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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Looking for Interacting Binaries in Old Open Clusters

We requested a 12 ks observation of the old open cluster NGC7142 with the aim to investigate the population of interacting binaries, and compare the properties with those of interacting binaries in other old open clusters. Unfortunately, the observation suffered from long periods of background flaring, and as a result the effective exposure time was shortened to only approximately 25% of the planned exposure. The sensitivity to detect sources in the cluster was therefore much reduced, hampering a useful comparison with other clusters observed with Chandra and XMM. We detect 5 sources (all less than 300 counts) in the full field of view of the detectors; based on the large separations from the cluster center, we expect that at least 3-4 are not associated with the cluster. A brief paper that reports the results is in preparation.

Grindley, Jonathan↗
NASA NTRS2005

Probing the Reverse Shock in an Oxygen-Rich Supernovae Remnant

The purpose of this investigation is to examine the O VI emission from the X-ray bright ring of the supernova remnant 1 E0102.2-729 in the small Magellanic cloud. Three pointings were positioned tangent to the ring, north (N), northeast (NE), and southeast (SE), to examine a range of X-ray emitting regions overlapping a range of optical [O III] nebulosity and to examine the velocity structure. One background pointing was also obtained, but it was contaminated by a star. The background levels in the pointings on the remnant were low enough that the background pointing was not required for the remaining analysis. The SE pointing was reobserved in August, 2004, in order to bring the total exposure up to the originally requested 15 ks. The archive notified us of the data's availability in mid September. Significant broad O VI 1032 and O VI 1038 emission was found, brightest in the NE and SE pointings. In the NE and SE pointings, the FWHM of the broad O VI component is approx.800-1000 km/s, while in the N pointing, the line is approx.1500 km/s wide. The O VI is redshifted in the N (approx.380 km/s) and NE (approx.60 km/s) but is blueshifted in the SE (approx. -160 km/s). These FUSE O VI velocity dispersions can be compared to the X-ray gas velocities inferred from Doppler distortions in the Chandra X-ray data as reported by Flanagan et al. 2004 (ApJ 605, 230). The bulk velocities in the X-ray bright ring of order +/- 1000 km/s, comparable to the velocity dispersion seen in the FUSE data. However, the X-ray data indicates a redshift of approx.1000 km/s in the SE, while the FUSE data show a blueshift of approx.160 km/s, underscoring the complex velocity structure in this remnant. The O VI fluxes estimated from the fits to the FUSE data were combined with X-ray (XMM- Newton) O VI1 and O VIII fluxes and compared with predictions from a plasma nonequilibrium ionization model in a "line-based" analysis. We found that the plasma departs significantly from collisional ionization equilibrium, particularly in the SE, and that the plasma excitation conditions vary among the pointings: the O plasma sees different conditions than the Ne and Mg plasmas.

Gaetz, Terrance↗
NASA NTRS2006

Swift and GRB's: Unveiling the Relativistic Universe

We report Swift observations of GRB 051109A, a bright, long burst detected with BAT. A bright afterglow was quickly detected with the X-Ray Telescope and Ultraviolet and Optical Telescope, and observations continued for more than 10 days. The X-ray light is complex with a rapid initial decay followed by a more gradual decay. There is evidence for a jet break with an indicated opening angle of a few degrees. UVOT observations with the V filter are consistent with a power-law day for the first 10 ks. We discuss the observations in light of current models.

Marshall, Francis E.↗
NASA NTRS2001

Suzaku Observation of Two Ultraluminous X-Ray Sources in NGC 1313

A study was made of two ultraluminous X-ray soures (ULXs) in the nearby face-on, late-type Sb galaxy NGC 1313 using data from Suzaku, the 5th Japanese X-ray satellite. Within the 90 ks observation, both sources named X-1 and X-2 exhibited luminosity change by about 50%. The 0.4-10 keV X-ray luminosity was measured to be 2.5 x 10(exp 40) erg per second and 5.8 x 10 erg per second for X-1 and X-2, respectively, requiring a black hole of 50-200 solar mass in order not to exceed the Eddingtion limit. For X-1: the spectrum exhibited a strong power-law component with a high energy cutoff which is thought to arise from strong Comptonization by a disk corona, suggesting the source was in a very high state. Absorption line features with equivalent widths of 40-80 eV found at 7.0 keV and 7.8 keV in the X-1 spectrum support the presence of a highly ionized plasma and a high mass accretion rate on the system. Oxygen abundance of the NGC 1313 circumstellar matter toward X-1 was found to be subsolar, viz. O/H = (5.0 plus or minus 1.0) x 10(exp -4). The spectrum of X-2 in fainter phase is best represented by a multicolor disk blackbody model with T (sub in) = 1.2-1.3 keV and becomes flatter as the flux increases; the source is interpreted to be in a slim disk state.

