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Proposal Number: 09400002

Title: Joint XMM-Newton/Chandra/RXTE Observations of Dips in Cyg X-1

PI Name: Joern Wilms

At phase 0, Cyg X-1 shows pronounced soft X-ray dips due to highly variable, partial blockage from the accretion stream. Studying these dips requires joint XMM/Chandra/RXTE observations: XMM will provide the continuum through the broad Fe line region (allowing a clean separation of the line into narrow and relativistically broadened components), and it will achieve higher S/N than Chandra at < 2keV, allowing the dipping events to be temporally resolved and spectrally modeled on short time scales. (RGS will have better spectral resolution than HETGS when both are binned to equal S/N on short time scales.) The Chandra data will provide high resolution spectroscopy of the dipping events, while RXTE - available via our ongoing monitoring campaign - will provide the hard X-ray continuum.

Proposal Number: 09400003

Title: Monitoring Observations of the Galactic Center Region

PI Name: Rudy Wijnands

We propose to continue our XMM-Newton and Chandra monitoring campaign of the inner 1.2 square degree region centered on Sgr A*. We will be able to detect very faint transients in this region with a peak luminosity of 1E33 - 1E35 ergs/s, 10-1000 times more sensitive than would be possible with other satellites (i.e., RXTE and INTEGRAL}. This allows us to observe a very poorly studied group of transients and to follow the luminosity behavior of faint (1E36 ergs/s) persistent sources.

Proposal Number: 09400014

Title: Chandra follow-up of a weak persistent source found in INTEGRAL maps: IGR J17204-3554

PI Name: Mariano Mendez

We propose to observe IGR J17204-3554 for 1 ksec exposure with the ACIS-I to obtain a sub-arcsec position of the X-ray source in combination with spectral characteristics. The unique Chandra positional capabilities will allow for an optical follow-up study, which is of paramount importance for the classification of the source.

Proposal Number: 09400018

Title: Chandra follow-up of weak persistent sources found in INTEGRAL maps

PI Name: Mariano Mendez

We propose to obtain a 1 ksec exposure of up to 2 newly found unclassified INTEGRAL sources which are weak persistent X-ray sources (we exclude from this proposal the bright new transients discovered by INTEGRAL). The unique Chandra positional capabilities will allow for an optical follow-up study. Follow-up observations are of paramount importance for the classification of the sources (e.g. as HMXBs/LMXBs, pulsars and pulsar wind nebula, or in a few rare cases as AXP/SGR or INS).

Proposal Number: 09400019

Title: Chandra follow-up of a weak persistent source found in INTEGRAL maps

PI Name: Mariano Mendez

We propose to observe XTE J1716-389 for 1 ksec exposure with the ACIS-I to obtain a sub-arcsec position of the X-ray source in combination with its X-ray spectral characteristics. The unique Chandra positional capabilities will allow for an optical follow-up study, which is of paramount importance for the classification of the source.

Proposal Number: 09400020

Title: The Galactic Bulge Survey: categorising the plethora of faint X-ray sources in the Galactic Bulge

PI Name: Mariano Mendez

We propose to image an area of 6x1 degrees centered on the Galactic Center at |b|=1.5 degrees. Here, we propose to obtain ~25% of this as part of SRON's GTO program. These regions have been selected because of their lower extinction and crowding in the optical and near-infrared than in the Galactic Center area, while still having a high density of X-ray sources. We will detect a plethora of faint X-ray sources that will constrain binary evolution models by way of a number count and by identifying predicted X-ray binary types that so far have eluded identification. Source identifications will be boosted by our obtained optical data. We expect to find (quiescent) eclipsing neutron star and black hole LMXBs. These are important for neutron star and black hole mass measurements.

Proposal Number: 09400055

Title: HETG Observations of the Accretion Disk Corona Source X1822-371

PI Name: Claude Canizares

X1822-371 is the prototype of the Accretion Disk Corona (ADC) sources, i.e., near edge-on low mass X-ray binaries where the primary emission is observed via scattering in a very spatially extended corona, and we are viewing the X-ray source partially eclipsed/absorbed by the atmosphere of the outer accretion disk. We therefore propose Chandra High Energy Transmission Gratings (HETG) observations to obtain line diagnostics of the disk atmosphere and structure. Our observations are designed to go substantially deeper than the existing archive observation, i.e., doubling the signal-to-noise, and thus providing a "legacy" dataset for HETG observations of ADC.

Proposal Number: 09400117

Title: Transient LMXBs in Globular Clusters: More Numerous Than We Thought?

