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http://hdl.handle.net/20.500.12386/25190
Titolo: | Discovery of spin-up in the X-ray pulsar companion of the hot subdwarf HD 49798 | Autori: | MEREGHETTI, Sandro Pintore, Fabio ESPOSITO, PAOLO LA PALOMBARA, NICOLA TIENGO, ANDREA ISRAEL, Gian Luca STELLA, Luigi |
Data pubblicazione: | 2016 | Rivista: | MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY | Numero: | 458 | Fascicolo: | 4 | Da pagina:: | 3523 | Abstract: | The hot subdwarf HD 49798 has an X-ray emitting compact companion with a spin-period of 13.2 s and a dynamically measured mass of 1.28 ± 0.05 M<SUB>☉</SUB>, consistent with either a neutron star or a white dwarf. Using all the available XMM-Newton and Swift observations of this source, we could perform a phase-connected timing analysis extending back to the ROSAT data obtained in 1992. We found that the pulsar is spinning up at a rate of (2.15 ± 0.05) × 10<SUP>-15</SUP> s s<SUP>-1</SUP>. This result is best interpreted in terms of a neutron star accreting from the wind of its subdwarf companion, although the remarkably steady period derivative over more than 20 yr is unusual in wind-accreting neutron stars. The possibility that the compact object is a massive white dwarf accreting through a disc cannot be excluded, but it requires a larger distance and/or properties of the stellar wind of HD 49798 different from those derived from the modelling of its optical/UV spectra. | URI: | http://hdl.handle.net/20.500.12386/25190 | URL: | https://academic.oup.com/mnras/article/458/4/3523/2613825 | ISSN: | 0035-8711 | DOI: | 10.1093/mnras/stw536 | Bibcode ADS: | 2016MNRAS.458.3523M | Fulltext: | open |
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