Chandra's First Decade of Discovery

Session 1: Stars and Star Formation

X-ray studies of star and planet formation

Eric Feigelson, Penn State University

Although hardly conceived during the preparation of the satellite, the Chandra X-ray Observatory is playing a surprisingly strong role in studies of star and planet formation. Chandra high-resolution images of active molecular clouds often reveal hundreds of low-mass young stars, from Class I protostars through Class III disk-free pre-main sequence stars, as well as massive OB stars. Chandra time series and spectra provide insights into powerful magnetic flares that are unavailable at other wavelengths. Though not fully confirmed, the illumination of protoplanetary disks by high energy output of these flares may play critical roles in diverse processes of planet formation. Chandra's contributions to several broad themes in star and planet formation are briefly outlined: history and efficiency of star formation in molecular clouds; universality of the stellar Initial Mass Function; triggered star formation on the periphery of HII regions; stellar environment of OB stars; the large-scale effects of OB winds on molecular clouds; and the X-ray irradiation of protoplanetary disks.

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Modeling the X-ray emission from jets observed with Chandra

Rosaria Bonito, DSFA-UNIPA-INAF-Osservatorio Astronomico di Palermo
S. Orlando (INAF-OAPA), G. Peres (DSFA-UNIPA-INAF-OAPA), F. Favata(European Space Agency, 8-10 rue Mario Nikis, 75015 Paris, France), M. Miceli (DSFA-UNIPA-INAF-OAPA), J. Eisloffel (Thüringer Landessternwarte, Tautenburg)

In the last decade, X-rays from jets have been discovered thanks to the unprecedented resolving power of Chandra. The first convincing evidence of X-ray jets came from HH2 (2000), HH154 following shortly thereafter. While more sources were detected later, HH154 remains a unique source being the nearest and the most luminous among the nearest jets: the details of the relevant X-ray morphology can be studied to a level impossible with more distant objects.Our group has investigated the mechanisms of X-ray emission from jets both analyzing multi-epochs Chandra data of HH154 and developing numerical models of jets where X-rays are generated by jets shocking onto the circumstellar medium. The analysis of Chandra data of HH 154 in different epochs allowed us to study for the first time the morphology and the evolution of the X-ray source on a time scale of 4years. We found that the source consists of an unresolved, point-like component with no detectable proper motion and an elongated component with a proper motion consistent with a shock moving away from the parent star.We present here the comparison between the Chandra observations of HH jets and our hydrodynamic model of a randomly ejected pulsed jet which reproduces the knotty morphology observed.

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X-rays from Planetary Nebulae: a Decade of Insight from Chandra

Joel Kastner, Rochester Institute of Technology

Planetary nebulae (PNe) represent very late stages in the lives of stars of initial mass 1-8 M. As such, PNe serve as proving grounds for theories concerning a wide range of astrophysical phenomena, from stellar nucleosynthesis to wind interactions to the impact of binarity on stellar evolution and the ultimate fates of binary (and, perhaps, exoplanet) systems. In the era of Chandra and XMM-Newton, the detection (or nondetection) of diffuse and/or point-like X-ray sources within PNe yields important, unique information concerning the evolutionary state of PN central star(s) and wind interactions as nebular shaping agents. Diffuse X-ray sources allow us to probe the energetic shocks within PN wind interaction regions, whether in the form of wind-blown bubbles or fast, collimated outflows impinging on PN progenitor ejecta. Chandra X-ray gratings spectroscopy of the superheated plasma in such a wind-shock region - within the PN BD +303639 - has yielded unparalleled insight into the crucial, late stages of nucleosynthesis within this PN's progenitor star. At the same time, searches for X-ray point sources within PNe provide a novel means to detect binary companions at PN cores, thereby constraining models in which the formation and shaping of PNe is directly linked to central star binarity and, perhaps, the presence of planetary-mass companions. I present highlights within each of these areas from among the X-ray results for PNe accumulated by Chandra and XMM-Newton over the past decade, and I discuss the pressing, unsolved questions in PN research that these X-ray observatories can best address in the coming years.

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The Chandra Carina Complex Project

Leisa Townsley, Penn State University

A recent Chandra VLP surveyed 1.4 square degrees of the Great Nebula in Carina with 22 ~60ks ACIS-I pointings, providing remarkable new views of this massive star-forming complex. We will explore some early results of this survey, highlighting physical processes that characterize the life of this “cluster of clusters,” an example of the fundamental building blocks of starburst galaxies. This Chandra survey reveals over 14,000 X-ray point sources in Carina; most are pre-main sequence stars accompanying >100 massive stars powering this extensive HII region complex. This X-ray-selected sample of young stars can be used to study disk frequency and evolution in the proximity of massive stars. Some of these massive stars are hard X-ray emitters; this may be a new indicator of close binarity or magnetic fields. Carina is suffused by diffuse X-ray structures, signatures of multi-million-degree plasmas created by fast O-star winds or by the deaths of massive stars that stayed close to their birthplaces, exploding as cavity supernovae within the proto-superbubble that the Carina complex is creating.

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