TY  - JOUR
A1  - Naze, Yael
A1  - Oskinova, Lida
A1  - Gosset, Eric
T1  - A detailed x-ray investigation of zeta puppis - II. the variability on  short and long timescales
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - Stellar winds are a crucial component of massive stars, but their exact properties still remain uncertain. To shed some light on this subject, we have analyzed an exceptional set of X-ray observations of zeta Puppis, one of the closest and brightest massive stars. The sensitive light curves that were derived reveal two major results. On the one hand, a slow modulation of the X-ray flux (with a relative amplitude of up to 15% over 16 hr in the 0.3-4.0 keV band) is detected. Its characteristic timescale cannot be determined with precision, but amounts from one to several days. It could be related to corotating interaction regions, known to exist in zeta Puppis from UV observations. Hour-long changes, linked to flares or to the pulsation activity, are not observed in the last decade covered by the XMM observations; the 17 hr tentative period, previously reported in a ROSAT analysis, is not confirmed either and is thus transient, at best. On the other hand, short-term changes are surprisingly small (<1% relative amplitude for the total energy band). In fact, they are compatible solely with the presence of Poisson noise in the data. This surprisingly low level of short-term variability, in view of the embedded wind-shock origin, requires a very high fragmentation of the stellar wind, for both absorbing and emitting features (>10(5) parcels, comparing with a two-dimensional wind model). This is the first time that constraints have been placed on the number of clumps in an O-type star wind and from X-ray observations.
KW  - stars: early-type
KW  - stars: individual (zeta Pup)
KW  - X-rays: stars
Y1  - 2013
U6  - https://doi.org/10.1088/0004-637X/763/2/143
SN  - 0004-637X
VL  - 763
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  -