Chandra Observations of SNR 1987A

We report on the results of our monitoring program of the X-ray remnant of supernova 1987A with the {\it Chandra X-Ray Observatory}. We have performed two new observations during the {\it Chandra} Cycle 3 period, bringing the total to six monitoring observations over the past three years. These six observations provide a detailed time history of the birth of a new supernova remnant in X-rays. The high angular resolution images indicate that soft X-ray bright knots are associated with the optical spots, while hard X-ray features are better correlated with radio images. We interpret this in terms of a model in which fast shocks propagating through the circumstellar HII region produce the hard X-ray and radio emission, while the soft X-ray and optical emission arise in slower shocks entering into dense knots in the circumstellar inner ring. New observations begin to show changes in the morphology that may herald a new stage in the development of this incipient supernova remnant. The observed X-ray fluxes increase by nearly a factor of three over the last 30 months. The X-ray remnant is expanding at a velocity of $\sim$5000 km s$^{-1}$.Comment: 8 pages, 6 figures, 2 color figures, To appear in AdSpR (Proceedings 34th COSPAR Synposium E1.4 "High Energy Studies of Supernova Remnants and Neutron stars" For high resolution color figures contact [email protected]

Probing Broad Absorption Line Quasar Outflows: X-ray Insights

Energetic outflows appear to occur in conjunction with active mass accretion onto supermassive black holes. These outflows are most readily observed in the approximately 10% of quasars with broad absorption lines, where the observer's line of sight passes through the wind. Until fairly recently, the paucity of X-ray data from these objects was notable, but now sensitive hard-band missions such as Chandra and XMM-Newton are routinely detecting broad absorption line quasars. The X-ray regime offers qualitatively new information for the understanding of these objects, and these new results must be taken into account in theoretical modeling of quasar winds.Comment: Submitted to Advances in Space Research for New X-ray Results from Clusters of Galaxies and Black Holes (Oct 2002; Houston, TX), eds. C. Done, E.M. Puchnarewicz, M.J. Ward. Requires cospar.sty (6 pgs, 5 figs

X-ray Spectroscopy and Variability of AGN Detected in the 2 Ms Chandra Deep Field-North Survey

We investigate the nature of the faint X-ray source population through X-ray spectroscopy and variability analyses of 136 AGN detected in the 2 Ms Chandra Deep Field-North survey with > 200 background-subtracted 0.5-8.0 keV counts [F(0.5-8.0 keV)=(1.4-200)e-15 erg cm^{-2} s^{-1}]. Our preliminary spectral analyses yield median spectral parameters of Gamma=1.61 and intrinsic N_H=6.2e21 cm^{-2} (z=1 assumed when no redshift available) when the AGN spectra are fitted with a simple absorbed power-law model. However, considerable spectral complexity is apparent (e.g., reflection, partial covering) and must be taken into account to model the data accurately. Moreover, the choice of spectral model (i.e., free vs. fixed photon index) has a pronounced effect on the derived N_H distribution and, to a lesser extent, the X-ray luminosity distribution. Ten of the 136 AGN (~7%) show significant Fe Kalpha emission-line features with equivalent widths in the range 0.1-1.3 keV. Two of these emission-line AGN could potentially be Compton thick (i.e., Gamma < 1.0 and large Fe Kalpha equivalent width). Finally, we find that 81 (~60%) of the 136 AGN show signs of variability, and that this fraction increases significantly (~80-90%) when better photon statistics are available.Comment: Submitted to Advances in Space Research for New X-ray Results from Clusters of Galaxies and Black Holes (Oct 2002; Houston, TX), eds. C. Done, E.M. Puchnarewicz, M.J. Ward. Requires cospar.sty (6 pgs, 10 figs

An X-ray and multiwavelength survey of highly radio-loud quasars at z&gt;4: jet-linked emission in the brightest radio beacons of the early Universe

