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Proposal Number: 09200028

Title: Search for triggered star formation in the unique bright rimmed cloud 4

PI Name: Gordon Garmire

In order to further our understanding of the radiation driven implosion (RDI) processes and provide an observational feedback to the theoretical modelling of these processes for a wide range of parameters, we propose to search for and study triggered star formation in the highly under-pressured with respect to its ionized boundary layer and one of the smallest among the known cataloged bright rimmed clouds (BRCs), BRC 4. The data and science analyses similar to those applied in our study of the BRC 38 (= IC 1396N) will be employed.

Proposal Number: 09200053

Title: ACIS Mapping Observation of W75N/DR21

PI Name: Gordon Garmire

W75N/DR21 is a complex of several massive star-forming regions at a distance of 2-3 kpc in Cygnus. Recent wide-field imaging survey program using Spitzer/IRAC, UKIRT/WFCAM, and JCMT/SCUBA revealed the entire picture of this complex, which is filled with various signatures of massive star birth. The central part of the complex, DR21, is scheduled to be observed by a deep ACIS-I pointing in the cycle 8. By adding two more ACIS-I pointings, we will cover all the major regions in this complex. The primary objective is to conduct a census of weak-line T Tauri stars using their elevated X-ray emission. By combining with the longer wavelength datasets that are sensitive to less evolved population, we will understand how the star formation proceeded in this region.

Proposal Number: 09200063

Title: X-Raying the debris disk of AU Mic

PI Name: Peter Predehl

We propose to measure the X-ray absorption by AU Mic s debris disk as well a high resolution spectrum of a flare star which allows us to perform density diagnostics in the N, O, and Ne triplet lines as well as perfrom an abundance analysis of the CNO elements.

Proposal Number: 09200064

Title: The HETG Orion Legacy Project: The Periastron Passage of Theta1 OriC's Massive Secondary

PI Name: Claude Canizares

The Trapezium Cluster is one of the youngest and closest (440 pc) star-forming regions. Many of the properties we know today are derived from X-ray signatures. This program has two goals. First we study highly resolved X-ray spectra of a large ensemble of very young and chemically similar PMS stars in terms of their magnetic and accretion properties. It is part of our HETG Orion Legacy Project which amouts to 430 ks by the end of AO8. This portion has a second purpose which aims to record the post-periastron passage of the recently discovered massive secondary of Theta 1 Ori C. Orion cannot be observed until midJuly 2007 from which on we will be able to record possible shock emission from colliding wind events or interacting magnetic fields.

Proposal Number: 09200065

Title: The HETG Orion Legacy Project: PMS Stellar Studies of the Orion Trapezium Cluster

PI Name: Claude Canizares

The Trapezium Cluster at the center of the Orion Nebula Cluster (ONC) is one of the youngest and closest (440 pc) star-forming regions. Many of the properties we know today are derived from X-ray signatures. Here we study highly resolved X-ray spectra of a large ensemble of very young and chemically similar PMS stars in terms of their magnetic and accretion properties. This is the forth of several installments of our Orion HETG Legacy Program, which already amounts to 430 ks by the end of AO8. There are two installments of 75 ks in AO9. This is the second installment which will lead to the final exposure of the project of 580 ks. On completion we expect about a dozen of well exposed HETG PMS star spectra and HETG Trapezium spectra of supreme quality. .

Proposal Number: 09200079

Title: Protostars and Jets in Cep A

PI Name: Steven Pravdo

Cep A is a region of intense star formation with a well-studied bi-polar molecular outflow, the nearest identified high-mass protostars, and X-ray Herbig-Haro (HH) objects. Unresolved areas of X-ray emission make it a prime target for Chandra/ACIS-I. We propose an 80 ks observation to measure the spatial structure, spectrum, light curve, and intensity of the X-rays, including HWX, the unresolved X-ray candidate for the power source, and to identify counterparts. The goal is to increase our understanding of the energy sources and the outflows. We will also image a nearby ridge of hard X-ray emission to investigate its origin. We will use Chandra s superior spatial resolution to clarify the puzzling offsets between the X-ray emission and the areas of peak optical excitation in HH 168.

