Open AccessDifferences between the two anomalous X‐ray pulsars: variations in the spin‐down rate of 1E 1048.1−5937 and an extended interval of quiet spin‐down in 1E 2259+586
Author(s) -
Baykal Altan,
Strohmayer Tod,
Swank Jean,
Ali Alpar M.,
Stark Michael J.
Publication year - 2000
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 - 10.1046/j.1365-8711.2000.03845.x
Subject(s) - physics , pulsar , astrophysics , luminosity , accretion (finance) , spin (aerodynamics) , quiet , noise (video) , flux (metallurgy) , astronomy , materials science , artificial intelligence , galaxy , computer science , metallurgy , image (mathematics) , thermodynamics
We analysed the Rossi X‐ray Timing Explorer ( RXTE ) archival data of 1E 1048.1−5937 covering a time‐span of more than one year. The spin‐down rate of this source decreases by ∼30 per cent during the observation. We could not resolve the X‐ray flux variations because of contamination by eta Carinae. We find that the level of pulse frequency fluctuations of 1E 1048.1−5937 is consistent with typical noise levels of accretion‐powered pulsars. Recent RXTE observations of 1E 2259+586 have shown a constant spin‐down with a very low upper limit on timing noise. We used the RXTE archival X‐ray observations of 1E 2259+586 to show that the intrinsic X‐ray luminosity times‐series is also stable, with an rms fractional variation of less than 15 per cent. The source could have been in a quiet phase of accretion with a constant X‐ray luminosity and spin‐down rate.