222 research outputs found
Radio sources in the Chandra Galactic Bulge Survey
Get PDFWe discuss radio sources in the Chandra Galactic Bulge Survey region. By cross-matching the X-ray sources in this field with the NRAO VLA Sky Survey archival data, we find 12 candidate matches. We present a classification scheme for radio/X-ray matches in surveys taken in or near the Galactic plane, taking into account other multiwavelength data. We show that none of the matches found here is likely to be due to coronal activity from normal stars because the radio to X-ray flux ratios are systematically too high. We show that one of the source could be a radio pulsar, and that one could be a planetary nebula, but that the bulk of the sources are likely to be background active galactic nuclei (AGN), with many confirmed through a variety of approaches. Several of the AGN are bright enough in the near-infrared (and presumably in the optical) to use as probes of the interstellar medium in the inner Galaxy
How rapidly do neutron stars spin at birth? Constaints from archival X-ray observations of extragalactic supernovae
No full textTraditionally, studies aimed at inferring the distribution of birth periods of neutron stars are based on radio surveys. Here we propose an independent method to constrain the pulsar spin periods at birth based on their X-ray luminosities. In particular, the observed luminosity distribution of supernovae (SNe) poses a constraint on the initial rotational energy of the embedded pulsars, via the correlation found for radio pulsars, and under the assumption that this relation continues to hold beyond the observed range. We have extracted X-ray luminosities (or limits) for a large sample of historical SNe observed with Chandra, XMM and Swift, which have been firmly classified as core-collapse SNe. We have then compared these observational limits with the results of Monte Carlo simulations of the pulsar X-ray luminosity distribution for a range of values of the birth parameters. We find that a pulsar population dominated by millisecond periods at birth is ruled out by the data
Imaging X-ray spectroscopy with micro-X and Chandra
Get PDFThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 245-258).High spectral resolution observations of X-ray phenomena have the potential to uncover new physics. Currently, only point sources can be probed with high resolution spectra, using gratings. Extended objects like supernova remnants cannot be dispersed, leaving the dense forest of emission lines blended by the moderate resolution of modern instruments. In the first half of this thesis, I undertake two investigations of the supernova remnant Cassiopeia A using the flagship X-ray observatory, Chandra. The first study combines the spatial resolution of the ACIS instrument with the spectral resolution of the dispersive HETG to investigate the evolution of ejecta knots. The second improves on statistical limits of radioactive ejecta, and simulates what higher resolution instruments may observe. Micro-X, a new high resolution X-ray telescope, is the focus of the second half. I detail the commissioning of this novel sounding rocket payload, which uses a focal plane of micro-calorimeters to achieve high spectral resolution in each pixel. The flight hardware is in a final state of testing and integration before the launch, which is anticipated in 2014.by John Rutherford.Ph.D
Chandra Survey of Nearby Galaxies: The Catalog
No full textWe searched the public archive of the Chandra X-ray Observatory as of 2016 March and assembled a sample of 719 galaxies within 50 Mpc with available Advanced CCD Imaging Spectrometer observations. By crosscorrelation with the optical or near-infrared nuclei of these galaxies, 314 of them are identified to have an X-ray active galactic nucleus (AGN). The majority of them are low-luminosity AGNs and are unlikely X-ray binaries based upon their spatial distribution and luminosity functions. The AGN fraction is around 60% for elliptical galaxies and early-type spirals, but drops to roughly 20% for Sc and later types, consistent with previous findings in the optical. However, the X-ray survey is more powerful in finding weak AGNs, especially from regions with active star formation that may mask the optical AGN signature. For example, 31% of the H II nuclei are found to harbor an X-ray AGN. For most objects, a single power-law model subject to interstellar absorption is adequate to fit the spectrum, and the typical photon index is found to be around 1.8. For galaxies with a non-detection, their stacked Chandra image shows an X-ray excess with a luminosity of a few times 1037. erg. s(-1) on average around the nuclear region, possibly composed of faint X-ray binaries. This paper reports on the technique and results of the survey; in-depth analysis and discussion of the results will be reported in forthcoming papers.National Key Program for Science and Technology Research and Development grant [2016YFA0400702]; National Natural Science Foundation of China [11633003]; Tsinghua University Initiative Scientific Research ProgramSCI(E)ARTICLE283