Proposal Number: 09200137

Title: Resolving the Xi Boo Binary

PI Name: Brian Wood

Due to its close proximity (d=6.7 pc), the primary of the Xi Boo binary (G8 V+K4 V) is one of the best targets for studying the coronal characteristics of moderately active stars. However, previous X-ray observations of Xi Boo are complicated by their inability to separate the emissions of the two stars. We propose to obtain LETG/HRC-S spectra of Xi Boo, which will easily resolve the stars and provide high quality spectra of both. We will then explore the nature of an apparent change in coronal character that exists at about the activity level of Xi Boo A by comparing the Xi Boo A spectrum with an existing LETGS spectrum of Epsilon Eri (K1 V), these two stars being on opposite sides of the transition.

Proposal Number: 09200153

Title: BP Psc: Chandra Takes a Close Look at a Pre-Main Sequence Star-Disk-Jet System

PI Name: Joel Kastner

Observational studies of disk-jet systems in pre-main sequence (PMS) stellar evolution provide insight into a diverse range of phenomena, including jet launching and collimation, protostellar accretion, and the formation and evolution of planetary systems. We propose to obtain Chandra/ACIS-S3 imaging spectroscopy of BP Psc, the only known actively accreting and jet-driving PMS star within 100 pc of Earth. These observations will take full advantage of this unparalleled opportunity to probe star-disk-jet interactions within ~30 AU of a PMS star, via X-rays.

Proposal Number: 09200162

Title: Are the Herbig Ae star HR 5999 and the peculiar A-type star HR 6000 X-ray emitter?

PI Name: Jan Robrade

We propose a 10 ksec pilot study with ACIS-I of the visual A-type binary HR 5999/HR 6000 located in the Lupus star forming region. HR 5999 is a X-ray bright Herbig Ae star, HR 6000 is a possibly magnetic X-ray bright A-type star. Both stars would be ideal grating targets. With the proposed ACIS pointing we want to verify that the X-ray emission does indeed come from the A-type stars.

Proposal Number: 09200198

Title: The coronae of ultracool dwarfs: Simultaneous X-ray and radio monitoring

PI Name: Beate Stelzer

In late-type stars the interaction of stellar magnetic fields with hot plasma trapped within the field lines gives rise to Halpha,X-ray and radio emission, as in the Sun. The coolest stars and brown dwarfs not follow this solar-stellar analogy: their radio emission tends to be overluminous by 3 dex with respect to their X-rays, and there is no clear rotation-activity connection. Possibly the situation in ultracool atmospheres is quite different from those of higher-mass stars, and new emission mechanisms need to be invoked. Since both radio and X-ray emission of these objects are strongly variable, the observational picture remains unclear as long as no simultaneous data is available in both bands. We propose here for joint Chandra/VLA observations of 3 ultracool dwarfs.

Proposal Number: 09200200

Title: Surveying Magnetic Activity in L and T Brown Dwarfs

PI Name: Marc Audard

We propose to continue our investigation of magnetic activity in L and T brown dwarfs in the X-rays with Chandra and in the radio with the VLA and ATCA. We propose to observe three brown dwarfs in the largely unexplored late-L and T regimes with Chandra. Our targets are close, old (~1 Gyr) brown dwarfs, whose Halpha emission should not be contaminated by any accretion mechanism as in young brown dwarfs. With this Chandra proposal, we aim to detect X-rays in brown dwarfs during quiescence or flares. Simultaneous radio observations with the VLA and ATCA are requested as well. This investigation will help us to obtain a census of magnetic activity in L and T brown dwarfs and to better understand the efficiency to generate magnetic fields at the bottom of the main sequence.

