Chandra Large and Very Large Projects

Proposal Number: 02200644

Title: TORTURED CORONAE IN THE RAPID BRAKING ZONE

PI Name: Thomas Ayres

Deep HETGS exposures of four key G0-G5 giants will address fundamental questions concerning their hot magnetized coronae by determining temperatures and densities, probing chemical fractionation processes, and exploring plasma dynamics. The giants lie in or near the "Rapid Braking Zone" where moderate mass stars undergo a radical transformation of their outer atmospheres, perhaps as a relic magnetosphere is disrupted by the onset of a solar-like dynamo. ACIS-I CCD spectra of five G/K supergiants will explore the even more extreme extension of the RBZ to higher masses: where hot coronae mix freely with cool stellar winds. These are ideal targets to exploit the experience gained in the Emission Line Project studies of the active binaries Capella and HR 1099.

Proposal Number: 04200312

Title: UNVEILING ETA CAR: CHANDRA OBSERVATIONS DURING THE 2003.5 EVENT

PI Name: Michael Corcoran

Understanding the supermassive star Eta Car is important for a variety of topics: the formation and evolution of extremely massive stars and their influence on their environments. Eta Car has been a mystery since its giant eruption in the 1840s. A possible key to the puzzle is the identification of periodic changes in some near IR emission lines, and the discovery of repeatable X-ray eclipses. The next X-ray eclipse will occur during AO4, and we propose to use HETG to observe the variations in the spectral and spatial distribution of the emission during this event. In conjunction with scheduled HST/STIS, INTEGRAL, IR and optical spectroscopy, and radio observations, these HETG observation provide key information which may finally help us solve the riddle of this star.

Proposal Number: 04200331

Title: AN ULTRADEEP CHANDRA STUDY OF THE ORION NEBULA (GUEST OBSERVER PORTION)

PI Name: Eric Feigelson

We propose a 850 ks ACIS-I observation of the Orion Nebula spanning 11.5 contiguous days, with GTO Teams providing 150 ks of the time. The Orion Nebula is the best target in the sky for Chandra study of stellar magnetic activity and star formation with extensive multiwavelength support. Science goals include: addressing the mass- and age-dependence of magnetic activity in brown dwarfs; uncovering the low-mass members of the deeply embedded clusters; elucidating the absence of an activity-rotation relation in pre-main sequence stars; measuring flare frequencies, flare plasma conditions and coronal structures in dozens of active stars; investigate the nature of OB wind shocks; and studying X-ray effects on circumstellar environments.

Proposal Number: 06200204

Title: A Chandra HETGS Survey of O-Stars

PI Name: Wayne Waldron

We are requesting HETGS observations of 6 normal O-stars to further explore the characteristics and the origin of the remarkably detailed X-ray line spectra that has been revealed by Chandra. These new targets have been carefully selected on the basis of their normal optical and UV spectra, instead of their X-ray brightness or peculiarity. Along with archival HETGS spectra, this collection will provide complete coverage of the O-star domain in the H-R diagram. The spectra from this unbiased sample will be assembled in a comprehensive X-ray atlas, which will be used to search for morphological trends in the emission lines as a function of stellar parameters. These trends will guide the development of quantitative models to explain the behavior of the X-ray emission lines of O-type stars.

Proposal Number: 06200294

Title: The X-ray Spectrum of a Planetary Nebula at High Resolution

PI Name: JOEL KASTNER

Planetary nebulae (PNs) provide unique insights into a wide range of astrophysical phenomena. X-ray imaging of PNs by CXO has now broken open the study of very high temperature gas in these objects. To make further progress, we require detailed information concerning gas temperature and composition as a function of position within X-ray emitting PN "hot bubbles." Such information can be obtained only from observations combining high spectral and spatial resolution. We propose a 300 ks LETG/ACIS-S exposure of BD+303639, a particularly X-ray-bright PN. Such a deep, high spectral resolution observation of a PN has yet to be attempted. The proposed observation thus represents a potential breakthrough in our understanding of the origin and evolution of PNs.

Proposal Number: 07200124

Title: The Initial Mass Function in the Outer Galaxy: The star forming region NGC 1893

PI Name: Giuseppina Micela

We will explore the effects of environmental conditions, which change dramatically between the inner and outer regions of the Galaxy, on the initial mass function (IMF) of the star forming region NGC 1893. Our proposed 450 ksec observation of NGC 1893, a SFR of ~3 Myr in the outer part of the Galaxy, joint with two hours of Spitzer data, will permit us to identify members down to 0.5 Msun and enable a comparison of NGC 1893's IMF with those derived for SFRs in the solar neighborhood. Our observations will help in determining, particularly in the low mass regime, how the IMF depends on galactic environment. With its spatial resolution and sensitivity, Chandra, with the support of Spitzer, is uniquely suited to achieve our objectives.