PI Name: David Pooley

Since the discovery of globular cluster LMXBs in the 1970s, it was assumed that there was only one bright LMXB per cluster. Deep Chandra observations of several globular clusters have revealed that they contain numerous quiescent LMXB systems, any of which could go into outburst. Our observations will determine whether new outbursts from transient LMXBs in NGC 6440, Terzan 5, and Terzan 1 are from the same sources that were previously seen in outburst.

Proposal Number: 09400125

Title: X-Ray Jets in Microquasars

PI Name: Stephane Corbel

We propose Target of Opportunity (ToO) observations for detailed studies of X-ray jets from microquasars. We describe our discovery of radio/X-ray jets in two microquasars, why X-ray jets are probably much more common than previously thought, and transient X-ray jets offer an exciting new way to probe the physics of relativistic jets from black holes. The proposed ToO observations are optimized to discover and study (flux evolution, morphology, SED, proper motion, ...) of new X-ray jets from microquasars, triggered by their detection as radio lobes. This will have implications not only for the study of jets from Galactic X-ray binaries, but also for our understanding of relativistic jets from active galactic nuclei (AGN).

Proposal Number: 09400192

Title: Crustal cooling in quiescent neutron stars

PI Name: Edward Cackett

We propose a 30 ksec observation of each of the quasi-persistent neutron-star low-mass X-ray transients KS 1731-260 and MXB 1659-29 in quiescence. The long outbursts in both of these sources heated the neutron star crust out of thermal equilibrium with the core. We have tracked the cooling of the neutron star crusts in both objects since they went in quiescence. We have preliminary evidence that the cooling has ceased, perhaps indicating that the crust is in equilibrium with the core. Our proposed observations will test the equilibrium suggestion, by placing tight limits on residual cooling and/or residual accretion, and determine the core temperature, constraining the equation of state of dense matter.

Proposal Number: 09400196

Title: The Galactic Bulge Survey: categorising the plethora of faint X-ray sources in the Galactic Bulge

PI Name: Peter Jonker

We propose to image an area of 6x1 degrees centered on the Galactic Center at |b|=1.5 degrees: the Galactic Bulge Survey. 25% of this area will be observed as an SRON GTO program in AO9. We here propose for another 25%. These regions have been selected because of their lower extinction and crowding in the optical and near-infrared than in the Galactic Center area, while still having a high density of X-ray sources. We will detect a plethora of faint X-ray sources that will constrain binary evolution models by way of a number count and by identifying predicted X-ray binary types that so far have eluded identification. We expect to find (quiescent) eclipsing neutron star and black hole LMXBs. These are important for neutron star and black hole mass measurements.

Proposal Number: 09400208

Title: Following a black hole candidate X-ray transient to quiescence

PI Name: Peter Jonker

There is increasing evidence that the quiescent state of BH X-ray binaries is different from the hard state that is observed at higher luminosities. Our recent Chandra campaigns on BH transient decays suggest that a transition takes place when the luminosity suddenly drops by almost three orders of magnitude during a period of only a few weeks. This transition has so far not been resolved, but there is strong evidence that the spectrum softens during this rapid decay. Both the decay and spectral evolution can provide important constraints for jet-dominated and ADAF-like models. We propose a more refined program than before and request 6 simultaneous Chandra/VLA TOO observations that aim to cover this rapid transition in full detail for the first time with X-ray and radio observations.

Proposal Number: 09400224

Title: High Resolution Spectroscopy of GRS 1915+105 in the 'Soft' State

PI Name: Yoshihiro Ueda

We propose to perform a TOO observation of GRS 1915+105 in the soft state with Chandra/HETGS. Investigation of iron-K absorption lines provide us with powerful diagnostics of highly ionized plasma associated with the accretion flow of microquasars. Although such features were discovered firstly from superluminal sources, the nature of the highly ionized plasma in GRS 1915+105 and its possible relation to relativistic jet ejection still remains unclear. This is because the source stays mostly in the low/hard state, where the ions are fully ionized by the strong hard X-ray flux and a very weak feature from H-like Fe ions is observable. Previous ASCA observations indicate that the iron-K absorption features become prominent in this state, thus best suited for detailed plasma diagnostics.

