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We selected 40 candidate Lyman Alpha Emitting galaxies (LAEs) at z ~=3.1 with observed frame equivalent widths >150A and inferred emission line fluxes >2.5x10^-17 ergs/cm^2/s from deep narrow-band and broad-band MUSYC images of the Extended Chandra Deep Field South. Covering 992 sq. arcmin, this is the largest ``blank field'' surveyed for LAEs at z ~3, allowing an improved estimate of the space density of this population of 3+-1x10^-4 h_70^3/Mpc^3. Spectroscopic follow-up of 23 candidates yielded 18 redshifts, all at z ~=3.1. Over 80% of the LAEs are dimmer in continuum magnitude than the typical Lyman break galaxy spectroscopic limit of R= 25.5 (AB), with a median continuum magnitude R ~=27 and very blue continuum colors, (V-z) ~=0. Over 80% of the LAEs have the right UVR colors to be selected as Lyman break galaxies, but only 10% also have R240A which might imply a non-standard IMF. One candidate is detected by Chandra, implying an AGN fraction of 2+-2% for LAE candidate samples. In summary, LAEs at z ~ 3 have rapid star formation, low stellar mass, little dust obscuration and no evidence for a substantial AGN component., ApJ Letters, in press, very minor revisions to match accepted version, 4 pages with 2 color figures

It was observed early on in the Chandra X-ray Observatory mission that the background rates of the Advanced CCD Imaging Spectrometer (ACIS) were highly variable on both short and long timescales. We present analysis of lightcurves of the high energy (> 15 keV) ACIS background spanning most of the mission lifetime. These high energy events are not produced by astrophysical X-rays, but by the particle background, primarily energetic protons. Temporal characteristics of both the quiescent background and background flares will be discussed as well as correlations with Chandra's orbital position and the solar activity cycle. The strength and frequency of background flares appear cyclic with a quasi-annual period, most likely from the motion of Chandra's orbit through the geomagnetic environment., 7 pages, 5 figures. To appear in ``The High Energy Universe at Sharp Focus'' (St. Paul, Minnesota 2001), eds Schlegel and Vrtilek (ASP Conference Series)

The flight calibration of the spectral response of the Advanced CCD Imaging Spectrometer (ACIS) below 1.5 keV is difficult because of the lack of strong lines in the calibration source on-board the Chandra X-ray Observatory. We have been using 1E0102.2-7219 (the brightest supernova remnant in the SMC) to evaluate the ACIS response matrices, since this remnant has strong lines of O, Ne and Mg below 1.5 keV. The spectrum of 1E0102.2-7219 has been well-characterized using the gratings on Chandra and XMM. We have used the high-resolution spectral data from both gratings instruments to develop a spectral model for the CCD spectra. Fits with this model are sensitive to any problems with the gain calibration and the spectral redistribution model. We have fit the data with the latest response matrix for the S3 device released in August 2001 (available in CALDB 2.7 or higher). We have also applied the charge-transfer inefficiency (CTI) correction software (version 1.37) developed at Penn State to both the Backside-illuminated (BI) and Front-side illuminated (FI) data and fit the data with the associated CTI-corrected response matrices. All fits show a significant improvement in the low energy response with the new matrices. The fits to the FI CCDs demonstrate the utility of the FI CCDs for spectral analysis, in spite of the radiation damage the devices suffered early in the mission., Comment: To appear in ``The High Energy Universe at Sharp Focus'' (St. Paul, Minnesota 2001), eds Schlegel and Vrtilek (ASP Conference Series)

The MIT and CXC ACIS teams have explored a number of measures to ameliorate the effects of radiation damage suffered by the ACIS FI CCDs. One of these measures is a novel CCD read-out method called ``squeegee mode''. A variety of different implementations of the squeegee mode have now been tested on the I0 CCD. Our results for the fitted FWHM at Al-K$\alpha$ and Mn-K$\alpha$ clearly demonstrate that all the squeegee modes provide improved performance in terms of reducing CTI and improving spectral resolution. Our analysis of the detection efficiency shows that the so-called squeegee modes ``Vanilla'' and ``Maximum Observing Efficiency'' provide the same detection efficiency as the standard clocking, once the decay in the intensity of the radioactive source has been taken into account. The squeegee modes which utilize the slow parallel transfer (``Maximum Spectral Resolution'', ``Maximum Angular Resolution'', and ``Sub-Array'') show a significantly lower detection efficiency than the standard clocking. The slow parallel transfer squeegee modes exhibit severe grade migration from flight grade 0 to flight grade 64 and a smaller migration into ASCA g7. The latter effect can explain some of the drop in detection efficiency. (ABRIDGED ABSTRACT), Comment: 11 pages, 5 figures. To appear in ``The High Energy Universe at Sharp Focus'' (St. Paul, Minnesota 2001), eds Schlegel and Vrtilek (ASP Conference Series). Paper also at http://hea-www.harvard.edu/~svirani/paper.html

The 3rd Suzaku international Conference "Energetic Cosmos : from Suzaku to ASTRO-H" (June 29-July 2, 2009. Grand Park Otaru Hotel), Otaru, Hokkaido Japan, We present results from a new 100 - ks Suzaku observation of the nearby radio galaxy 3C 33, and investigate the nature of absorption, reflection, and jet production in this source. We model the 2 - 70 keV nuclear continuum with a power law that is absorbed either through one or more layers of pc-scale neutral material, or through a modestly ionized pc-scale obscurer. The expected signatures of reflection from a neutral accretion disk are absent in 3C 33 : there is no evidence of a relativistically blurred Fe Kalpha emission line, and no Compton reflection hump above 10 keV. We discuss the implications of this for the nature of jet production in 3C 33., Meeting sponsors: The University of Tokyo, The Institute of Physical and Chemical Research, The Japan Society for the Promotion of Science, 資料番号: AA0064574123, レポート番号: JAXA-SP-09-008E

The Chandra X-ray Observatory (CXO) was launched on July 23, 1999 and reached its final orbit on August 7, 1999. The CXO is in a highly elliptical orbit, approximately 140,000 km x 10,000 km, and has a period of approximately 63.5 hours (~ 2.65 days). It transits the Earth's Van Allen belts once per orbit during which no science observations can be performed due to the high radiation environment. The Chandra X-ray Observatory Center (CXC) currently uses the National Space Science Data Center's ``near Earth'' AP-8/AE-8 radiation belt model to predict the start and end times of passage through the radiation belts. However, our scheduling software uses only a simple dipole model of the Earth's magnetic field. The resulting B, L magnetic coordinates, do not always give sufficiently accurate predictions of the start and end times of transit of the Van Allen belts. We show this by comparing to the data from Chandra's on-board radiation monitor, the EPHIN (Electron, Proton, Helium Instrument particle detector) instrument. We present evidence that demonstrates this mis-timing of the outer electron radiation belt as well as data that also demonstrate the significant variablity of one radiation belt transit to the next as experienced by the CXO. We also present an explanation for why the dipole implementation of the AP-8/AE-8 model is not ideally suited for the CXO. Lastly, we provide a brief discussion of our on-going efforts to identify a model that accounts for radiation belt variability, geometry, and one that can be used for observation scheduling purposes., 12 pgs, 6 figs, for SPIE 4012 (Paper 76)