We present a systematic study of the X-ray and multiwavelength properties of a sample of 17 highly radio-loud quasars (HRLQs) at z > 4 with sensitive X-ray coverage from new Chandra and archival Chandra, XMM-Newton, and Swift observations. Eight of the new and archival observations are reported in this work for the first time. New Chandra observations of two moderately radio-loud and highly optically luminous quasars at z >~ 4 are also reported. Our HRLQ sample represents the top ~5% of radio-loud quasars (RLQs) in terms of radio loudness. We found that our HRLQs have an X-ray emission enhancement over HRLQs at lower redshifts (by a typical factor of 483), and this effect, after controlling for several factors which may introduce biases, has been solidly estimated to be significant at the 3\u3c3-4\u3c3 level. HRLQs at z = 3-4 are also found to have a similar X-ray emission enhancement over z 4 HRLQs generally have higher X-ray luminosities than those for the composite broadband spectral energy distributions of HRLQs at lower redshift, which further illustrates and supports the X-ray emission enhancement of z > 4 HRLQs. Some of our HRLQs also show an excess of mid-infrared emission which may originate from the synchrotron emission of the relativistic jets. None of our z > 4 HRLQs is detected by the Fermi-LAT two-year survey, which provides constraints on jet-emission models

The Chandra Deep Field North Survey. VI. The nature of the optically faint X-ray source population

We provide constraints on the nature of the optically faint (I 24) X-ray source population from a 1 Ms Chandra exposure of a 84 × 84 region within the Hawaii flanking-field area containing the Hubble Deep Field North region. We detect 47 (2400 deg-2) optically faint sources down to 0.52.0 keV and 2.08.0 keV fluxes of 3 × 10-17 ergs cm-2 s-1 and 2 × 10-16 ergs cm-2 s-1, respectively; these sources contribute 14% and 21% of the 0.52.0 keV and 2.08.0 keV X-ray background radiation, respectively. The fraction of optically faint X-ray sources is approximately constant (at 35%) for 0.58.0 keV fluxes from 3 × 10-14 ergs cm-2 s-1 down to the X-ray flux limit. A considerable fraction (30%) of the optically faint X-ray sources are Very Red Objects (I-K 4). Analysis of the optical and X-ray properties suggests a large number of optically faint X-ray sources are likely to host obscured active galactic nucleus (AGN) activity at z = 13. From these results we calculate that a significant fraction (5%45%) of the optically faint X-ray source population could be obscured QSOs (rest-frame unabsorbed 0.58.0 keV luminosity >3 × 1044 ergs s-1) at z 3. Given the number of X-ray sources without I-band counterparts, there are unlikely to be more than 15 sources at z > 6. We provide evidence that the true number of z > 6 sources is considerably lower. We investigate the multiwavelength properties of optically faint X-ray sources. Nine optically faint X-ray sources have Jy radio counterparts; 53% of the optically faint Jy radio sources in this region. The most likely origin of the X-ray emission in these X-ray detected, optically faint Jy radio sources is obscured AGN activity. However, two of these sources have been previously detected at submillimeter wavelengths, and the X-ray emission from these sources could be due to luminous star formation activity. Assuming the spectral energy distribution of NGC 6240, we estimate the 175 m flux of a typical optically faint X-ray source to be less than 10 mJy; however, those sources with detectable submillimeter counterparts (i.e., f850 m > 3 mJy) could be substantially brighter. Hence, most optically faint X-ray sources are unlikely to contribute significantly to the far-IR (140240 m) background radiation. However, as expected for sources with AGN activity, the two optically faint X-ray sources within the most sensitive area of the ISOCAM HDF-N region have faint (50 Jy) 15 m counterparts. We also provide constraints on the average X-ray properties of classes of optically faint sources not individually detected at X-ray energies. Stacking analyses of optically faint Jy radio sources not individually detected with X-ray emission yields a possible detection (at 98.3% confidence) in the 0.52.0 keV band; this X-ray emission could be produced by star formation activity at z = 13. None of the optically faint AGN-candidate sources in the HDF-N itself are detected at X-ray energies either individually or with stacking analyses, showing that these sources have low X-ray luminosities if they are indeed AGNs