Please use this identifier to cite or link to this item:
|Title:||Discovery of a 2.8 s Pulsar in a 2 Day Orbit High-mass X-Ray Binary Powering the Ultraluminous X-Ray Source ULX-7 in M51||Authors:||RODRIGUEZ CASTILLO, Guillermo Andres
ISRAEL, Gian Luca
DE LUCA, Andrea
Earnshaw, H. P.
Harrison, F. A.
Roberts, T. P.
Walton, D. J.
WOLTER, Anna Luisa Maria
|Issue Date:||2020||Journal:||THE ASTROPHYSICAL JOURNAL||Number:||895||Issue:||1||First Page:||60||Abstract:||We discovered 2.8 s pulsations in the X-ray emission of the ultraluminous X-ray source (ULX) M51 ULX-7 within the UNSEeN project, which was designed to hunt for new pulsating ULXs (PULXs) with XMM-Newton. The pulse shape is sinusoidal, and large variations of its amplitude were observed even within single exposures (pulsed fraction from less than 5% to 20%). Source M51 ULX-7 is variable, generally observed at an X-ray luminosity between 1039 and 1040 erg s-1, located in the outskirts of the spiral galaxy M51a at a distance of 8.6 Mpc. According to our analysis, the X-ray pulsar orbits in a 2 day binary with a projected semimajor axis aXsinI≃ 28 lt-s. For a neutron star (NS) of 1.4 M☉, this implies a lower limit on the companion mass of 8 M☉, placing the system hosting M51 ULX-7 in the high-mass X-ray binary class. The barycentric pulse period decreased by ≃0.4 ms in the 31 days spanned by our 2018 May-June observations, corresponding to a spin-up rate P˙≃−1.5×10−10s s−1 . In an archival 2005 XMM-Newton exposure, we measured a spin period of ∼3.3 s, indicating a secular spin-up of P˙sec≃−10−9s s−1 , a value in the range of other known PULXs. Our findings suggest that the system consists of a massive donor, possibly an OB giant or supergiant, and a moderately magnetic (dipole field component in the range 1012 G ≲Bdip≲1013 G) accreting NS with weakly beamed emission ( 1/12≲b≲1/4 ).||URI:||http://hdl.handle.net/20.500.12386/29846||URL:||https://iopscience.iop.org/article/10.3847/1538-4357/ab8a44||ISSN:||0004-637X||DOI:||10.3847/1538-4357/ab8a44||Bibcode ADS:||2020ApJ...895...60R||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
Show full item record
Files in This Item:
|1906.04791.pdf||postprint||4.35 MB||Adobe PDF||View/Open|
|Rodríguez_Castillo_2020_ApJ_895_60.pdf||Pdf editoriale||1.8 MB||Adobe PDF||View/Open|
checked on Jun 19, 2021
checked on Jun 19, 2021
Items in DSpace are published in Open Access, unless otherwise indicated.