Proposal Number: 09400231

Title: ToO observation of a new bright transient discovered by GLAST and Swift in the Galactic plane

PI Name: Isabelle Grenier

We propose a TOO observation of a new intense transient detected by GLAST-LAT and followed by a Swift-XRT detection, at |b|<5 deg. Our goal is to determine the nature of an event similar to the intense, non-blazar, transient that EGRET saw in the Galactic plane once in its lifetime. The lack of a radio-loud source and of a known X-ray binary in the error box indicates either a new facet of Galactic compact objects or a new manifestation of a non-blazar active galaxy behind the Milky way. A significant XRT detection of a counterpart will trigger the proposed 30 ks Chandra observation to precisely locate the source in crowded Galactic regions, to constrain the X-ray decay time, and to measure the source spectrum and absorption.

Proposal Number: 09400314

Title: Photoionization in the Microquasar Circinus X-1

PI Name: Norbert Schulz

We propose to reobserve the X-ray binary Circinus X-1 for a total of 35 ks within an orbital phase window of 0.96 - 0.99 within its 16.5 day orbital cycle using the HETGS. Circinus~X-1 is currently in a low flux state with respect to its longterm (30 yr) lightcurve. A short previous observation of the source at this phase revealed a remarkable emission line spectrum rich in high Z K-shell lines from Si, S, Ar, Ca, and Fe. While the overall spectrum was successfully modeled using the most recent version of the photoionization code XSTAR, we encountered problems in the modeling of specific lines which to a large extent are related to the short exposure and shortcomings in the instrumental setup.

Proposal Number: 09400351

Title: Crust cooling of HETE J1900.1-2455 and Swift J1626.6-5156

PI Name: Nathalie Degenaar

We propose Chandra ToO observations of the two neutron star quasi-persistent X-ray binaries HETE J1900.1-2455 and Swift J1626.6-5156 in quiescence. Currently, both sources exhibit an outburst phase that started about 1.5 years ago. Neutron stars that undergo such a prolonged accretion period serve perfectly to study their cooling behavior, which depends sensitively on stellar parameters such as composition and compactness. We want to explore the effect of a strong magnetic field on the thermal evolution of transiently accreting neutron stars. Cooling models for neutron stars with a low magnetic field currently exist, and also magnetars are well studied. Our selected targets fall right in between this regime and can provide new physical input in the existing theory of cooling neutron stars.

Proposal Number: 09400355

Title: Quasi-persistent neutron-star X-ray binaries in quiescence

PI Name: Rudy Wijnands

We propose to observe the next (quasi-)persistent neutron-star low-mass X-ray binary that turns off and becomes quiescent. This will provide an excellent opportunity to study the effects of prolonged accretion on the neutron-star properties (i.e., crust and core and thus the properties of ultradense matter) and the quiescent properties of low-mass X-ray binaries. Two follow-up observations taken several months later will provide important information about the time evolution of the quiescent properties. In particular, if indeed the quiescent X-rays are emitted by the crust, we will be able to study its evolution in time,thus setting strong constraints on the crust cooling models and the exact structure of the crust.

Proposal Number: 09400380

Title: First Chandra observation of the ultra-compact X-ray binary 4U~1850--087 during its high luminosity state

PI Name: DIEGO ALTAMIRANO

4U~1850--087 is a candidate ultra-compact X-ray binary. A soft excess near 0.7 keV has been reported for this source with ASCA and interpreted as due to neutral Ne-rich material local to the binary. Recent XMM-Newton and Chandra observations of the source at low X-ray luminosity do not confirm the ASCA results and therefore different physical interpretations are possible. We propose at 30 ks Chandra LETGS observation of this source during its high luminosity state in order to understand how the luminosity affects the abundances observed in the X-ray spectrum.

Proposal Number: 09400397

Title: Monitoring observations of the Galactic Center region

PI Name: Rudy Wijnands

We propose to continue our Chandra and XMM-Newton monitoring campaign of the 1.2 square degree region centered on Sgr A*. We will be able to detect very faint transients with a peak luminosity of 1E33-1E35 ergs/s, 10-1000 times more sensitive than would be possible with other satellites. This allows us to observe a poorly studied group of transients and to follow the luminosity behavior of faint (1E34-1E36 ergs/s) persistent sources. The Chandra observations are necessary to facilitate rapid follow-up observations of the detected transients at IR and radio wavelengths; the XMM-Newton observations are needed to increase the likelihood of detecting transients in outburst and to obtain better constraints on the long-term time averaged accretion rates of the transients present in the FOV.