Proposal Number: 09200214

Title: NGC 3576: Spontaneous or Triggered Formation of a Giant HII Region

PI Name: Leisa Townsley

Our understanding of massive star formation is uncertain at all levels, from individual stars to massive stellar clusters to OB associations. Our first Chandra observation of the Galactic giant HII region NGC 3576 addressed one example of the first of these problems: because hard X-rays penetrate even very large columns of obscuring material, we were able to pinpoint massive, young, embedded stars that remained undetected even at 3.5 microns, solving the mystery of NGC 3576's missing ionizing sources. With a new ACIS-I pointing and the first Spitzer observation of this target, we will address the second two of these problems: how massive clusters form and how they are related to the formation and evolution of the larger-scale, unbound populations known as OB associations.

Proposal Number: 09200253

Title: The Further Fainting of Alpha Cen A

PI Name: Thomas Ayres

Alpha Centauri (G2V + K1V) is the nearest system of solar-like stars. The primary has long been regarded a solar twin. Previous X-ray missions have been able to separate the coronal point sources (14" apart in Y2000), although the orbit now is closing rapidly and beyond 2006 can only be resolved easily by Chandra. The 25 year X-ray record has revealed striking long term changes in the Alpha Cen coronae, likely related to analogs of the still mysterious solar sunspot cycle. Recent work suggests that the K star is falling into a cycle minimum, while the G star is relapsing following a brief recovery from an unprecedented deep X-ray minimum in 2005 (that fully challenges our understanding of stellar dynamos). Two 10 ks HRC-I snapshots in 2008 will build on this remarkable coronal narrative.

Proposal Number: 09200255

Title: A Survey of X-ray Emission from Nitrogen-rich Wolf-Rayet Stars

PI Name: Stephen Skinner

The winds of Wolf-Rayet (WR) stars enrich the ISM with heavy elements that will be recycled into future generations of stars and WR stars end their lives as supernovae, creating powerful shock waves that will trigger new star formation. Previous X-ray studies of WR stars have focused on X-ray bright WR+O binary systems and little is known about the origin of X-ray emission from single WR stars. We propose to conduct a limited survey of the closest known single nitrogen-rich (WN subtype) Wolf-Rayet stars. This study will complement a parallel survey of more evolved carbon-rich (WC subtype) WR stars now underway. This pilot survey will break new ground and will provide basic information on X-ray properties needed to test wind-shock theories.

Proposal Number: 09200257

Title: The clear view of WR140's collisionless shocks through the companion O-star wind

PI Name: Andrew Pollock

In January 2009, two extraordinary high-mass colliding-wind binary systems, eta Car and WR140, will go through the periastron passages of their respective 5.5 and 7.9 year orbits. The preceding months are the most favorable for observing the rapid rise to X-ray maximum and learning fundamental lessons about shocks, hot plasmas and mass-loss in the upper HR diagram. Three HETGS snapshot spectra of WR140 will capture the line-profile and global spectral responses of its collisionless shocks to the changing physical conditions that follow the well-defined orbital geometry, offering unique information about the plasma and mass loss from both stellar components. This proposal, and one on eta Car, will take advantage of opportunities for X-ray specroscopy that might not arise again.

Proposal Number: 09200270

Title: Filling in the Coronal Graveyard

PI Name: Thomas Ayres

20 ks Chandra HRC-I pointings on 5 late-type G/K supergiants in the depths of the "coronal graveyard" will complete a survey of the limits of X-ray activity in evolved cool stars. Our ambition is to gain insight into magnetic generation in the absence of sensible rotation, and the disposition of hot coronal structures in the extended outer envelopes of these objects, possibly partially smothered under a "cool absorber." Such buried activity might be the long sought initiator of chromospheric winds in the giant branch. Coronal activity is important to the Sun-Earth connection, the fate of primitive planetary atmospheres, and a broad reaching set of magnetic phenomena in diverse cosmic environments. Understanding the activity, and its evolution, is a key objective of stellar astrophysics.