Mizuno, T.↗
NASA NTRS2007

Suzaku Observation of Two Ultraluminous X-ray Sources in NGC 1313

TA study was made of two ultraluminous X-ray sources (ULXs) in the nearby faceon, late-type Sb galaxy NGC 1313 using data from Suzaku, the 5th Japanese X-ray satellite. Within the 90 ks observation, both sources named X-1 and X-2 exhibited luminosity change by about 50%. The o.4-10keV X-ray luminosity was measured. For X-1, the spectrum exhibited a strong power-law component with a high energy cutoff which is thought to arise from strong Comptonization by a disk corona, suggesting the source was in a very high state. Absorption line features with equivalent widths of 40-80 eV found at 7.00 keV and 7.8 keV in the X-1 spectrum support the presence of a highly ionized plasma and a high mass accretion rate on the system. The spectrum of X-2 in fainter phase is presented by a multicolor disk blackbody model.

Mizuno, T.↗
NASA NTRS2000

Extending the ICRF into the Infrared: 2MASS - UCAC Astrometry

An external comparison between the infrared 2MASS and the optical UCAC positions was performed, both being on the same system, the ICRS. About 48 million sources in common were identified. Random errors of the 2MASS catalog positions are about 60 to 70 mas per coordinate for the Ks = 4 to 14 range, increasing to about 100 to 150 mas for saturated and very faint stars. Systematic position differences between the 2 catalogs are very small, about 5 to 10 mas as a function of magnitude and color, with somewhat larger errors as a function of right ascension and declination. The extension of the ICRF into the infrared has become a reality.

USNO CCD Astrograph Catalog (UCAC)↗
NASA NTRS2007

The Remarkable X-ray Spectrum of the Broad-Line Radio Galaxy 3C 445

The nearby (z=0.057) radio-loud source 3C 445, optically classified as a Broad-Line Radio Galaxy, exhibits an X-ray spectrum strongly reminiscent of an obscured AGN, suggesting we are seeing this source at a relatively large angle from the radio jet. Here we present an archival 15 ks XMM-Newton observation of 3C 445 which confirms the remarkable complexity of its X-ray emission. The X-ray emission is described by a power law continuum with GAMMA approximately equal to 1.4, absorbed by several layers of cold gas, plus strong cold reflection. A narrow, unresolved Fe Kalpha emission line is detected, confirming previous findings, with EW approximately equal to 400 eV. A soft excess is present below 2 keV over the extrapolation of the hard X-ray power law, which we model with a power law with the same photon index and absorbed by a column density N(sub H)5 approximately equal to 10(sup 20) cm(sup -2) in excess to Galactic. Remarkably, a host of emission lines are present below 2 keV, confirming previous indications from ASCA, due to H- and He-like O, Mg, and Si. The detection of two features at 0.74 and 0.87 keV, identified with OVII and OVIII Radiative Recombination Continuum features, suggest an origin of the lines from a photoionized gas, with properties very similar to radio-quiet obscured AGN. Two different ionized media, or a single stratified medium, are required to fit the soft X-ray data satisfactorily. The similarity of the X-ray spectrum of 3C 445 to Seyferts underscores that the central engines of radio-loud and radio-quiet AGN similarly host both cold and warm gas.

Sambruna, R. M.↗
NASA NTRS2007

Deep RGS Observations of Clusters

This viewgraph presentation reviews the Reflection Grating Spectrometers (RGS) observations of clusters. It includes charts detailing the resolution difference between the European Photon Imaging Camera (EPIC) and the RGS and a partial review of existing observations, in graphic format, and as a table. Other sources show up in the ROSAT observations. The presentation reviews possible results that could be achieved in the event that 300 ks of time were allocated for the observations of clusters.

