# Astronomy:HD 150136

Short description: Binary star in the constellation Ara
Observation dataEquinox J2000.0]] (ICRS) Constellation Location of HD 150136 (circled) Ara 16h 41m 20.42426s[1] −48° 45′ 46.7490″[1] 5.54[2] O3 V((f*)) - O3.5 V((f+)) + O5.5-6 V((f)) + O6.5-7 V((f))[3] −0.76[2] +0.20[2] Radial velocity (Rv) −27[4] km/s Proper motion (μ) RA: +9.73[1] mas/yr Dec.: −7.31[1] mas/yr Parallax (π) −3.11 ± 2.94[1] mas Distance 4,310 ± 390 ly (1,320 ± 120 pc)[5] ly Absolute magnitude (MV) −6.47 (−5.91 + −4.90 + −4.44)[3] Primary Primary Companion Secondary Period (P) 2.67454 days Semi-major axis (a) 38.2 R☉[3] Eccentricity (e) 0 Inclination (i) 49.6° Semi-amplitude (K1)(primary) 208.3 km/s Semi-amplitude (K2)(secondary) 334.5 km/s Primary Primary/Secondary Companion Tertiary Period (P) 3,008 days Semi-major axis (a) 20.9 AU Eccentricity (e) 0.73 Inclination (i) 107.9° Semi-amplitude (K1)(primary) 25.8 km/s Semi-amplitude (K2)(secondary) 79.8 km/s Mass 63[5] M☉ Radius 12.13 R☉ Luminosity 724,000 L☉ Surface gravity (log g) 4.00 cgs Temperature 46,500 K Rotational velocity (v sin i) 171 km/s Mass 40[5] M☉ Radius 9.54 R☉ Luminosity 209,000 L☉ Surface gravity (log g) 4.00 cgs Temperature 40,000 K Rotational velocity (v sin i) 136 km/s Age 0-2 Myr Mass 33[5] M☉ Radius 8.24 R☉ Luminosity 102,000 L☉ Surface gravity (log g) 3.50 cgs Temperature 36,000 K Rotational velocity (v sin i) 72 km/s Age 1-3 Myr HD 150136, CD−48°11070, HIP  81702, HR 6187, SAO 227049, WDS J16413-4846 SIMBAD data

HD 150136 is a multiple star system in the southern constellation of Ara, around 4,300 light years away. It is the brightest member of the faint open cluster NGC 6193, part of the Ara OB1 association.

## System

HD 150136 is listed in the Washington Double Star Catalog as having seven visual components within 30 arc seconds. Component A is a close triple system containing three massive class O main sequence stars. The brightest companion is catalogued individually as HD 150135 as well as component C of the multiple system, separated by only 10 arc-seconds. It is another O class spectroscopic binary and also a member of NGC 5193. The other stars are all 10th to 12th magnitude, similar to many other stars known to be members of NGC 6193.[6]

The primary star consists of a double-lined spectroscopic binary[4] with a more distant tertiary companion. The third star is orbiting the other two with a period of 8.2 years, an eccentricity of 0.73, and an inclination of 108°. The close binary stars are separated by hardly more than their own diameters and orbit in less than 3 days, but the third is separated enough to have been resolved visually by VLTI. The measured separation in 2012 was 9 milli arc seconds, corresponding to 11-12 AU.[5]

## Properties

All three (four, including HD 150135) of the brightest stars are massive luminous O class main sequence stars, 33-63 times as massive as the sun. They are around 10 times the size of the sun, but 6-8 times hotter and each is over 100,000 times as luminous. The primary star is the closest O3 star to Earth, 46,500 K, visually 18,000 times as bright as the sun, but because of its high temperature it is around three quarters of a million times more luminous including all wavelengths.[3]

## References

1. van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. doi:10.1051/0004-6361:20078357. Bibcode2007A&A...474..653V.
2. Schild, R. E. et al. (April 1983). "UBV photometry for southern OB stars". Astrophysical Journal Supplement Series 51: 321–336. doi:10.1086/190852. Bibcode1983ApJS...51..321S.
3. Mahy, L.; Gosset, E.; Sana, H.; Damerdji, Y.; De Becker, M.; Rauw, G.; Nitschelm, C. (2012). "Evidence for a physically bound third component in HD 150136". Astronomy & Astrophysics 540: A97. doi:10.1051/0004-6361/201118199. Bibcode2012A&A...540A..97M.
4. Pourbaix, D. et al. (2004). "SB9: The ninth catalogue of spectroscopic binary orbits". Astronomy & Astrophysics 424 (2): 727–732. doi:10.1051/0004-6361:20041213. Bibcode2004A&A...424..727P.
5. Sana, H. et al. (May 2013). "Three-dimensional orbits of the triple-O stellar system HD 150136". Astronomy & Astrophysics 553: 5. doi:10.1051/0004-6361/201321189. A131. Bibcode2013A&A...553A.131S.
6. Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal 122 (6): 3466–3471. doi:10.1086/323920. Bibcode2001AJ....122.3466M.