Chandra Detection of Intracluster X-Ray sources in Virgo
No full textWe present a survey of X-ray point sources in the nearest and dynamically young galaxy cluster, Virgo, using archival Chandra observations that sample the vicinity of 80 early-type member galaxies. The X-ray source populations at the outskirts of these galaxies are of particular interest. We detect a total of 1046 point sources (excluding galactic nuclei) out to a projected galactocentric radius of similar to 40 kpc and down to a limiting 0.5-8 keV luminosity of similar to 2 x 10(38) erg s(-1). Based on the cumulative spatial and flux distributions of these sources, we statistically identify similar to 120 excess sources that are not associated with the main stellar content of the individual galaxies, nor with the cosmic X-ray background. This excess is significant at a 3.5 sigma level, when Poisson error and cosmic variance are taken into account. On the other hand, no significant excess sources are found at the outskirts of a control sample of field galaxies, suggesting that at least some fraction of the excess sources around the Virgo galaxies are truly intracluster X-ray sources. Assisted with ground-based and HST optical imaging of Virgo, we discuss the origins of these intracluster X-ray sources, in terms of supernova-kicked low-mass X-ray binaries (LMXBs), globular clusters, LMXBs associated with the diffuse intracluster light, stripped nucleated dwarf galaxies and free-floating massive black holes.National Science Foundation of China [11133001]; National Key Basic Research Program of China [2015CB857002]; NSFC [11673017, 11203017, 11433002]; Recruitment Program of Global Youth ExpertsSCI(E)ARTICLE284
Chandra observations of old novae
Get PDFWe present highlights of Chandra observations of two old novae, DQ Her and V603 Aql, with the main aim of improving our understanding of the underlying binaries decades after their respective nova eruptions. In DQ Her, we find a partial X-ray eclipse; it is likely that we observe photons scattered in an accretion disk wind. The X-ray spectrum of V603 Aql suggests an origin in multi-temperature plasma; while the low energy lines suggest modest density, the 6.4 keV Fe Kα line suggests that the hard continuum arises in a compact emission region. We also report on our searches for nebular X-ray emission around these old novae.The following article appeared in AIP Conference Proceedings, Vol. 637, page 372-376 and may be found at http://dx.doi.org/doi/10.1063/1.1518232. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.Publisher version: https://doi.org/10.1063/1.151823
Multi-scale Radio and X-Ray Structure of the High-redshift Quasar PMN J0909+0354
No full textThe high-redshift quasar PMN J0909+0354 (z = 3.288) is known to have a parsec-scale compact jet structure, based on global 5 GHz very long baseline interferometry (VLBI) observations performed in 1992. Its kiloparsec-scale structure was studied with the Karl G. Jansky Very Large Array (VLA) in the radio and the Chandra space telescope in X-rays. Apart from the north-northwestern jet component seen in both the VLA and Chandra images at 2.″3 separation from the core, there is another X-ray feature at 6.″48 in the northeastern (NE) direction. To uncover more details and possible structural changes in the inner jet, we conducted new observations at 5 GHz using the European VLBI Network in 2019. These data confirm the northward direction of the one-sided inner jet already suspected from the 1992 observations. A compact core and multiple jet components were identified that can be traced up to ∼0.25 kpc projected distance toward the north, where the structure becomes more and more diffuse. A comparison with arcsecond-resolution imaging with the VLA shows that the radio jet bends by ∼30 between the two scales. The direction of the parsec-scale jet as well as the faint optical counterpart found for the newly detected X-ray point source (NE) favors the nature of the latter as being a background or foreground object in the field of view. However, the extended (∼160 kpc) emission around the positions of the quasar core and NE detected by the Wide-field Infrared Survey Explorer in the mid-infrared might suggest a physical interaction of the two objects. Accepted Author ManuscriptsAstrodynamics & Space Mission
X-Ray Jet Emission from the Black Hole X-Ray Binary XTE J1550-564 with Chandra in 2000
