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We observed the accreting white dwarf 1E1339.8+2837 (1E1339) in the globular cluster M3 in Nov. 2003, May 2004 and Jan. 2005, using the Chandra ACIS-S detector. The source was observed in 1992 to possess traits of a supersoft X-ray source (SSS), with a 0.1-2.4 keV luminosity as large as 2x10^{35} erg/s, after which time the source's luminosity fell by roughly two orders of magnitude, adopting a hard X-ray spectrum more typical of CVs. Our observations confirm 1E1339's hard CV-like spectrum, with photon index Gamma=1.3+-0.2. We found 1E1339 to be highly variable, with a 0.5-10 keV luminosity ranging from 1.4+-0.3x10^{34} erg/s to 8.5+4.9-4.6x10^{32} erg/s, with 1E1339's maximum luminosity being perhaps the highest yet recorded for hard X-ray emission onto a white dwarf. In Jan. 2005, 1E1339 displayed substantial low-energy emission below 0.3 keV. Although current Chandra responses cannot properly model this emission, its bolometric luminosity appears comparable to or greater than that of the hard spectral component. This raises the possibility that the supersoft X-ray emission seen from 1E1339 in 1992 may have shifted to the far-UV., Comment: ApJ in press, 6 pages, 5 figures

We report on archival Hubble Space Telescope (HST) observations of the globular cluster M71 (NGC 6838). These observations, covering the core of the globular cluster, were performed by the Advanced Camera for Surveys (ACS) and the Wide Field Planetary Camera 2 (WFPC2). Inside the half-mass radius (r_h = 1.65') of M71, we find 33 candidate optical counterparts to 25 out of 29 Chandra X-ray sources while outside the half-mass radius, 6 possible optical counterparts to 4 X-ray sources are found. Based on the X-ray and optical properties of the identifications, we find 1 certain and 7 candidate cataclysmic variables (CVs). We also classify 2 and 12 X-ray sources as certain and potential chromospherically active binaries (ABs), respectively. The only star in the error circle of the known millisecond pulsar (MSP) is inconsistent with being the optical counterpart. The number of X-ray faint sources with L_x>4x10^{30} ergs/s (0.5-6.0 keV) found in M71 is higher than extrapolations from other clusters on the basis of either collision frequency or mass. Since the core density of M71 is relatively low, we suggest that those CVs and ABs are primordial in origin., 12 pages, 6 figures. Accepted for publication in Astronomy and Astrophysics

We describe our participation in two of the tasks organizedwithin Senseval-3: Automatic Labeling of Semantic Roles and Identification of Logic Forms in English.

We report the discovery of an optical counterpart to a quiescent neutron star in the globular cluster Omega Centauri (NGC 5139). The star was found as part of our wide-field imaging study of Omega Cen using the Advanced Camera for Surveys (ACS) on Hubble Space Telescope. Its magnitude and color (R_625 = 25.2, B_435 - R_625 = 1.5) place it more than 1.5 magnitudes to the blue side of the main sequence. Through an H-alpha filter it is ~ 1.3 magnitudes brighter than cluster stars of comparable M_625 magnitude. The blue color and H-alpha excess suggest the presence of an accretion disk, implying that the neutron star is accreting from a binary companion and is thus a quiescent low-mass X-ray binary. If the companion is a main-sequence star, then the faint absolute magnitude (M_625 ~ 11.6) constrains it to be of very low mass (M, Comment: Accepted for Publication in the Astrophysical Journal. 5 pages, 4 figures, 1 table, uses emulateapj.sty. Figures 1 and 3 at reduced resolution. New version contains revised magnitude calibrations

We report results of the Chandra deep imaging observation of the closest post-core collapse globular cluster, NGC 6397. Some 25 sources are detected within 2 arcmin of the cluster center of which about 20 are likely cluster members with L_x ~ 3x10^29 erg/s. The x-ray spectra suggest identifications with 1 quiescent low mass x-ray binary (qLMXB) detected by the thermal emission from its neutron star (NS) and 9 cataclysmic variables (CVs), 8 of which are identified in our deep HST imaging survey (reported separately). Three (of 16) BY Draconis main sequence binary candidates identified in our earlier HST imaging study (Taylor et al) are detected of which one is indeed the counterpart of the eclipsing millisecond pulsar (MSP) recently located by D'Amico et al. Two other BY Dra candidates are also detected, whereas none of the probable He white dwarf (WD) binaries identified by Taylor et al are indicating they do not contain MSP primaries. The x-ray color magnitude diagram suggests that the remaining 5 probable cluster sources are a mixture of faint CVs, BY Dra binaries and MSPs. Compact binaries containing WDs appear to dominate this cluster, in contrast to those containing NSs in 47Tuc., Comment: submitted to ApJ Letters. 4 pages (emulateapj) and 3 figures (figs. 1 and 2 are color)

We report spectral and variability analysis of two quiescent low mass x-ray binaries (previously identified with ROSAT HRI as X5 and X7) in the globular cluster 47 Tuc, from a Chandra ACIS-I observation. X5 demonstrates sharp eclipses with an 8.666+-0.008 hr period, as well as dips showing an increased N_H column. Their thermal spectra are well-modelled by unmagnetized hydrogen atmospheres of hot neutron stars, most likely heated by transient accretion, with little to no hard power law component., Comment: 4 pages, 2 figures, to appear in "Neutron Stars in Supernova Remnants" (ASP Conference Proceedings), eds P. O. Slane and B. M. Gaensler

We present near-ultraviolet and optical Hubble Space Telescope observations of the likely white dwarf companions to radio millisecond pulsars 47 Tuc Q, S, T, Y, and the previously identified white dwarf counterpart to 47 Tuc U. All five near-ultraviolet companions show colors that agree with the ones resulting from He-core white dwarf (He WD) cooling models for white dwarf masses ∼ 0.16−0.3 M. We find that the counterparts to 47 Tuc U and 47 Tuc T show Hα absorption, as is characteristic for white dwarfs with a H envelope, such as He WDs