2017A&A...606A..91S


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.04CEST14:45:06

2017A&A...606A..91S - Astronomy and Astrophysics, volume 606A, 91-91 (2017/10-1)

A combined HST and XMM-Newton campaign for the magnetic O9.7 V star HD 54879. Constraining the weak-wind problem of massive stars.

SHENAR T., OSKINOVA L.M., JARVINEN S.P., LUCKAS P., HAINICH R., TODT H., HUBRIG S., SANDER A.A.C., ILYIN I. and HAMANN W.-R.

Abstract (from CDS):

Context. HD 54879 (O9.7 V) is one of a dozen O-stars for which an organized atmospheric magnetic field has been detected. Despite their importance, little is known about the winds and evolution of magnetized massive stars.
Aims. To gain insights into the interplay between atmospheres, winds, and magnetic fields of massive stars, we acquired UV and X-ray data of HD 54879 using the Hubble Space Telescope and the XMM-Newton satellite. In addition, 35 optical amateur spectra were secured to study the variability of HD 54879.
Methods. A multiwavelength (X-ray to optical) spectral analysis is performed using the Potsdam Wolf-Rayet (PoWR) model atmosphere code and theXSPEC software.
Results. The photospheric parameters (T*=30.5kK, logg=4.0[cm/s2], logL=4.45[L]) are typical for an O9.7 V star. The microturbulent, macroturbulent, and projected rotational velocities are lower than previously suggested (ξph,vmac,vsini≥4km/s). An initial mass of 16M and an age of 5Myr are inferred from evolutionary tracks. We derive a mean X-ray emitting temperature of log TX=6.7[K] and an X-ray luminosity of LX=1x1032erg/s. Short- and long-scale variability is seen in the Hα line, but only a very long period of P~=5 yr could be estimated. Assessing the circumstellar density of HD 54879 using UV spectra, we can roughly estimate the mass-loss rate HD 54879 would have in the absence of a magnetic field as logMB=0~=-9.0[M/yr]. The magnetic field traps the stellar wind up to the Alfven radius rA≥12R*, implying that its true mass-loss rate is log M≥-10.2[M/yr]. Hence, density enhancements around magnetic stars can be exploited to estimate mass-loss rates of non-magnetic stars of similar spectral types, essential for resolving the weak wind problem.
Conclusions. Our study confirms that strongly magnetized stars lose little or no mass, and supplies important constraints on the weak-wind problem of massive main sequence stars.

Abstract Copyright: © ESO, 2017

Journal keyword(s): stars: massive - stars: magnetic field - stars: mass-loss - stars: individual: HD 54879 - stars: individual: HD 54879

Simbad objects: 9

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Number of rows : 9

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 NGC 1624 2 * 04 40 37.2813790162 +50 27 41.003169135 11.9 12.47 11.57     O7f?cp 42 0
2 * ups Ori V* 05 31 55.8601879 -07 18 05.537157 3.30 4.36 4.63 4.75 5.01 O9.7V 379 0
3 * tet01 Ori C ** 05 35 16.46375 -05 23 22.8486 4.20 5.15 5.13 4.91 4.73 O7Vp 1271 1
4 NAME CMa OB1 As* 07 07.0 -10 28           ~ 123 0
5 HD 54879 SB* 07 10 08.1488998239 -11 48 09.835011060 6.8 7.60 7.65     O9.7V 65 0
6 HD 57682 * 07 22 02.0544956184 -08 58 45.761168747 5.20 6.24 6.43     O9.2IV 232 0
7 CPD-59 2629 * 10 45 08.2353841063 -59 46 06.975974457 10.780 11.336 10.848   9.971 O8.5Vp 57 0
8 * tau Sco * 16 35 52.9528530 -28 12 57.661515 1.55 2.56 2.81 2.93 3.18 B0.2V 854 0
9 * 10 Lac ** 22 39 15.6786372 +39 03 00.971152 3.650 4.670 4.880 4.98 5.19 O9V 718 0

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2020.07.04-14:45:06

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