Proposal Number: 09200326

Title: Search for X-Ray Emission from TW Hya Association Brown Dwarfs

PI Name: John Gizis

There are four known brown dwarfs which are members of the TW Hya Association (TWA). With an age of 10 Myr and a distance of only fifty parsecs, this association is the best opportunity to study young brown dwarfs in detail. Chandra has already observed two of the TWA brown dwarfs; we propose here to observe the other two. By doubling the sample, we will test ideas about coronal and chromospheric emission and about activity due to accretion from circumstellar disks. Spitzer observations for all of these brown dwarfs have been taken or are scheduled.

Proposal Number: 09200357

Title: Survey of Class 0 Protostars in the Smallest Clouds 'Bok Globules'

PI Name: Yohko Tsuboi

We propose a survey of six nearby Bok globules to search for X-rays from Class 0 protostars. X-rays from Young Stellar Objects are likely to originate from the near vicinity of the star itself. The detection of the X-rays from Class 0 protostars, therefore, is of particular importance, providing direct evidence that the central star has been born. However, protostars are usually deeply embedded within the cloud, so that, even the X-rays are completely absorbed. Bok globules are known as star formation sites surrounded by light and small molecular clouds of 10 Mo. The small absorption column of Bok globules provides us an opportunity to search for whether X-rays ``turn on'' during the Class 0 phase and if so, when?

Proposal Number: 09200403

Title: The Coolest X-ray Emitting White Dwarfs?

PI Name: Marcel Agueros

Among the ~6000 new white dwarfs (WDs) spectroscopically confirmed by the Sloan Digital Sky Survey (SDSS) are three cool DAs and two cool DBs within 1' of super-soft ROSAT All-Sky Survey (RASS) sources. WDs at these relatively low temperatures (<23,000 K) are not expected to be X-ray emitters, but the SDSS photometric and spectroscopic data fail to identify any other obvious optical counterparts to the RASS sources to the SDSS limits (g~22 mag in photometry). We propose a total of 25 ksec of Chandra observations of these five SDSS WDs to obtain pinpoint X-ray positions and improved flux measures for these objects. If Chandra data confirm that the five WDs are X-ray sources, they will be of great interest; in particular, work will be required to explain how such cool WDs can emit X rays.

Proposal Number: 09200488

Title: The Full Picture of Magnetic Activity in Ultracool Dwarfs: Simultaneous Observations of Coronae and Chromospheres

PI Name: Edo Berger

Only a decade ago, theoretical expectation was that magnetic activity would disappear beyond M5. While we now know that stellar activity exists in some late-M dwarfs, only a few such objects have been observed in the X-rays. Thus, the ubiquity and physics of coronae and magnetic fields remain unclear. This is exacerbated by the shift to flaring emission, whose properties are poorly characterized due to the lack of simultaneous observations. It is therefore time to produce a complete picture of the coronae and chromospheres in ultracool dwarfs, and directly implicate magnetic fields in this activity. Here we propose to delineate the underlying physics of the magnetic activity with fully simultaneous observations in the X-ray, radio, and H-alpha bands.

Proposal Number: 09200532

Title: X-raying the Giant HII Region G305

PI Name: Marc Gagne

G305, one of the nearest giant HII regions, contains a WR binary, eight distinct clusters each containing hundreds of stars and eight maser sources and ucHII regions each containing 4-8 very young O stars. The bubble contains ~30 O stars suggesting a population ~15,000 cluster members. A 125-ks ACIS exposure will detect all of the high-mass stars and a high fraction of the low-mass YSOs in the central clusters and HII regions. A 60-ks EPIC exposure will do the same in the sparser outer clusters and HII regions. The EPIC observation may detect diffuse emission in the inner cavity or within the optical HII region RCW 74. Our goals are to obtain ACIS and EPIC spectra of the high-mass stars, EPIC and RGS spectra of WR 48a, EPIC spectra of diffuse X-rays and a census of the low-mass YSOs.

Proposal Number: 09200535

Title: An Emerging Class of Hot Emission Line Stars: HD 119682

PI Name: Cara Rakowski

Herein we propose to observe the dispersed spectrum of the emission line star HD 119682. Existing CCD-resolution observations show this source to be both luminous and impressively hot, such that its emission cannot be explained by the standard radiatively-driven-wind model for O stars. At more the 4 Myr old, a magnetically confined wind would be unprecedented for a star of its age. Alternatively this may be an example of an emerging class of "gamma Cas analogs", emission-line early B stars with a narrow range of optical properties and X-ray spectra dominated by a hot (>8 keV) thermal component.

