The talks are in the same order as the Program Schedule.
Grupe, Dirk - The late-time light curves of GRB X-ray afterglows with Chandra
Slane, Patrick - Chandra and Spitzer Constraints on the Evolution of G54.1+0.3 and 3C 58
LEMIERE, ANNE - CHANDRA OBSERVATION OF HESSJ1640-465 REVEALS AN X-RAY NEBULA AND ITS PUTATIVE PULSAR
Kaspi, Victoria - Target-of-Opportunity Chandra Observations of Anomalous X-ray Pulsars
Dirk Grupe (Pennsylvania State University) , Davie Burrows (PSU)
For a brief moment in time when they occur, Gamma-Ray Bursts (GRBs) are the most energetic events in the Universe. One of the predictions of the standard fireball model of GRBs is the formation of a jet. The opening angle of this jet is the crucial parameter for the energetics of the burst. This opening angle can be inferred from the 'jet break' when the jet decelerates by interacting with the interstellar gas. Jet breaks are therefore crucial for our understanding of GRBs. We will summarize our late-time detections of GRB X-ray afterglows with Chandra. For the two soft GRBs 070524 and 071221A we were able to follow both X-ray afterglows for more than 3 weeks and found no jet break in 050724 and a jet break 4 days after the burst in GRB 051221A. As for long bursts we had three observations of the extraordinary GRB 060729 with the latest 11 month after the burst - the latest detection of an X-ray afterglow ever. GRB 060729 will still be detectable by Chandra in 2008 and has just been recommended for two Chandra observation next year by the peer review. In all these cases Chandra observations were essential to get late-time detection which are important for the interpretation of the physics involved in GRBs. The detection or non detections of a jet break in GRB X-ray light curves puts tight constraints on the energetics of a GRB. No jet break means that it requires a much larger energy injection and a continuous energy input from the central engine. Only Chandra is able to detect X-ray afterglows at very late times.
Patrick Slane (Harvard-Smithsonian Center for Astrophysics)
The injection of particles and magnetic flux from a rapidly-rotating neutron star into its surroundings produces a synchrotron-emitting bubble known as a pulsar wind nebula (PWN). The particle spectrum injected into the nebula, as well as the density profile of the material into which the nebula expands, strongly constrain its spectral and dynamical evolution. Here I describe recent work using Chandra and Spitzer observations to constrain the spectrum at the innermost regions of 3C 58, for comparison with the broadband spectrum of the entire nebula, and the identification of a shell of emission surrounding G54.1+0.3, presumably corresponding to the previously unseen ambient material into which the PWN is evolving.
ANNE LEMIERE (CFA-Harvard) , A. Lemiere, P. Slane , B. Gaensler
During 2004-2006 H.E.S.S. performed a survey of the inner part of the Galaxy where its excellent capability allowed to mark a breakthrough in the field of PWN study: for the first time the morphological structure of many pulsar wind nebulae (PWN) was resolved in the gamma-ray band. We present here a Chandra X-ray observation of one of these sources which fills the center of the SNR G338.3-0.0: HESSJ1640-465. We resolve a point source surrounded by a diffuse emission that fills the centroid of the HESS source, within the shell of the radio supernova remnant. The morphology of the diffuse emission strongly resembles that of a PWN and extends assymetrically in the South East part of the point source that we designate as the putative pulsar. We explore the morphological and spectral characteristics of this object and discuss their implications in term of energies and interaction with the surrounding environment. We finally discuss a scenario in which the gamma-rays originate from this object in term of a time-dependent leptonic model.
Werner Becker (MPE-Garching) , C.Y. Hui, H.H. Huang
Young and middle aged neutron stars, which emit strong pulsed non-thermal and/or surface hot-spot plus cooling emission, were studied reasonable well by previous X-ray observatories. In contrast, most old radio pulsars were too faint for a detailed examination of their X-ray emission and are clearly sources which required the sensitivity of Chandra and XMM-Newton to be studied in sufficient detail. In my talk I will review recent results on the X-ray emission properties of old pulsars and report on a study of the diffuse trail like emission components found in some of them.
Victoria Kaspi (McGill University) , P. M. Woods (Dynetics), F. P. Gavriil (NASA/GSFC), R. Dib (McGill), C. Tam (McGill)
Since Cycle 4, we have led a Chandra Target-of-Opportunity program to observe Anomalous X-ray Pulsars (AXPs), a small class of isolated neutron stars thought to be magnetars, in outburst. Under this program, we have obtained a total of seven ToO observations of three different AXPs (three of CXOU J164710.2-455216, three of 1E 1048.1-5937 and one of 4U 0142+61), in order to study their rotational, spectral and pulsed fraction evolutions during times of instability. We describe here what we have learned from these observations. In particular we report on a tight, quantitative correlation between flux and pulsed fraction in 1E 1048.1-5937; the first measurement of a period derivative (hence magnetic field) in CXOU J164710.2-455216, thus confirming its AXP nature; as well unique pulse profile evolution, both in the short- and long-terms, in 4U 0142+61. These Chandra observations support the magnetar model for these sources, and put tight constraints on a variety of the outstanding physical questions remaining about magnetars.
Alicia Soderberg (Princeton University)
Over the past few years, long-duration gamma-ray bursts (GRBs), including the subclass of X-ray flashes (XRFs), have been revealed to be a rare variety of Type Ibc supernova (SN Ibc). While all these events result from the death of massive stars, the electromagnetic luminosities of GRBs and XRFs exceed those of ordinary Type Ibc SNe by many orders of magnitude. The observed diversity of stellar death corresponds to large variations in the energy, velocity, and geometry of the explosion ejecta. Using multi-wavelength (radio, optical, X-ray) observations of the nearest GRBs, XRFs, and SNe Ibc, I show that while GRBs and XRFs couple at least 10^48 erg to relativistic material, SNe Ibc typically couple less than 10^48 erg to their fastest (albeit non-relativistic) outflows. Specifically, I find that less than 3 percent of local SNe Ibc show any evidence for relativistic ejecta which may be attributed to an associated GRB or XRF. Recently, a new class of GRBs and XRFs has been revealed which are under-luminous in comparison with the statistical sample of GRBs. Owing to their faint high-energy emission, these sub-energetic bursts are only detectable nearby (z < 0.1) and are likely 10 times more common than cosmological GRBs. In comparison with local SNe Ibc and typical GRBs/XRFs,these explosions are intermediate in terms of both volumetric rate and energetics. Yet the essential physical process that causes a dying star to produce a GRB, XRF, or sub-energetic burst, and not just a SN, remains a crucial open question. Progress requires a detailed understanding of ordinary SNe Ibc which will be facilitated with the launch of wide-field optical surveys in the near future.