A new investigation of the possible X-ray counterparts of the magnetar candidate AX J1845-0258

Pintore, FabioFabioPintoreMEREGHETTI, SandroSandroMEREGHETTI2020-05-262020-05-2620160035-8711http://hdl.handle.net/20.500.12386/25192AX J1845-0258 is a transient X-ray pulsar, with spin period of 6.97 s, discovered with the ASCA satellite in 1993. Its soft spectrum and the possible association with a supernova remnant suggest that AX J1845-0258 might be a magnetar, but this has not been confirmed yet. A possible counterpart one order of magnitude fainter, AX J184453-025640, has been found in later X-ray observations, but no pulsations have been detected. In addition, some other X-ray sources are compatible with the pulsar location, which is in a crowded region of the Galactic plane. We have carried out a new investigation of all the X-ray sources in the ASCA error region of AX J1845-0258, using archival data obtained with Chandra in 2007 and 2010, and with XMM-Newton in 2010. We set an upper limit of 6 per cent on the pulsed fraction of AX J184453-025640 and confirmed its rather hard spectrum (power-law photon index of 1.2 ± 0.3). In addition to the other two fainter sources already reported in the literature, we found other X-ray sources positionally consistent with AX J1845-0258. Although many of them are possibly foreground stars likely unrelated to the pulsar, at least another new source, CXOU J184457.5-025823, could be a plausible counterpart of AX J1845-0258. It has a flux of 6 × 10-14 erg cm-2 s-1 and a spectrum well fitted by a power law with photon index ∼1.3 and NH ∼ 1022 cm-2.STAMPAenA new investigation of the possible X-ray counterparts of the magnetar candidate AX J1845-0258Article10.1093/mnras/stw10362-s2.0-84978976741000379835200068https://academic.oup.com/mnras/article/460/1/1033/26088362016MNRAS.460.1033PFIS/05 - ASTRONOMIA E ASTROFISICA