Proposal Number: 09200536

Title: ToO Studies with CXO of Pre-Main Sequence Stars Undergoing Optical Outbursts

PI Name: David Weintraub

Dramatic optical outbursts, which signal the onset of rapid and dramatic accretion onto pre-main sequence stars through their disks, cannot be predicted; however, our previous CXO campaign to study the outburst source V1647 Ori demonstrates that studies of such stars made with CXO beginning immediately after outburst can dramatically increase our knowledge about how and why such stars undergo outbursts and accrete mass. We therefore propose a target of opportunity campaign to observe any such stars discovered during Cycle 9. We will use ACIS-S, to enable us to carry out 20ks - 30 ks imaging spectroscopy observations, spaced by intervals of two and later three months, beginning immediately after discovery and continuing through the end of Cycle 9.

Proposal Number: 09200559

Title: Effects of massive star radiation on circumstellar disks evolution in the Eagle Nebula

PI Name: Mario Guarcello

We will determine the frequency of disk and disk-less stars in the outer regions (relatively poor of massive stars) of the young cluster NGC 6611, with the aim to study the effects of UV flux due to massive stars on the evolution of circumstellar disks around low mass stars. Our previous results for the central region of the cluster show that this effect may be present, but we need to observe stars at larger distance from massive stars. This cluster is particularly well suited for our study, thanks to the irregular spatial distribution of its OB stars. CHANDRA observations are crucial for identifying the disk-less population undetectable with other method.

Proposal Number: 09200564

Title: X-ray and Radio Imaging of the Protostar Complex Adjacent to IC 348

PI Name: Scott Wolk

Among several classes of active stars and solar flares, a tight relation between X-ray and radio luminosities is found. This relation implies an intimate physical connection. We propose a pair of 40 ks coordinated VLA/ACIS-I observations of a newly revealed filamentary structure of nearly two dozen protostars and pre-stellar cores just southwest of IC 348. Using extant Spitzer and SCUBA data we have a full inventory of the stellar types in this cluster which contains Class 0 and Class I protostars and outflow sources in addition to classical and weak T-Tauri stars. We will complete the census of this nearby, actively forming, sub-cluster and study the causal relation of radio and X-ray emission for all types of young stars, both in flare and quiescent.

Proposal Number: 09200584

Title: Shock Dynamics in Eta Carinae Approaching the 2009 Periastron Passage: A Twisted Tail

PI Name: Michael Corcoran

In January 2009, the two most extraordinary high-mass colliding-wind binary systems, eta Car and WR140, will go through the periastron passages of their respective 5.5 and 7.9 year orbits. The months before, during their rapid rise to X-ray maximum, are the most favorable time for observing X-ray emission at high resolution and learning fundamental lessons about shocks, hot plasmas and mass-loss in the upper HR diagram. Three HETGS observations of Eta Car will monitor X-ray line and continuum changes to obtain unique information about the X-ray emitting plasma in the wind-wind collision, as a probe of mass loss from Eta Car and from the hidden companion star. This proposal, and a complementary one on WR 140, will take advantage of an opportunity that may never arise again.

Proposal Number: 09200644

Title: Polar Exploration and Coronal Structure in the Active Binary HR 5110

PI Name: Rachel Osten

Overwhelming evidence exists for the importance of polar regions in controlling stellar atmospheric structure and dynamics in active binary systems. Uncertainties about the geometry of coronal emission have made conclusions about coronal structures on such stars ambiguous. We seek Chandra, VLA and VLBA observations of the nearly pole-on active binary system HR 5110 in order to investigate coronal structures without such ambiguity. An 80 ks Chandra observation will constrain thermal coronal volumes through electron densities; radio observations will constrain nonthermal coronal volumes directly, and allow an estimation of the relative importance of thermal and nonthermal plasma in controlling and structuring active stellar coronae.

