous stars known, at 196 M☉ and nearly 4.7 million L☉, and is also one of the hottest, at around 46,000 K. It is a Wolf–Rayet star at the center of R136, the central concentration of stars of the large NGC 2070 open cluster in the Tarantula Nebula in the Large Magellanic Cloud. The cluster can be seen in the far southern celestial hemisphere with binoculars or a small telescope, at magnitude 7.25. R136a1 itself is 100 times fainter than the cluster and can only be resolved using speckle interferometry.

<span class="mw-page-title-main">HD 5980</span> Triple star system in the constellation Tucana

HD 5980 is a multiple star system on the outskirts of NGC 346 in the Small Magellanic Cloud (SMC) and is one of the brightest stars in the SMC.

<span class="mw-page-title-main">AB7</span> Binary star in the Small Magellanic Cloud in the constellation Tucana

AB7, also known as SMC WR7, is a binary star in the Small Magellanic Cloud. A Wolf–Rayet star and a supergiant companion of spectral type O orbit in a period of 19.56 days. The system is surrounded by a ring-shaped nebula known as a bubble nebula.

<span class="mw-page-title-main">Melnick 42</span> Massive blue supergiant star in the constellation Dorado

Melnick 42 is a massive blue supergiant star in the Tarantula Nebula in the Large Magellanic Cloud located in the constellation Dorado. Although it is only 21 times the size of the sun, its high temperature of 47,300 K makes it one of the most luminous stars of the Tarantula Nebula at 3,600,000 L☉. It is less than two parsecs from the centre of the R136 cluster, although that is well outside the central core.

<span class="mw-page-title-main">WR 25</span> Binary star system in the constellation Carina

WR 25 is a binary star system in the turbulent star-forming region the Carina Nebula, about 6,800 light-years from Earth. It contains a Wolf-Rayet star and a hot luminous companion and is a member of the Trumpler 16 cluster. The name comes from the Catalogue of Galactic Wolf–Rayet Stars.

<span class="mw-page-title-main">R136a2</span> Star in the constellation Dorado

R136a2 is a Wolf-Rayet star residing near the center of the R136, the central concentration of stars of the large NGC 2070 open cluster in the Tarantula Nebula, a massive H II region in the Large Magellanic Cloud which is a nearby satellite galaxy of the Milky Way. It has one of the highest confirmed masses and luminosities of any known star, at about 151 M☉ and 3.5 million L☉ respectively.

<span class="mw-page-title-main">R136c</span> Star in the constellation Dorado

R136c is a star located in R136, a tight knot of stars at the centre of NGC 2070, an open cluster weighing 450,000 solar masses and containing 10,000 stars. At 142 M☉ and 3.8 million L☉, it is the one of the most massive stars known and one of the most luminous, along with being one of the hottest, at over 40,000 K. It was first resolved and named by Feitzinger in 1980, along with R136a and R136b.

HD 38282 is a massive spectroscopic binary star in the Tarantula Nebula, consisting of two hydrogen-rich Wolf-Rayet stars.

<span class="mw-page-title-main">R136a3</span> Star in the constellation Dorado

R136a3 is a Wolf–Rayet star in R136, a massive star cluster located in Dorado. It is located near R136a1, the most massive and luminous star known. R136a3 is itself one of the most massive and most luminous stars known at about 179 times more massive and 5 million times more luminous than the Sun.

<span class="mw-page-title-main">WR 148</span> Binary star in the constellation of Cygnus

WR 148 is a spectroscopic binary in the constellation Cygnus. The primary star is a Wolf–Rayet star and one of the most luminous stars known. The secondary has been suspected of being a stellar-mass black hole but may be a class O main sequence star.

<span class="mw-page-title-main">Melnick 34</span> Binary star in the Large Magellanic cloud

Melnick 34, also called BAT99-116, is a binary Wolf–Rayet star near R136 in the 30 Doradus complex in the Large Magellanic Cloud. Both components are amongst the most massive and most luminous stars known, and the system is the most massive known binary system.

BAT99-98 is a star in the Large Magellanic Cloud. It is located near the R136 cluster in the 30 Doradus nebula. At 226 M☉ and 5,000,000 L☉ it is one of the most massive and luminous stars known.

R99 is a star in the Large Magellanic Cloud in the constellation Dorado. It is classified as a possible luminous blue variable and is one of the most luminous stars known.

<span class="mw-page-title-main">AB8 (star)</span> Binary star located in the Small Magellanic Cloud in the constellation Hydrus

AB8, also known as SMC WR8, is a binary star in the Small Magellanic Cloud (SMC). A Wolf-Rayet star and a main sequence companion of spectral type O orbit in a period of 16.638 days. It is one of only nine known WO stars, the only Wolf-Rayet star in the SMC not on the nitrogen sequence, and the only Wolf-Rayet star in the SMC outside the main bar.

<span class="mw-page-title-main">WR 12</span> Star in the constellation Vela

WR 12 is a spectroscopic binary in the constellation Vela. It is an eclipsing binary consisting of a Wolf-Rayet star and a luminous companion of unknown spectral type. The primary is one of the most luminous stars known.

