Naze, Y;
Ramiaramanantsoa, T;
Stevens, IR;
Howarth, ID;
Moffat, AFJ;
(2018)
A detailed X-ray investigation of zeta Puppis IV. Further characterization of the variability.
Astronomy & Astrophysics
, 609
, Article A81. 10.1051/0004-6361/201730729.
Preview |
Text
aa30729-17.pdf - Published Version Download (945kB) | Preview |
Abstract
CONTEXT: One of the optically brightest and closest massive stars, ζ Pup, is also a bright X-ray source. Previously, its X-ray emission was found to be variable with light curves harbouring “trends” with a typical timescale longer than the exposure length, i.e. >1 d. The origin of these changes was proposed to be linked to large-scale structures in the wind of ζ Pup, but further characterization of the variability at high energies was needed to investigate this scenario. AIMS: Since the previous papers of this series, a number of new X-ray observations have become available. Furthermore, a cyclic behaviour with a 1.78 d period was identified in long optical photometric runs, which is thought to be associated with the launching mechanism of large-scale wind structures. METHODS: We analysed these new X-ray data, revisited the old data, and compared the X-ray light curves with the optical data, notably those taken simultaneously. RESULTS: The behaviour of ζ Pup in X-rays cannot be explained in terms of a perfect clock because the amplitude and shape of its variations change with time. For example, ζ Pup was much more strongly variable between 2007 and 2011 than before and after this interval. Comparing the X-ray spectra of the star at maximum and minimum brightness yields no compelling difference beyond the overall flux change: the temperatures, absorptions, and line shapes seem to remain constant, well within errors. The only common feature between X-ray datasets is that the variation amplitudes appear maximum in the medium (0.6–1.2 keV) energy band. Finally, no clear and coherent correlation can be found between simultaneous X-ray and optical data. Only a subgroup of observations may be combined coherently with the optical period of 1.78 d, although the simultaneous optical behaviour is unknown. CONCLUSIONS: The currently available data do not reveal any obvious, permanent, and direct correlation between X-ray and optical variations. The origin of the X-ray variability therefore still needs to be ascertained, highlighting the need for long-term monitoring in multiwavelengths, i.e. X-ray, UV, and optical.
| Type: | Article |
|---|---|
| Title: | A detailed X-ray investigation of zeta Puppis IV. Further characterization of the variability |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1051/0004-6361/201730729 |
| Publisher version: | http://doi.org/10.1051/0004-6361/201730729 |
| Language: | English |
| Additional information: | © ESO 2018. This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | Science & Technology, Physical Sciences, Astronomy & Astrophysics, stars: early-type, stars: winds, outflows, X-rays: stars, stars: individual: zeta Puppis, O-TYPE STARS, REFLECTION GRATING SPECTROMETER, LINE-PROFILE VARIABILITY, DRIVEN STELLAR WINDS, IUE MEGA CAMPAIGN, HOT STARS, XMM-NEWTON, OEF STARS, MASS-LOSS, EMISSION |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10042045 |
Archive Staff Only
 |
View Item |
