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Post Info TOPIC: NGC 1624-2
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Scientists discover a giant super-magnetic star

Scientists have discovered a new star that has a magnetic field 20,000 times stronger and a mass 35 times than that of the Sun.
The newly discovered star, NGC 1624-2 lies about 20,000 light-years from Earth in the constellation Perseus and has about 35 times the sun's mass.
This massive star possesses a magnetic field 20,000 times stronger than the sun's and nearly 10 times stronger than that detected around any other high-mass star.
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Title: NGC 1624-2: A slowly rotating, X-ray luminous Of?cp star with an extraordinarily strong magnetic field
Authors: G.A. Wade, J. Maíz Apellaniz, F. Martins, V. Petit, J. Grunhut, N. R. Walborn, R.H. Barbá, M. Gagné, E. García-Melendo, J. Jose, A.F.J. Moffat, Y. Nazé, C. Neiner, A. Pellerin, M. Penade ?s Ordaz, M. Shultz, S. Simón-Díaz, A. Sota, the MiMeS Collaboration, the MiMeS Collaboration

This paper presents a first observational investigation of the faint Of?cp star NGC 1624-2, yielding important new constraints on its spectral and physical characteristics, rotation, magnetic field strength, X-ray emission and magnetospheric properties. Modelling the spectrum and spectral energy distribution, we conclude that NGC 1624-2 is a main sequence star of mass M \simeq 30 solar masses, and infer an effective temperature of 35 ±2 kK and log g = 4.0 ±0.2. Based on an extensive time series of optical spectral observations we report significant variability of a large number of spectral lines, and infer a unique period of 157.99 ±0.94 d which we interpret as the rotational period of the star. We report the detection of a very strong - 5.35 ± 0.5 kG - longitudinal magnetic field <Bz>, coupled with probable Zeeman splitting of Stokes I profiles of metal lines confirming a surface field modulus <B> of 14 ±1 kG, consistent with a surface dipole of polar strength >~ 20 kG. This is the largest magnetic field ever detected in an O-type star, and the first report of Zeeman splitting of Stokes I profiles in such an object. We also report the detection of reversed Stokes V profiles associated with weak, high-excitation emission lines of O iii, which we propose may form in the close magnetosphere of the star. We analyse archival Chandra ACIS-I X-ray data, inferring a very hard spectrum with an X-ray efficiency log Lx/Lbol = -6.4, a factor of 4 larger than the canonical value for O-type stars and comparable to that of the young magnetic O-type star \theta1 Ori C and other Of?p stars. Finally, we examine the probable magnetospheric properties of the star, reporting in particular very strong magnetic confinement of the stellar wind, with \eta* \simeq 1.5 x 10^4, and a very large Alfven radius, RAlf = 11.4 R*.

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