Smith, R.↗
NASA NTRS2004

Chandra X-ray Observations of Young Clusters: Orion Flanking Fields Data - Volume II

We present results of Chandra observations of two flanking fields (FFs) in Orion, outside the Orion Nebula Cluster (ONC). The observations were taken with the ACIS-I camera with an exposure time of about 48 ks each field. We present a catalog of 417 sources, which includes X-ray luminosity, optical and infrared photometry, and X-ray variability information. We have found 91 variable sources, 33 of which have a flarelike light curve and 11 of which have a pattern of a steady increase or decrease over a 10 hr period. The optical and infrared photometry for the stars identified as X-ray sources are consistent with most of these objects being pre-main-sequence stars with ages younger than 10 Myr. We present evidence for an age difference among the X-ray-selected samples of NGC 2264, Orion FFs, and ONC, with NGC 2264 being the oldest and ONC being the youngest.

pre-main sequence↗
NASA NTRS2003

Confirmation of a Radio-Selected Galaxy Overdensity at z=1.11

We report the discovery of a galaxy overdensity at z = 1.11 associated with the z = 1.110 high-redshift radio galaxy MG1 J04426+0202 (hereafter MG 0442+0202). The group, Cl 0442+0202, was found in a near-infrared survey of z > 1 radio galaxies undertaken to identify spatially coincident regions with a high density of objects red in I-K' color, typical of z > 1 elliptical galaxies. Spectroscopic observations from the Keck I telescope reveal five galaxies within 35" of MG 0442+0202 at 1.10 < z < 1.11. These member galaxies have broadband colors and optical spectra consistent with passively evolving elliptical galaxies formed at high redshift. Archival ROSAT observations reveal a 3 (sigma) detection of soft X-ray emission coincident with Cl 0442+0202 at a level 5 times greater than expected for the radio galaxy. These data suggest a rich galaxy cluster and inspired a 45 ks Chandra X-Ray Observatory observation. As expected, the radio galaxy is unresolved by Chandra but is responsible for approximately half the observed X-ray flux. The remaining ROSAT flux is resolved into four point sources within 15' of the radio galaxy, corresponding to a surface density 2 orders of magnitude higher than average for X-ray sources at these flux levels [S(0.5-2 keV) > 5 x 10(exp -16) ergs cm (exp -2) s(exp -1)]. One of these point sources is identified with a radio-quiet type II quasar at z = 1.863, akin to sources recently reported in deep Chandra surveys. The limit on an extended hot intracluster medium in the Chandra data is S(1-6 keV) < 1.9 x 10-15 ergs cm (exp -2) s(exp -1) (3 (sigma), 30" radius aperture). Though the X-ray observations do not confirm the existence of a massive bound cluster at z > 1, the success of the optical/near-infrared targeting of early-type systems near the radio galaxy validates searches using radio galaxies as beacons for high-redshift large-scale structure. We interpret Cl 0442+0202 as a massive cluster in the process of formation.

galaxies↗
NASA NTRS2008

Joint XMM-Newton, Chandra, and RXTE Observations of Cyg X-1 at Phase Zero

We present first results of simultaneous observations of the high mass X-ray binary Cyg X-1 for 50 ks with XMM-Newton, Chandra-HETGS and RXTE in 2008 April. The observations are centered on phase 0 of the 5.6 d orbit when pronounced dips in the X-ray emission from the black hole are known to occur. The dips are due to highly variable absorption in the accretion stream from the O-star companion to the black hole. Compared to previous high resolution spectroscopy studies of the dip and non-dip emission with Chandra, the addition of XMM-Newton data allows for a better determination of the continuum, especially through the broad iron line region (with RXTE constraining the greater than 10 keV continuum).

Pottschmidt, Katja↗
NASA NTRS2007

The Swift-XRT imaging Performances and Serendipitous Survey

We are exploiting thc Swift X-ray Telescope (XRT) deepest GR.B follow-up observations to study the cosmic X-Ray Background (XRB) population in the 0.2-10 keV energy band. We present some preliminary results of a serendipitous survey performed on 221 fields observed with exposure longer than 10 ks. We show that the XRT is a profitable instrument for surveys and that it is particularly suitable for the search and observation of ext,ended objects like clusters of galaxies. We used the brightest serendipitous sources and the longest observations to test. the XRT optics performance and the background characteristics all over the field of view, in different energy bands during the first 2.5 years of fully operational missions.