Proposal Number: 07200367

Title: Winds, OB Populations, and Young Stars: New Science from M17

PI Name: Leisa Townsley

We propose to use two ACIS-I pointings centered on the young, massive OB cluster in M17 (the Omega Nebula) and on its powerful X-ray outflow as a testbed for understanding recent and ongoing star formation in the M17 complex and its environmental impact. This rich field is perfect for studying X-ray emission from high-mass as well as intermediate/low-mass stars and for comparing the X-ray luminosity function in a high-mass complex to that in the closer, less powerful Orion Nebula Cluster, recently established by a long Chandra exposure. M17 is ideal for exploring the properties of diffuse X-ray emission to elucidate wind/wind and wind/cloud shock physics in HII regions and for studying embedded stellar clusters and massive protostars forming as M17 interacts with its molecular cloud.

Proposal Number: 08200704

Title: Accretion or a Corona? Definitive Observations of the Young Accreting Star TW Hydrae

PI Name: Nancy Brickhouse

We propose a 500 ks observation of the prototypical accreting young star TW Hydrae to determine whether the X-ray emission is from a hot corona or an accretion shock. In the short archival spectrum, O VII and Ne IX forbidden to intercombination lines signal either extremely high densities that must be associated with a shock, or photoexcitation by UV continuum emission. The definitive measurement for the density is the analogous Mg XI line ratio. We will also measure velocity shifts and line broadening, search for rotational modulation, and determine elemental abundances using standard emission measure distribution techniques. This deep spectrum will probe the density and structure of the magnetic regions associated with the accretion process during star formation.

Proposal Number: 10200509

Title: Testing the Colliding Wind Paradigm: X-rays from the Wolf-Rayet Binary System WR 147

PI Name: Svetozar Zhekov

We propose a deep HETG exposure of the Wolf-Rayet binary system WR 147. The excellent gratings and zero-order data will be used to put tight constraints on the validity of the colliding stellar wind (CSW) mechanism assumed responsible for the X-rays from this object. The detection of broad emission lines with profiles and centroids in agreement with synthetic colliding wind spectra, along with confirmation of the spatially extended X-ray emission reported from the previous short HRC-I exposure, would support the colliding wind picture. On the other hand, narrow (or unresolved) unshifted emission lines would require an interpretation other than CSW. Thus, this study will be the most rigorous test of the CSW paradigm in a WN+OB binary so far.

Proposal Number: 11200169

Title: Cosmic archaeology with Chandra: from a supergiant shell to young stellar objects in NGC 602

PI Name: Lidia Oskinova

The Wing of the SMC has low metalicity, and low content of gas and dust. It provides an ideal nearby laboratory to study star formation and feedback in an environment that resembles the early Universe. We propose a 300 ks Chandra observation of NGC602, a massive star cluster at the edge of a supergiant shell in the Wing. This cluster has a simple morphology and is located in a region of high transparency for X-rays. The Chandra data will help to answer the fundamental questions about the mechanisms that sculpture the largest structures in the ISM, and trigger the formation of stars. This observation will be complemented with data from other NASA Great Observatories HST and Spitzer, and will establish a template for studies of active star formation in external galaxies.

Proposal Number: 11200420

Title: New Thrust for Jets: Understanding the Physics of Young Stellar Jets and Outflows

PI Name: Manuel Guedel

We propose a deep ACIS observation of the jet system of the classical T Tauri star DG Tau. DG Tau is so far unique because both its jet and counter-jet have been detected in X-rays. We will study jet structure, temperatures and proper motions of the sources and model the heating, propagation, and cooling physics of the hot plasma jets. The system orientation allows the counter-jet to be viewed through the circumstellar disk. X-ray absorption by the disk gas can thus be reliably determined and be used, together with optical information, to determine the gas-to-dust ratio in the disk. We will request radio (VLA) observations for complementary imaging, and near-IR (VLT) observing time for high-resolution spectroscopy to characterize the jet shocks and measure extinction along the jets.

Proposal Number: 11200698

Title: The Chandra Cygnus OB2 Survey

PI Name: Jeremy Drake

Understanding massive "starburst" clusters is crucial for the first stars, starburst galaxies, galactic and ISM evolution, and star and planet formation on universal and galactic scales. But Galactic superclusters are generally too distant for detailed study. Recent awareness that Cygnus OB2 (1.5kpc; ~2Myr old) has supercluster characteristics has sparked a multiwavelength legacy effort exploiting its proximity to study starburst astrophysics. This Chandra Legacy project will provide an exquisite vision of the anatomy of a massive "collapse" mode of star formation, allowing detailed archeology of its history and content. 8000-10000 detections down to 0.1Msun will incisively test theories of giant molecular cloud collapse, massive star formation and protoplanetary disk evolution.