Open AccessTiming analysis of the isolated neutron star RX J0720.4–3125 revisited
Author(s) -
Cropper Mark,
Haberl Frank,
Zane Silvia,
Zavlin Vyacheslav E.
Publication year - 2004
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.07854.x
Subject(s) - physics , rosat , astrophysics , neutron star , magnetar , barycentric coordinate system , light curve , star (game theory) , astronomy , geometry , mathematics , galaxy
We present a reanalysis of the X‐ray data for RX J0720.4–3125 presented in our previous paper, Zane et al., using more data recently available from XMM–Newton and Chandra . This analysis also corrects the ROSAT data used in that paper to the barycentric dynamical time ( tdb ) system, incorporates the revised XMM–Newton barycentric correction available since then, and corrects the definition of the instantaneous period in the maximum likelihood periodogram search. However, we are now unable to find a single coherent period that is consistent with all ROSAT , Chandra and XMM–Newton data sets. From an analysis of the separate data sets, we have derived limits on the period change of at 99 per cent confidence level. This is stronger than the value presented in Zane et al., but sufficiently similar that their scientific conclusions remain unchanged. We examine the implications in more detail, and find that RX J0720.4–3125 can have been born as a magnetar provided that it has a young age of ∼10 4 yr. A more conservative interpretation is that the field strength has remained relatively unchanged at just over 10 13 G, over the ∼10 6 ‐yr lifetime of the star.