Proposal Number: 09400409

Title: Faint persistent X-ray sources in the Galactic Bulge

PI Name: Marc Klein-Wolt

We propose short (1 ksec) observations with the HRC-I of a selection of faint persistent X-ray sources in the Galactic Bulge for which very little is know. These sources are detected in the PCA/RXTE bulge scan project at luminosities below 10^36 erg/sec and are most likely HMXB or LMXB; they are either Be/X-ray binaries, and hence candidates to show slow X-ray pulsations, or they are ultra-compact binaries in which the compact object is accreting from a degenarate donor and in which case they are candidates to show gravitational waves. The HRC observations will allow us to search for slow pulsations as well give for the first time an accurate position that will allow for optical/IR follow-up studies to determine the binary parameters.

Proposal Number: 09400414

Title: INVESTIGATING NEW INTEGRAL SOURCES WITH CHANDRA

PI Name: Adamantia Paizis

We propose to trigger a maximum of 2 Chandra medium (4-12 days) ToO observations on new sources discovered by the INTEGRAL Observatory. We ask for 20 ksec per observation, using HETGS. The scientific aim is to determine the source position with subarcsecond accuracy that only Chandra can provide, enabling multiwavelength follow-up observations (coordinated within the proposing team), and to obtain the high resolution HETG X-Ray spectrum, essential to determine the nature of the new source. With this proposal we aim to continue the successful INTEGRAL-Chandra monitoring program started since Chandra AO5.

Proposal Number: 09400441

Title: Chandra observations of an engimatic class of faint accreting slow pulsators

PI Name: Rudy Wijnands

We propose a series of 1 ksec Chandra observations of an enigmatic class of objects: faint to very faint accreting slow pulsators with period greater than several hundreds of seconds. The nature of these objects is unclear; likely they are neutron stars accreting from a high-mass companion star, but often an accreting magnetized white dwarf nature (i.e., an intermediate polar) cannot be excluded. With our proposed Chandra observations we will obtain a position of these sources which will be used to identify their optical/IR counterpart, crucial in determining the exact nature of these systems. In addition, we request short (5 ksec) XMM-Newton observations of the same targets which will result in good spectra and allow for searches to be undertaken for any spin-period derivatives.

Proposal Number: 09400498

Title: TOO observation of the microquasar GRS 1915+105 in quiescence

PI Name: Paolo Soleri

We propose a 40ks Chandra observation to detect the microquasar GRS 1915+105 in quiescence, should its current 15-year-long outburst end during the 9th Chandra observing cycle. This system has never been observed in quiescence: its properties suggest that its quiescent X-ray flux would be rather high, allowing a measurement of the spectrum and a test of models for quiescent emission in black-hole binaries. In addition, it will be possible to detect a fossil jet similar to that detected in the neutron star X-ray binary 4U 1755-33.

Proposal Number: 09400544

Title: Precise Localization of Neutron Star Soft X-ray Transients

PI Name: Deepto Chakrabarty

We propose to observe four neutron star (NS) soft X-ray transients in outburst to obtain accurate source positions, continuing an ongoing successful program we initiated in Cycle 6. This continuing study will allow for the reobservation of such sources in future cycles to study the quiescent X-ray emission in NS SXTs. Recent results from Chandra and XMM suggest that the standard picture of NS SXT emission may not be as straightforward as previously thought. This proposal will increase the number of known SXTs with good positions, providing a more uniform sample of the population for future work.

Proposal Number: 09400550

Title: High Resolution Spectroscopy of a Black Hole Transient

PI Name: Jon Miller

We propose to continue our ongoing study of Galactic black hole transients in outburst in a streamlined form, via two (2) 30 ksec HETGS observations. This program has revealed relativistic Fe K disk lines, warm-absorber-like disk winds, and now a possible anti-correlation between winds and jets. Observations of a new transient outburst will permit a black hole spin constraint, and test connections between disks, winds, and jets as a function of accretion rate. We will support this program with a global multi-wavelength network of observatories.

Proposal Number: 09400622

Title: The Nature of the Intermediate-Luminosity X-ray Sources in Globular Clusters

PI Name: Craig Heinke

We propose short observations of four globular clusters seen to contain relatively bright (L_X[0.5-7 keV]=5x10^33 to 10^35 ergs/s) low-luminosity X-ray sources by Einstein, ROSAT and/or Chandra HRC observations. These objects are either extremely bright cataclysmic variables in unusual accretion states, or quiescent low-mass X-ray binaries showing very low-level accretion activity. With 5 to 10-ksec snapshots, we will constrain the luminosities, spectra, positions, and nature of each object.