Get PDFGeneral rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. ABSTRACT We have discovered an X-ray jet due to material ejected from the black hole X-ray transient XTE J1550À564. The discovery was first reported in 2002 by Corbel and coworkers, and here we present an analysis of the three Chandra observations made between 2000 June and September. For these observations, a source is present that moves in an eastward direction away from the point source associated with the compact object. The separation between the new source and the compact object changes from 21>3 in June to 23>4 in September, implying a proper motion of 21:2 AE 7:2 mas day À1 , a projected separation of 0.31-0.85 pc, and an apparent jet velocity between 0:34 AE 0:12 and 0:93 AE 0:32 times the speed of light for a source distance range of d ¼ 2:8 7:6 kpc. These observations represent the first time that an X-ray jet proper-motion measurement has been obtained for any accretion-powered Galactic or extragalactic source. While this work deals with the jet to the east of the compact object, the western jet has also been detected in the X-ray and radio bands. The most likely scenario is that the eastern jet is the approaching jet and that the jet material was ejected from the black hole in 1998. Along with a 1998 VLBI proper-motion measurement, the Chandra proper motion indicates that the eastern jet decelerated between 1998 and 2000. There is evidence that the eastern jet is extended by AE2 00 -3 00 in the direction of the proper motion. The upper limit on the source extension in the perpendicular direction is AE1>5, which corresponds to a jet opening angle of less than 7=5. The X-ray jet energy spectrum is well but not uniquely described by a power law with an energy index of ¼ À0:8 AE 0:4 (S / ) and interstellar absorption. The eastern jet was also detected in the radio band during an observation made within 7.4 days of the June Chandra observation. The overall radio flux level is consistent with an extrapolation of the X-ray power law with ¼ À0:6. The 0.3-8 keV X-ray jet luminosity is in the range ð3 24Þ Â 10 32 ergs s À1 for the June observation using the distance range above but is a factor of $2-3 lower for the later observations. We cannot definitively determine the X-ray emission mechanism, but a synchrotron origin is viable and may provide the simplest explanation for the observations
The X-ray source population of the globular cluster M15: Chandra high-resolution imaging
No full textThis is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.The globular cluster M15 was observed on three occasions with the High Resolution Camera on-board Chandra in 2001 in order to investigate the X-ray source population in the cluster centre. After subtraction of the two bright central sources, four faint sources were identified within 50 arcsec of the core. One of these sources is probably the planetary nebula K648, making this the first positive detection of X-rays from a planetary nebula inside a globular cluster. Another two are identified with UV variables (one previously known), which we suggest are cataclysmic variables (CVs). The nature of the fourth source is more difficult to ascertain, and we discuss whether it is possibly a quiescent soft X-ray transient or also a CV.DCH is grateful to the Academy of Finland and to PPARC for financial support. MBD gratefully acknowledges the support of a Swedish Royal Academy of Sciences (KVA) Research Fellowship. The authors thank Craig Heinke, Bruce Balick and Joel Kastner for valuable comments. The authors also wish to thank Jonathan C. McDowell for useful suggestions, Miriam Krauss at the Chandra HelpDesk, and the anonymous referee for useful comments. DCH is grateful to Panu Muhli for useful comments. This research has made use of NASA's Astrophysics Data System, SAOImage DS9, developed by Smithsonian Astrophysical Observatory, and of the SIMBAD database operated at CDS, Strasbourg, France. Part of this work was based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555
X-ray and optical properties of ULXs in NGC 4490/4485
No full textTurkish Physical Society 33rd International Physics Congress, TPS 2017 --6 September 2017 through 10 September 2017 -- --The X-ray and optical properties of seven ultraluminous X-ray Sources (ULXs) in the interacting galaxies NGC 4490/4485 were examined in this study. The XMM-Newton and Chandra archival data were used for X-ray analyses. To study the optical counterparts of ULXs, the Hubble Space Telescope, (HST) archival data were used. After the relative astrometric correction between the Chandra and HST images, bright optical counterpart candidates were found for three ULXs (X-4, X-6 and X-7). © 2018 Author(s)
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