HD 15558

HD 15558 (HIP 11832) is a massive O-type multiple star system in Cassiopeia (constellation) and is specifically in our galaxy's Heart Nebula in open cluster IC 1805. The primary is a very massive star with 152 M☉ and 660,000 L☉.

HD 15558
An H-alpha image of the Heart Nebula. HD 15558 is located at the centre of the cluster, circled.
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cassiopeia
Right ascension 02h 32m 42.54s[1]
Declination 61° 27′ 21.58″[1]
Apparent magnitude (V) 7.87[2]
Characteristics
Spectral type O4.5III(f)[3] (O5.5III(f) + O7V[4])
U−B color index -0.55[2]
B−V color index +0.43[2]
V−R color index +0.38[2]
R−I color index +0.40[2]
J−H color index +0.18[2]
Astrometry
Radial velocity (Rv)-45.10±1.50[5] km/s
Proper motion (μ) RA: -1.60±1.50[1] mas/yr
Dec.: -2.50±1.50[1] mas/yr
Parallax (π)0.97 ± 1.17[1] mas
Distance7,500[4] ly
(2,300[4] pc)
Details
Mass>152 ± 51[4] M☉
Radius16.4[6] R☉
Luminosity~660,000[4] L☉
Surface gravity (log g)3.7[6] cgs
Temperature39,500[6] K
Age0.7-3[4][7] Myr
secondary
Mass46 ± 11[4] M☉
Radius5.6[6] R☉
Orbit
Period (P)442 days[4]
(1.2 [4] yr)
Semi-major axis (a)726 R☉[4]
Eccentricity (e)0.37±-0.410.7[4]
Argument of periastron (ω)
(secondary)		120[4]°
Other designations
HD 15558, HIP 11832, SAO 12326, IDS 02251+6101, TYC 4046-44-1, UBV 2530, GCRV 1424, 2MASS J02324253+6127215, WDS J02327+6127, PPM 13720, BD+60°502, GSC 04046-00044, CCDM J02327+6127, IC 1805 148
Database references
SIMBADdata

Physical characteristics

HD 15558 A is a spectroscopic binary system containing at least two massive luminous class O stars. The primary is an O4.5 giant star with a surface temperature over 46,800 K. It has a mass of 152 M☉ and a luminosity of 660,000 L☉, making it one of the most massive stars in the Milky Way Galaxy. The star loses 1.5×10−5 M☉ per year.[7] The secondary is an O7V star. It has a mass of 46 M☉. The primary may itself be a double star, suggested by the improbably large mass found from the binary orbit when compared to the other stellar parameters.[4]

The Washington Double Star Catalog lists 11 companions within one arc minute of HD 15558 A, all fainter than 10th magnitude. In addition, it lists component E just over one arc minute away; it is another hot massive star, the 9th magnitude BD+60°501 with a spectral type of O7 V(n)((f))z.[3][8]

See also

References
  1. Van Leeuwen, F. (2007). "F. Validation of the new Hipparcos reduction". Astronomy & Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
  2. Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
  3. Sota, A.; Mainz Apellantiz, J.; Morrell, N.L; Barba, R.H; Walborn, N.R; et al. (2014). "The Galactic O-star spectroscopic survey (GOSSS). II. Bright southern stars". The Astrophysical Journal Supplement. 211 (1): 10. arXiv:1312.6222. Bibcode:2014ApJS..211...10S. doi:10.1088/0067-0049/211/1/10. S2CID 118847528.
  4. De Becker, M.; Rauw, G.; Manfroid, J.; Eenens, P. (2006). "Early-type stars in the young open cluster IC 1805. II. The probably single stars HD 15570 and HD 15629, and the massive binary/triple system HD 15558". Astronomy & Astrophysics. 456 (3): 1121. arXiv:astro-ph/0606379. Bibcode:2006A&A...456.1121D. doi:10.1051/0004-6361:20065300. S2CID 16519684.
  5. Pourbaix, D.; Tokovinin, A. A.; Batten, A. H.; Fekel, F. C.; Hartkopf, W. I.; et al. (2004). "SB9: The ninth catalogue of spectroscopic binary orbits". Astronomy & Astrophysics. 424 (2): 727–732. arXiv:astro-ph/0406573. Bibcode:2004A&A...424..727P. doi:10.1051/0004-6361:20041213. S2CID 119387088.
  6. Hillwig, T. C.; Gies, D. R.; Huang, W.; McSwain, M. V.; Wingert, D. W. (2006). "Binary and Multiple O-Type Stars in the Cassiopeia OB6 Association". The Astrophysical Journal. 639 (2): 1069–1080. arXiv:astro-ph/0512407. Bibcode:2006ApJ...639.1069H. doi:10.1086/499771. S2CID 119451956.
  7. Garmany, C. D.; Massey, P. (1981). "HD 15558 - an extremely luminous O-type binary star". Publications of the Astronomical Society of the Pacific. 93: 500. Bibcode:1981PASP...93..500G. doi:10.1086/130866.
  8. 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. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.

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