2009/01/12 by V. S. Dhillon, T. R. Marsh, S. P. Littlefair +9 · 7 citations
Earth and Planetary Sciences · Physics and Astronomy · #Astrophysical Phenomena and Observations #High-pressure geophysics and materials #Pulsars and Gravitational Waves Research #astro-ph.HE
paper · pdf · doi:10.1111/j.1745-3933.2009.00623.x
5 pages, 3 figures, accepted for publication in MNRAS Letters
arxiv created 2009/01/12 · openalex publication_date 2009/02/18 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Abstract We present high-speed optical photometry of the anomalous X-ray pulsar 1E 1048.1-5937 obtained with ULTRACAM on the 8.2-m Very Large Telescope in 2007 June. We detect 1E 1048.1-5937 at a magnitude of i′= 25.3 ± 0.2, consistent with the values found by Wang et al. and hence confirming their conclusion that the source was approximately 1 mag brighter than in 2003–06 due to an on-going X-ray flare that started in 2007 March. The increased source brightness enabled us to detect optical pulsations with an identical period (6.458 s) to the X-ray pulsations. The root-mean-square (rms) pulsed fraction in our data is 21 ± 7 per cent, approximately the same as the 2–10 keV X-ray rms pulsed fraction. The optical and X-ray pulse profiles show similar morphologies and appear to be approximately in phase with each other, the latter lagging the former by only 0.06 ± 0.02 cycles. The optical pulsations in 1E 1048.1-5937 are very similar in nature to those observed in 4U 0142+61. The implications of our observations for models of anomalous X-ray pulsars are discussed.