BAT99-7 is a WN-type Wolf-Rayet star located in the Large Magellanic Cloud, in the constellation of Dorado, about 160,000 light years away. The star has a spectrum containing extremely broad emission lines, and is the prototype for the "round line" stars, Wolf-Rayet stars whose spectra are characterized by strong and broad emission lines with round line profiles. The broad emission lines hint at an extremely high temperature of nearly 160,000 Kelvin, which would make it the hottest of all WN stars with known temperatures, as well as an extraordinarily large mass loss rate for a Wolf-Rayet star in the LMC, at 10−4.48 M☉/yr, which means that every 30,200 years, the star loses 1 solar mass worth of mass.

References

  1. 1 2 Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27. Bibcode:2000A&A...355L..27H. doi:10.1888/0333750888/2862. ISBN   0333750888.
  2. 1 2 Doran, E. I.; Crowther, P. A.; De Koter, A.; Evans, C. J.; McEvoy, C.; Walborn, N. R.; Bastian, N.; Bestenlehner, J. M.; Gräfener, G.; Herrero, A.; Köhler, K.; Maíz Apellániz, J.; Najarro, F.; Puls, J.; Sana, H.; Schneider, F. R. N.; Taylor, W. D.; Van Loon, J. Th.; Vink, J. S. (2013). "The VLT-FLAMES Tarantula Survey. XI. A census of the hot luminous stars and their feedback in 30 Doradus". Astronomy & Astrophysics. 558: A134. arXiv: 1308.3412 . Bibcode:2013A&A...558A.134D. doi:10.1051/0004-6361/201321824. S2CID   118510909.
  3. 1 2 3 4 5 6 7 8 9 10 Shenar, T.; et al. (2016). "The Tarantula Massive Binary Monitoring project: II. A first SB2 orbital and spectroscopic analysis for the Wolf-Rayet binary R145". Astronomy & Astrophysics. 598: A85. arXiv: 1610.07614 . Bibcode:2017A&A...598A..85S. doi:10.1051/0004-6361/201629621. S2CID   118546102.
  4. ↑ Feitzinger, J. V.; Isserstedt, J. (1983). "Photoelectric UBV-photometry of Wolf-Rayet stars in the Large Magellanic Cloud". Astronomy and Astrophysics Supplement Series. 51: 505. Bibcode:1983A&AS...51..505F.
  5. ↑ Pietrzyński, G; D. Graczyk; W. Gieren; I. B. Thompson; B. Pilecki; A. Udalski; I. Soszyński; et al. (7 March 2013). "An eclipsing-binary distance to the Large Magellanic Cloud accurate to two per cent". Nature. 495 (7439): 76–79. arXiv: 1303.2063 . Bibcode:2013Natur.495...76P. doi:10.1038/nature11878. PMID   23467166. S2CID   4417699.
  6. ↑ Cannon, A. J. (1925). "The Henry Draper extension". Annals of the Astronomical Observatory of Harvard College. 100: 17. Bibcode:1925AnHar.100...17C.
  7. ↑ Feast, M. W.; Thackeray, A. D.; Wesselink, A. J. (1960). "The brightest stars in the Magellanic Clouds". Monthly Notices of the Royal Astronomical Society. 121 (4): 337–385. Bibcode:1960MNRAS.121..337F. doi: 10.1093/mnras/121.4.337 .
  8. ↑ Breysacher, J. (1981). "Spectral Classification of Wolf-Rayet Stars in the Large Magellanic Cloud". Astronomy and Astrophysics Supplement. 43: 203. Bibcode:1981A&AS...43..203B.
  9. ↑ Breysacher, J.; Azzopardi, M.; Testor, G. (1999). "The fourth catalogue of Population I Wolf-Rayet stars in the Large Magellanic Cloud". Astronomy and Astrophysics Supplement. 137: 117–145. Bibcode:1999A&AS..137..117B. doi: 10.1051/aas:1999240 .
  10. ↑ Evans, C. J.; Taylor, W. D.; Hénault-Brunet, V.; Sana, H.; De Koter, A.; Simón-Díaz, S.; Carraro, G.; Bagnoli, T.; Bastian, N.; Bestenlehner, J. M.; Bonanos, A. Z.; Bressert, E.; Brott, I.; Campbell, M. A.; Cantiello, M.; Clark, J. S.; Costa, E.; Crowther, P. A.; De Mink, S. E.; Doran, E.; Dufton, P. L.; Dunstall, P. R.; Friedrich, K.; Garcia, M.; Gieles, M.; Gräfener, G.; Herrero, A.; Howarth, I. D.; Izzard, R. G.; et al. (2011). "The VLT-FLAMES Tarantula Survey. I. Introduction and observational overview". Astronomy & Astrophysics. 530: A108. arXiv: 1103.5386 . Bibcode:2011A&A...530A.108E. doi:10.1051/0004-6361/201116782. S2CID   54501763.
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