Star Gobbles Up Its Friend by Universe today Star Eats Companion by ESA news 6 September 2005 Integral and RXTE observations of accreting millisecond pulsar IGR J in outburst October 23, 2005 M. Falanfa, L. Kuiper, J. Poutanen et al.

ESA’s Integral space observatory, together with NASA's Rossi X-ray Timing Explorer spacecraft, has found a fast-spinning pulsar in the process of devouring its companion. This pulsar, called IGR J , belongs to a category of 'X-ray millisecond pulsars‘, which pulse with the X-ray light several hundred times a second, one of the fastest known and the sixth pulsar known in AMSPs. It has a period of 1.67 ms and ν= 8.4X Hz s -1 at MJD (J. Poutanen, 2005)

"We now have direct evidence for the star spinning faster whilst cannibalising its companion, something which no one had ever seen before for such a system," said Dr Lucien Kuiper from the Netherlands Institute for Space Research (SRON), in Utrecht. "This object was about ten times more energetic than what is usually observed for similar sources," said Falanga. "Only some kind of monster emits at these energies, which corresponds to a temperature of almost a billion degrees." The time averaged broad-band spectrum from keV obtained with JEM-X/ISGRI is well described by a thermal Comptonization model with seed photons from the Neutron Star surface scattered in a shocked-heated accretion column above the hot spot region. They use data from the coded mask imager IBIS/ISGRI (Ubertini et al. 2003; Lebrun et al. 2003) at energies from 20 to ~200 keV (total exposure ks) and from the JEM-X monitor (Lund et al. 2003) at Energies 5 to ~20 keV (total exposure time of ks) (M. Falanga et al. 2005)

The ISGRI data from INTEGRAL revolution (Table 1) were used in timing analysis. They also used the PCA events from 2004 Dec To verify their ISGRI timing results they also produced pulse phase distributions based on HEXTE ( keV) data.

The pulse profiles detected by the PCA, JEM-X, HEXTE and ISGRI are fully consistent in shape and absolute timing. (M. Falanga et al. 2005) They corrected time stamps of the PCA events from the 2004 Dec observations to arrival times at the solar system barycenter using the JPL DE200 solar system ephemeries and the pos- -ition of IGR J given in Table 3, taking into account the binary nature of the system. "Accretion is expected to cease after a billion of years or so," said Dr Duncan Galloway of the Massachusetts Institute of Technology, USA, responsible for the Rossi observations. "This Integral-Rossi discovery provides more evidence of how pulsars evolve from one phase to another - from an initially slowly spinning binary neutron star emitting high energies, to a rapidly spinning isolated pulsar emitting in radio wavelengths."