Aşırı Parlak X-Işın Kaynağı M51 ULX-8’deki Nötron Yıldızının Dönme Periyodu Üzerine

Galaksimizi de içermek üzere yakın galaksilerdeki aşırı parlak X-ışın kaynak (APX) ailesinin bazı üyelerinden geldiği kısa süre öncekeşfedilen periyodik pulsasyonlar madde yığıştıran yoğun cismin doğasını ortaya çıkarmıştır. Pulsasyon gözlensin veya gözlenmesin,günümüzde, önemli sayıda APX’e karadeliklerden daha çok nötron yıldızlarının güç sağladığına inanılmaktadır. Bir APX’in X-ışıntayfındaki siklotron soğurma çizgilerinin saptanması yoğun cismin bir nötron yıldızı olarak tanımlanabilmesi için alternatif bir yolsağlamaktadır. Pulsasyon göstermeyen APX’lerin arasında bulunan M51 ULX-8’in tayfındaki bir siklotron rezonans saçılım yapısının(SRSY) varlığı rapor edilmişti. Bu çalışmada, gözlenen SRSY’nin enerjisinden M51 ULX-8’deki nötron yıldızının yüzeyindekimanyetik alan yeğinliği çıkarsanarak X-ışın salınımındaki hüzmeleme oranı ve daha da önemlisi yakın gelecekteki uzay görevlerisayesinde keşfedilmesi beklenen nötron yıldızının yakalanamamış dönme periyodunun gözlenebilme aralığı kestirilmektedir.

On the Spin Period of the Neutron Star in the Ultraluminous X-RaySource M51 ULX-8

The recent discovery of periodic pulsations from several members of the ultraluminous X-ray source (ULX) family in nearby galaxiesas well as in our own galaxy unveiled the nature of the accreting compact object. Neutron stars rather than black holes are currentlybelieved to power a substantial number of ULXs whether or not pulsations are observed. The detection of cyclotron absorption lines in the X-ray spectrum of a ULX provides an alternative way to identify the compact object as a neutron star. Among the non-pulsatingULXs, the presence of a cyclotron resonance scattering feature (CRSF) in the spectrum of M51 ULX-8 has been reported. In thepresent work, the magnetic field strength on the surface of the neutron star in M51 ULX-8 is inferred from the energy of the observedCRSF to estimate the beaming fraction in X-ray emission and more importantly the observable range for the elusive neutron-star spinperiod to be hopefully discovered by the forthcoming space missions in the near future.

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