The changing UV and X-ray properties of the Of?p star CPD -28°2561

Yaël Nazé, Jon O. Sundqvist, Alex W. Fullerton, Asif Ud-Doula, Gregg A. Wade, Gregor Rauw, Nolan R. Walborn

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15 Scopus citations


The Of?p star CPD -28°2561 was monitored at high energies with XMM-Newton and HST. In X-rays, this magnetic oblique rotator displays bright and hard emission that varies by ~55 per cent with rotational phase. These changes occur in phase with optical variations, as expected for magnetically confined winds; there are two maxima and two minima in X-rays during the 73 d rotational period of CPD -28°2561. However, contrary to previously studied cases, no significant hardness variation is detected between minima and maxima, with the exception of the second minimum which is slightly distinct from the first one. In the UV domain, broad-band fluxes remain stable while line profiles display large variations. Stronger absorptions at low velocities are observed when the magnetic equator is seen edgeon, which can be reproduced by a detailed 3D model. However, a difference in absorption at high velocities in the C IV and NV lines is also detected for the two phases where the confined wind is seen nearly pole-on. This suggests the presence of strong asymmetries about the magnetic equator, mostly in the free-flowing wind (rather than in the confined dynamical magnetosphere).

Original languageEnglish (US)
Pages (from-to)2641-2653
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
StatePublished - Oct 27 2015

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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