Astronomy:NGC 1624-2

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Short description: Star in the constellation Perseus
NGC 1624-2
Tribble Nebulae.jpg
NGC 1624-2 is the brightest star at the centre of NGC 1624 on the left of this image spanning about one degree.
Observation data
Equinox J2000.0]] (ICRS)
Constellation Perseus
Right ascension  04h 40m 37.276s[1]
Declination 50° 27′ 41.04″[1]
Apparent magnitude (V) 11.57[2]
Characteristics
Evolutionary stage O-type star
Spectral type O7f?cp[3]
U−B color index −0.57[2][4]
B−V color index 0.9[2]
Astrometry
Proper motion (μ) RA: 0.025[1] mas/yr
Dec.: 0.108[1] mas/yr
Parallax (π)−0.3521 ± 0.1716[1] mas
Distance5,152.3[5] pc
Details
Mass34[5] M
Radius10[5] R
Luminosity126,000[5] L
Surface gravity (log g)3.55[1] cgs
Temperature35,000[5] K
Metallicity [Fe/H]+0.07[1] dex
Rotation315.98 d[6]
Rotational velocity (v sin i)<3[5] km/s
Other designations
TYC 3350-255-1, ALS 18660, 2MASS J04403728+5027410
Database references
SIMBADdata

NGC 1624-2 is a massive O-type star located in the star cluster NGC 1624, in the constellation of Perseus, about 16,800 light years away. NGC 1624-2 is notable for being most strongly magnetised O-type star known,[6] with a magnetic field strength of 20 kG, or about 20,000 times the Sun's magnetic field strength.[5] It hosts a large and dense magnetosphere, formed from the interaction between its very strong magnetic field and its dense, radiatively-driven stellar wind, which also absorbs up to 95% of x-rays generated from around the star.[5]

Properties

NGC 1624-2 is a very massive, young, blue star no more than 4 million years old. It is an Of?p star a type of highly magnetic star that has unusual emission lines of multiply-ionized carbon and nitrogen. In NGC 1624-2, the carbon emission is particularly extreme. The luminosity class is uncertain because of the unusual spectrum; it is most commonly given as V (main sequence), but has also been given as I (supergiant).[7]

Analysis of its spectral energy distribution with CHORIZOS modelling yields an effective temperature of 35,000 K, a luminosity of 125,900 L (105.1 L) and a radius of about 10 R. Assuming a log g of 4.0 yields a mass of 34 M, but evolutionary models tend towards a current mass of 28 M, given the results from the modelling. However, this assumes that NGC 1624-2 is a normal star, while it is not, so it should only be taken as an indication of its true mass. NGC 1624-2 is currently losing mass at a rate of 10−6.8 M/year, through a stellar wind with a terminal velocity of 2,875 km/s.[5]

Rotation

NGC 1624-2 rotates very slowly, only once every 316 days.[6] This slow rotation is typical for very magnetic O-type stars as their magnetic fields slow down their rotation in a process known as magnetic braking, where angular momentum is quickly shed by the stellar wind via the strong magnetic field, which also minimises mass loss throughout the main sequence.[5][6]

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  2. 2.0 2.1 2.2 Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P. et al. (2000-03-01). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics 355: L27–L30. ISSN 0004-6361. Bibcode2000A&A...355L..27H. 
  3. Sota, A.; Maíz Apellániz, J.; Morrell, N. I.; Barbá, R. H.; Walborn, N. R.; Gamen, R. C.; Arias, J. I.; Alfaro, E. J. (2014-03-01). "The Galactic O-Star Spectroscopic Survey (GOSSS). II. Bright Southern Stars". The Astrophysical Journal Supplement Series 211 (1): 10. doi:10.1088/0067-0049/211/1/10. ISSN 0067-0049. Bibcode2014ApJS..211...10S. 
  4. Reed, B. Cameron (2003-05-01). "Catalog of Galactic OB Stars". The Astronomical Journal 125 (5): 2531–2533. doi:10.1086/374771. ISSN 0004-6256. Bibcode2003AJ....125.2531R. 
  5. 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 Wade, G. A.; Maíz Apellániz, J.; Martins, F.; Petit, V.; Grunhut, J.; Walborn, N. R.; Barbá, R. H.; Gagné, M. et al. (2012-09-01). "NGC 1624-2: a slowly rotating, X-ray luminous Of?cp star with an extraordinarily strong magnetic field". Monthly Notices of the Royal Astronomical Society 425 (2): 1278–1293. doi:10.1111/j.1365-2966.2012.21523.x. ISSN 0035-8711. Bibcode2012MNRAS.425.1278W. 
  6. 6.0 6.1 6.2 6.3 David-Uraz, A.; Petit, V.; Shultz, M. E.; Fullerton, A. W.; Erba, C.; Keszthelyi, Z.; Seadrow, S.; Wade, G. A. (2021-02-01). "New observations of NGC 1624-2 reveal a complex magnetospheric structure and underlying surface magnetic geometry". Monthly Notices of the Royal Astronomical Society 501 (2): 2677–2687. doi:10.1093/mnras/staa3768. ISSN 0035-8711. Bibcode2021MNRAS.501.2677D. 
  7. Skiff, B. A (2014). "VizieR Online Data Catalog: Catalogue of Stellar Spectral Classifications (Skiff, 2009-2016)". VizieR On-line Data Catalog: B/Mk. Originally Published in: Lowell Observatory (October 2014) 1. Bibcode2014yCat....1.2023S.