Proposal Number: 09400640

Title: Observations during the rare dips observed on the X-ray binary SLX 1735--269

PI Name: DIEGO ALTAMIRANO

SLX~1735--269 is a (candidate) ultra-compact X-ray binary. It is a persistent source which shows rare dips that cannot be explain as periodic obscuration by material located in a thickened outer region of the accretion disk due to its interaction with the inflowing gas stream from the companion. We propose to observe this source for 10~ksec during one of its dips in order to understand if the accretion on the compact object ceases, or remains at very low levels undetectable with RXTE. The observations will also allow us to estimate the temperature of the neutron star crust.

Proposal Number: 09400681

Title: Understanding the nature of high inclination low mass X-ray binaries: broad-band and line spectra from A1744-361

PI Name: Tod Strohmayer

We propose to observe the transient dipping LMXB system A1744-361 during an outburst with Chandra HETGS, and contemporaneously with RXTE PCA. This will be the first observation of A1744-361 with a high resolution spectral instrument, and will facilitate; (1) sigficant detection of narrow spectral lines for the first time from A1744-361, (2) detection and line profile measurement of its broad iron emisson line, (3) unambiguous determination of source orbital period, (4) unambiguous determination of source position, (5) sigficant detection of kHz QPOs, and (6) understanding of the ionized plasma in the immediate environs of A1744-361, and dippers in general. These science goals rely on the unique qualities of Chandra (e.g., high spectral and angular resolution) and RXTE.

Proposal Number: 09400783

Title: From Super-Eddington to zero: following a Z source into quiescence

PI Name: Jeroen Homan

XTE J1701-462 is probably the most luminous Galactic transient neutron star LMXB (NSXB) in the history of X-ray astronomy. Early observations have already clarified our view on the role of mass accretion rate in NSXBs. Observing XTE J1701-462 as it returns to quiescence will create a unique opportunity to study the effects of mass-accretion rate on the spectral/variability properties in a single NSXB over an unprecedented luminosity range. We propose a Chandra/XMM-Newton TOO program with two goals: 1) observe the source during the end of the decay and in quiescence, to complete what might well become a 'Rosetta stone' for NSXBs and 2) constrain the structure of neutron stars by studying the effects of near-Eddington accretion on the cooling of the crust/core in transient NSXBs.

Proposal Number: 09400813

Title: Localization and Spectra of INTEGRAL-Selected Sources in the Galactic Plane

PI Name: John Tomsick

The INTEGRAL satellite is discovering a large number of new hard X-ray sources in the Galactic plane. In most cases, the few arcminute INTEGRAL positions do not allow for identification of these IGR sources at other wavelengths, leaving their nature unclear. Chandra can make a major contribution to studies of IGR sources by localizing the sources to allow for the identification of multi-wavelength counterparts and by constraining their soft X-ray spectra. Many of the IGR sources that have been identified are High-Mass X-ray Binaries (HMXBs) with interesting properties. We propose for relatively short Chandra observations of 24 unidentified IGR sources in the Galactic plane to search for HMXBs or other unusual Galactic sources.

Proposal Number: 09400831

Title: Spectroscopy of a bright burst from 4U 1812-12

PI Name: Johannes in 't Zand

Our goal is to measure with the HETGS a bright type-I X-ray burst with photospheric radius expansion (PRE), search for signatures of the ashes of nuclear burning and, if succesful, attempt a measurement of the gravitational redshift. The target, 4U 1812-12, is an ultracompact X-ray binary whose bursts are known to be consistently very bright, show strong PRE and are fairly predictable in occurrence. We request a joint RXTE observation to measure the neutron star spin via burst oscillations.

Proposal Number: 09400910

Title: Spitzer-Chandra ToO Observations of a Short Duration GRB

PI Name: Kevin Hurley

We propose an ambitious multiwavelenth approach to the short GRB problem, leveraging Spitzer with Chandra as well as numerous ground−based telescopes. By measuring the broad−band spectrum of the afterglow and any concurrent "mini−supernova" over a wide range of wavelengths at several epochs, we can distinguish between models proposed to explain this type of burst. We will constrain the energetics of the explosion and the short GRB bursting rate (an important number for gravitational wave observatories), and measure with unprecedented detail the stellar content of a short burst host galaxy. Given the high impact nature of these observations and the rarity of short bursts, we are requesting multiepoch Target of Opportunity observations on a single event in Cycle 4.

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The Chandra X-Ray Center (CXC) is operated for NASA by the Smithsonian Astrophysical Observatory. 60 Garden Street, Cambridge, MA 02138 USA.   Email:   cxchelp@head.cfa.harvard.edu Smithsonian Institution, Copyright © 1998-2024. All rights reserved.