Moretti, A.↗
NASA NTRS2008

Chandra X-ray Spectroscopy of the Focused Wind In the Cygnus X-1 System I. The Non-Dip Spectrum in the Low/Hard State

We present analyses of a 50 ks observation of the supergiant X-ray binary system CygnusX-1/HDE226868 taken with the Chandra High Energy Transmission Grating Spectrometer (HETGS). CygX-1 was in its spectrally hard state and the observation was performed during superior conjunction of the black hole, allowing for the spectroscopic analysis of the accreted stellar wind along the line of sight. A significant part of the observation covers X-ray dips as commonly observed for CygX-1 at this orbital phase, however, here we only analyze the high count rate non-dip spectrum. The full 0.5-10 keV continuum can be described by a single model consisting of a disk, a narrow and a relativistically broadened Fe K line, and a power law component, which is consistent with simultaneous RXTE broad band data. We detect absorption edges from overabundant neutral O, Ne and Fe, and absorption line series from highly ionized ions and infer column densities and Doppler shifts. With emission lines of He-like Mg XI, we detect two plasma components with velocities and densities consistent with the base of the spherical wind and a focused wind. A simple simulation of the photoionization zone suggests that large parts of the spherical wind outside of the focused stream are completely ionized, which is consistent with the low velocities (<200 km/s) observed in the absorption lines, as the position of absorbers in a spherical wind at low projected velocity is well constrained. Our observations provide input for models that couple the wind activity of HDE 226868 to the properties of the accretion flow onto the black hole.

Hanke, Manfred↗
NASA NTRS2008

Solar Wind Change Exchange from the Magnetosheath

We report the results of a long (approximately 100 ks) XMM-Newton observation designed to observe solar wind charge exchange emission (SWCX) from Earth's magnetosheath. By luck, the observation took place during a period of minimal solar wind flux so the SWCX emission was also minimal. Never-the-less, there is a significant if not stunning correlation between the observed O VIII count rate and our model for magnetosheath emission. We also report on the observed O VII and O VII emission.

Snowden, Steve↗
NASA NTRS2008

Spectral Analysis of the Accretion Flow in NGC 1052 with Suzaku

We present an analysis of the 101 ks, 2007 Suzaku spectrum of the LINER galaxy NGC 1052. The 0:3..10 keV continuum is well-modeled by a power-law continuum modified by Galactic and intrinsic absorption, and exhibits a soft, thermal emission component below 1 keV. Both a narrow core and a broader component of Fe-Ka emission are robustly detected at 6:4 keV. While the narrow line is consistent with an origin in material distant from the black hole, the broad line is best fit empirically by a model that describes fluorescent emission from the inner accretion disk around a rapidly rotating black hole. We find no direct evidence for Comptonized reflection of the hard X-ray source by the disk above 10 keV, however, which casts doubt on the hypothesis that the broad iron line is produced in a standard accretion disk. We explore other possible scenarios for producing this spectral feature and conclude that the high equivalent width and full width half maximum velocity of the broad iron line (v greater than or equals 0:37c) necessitate an origin within d approx. 8r(sub g) of the hard X-ray source. Based on the confirmed presence of a strong radio jet in this source, the broad iron line may be produced in dense plasma at the base of the jet, implying that emission mechanisms in the central-most portions of active galactic nuclei are more complex than previously thought.

Brenneman, L. W.↗
NASA NTRS2009

A Compton-thick Wind in the High Luminosity Quasar, PDS 456

PDS 456 is a nearby (z=0.184), luminous (L(sub bol) approximately equal to 10(exp 47) ergs(exp -1) type I quasar. A deep 190 ks Suzaku observation in February 2007 revealed the complex, broad band X-ray spectrum of PDS 456. The Suzaku spectrum exhibits highly statistically significant absorption features near 9 keV in the quasar rest-frame. We show that the most plausible origin of the absorption is from blue-shifted resonance (1s-2p) transitions of hydrogen-like iron (at 6.97 keV in the rest frame). This indicates that a highly ionized outflow may be present moving at near relativistic velocities (0.26-0.31c). A possible hard X-ray excess is detected above 15 keV with HXD (at 99.8% confidence), which may arise from high column density gas (N(sub H) greater than 10(exp 24)cm(exp -2) partially covering the X-ray emission, or through strong Compton reflection. Here we propose that the iron K-shell absorption in PDS 456 is associated with a thick, possibly clumpy outflow, covering about 20% of 4(pi) steradian solid angle. The outflow is likely launched from the inner accretion disk, within 15-100 gravitational radii of the black hole. The kinetic power of the outflow may be similar to the bolometric luminosity of PDS 456. Such a powerful wind could have a significant effect on the co-evolution of the host galaxy and its supermassive black hole, through feedback.

Reeves, J. N.↗