Proposal Number: 09200659

Title: Catching the Post-Outburst State of the Erupting Star V1118 Ori

PI Name: Marc Audard

We propose to catch the post-outburst state of the young accreting star V1118 Ori with Chandra and Spitzer. V1118 Ori underwent an optical outburst in January 2005 and has now returned to a ``quiescent'' state. Our X-ray monitoring observations have shown that the X-ray spectrum softened after the outburst, maybe due to changes in the magnetic structure near the star as a result of the increased accretion load. Our long-term monitoring indicates that the X-ray flux correlates with the optical flux, a signature that accretion can impact the X-ray emission of outbursting young stars. We propose also to obtain the post-outburst spectral energy distribution in the mid-infrared with Spitzer. We will compare the new data with those taken by us in the early phase of the outburst.

Proposal Number: 09200673

Title: Can different elements move with different velocities in a radiatively driven stellar wind?

PI Name: Lidia Oskinova

B-type stars of lower luminosity classes have relatively weak stellar winds. In this respect they resemble presumably the more massive, but metal-poor stars in the early Universe. Theory predicts that very thin stellar winds are multi-component fluids. The ions of iron group metals are accelerated by radiation pressure, but do not transfer their momentum to the bulk of material. This dynamical decoupling is not yet observationally confirmed. LETG HRC-S spectra of the X-ray brightest non-degenerate massive star alpha Cru will allow to detect different velocities of particle species in stellar wind. These observations will empirically confirm or disprove the effect of dynamical decoupling in a thin stellar wind.

Proposal Number: 09200690

Title: The Evolution of X-ray Emission in the Planet-Forming Era

PI Name: Jon Miller

The 4-30 Myr age range is particularly important in the life of pre-main sequence stars. It is in this age range where disks dissipate, as evidenced by a decrease in infrared excess emission arising from disks. Giant planets are expected to form in this age range, and the possible link between planet formation and disk dissipation is presently one of the most studied topics in star and planet formation. The dissipation of disks must have profound and testable consequences for the X-ray emission in this age range. Yet we are still lacking information on the early evolution of the X-ray emission in pre-main sequence stars. We therefore propose to make ACIS-I observations of fields in four 4-10 Myr clusters: NGC 7160, Tr 37, 25 Ori, and Ori OB1b.

Proposal Number: 09200730

Title: X-ray Emission from a 7 Myr Old, Accreting Herbig Ae star and its Jet: MWC 480

PI Name: Carol Grady

We are requesting Chandra ACIS-S imagery of MWC 480, a 7 Myr old Herbig Ae star with an accretion rate of 1E-8 solar masses/yr, intermediate between younger, accreting stars and older stars with transitional disks. The proposed integration will allow us to better delineate the evolution of X-ray activity in Herbig Ae stars, testing the hypothesis that the L_x is correlated with accretion signatures, rather than originating in coronal emission associated with a decaying dynamo. MWC 480 is also associated with a parsec-scale bipolar outflow, HH 728, with a 50" long counterjet which terminates in large, bright Herbig-Haro (HH) knot which will permit us to test models for X-ray production in HH knots over a wider range in outflow parameters than has been done to date.

Proposal Number: 09200763

Title: X-RAY AND UV PHOTOIONIZATION AND PHOTOEXCITATION OF PRE-MAIN-SEQUENCE STAR TRANSITIONAL DISKS

PI Name: Alexander Brown

Transitional disks are one of the most crucial and important stages of the evolution of pre-main-sequence stars and protoplanetary systems. These disks have transformed most of the dust and gas in their inner regions into planetesimals and show clear inner ``holes'' that almost certainly harbor infant planetary systems. We propose to observe 3 young stars with transitional disks (T Cha, GM Aur, LkHa 330) using ACIS-S to measure their X-ray radiation field and coronal emission properties and HST ACS-SBC to image the fluorescently excited molecular hydrogen in these systems to determine if the gas distribution follows the behavior seen in the dust distribution. Our broader goal is to model the X-ray/UV photoionization and photoexcitation of the disks and study their photochemistry.

