NGC 1624-2

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NGC 1624-2
NGC 1624 PanS.jpg
NGC 1624-2 is the brightest star at the centre of NGC 1624
Observation data
Epoch J2000       Equinox J2000
Constellation Perseus
Right ascension 04h 40m 37.276s [1]
Declination +50° 27′ 41.04″ [1]
Apparent magnitude  (V)11.57 [2]
Characteristics
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  mas [1]
Distance 5,152.3 [5]   pc
Details
Mass 34 [5]   M☉
Radius 10 [5]   R☉
Luminosity 126,000 [5]   L☉
Surface gravity (log g)3.55 [1]   cgs
Temperature 35,000 [5]   K
Metallicity [Fe/H]+0.07 [1]   dex
Rotation 315.98 d [6]
Rotational velocity (v sin i)<3 [5]  km/s
Other designations
TYC 3350-255-1, ALS 18660, 2MASS  J04403728+5027410
Database references
SIMBAD data

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]

Contents

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☉ (10×105.1 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 2 3 4 5 6 7 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv: 2208.00211 . Bibcode:2023A&A...674A...1G. doi: 10.1051/0004-6361/202243940 . S2CID   244398875. Gaia DR3 record for this source at VizieR.
  2. 1 2 3 Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000-03-01). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27 –L30. Bibcode:2000A&A...355L..27H. ISSN   0004-6361.
  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. arXiv: 1312.6222 . Bibcode:2014ApJS..211...10S. doi:10.1088/0067-0049/211/1/10. ISSN   0067-0049. S2CID   118847528.
  4. ↑ Reed, B. Cameron (2003-05-01). "Catalog of Galactic OB Stars". The Astronomical Journal. 125 (5): 2531–2533. Bibcode:2003AJ....125.2531R. doi: 10.1086/374771 . ISSN   0004-6256. S2CID   121285799.
  5. 1 2 3 4 5 6 7 8 9 10 Wade, G. A.; Maíz Apellániz, J.; Martins, F.; Petit, V.; Grunhut, J.; Walborn, N. R.; Barbá, R. H.; Gagné, M.; García-Melendo, E.; Jose, J.; Moffat, A. F. J.; Nazé, Y.; Neiner, C.; Pellerin, A.; Penadés Ordaz, M. (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. arXiv: 1206.2834 . Bibcode:2012MNRAS.425.1278W. doi: 10.1111/j.1365-2966.2012.21523.x . ISSN   0035-8711. S2CID   53360606.
  6. 1 2 3 4 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. arXiv: 2010.07482 . Bibcode:2021MNRAS.501.2677D. doi: 10.1093/mnras/staa3768 . ISSN   0035-8711.
  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. Bibcode:2014yCat....1.2023S.
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