The apparent neutron-star radius during bursts

Measuring the radius of neutron stars is hard — ask anyone. (They're really small, and really far away; imagine trying to measure something the width of a human hair... on Pluto). The X-ray emission during the bursts seems to come from the entire surface, and is consistent with a blackbody, so it should be possible to infer the radius indirectly, but the apparent radius behaves in very unexpected ways — usually increasing or decreasing during the burst. Sudip Bhattacharyya & Cole Miller found a correlation between the slope of the radius evolution and the duration of the burst (a proxy for the burst fuel composition), based on the data from the RXTE burst catalog. Our paper was just accepted by MNRAS.

Read the paper (arXiv.org:0908:4245)
Astronomers get neutron star's measure @ ABC Science

IGR J00291+5934 in the news

Maurizio Falanga (CEA), Chris Wanjek (NASA) and I prepared a press release (courtesy SpaceflightNow) following the acceptance of Maurizio's A&A paper. The release first appeared at ESA on 6^th September 2005. See also Une étoile « cannibale » at CEA (French) and the more detailed Festin stellaire: un pulsar milliseconde s'échauffe et accélère at SAp (French)
Earlier post: New millisecond X-ray pulsar IGR J00291+5934

Suzaku (aka ASTRO-EII) launched

Suzaku (aka ASTRO-EII) successfully entered its intended orbit early this morning (local time), according to a JAXA Press Release. All stations (Christmas island, Santiago, and Uchinoura) have confirmed detection of the signal indicating the satellite's separation from the launcher.
Suzaku, like ASCA, is the name of a legendary bird god. ASTRO-EII is the replacement for the unsuccessful ASTRO-E satellite, destroyed shortly following launch in Feburary 2000. ASTRO-EII will cover the energy range 0.2 - 600 keV with the three instruments, X-ray micro-calorimeter (X-ray Spectrometer; XRS), X-ray CCDs (X-ray Imaging Spectrometer; XIS), and the hard X-ray detector (HXD). The operational status will be confirmed in about 5 days. Congratulations JAXA!
UPDATE Unfortunately, the liquid helium for the cryogenically-cooled XRS unexpectedly evaporated during initial operations, rendering it useless. The active lifetime for this instrument was expected to be 2 years. The ASTRO-EII team are expected to announce a new call for proposals with the remaining science instruments in January.
See the Quicktime launch video
Astro-E2 Guest Observer Facility at HEASARC

New millisecond X-ray pulsar IGR J00291+5934

Initially identified as a new X-ray transient by ESA's INTEGRAL satellite, IGR J00291+5934 was found in RXTE observations to be a 599 Hz millisecond pulsar. Subsequent observations revealed a 2.46 hr orbit, making the source very similar to the original millisecond X-ray pulsar, SAX J1808.4-3658.

Read the paper (ApJ 622, 45L 2005)
INTEGRAL team discovery paper (Shaw et al. 2005, A&A, 432, L13)
U. Southampton press release Feb 16^th 2005
New Scientist breaking news Feb 22^nd 2005

Gravitational waves may set speed limit for pulsar spin

Gravitational radiation - ripples in the fabric of space predicted by Albert Einstein - may serve as a cosmic traffic enforcer, protecting reckless pulsars from spinning too fast and blowing apart.

Read the paper (Nature 424:6944, 42) or the press release

Going, going, almost gone

MIT scientists have found a pulsar in a binary system that has all but completely whittled away its companion star, leaving this companion only about 10 times more massive than Jupiter.

Read the paper (s) (ApJ 576, L137; ApJ, 587, 754) or the press release