2005/08/29 by M. Falanga, L. Kuiper, Juri Poutanen +8 · 5 citations
Physics and Astronomy · #Accretion (finance) #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Light curve #Millisecond #Millisecond pulsar #Neutron star #Physics #Pulsar #Pulsars and Gravitational Waves Research #X-ray pulsar #astro-ph
paper · pdf · doi:10.1051/0004-6361:20053472
11 pages, 8 figures, 3 tables, accepted for publication on A&A
arxiv created 2005/08/29 · openalex publication_date 2005/11/21 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Simultaneous observations of the accretion-powered millisecond pulsar IGR J00291+5934 by the International Gamma-Ray Astrophysics Laboratory and Rossi X-ray Timing Explorer during the 2004 December outburst are analysed. The average spectrum is well described by thermal Comptonization with an electron temperature of 50 keV and Thomson optical depth in a slab geometry. The spectral shape is almost constant during the outburst. For the first time we detect a spin-up, , of an accreting millisecond pulsar. The ISGRI data reveal the pulsation of X-rays at a period of 1.67 milliseconds up to keV. The pulsed fraction is shown to increase from 6 per cent at 6 keV to 12–20 per cent at 100 keV. This is naturally explained by the action of the Doppler effect on the exponentially cutoff Comptonization spectrum from the hot spot. The nearly sinusoidal pulses show soft lags with a complex energy dependence, increasing up to 7 keV, then decreasing to 15 keV, and seemingly saturating at higher energies.