Proposal Number: 09200803

Title: A detailed investigation of coronal/magnetic and rotational changes in cool stars using NGC 3532

PI Name: Steven Saar

We propose to use Chandra ACIS-I to study the one-to-one correspondence recently proposed between coronal/dynamo and rotational changes in cool stars. The goal is insight into the physical basis underlying the 3-part X-ray classification of cool stars (saturated, super-saturated, and normal rotation-activity), crucial to fully interpreting the rotational/magnetic/activity evolution of cool stars. We already have copious optical data on our rich target open cluster NGC 3532, including 83 rotation periods for the cluster members, making it uniquely useful for rotation-activity studies. Furthermore, its age, 300Myr, nicely bridges a gap in the age sequence of the best studied clusters between 100Myr (Pleiades) and 600Myr (Hyades), permitting detailed study of evolution between these epochs.

Proposal Number: 09200839

Title: X-ray Emission from the Hot White Dwarf KPD 0005+5106: Corona or Accretion?

PI Name: You-Hua Chu

X-rays at energies >0.5 keV, not expected from the photosphere of a white dwarf (WD), can be produced only in stellar coronae or from accretion of material onto a WD's surface. KPD 0005+5106 and WD 2226-210 are two outstanding cases of single WDs with X-ray emission at 1 keV. Recent Spitzer observations of WD 2226-210, the central star of the Helix Nebula, reveal excess continuum emission starting at 8 um and peaking at 24-70 um, indicating the existence of a dust disk at 50-100 AU from the star. The dust is most likely produced by collisions among Kuiper Belt-like objects (KBOs). Stray KBOs impacting the WD surface may produce the 1 keV emission. We request Chandra and Spitzer observations of KPD 0005+5106 to search for a similar dust disk and determine the origin of its 1 keV emission.

Proposal Number: 09200905

Title: Evaluating the Role of Photoevaporation in Protoplanetary Disk Dispersal

PI Name: Gregory Herczeg

Emission produced by accretion onto the central star leads to photoevaporation, which may play a fundamental role in disk dispersal. Models of disk photoevaporation by the central star are challenged by two potential problems: the emission produced by accretion will be substantially weaker for low-mass stars, and photoevaporation must continue as accretion slows. We propose use HST/ACS SBC PR130L to obtain FUV spectra of WTTSs and of CTTSs at low masses and mass accretion rates to provide crucial data to evaluate photoevaporation models. We will estimate the FUV and EUV luminosities of low-mass CTTSs with small mass accretion rates, CTTSs with transition disks and slowed accretion, and of magnetically-active WTTSs.

Proposal Number: 09200907

Title: A Hard Look at Stellar Disks at the Epoch of Planet Formation

PI Name: Lee Hartmann

We propose to use the HST/ACS/SBC and Chandra/ACIS-S3 to observe the high energy fluxes of 4 stars surrounded by disks in the newly discovered aggregate 25 Ori, the most populous 10 Myr group known within 500 pc. Our observations will cover the 1-25 A and 1250-2000 A bandpasses, and will complement our optical and Spitzer data for these objects, to provide essential input to physically-consistent models of disk structure and chemistry in the age range around 10 Myr, thought to be a critical period in the planet-forming process. Our proposed observations will double the number of 10 Myr old accreting stars with known high energy radiation fields, and will be the first FUV observations of low mass accreting stars in an OB association.

Proposal Number: 09200909

Title: Probing the Gas in the Planet Forming Regions of Protoplanetary Disks

PI Name: Nuria Calvet

The origin of planets is intricately tied to the evolution of primeval disks. The finer details of how the disk material evolves from an initially well-mixed distribution of gas and dust to a system composed mostly of large solids and gas giants like our own solar system is not well understood and is a fundamental question in astronomy. We can refine theories of planet formation and develop timescales for the evolution of planetary systems by studying the inner, planet-forming regions of protoplanetary disks.

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