Details

Autor(en) / Beteiligte

• Rodríguez Castillo, G. A.
• Israel, G. L.
• Belfiore, A.
• Bernardini, F.
• Esposito, P.
• Pintore, F.
• De Luca, A.
• Papitto, A.
• Stella, L.
• Tiengo, A.
• Zampieri, L.
• Bachetti, M.
• Brightman, M.
• Casella, P.
• D'Agostino, D.
• Dall'Osso, S.
• Earnshaw, H. P.
• Fürst, F.
• Haberl, F.
• Harrison, F. A.
• Mapelli, M.
• Marelli, M.
• Middleton, M.
• Pinto, C.
• Roberts, T. P.
• Salvaterra, R.
• Turolla, R.
• Walton, D. J.
• Wolter, A.

Titel

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

Ist Teil von

• The Astrophysical journal, 2020-05, Vol.895 (1), p.60

Ort / Verlag

Philadelphia: The American Astronomical Society

Erscheinungsjahr

2020

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• 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 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 . In an archival 2005 XMM-Newton exposure, we measured a spin period of ∼3.3 s, indicating a secular spin-up of , 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 G) accreting NS with weakly beamed emission ( ).