Australia Telescope National Facility

About: Australia Telescope National Facility is a facility organization based out in Sydney, New South Wales, Australia. It is known for research contribution in the topics: Galaxy & Pulsar. The organization has 699 authors who have published 2774 publications receiving 151507 citations. The organization is also known as: ATNF.

A Stellar Wind Bubble Coincident with the Anomalous X-Ray Pulsar 1E 1048.1–5937: Are Magnetars Formed from Massive Progenitors?

Abstract: We present 21 cm H I observations from the Southern Galactic Plane Survey of the field around the anomalous X-ray pulsar 1E 1048.1-5937, a source whose X-ray properties imply that it is a highly magnetized neutron star (a "magnetar"). These data reveal an expanding hydrogen shell, GSH 288.3-0.5-28, centered on 1E 1048.1-5937, with a diameter of 35 × 23 pc (for a distance of 2.7 kpc) and an expansion velocity of ≈7.5 km s-1. We interpret GSH 288.3-0.5-28 as a wind bubble blown by a 30-40 M☉ star, but no such central star can be readily identified. We suggest that GSH 288.3-0.5-28 is the wind bubble blown by the massive progenitor of 1E 1048.1-5937 and consequently propose that magnetars originate from more massive progenitors than do radio pulsars. This may be evidence that the initial spin period of a neutron star is correlated with the mass of its progenitor and implies that the magnetar birthrate is only a small fraction of that for radio pulsars.

The birth of black holes: neutron star collapse times, gamma-ray bursts and fast radio bursts

Abstract: Recent observations of short gamma-ray bursts (SGRBs) suggest that binary neutron star (NS) mergers can create highly magnetised, millisecond NSs. Sharp cut-offs in X-ray afterglow plateaus of some SGRBs hint at the gravitational collapse of these remnant NSs to black holes. The collapse of such `supramassive' NSs also describes the blitzar model, a leading candidate for the progenitors of fast radio bursts (FRBs). The observation of an FRB associated with an SGRB would provide compelling evidence for the blitzar model and the binary NS merger scenario of SGRBs, and lead to interesting constraints on the NS equation of state. We predict the collapse times of supramassive NSs created in binary NS mergers, finding that such stars collapse $\sim10\,{\rm s}$ -- $4.4\times10^{4}\,{\rm s}$ (95% confidence) after the merger. This directly impacts observations targeting NS remnants of binary NS mergers, providing the optimal window for high time resolution radio and X-ray follow-up of SGRBs and gravitational wave bursts.

12.2-GHz methanol masers towards 1.2-mm dust clumps: quantifying high-mass star formation evolutionary schemes

Abstract: We report the results of a search for 12.2-GHz methanol maser emission, targeted towards 113 known 6.7-GHz methanol masers associated with 1.2-mm dust continuum emission. Observations were carried out with the Australia Telescope National Facility (ATNF) Parkes 64-m radio telescope in the period 2008 June 20–25. We detect 68 12.2-GHz methanol masers with flux densities in excess of our 5σ detection limit of 0.55 Jy, 30 of which are new discoveries. This equates to a detection rate of 60 per cent, similar to previous searches of comparable sensitivity. We have made a statistical investigation of the properties of the 1.2-mm dust clumps with and without associated 6.7-GHz methanol maser and find that 6.7-GHz methanol masers are associated with 1.2-mm dust clumps with high-flux densities, masses and radii. We additionally find that 6.7-GHz methanol masers with higher peak luminosities are associated with less dense 1.2-mm dust clumps than those 6.7-GHz methanol masers with lower luminosities. We suggest that this indicates that more luminous 6.7-GHz methanol masers are generally associated with a later evolutionary phase of massive star formation than less luminous 6.7-GHz methanol maser sources. Analysis of the 6.7-GHz associated 1.2-mm dust clumps with and without associated 12.2-GHz methanol maser emission shows that clumps associated with both class II methanol maser transitions are less dense than those with no associated 12.2-GHz methanol maser emission. Furthermore, 12.2-GHz methanol masers are preferentially detected towards 6.7-GHz methanol masers with associated OH masers, suggesting that 12.2-GHz methanol masers are associated with a later evolutionary phase of massive star formation. We have compared the colours of the Spitzer Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) point sources associated with the maser sources in the following two subgroups: 6.7-GHz methanol masers with and without associated 12.2-GHz methanol masers; and 6.7-GHz methanol masers with high- and those with low-peak luminosities. There is little difference in the nature of the associated GLIMPSE point sources in any of these subgroups, and we propose that the masers themselves are probably much more sensitive than mid-infrared data to evolutionary changes in the massive star formation regions that they are associated with. We present an evolutionary sequence for masers in high-mass star formation regions, placing quantitative estimates on the relative lifetimes for the first time.

The ATCA/VLA OH 1612 MHz survey. I. Observations of the galactic bulge Region

Abstract: We present observations of the region between j' j10 and jb j 3 in the OH 1612.231 MHz line, taken in 1993 October and November with the Australia Telescope Compact Array 1 . The region was systematically searched for OH/IR stars and was covered completely with 539 pointing centres separated by 30 0 .T he size of the dataset calls for a special reduction technique that is fast, reliable and minimizes the output (positions and velocities of possible stars only). Having developed such a reduction method we found 307 OH masing objects, 145 of which are new detections. Out of these, 248 have a standard double-peaked spectral prole, 55 a single-peaked prole and 4 have nonstandard or irregular proles. In this ar- ticle we analyse the data statistically and give classica- tions and identications with known sources where pos- sible. The astrophysical, kinematical, morphological and dynamical properties of subsets of the data will be ad- dressed in future articles. These observations are part of a larger survey, coveringj'j45 andjbj 3 ,w ith the Australia Telescope Compact Array and the Very Large Array. The electronic version of this paper, that includes ta- ble and spectra, can be obtainded from http://www.ed- phys.fr. The table is also available via anonymous ftp (130.79.128.5) or through the World Wide Web (http://cdsweb.u-strasbg.fr/Abstract.html).

Fermi large area telescope observations of the vela pulsar

Abstract: The Vela pulsar is the brightest persistent source in the GeV sky and thus is the traditional first target for new gamma-ray observatories. We report here on initial Fermi Large Area Telescope observations during verification phase pointed exposure and early sky survey scanning. We have used the Vela signal to verify Fermi timing and angular resolution. The high quality pulse profile, with some 32,400 pulsed photons at E>0.03 GeV, shows new features, including pulse structure as fine as 0.3ms and a distinct third peak, which shifts in phase with energy. We examine the high energy behavior of the pulsed emission; initial spectra suggest a phase-averaged power law index of Gamma=1.51{+0.05/-0.04} with an exponential cut-off at E_c=2.9+/-0.1 GeV. Spectral fits with generalized cut-offs of the form e^{-(E/E_c)^b} require b<1, which is inconsistent with magnetic pair attenuation, and thus favor outer magnetosphere emission models. Finally, we report on upper limits to any unpulsed component, as might be associated with a surrounding synchrotron wind nebula (PWN).