* Astronomy

Title: Formation of "Lightnings" in a Neutron Star Magnetosphere and the Nature of RRATs
Authors: Ya. N. Istomin, D. N. Sobyanin (Lebedev Physical Institute)

The connection between the radio emission from "lightnings" produced by the absorption of high-energy photons from the cosmic gamma-ray background in a neutron star magnetosphere and radio bursts from rotating ratio transients (RRATs) is investigated. The lightning length reaches 1000 km; the lightning radius is 100 m and is comparable to the polar cap radius. If a closed magnetosphere is filled with a dense plasma, then lightnings are efficiently formed only in the region of open magnetic field lines. For the radio emission from a separate lightning to be observed, the polar cap of the neutron star must be directed toward the observer and, at the same time, the lightning must be formed. The maximum burst rate is related to the time of the plasma outflow from the polar cap region. The typical interval between two consecutive bursts is ~100 s. The width of a single radio burst can be determined both by the width of the emission cone formed by the lightning emitting regions at some height above the neutron star surface and by a finite lightning lifetime. The width of the phase distribution for radio bursts from RRATs, along with the integrated pulse width, is determined by the width of the bundle of open magnetic field lines at the formation height of the radio emission. The results obtained are consistent with the currently available data and are indicative of a close connection between RRATs, intermittent pulsars, and extreme nullers.

Read more (18kb, PDF)

High-School Student Discovers Strange Astronomical Object
A West Virginia high-school student analysing data from a giant radio telescope has discovered a new astronomical object -- a strange type of neutron star called a rotating radio transient.
Lucas Bolyard, a sophomore at South Harrison High School in Clarksburg, WV, made the discovery while participating in a project in which students are trained to scrutinize data from the National Science Foundation's giant Robert C. Byrd Green Bank Telescope (GBT).
The project, called the Pulsar Search Collaboratory (PSC), is a joint project of the National Radio Astronomy Observatory (NRAO) and West Virginia University (WVU), funded by a grant from the National Science Foundation.
Bolyard made the discovery in March, after he already had studied more than 2,000 data plots from the GBT and found nothing.

"I was home on a weekend and had nothing to do, so I decided to look at some more plots from the GBT. I saw a plot with a pulse, but there was a lot of radio interference, too. The pulse almost got dismissed as interference" - Lucas Bolyard.

Nonetheless, he reported it, and it went on a list of candidates for West Virginia University astronomers Maura McLaughlin and Duncan Lorimer to re-examine, scheduling new observations of the region of sky from which the pulse came. Disappointingly, the follow-up observations showed nothing, indicating that the object was not a normal pulsar. However, the astronomers explained to Bolyard that his pulse still might have come from a rotating radio transient.

Read more

Title: Timing observations of RRAT J1819-1458 at Urumqi Observatory
Authors: A. Esamdin, C. S. Zhao, Y. Yan, N. Wang, H. Nizamidin, Z. Y. Liu

We report the timing-analysis results obtained for RRAT J1819-1458 from regular timing observations at 1.54 GHz using the Urumqi 25 m radio telescope between 2007 April to 2008 March. RRAT J1819-1458 is a relatively young and highly magnetised neutron star discovered by its sporadic short bursts in the Parkes Multibeam Pulsar Survey data. In 94 hrs of observation data, we detected a total of 162 dispersed bursts of RRAT J1819-1458 with the signal-to-noise ratios (S/Ns) above 5-\sigma threshold. Among them, 5 bursts clearly show two-component structure. The S/N of the strongest burst is 13.3. The source's DM measured through our data is 196.0 ±0.4 pc cm^{-3}. The timing position, frequency and its first derivative were determined using standard pulsar timing techniques on the arrival times of these individual bursts. The accuracy of the solved rotating parameters are improved comparing with that in previous publication. Our timing position with 2-\sigma error is consistent with the position of its X-ray counterpart CXOU J181934.1-145804. The effect of timing noise and the phase fluctuation of the individual short bursts on the timing residuals is briefly discussed. The distribution of the timing residuals is bimodal, which cannot be explained readily by timing irregularity.

Read more (919kb, PDF)

XMM-Newton has detected periodic X-ray emission, or the pulsed heartbeat of a weird new type of star. Collecting the X-rays from the so-called rotating radio transient has confirmed the nature of the underlying celestial object and given astronomers a new insight into these exotic objects.
The observations were made using XMM-Newton`s European Photon Imaging Camera (EPIC), which targeted the celestial object RRAT J1819 -1458. Astronomers observed the object for around 12 hours and detected pulsations in the X-ray data that show the source to be rotating once every 4.26 seconds.

Read more