21 research outputs found
The interstellar oxygen-K absorption edge as observed by XMM-Newton
High resolution X-ray spectra of the Reflection Grating Spectrometer (RGS) on
board the XMM satellite are used to resolve the oxygen K absorption edge. By
combining spectra of low and high extinction sources, the observed absorption
edge can be split in the true interstellar (ISM) extinction and the
instrumental absorption. The detailed ISM edge structure closely follows the
edge structure of neutral oxygen as derived by theoretical R-matrix
calculations. However, the position of the theoretical edge requires a
wavelength shift. In addition the detailed instrumental RGS absorption edge
structure is presented. All results are verified by comparing to a subset of
Chandra LETG-HRC observations.Comment: LaTeX2e A&A style, 10 pages, 12 postscript figures, accepted for
publication in Astronomy and Astrophysic
First Light Measurements with the XMM-Newton Reflection Grating Spectrometers: Evidence for an Inverse First Ionisation Potential Effect and Anomalous Ne A bundance in the Coronae of HR 1099
The RS CVn binary system HR 1099 was extensively observed by the XMM-Newton
observatory in February 2000 as its first-light target. A total of 570 ks of
exposure time was accumulated with the Reflection Grating Spectrometers (RGS).
The integrated X-ray spectrum between 5-35 Angstrom is of unprecedented quality
and shows numerous features attributed to transitions of the elements C, N, O,
Ne, Mg, Si, S, Fe, and Ni. We perform an in-depth study of the elemental
composition of the average corona of this system, and find that the elemental
abundances strongly depend on the first ionisation potential (FIP) of the
elements. But different from the solar coronal case, we find an inverse FIP
effect, i.e., the abundances (relative to oxygen) increase with increasing FIP.
Possible scenarios, e.g., selective enrichment due to Ne-rich flare-like
events, are discussed.Comment: 5 pages, 4 figures. Accepted by A&A Letters, XMM issu
Interstellar X-Ray Absorption Spectroscopy of Oxygen, Neon, and Iron with the Chandra LETGS Spectrum of X0614+091
We find resolved interstellar O K, Ne K, and Fe L absorption spectra in the Chandra X-Ray Observatory Low-Energy Transmission Grating Spectrometer (LETGS) spectrum of the low-mass X-ray binary X0614+091. We measure the column densities in O and Ne and find direct spectroscopic constraints on the chemical state of the interstellar O. These measurements probably probe a low-density line of sight through the Galaxy, and we discuss the results in the context of our knowledge of the properties of interstellar matter in regions between the spiral arms
X-ray emitting young stars in the Orion Nebula
The Orion Nebula Cluster and the molecular cloud in its vicinity have been
observed with the ACIS-I detector on board the Chandra X-ray Observatory with
23 hours exposure. We detect 1075 X-ray sources: 91% are spatially associated
with known stellar members of the cluster, and 7% are newly identified deeply
embedded cloud members. This provides the largest X-ray study of a pre-main
sequence stellar population. We examine here the X-ray properties of Orion
young stars as a function of mass. Results include: (a) the discovery of rapid
variability in the O9.5 31 M_o star \theta^2A Ori, and several early B stars,
inconsistent with the standard model of X-ray production in small wind shocks;
(b) support for the hypothesis that intermediate-mass mid-B through A type
stars do not themselves produce significant X-ray emission; (c) confirmation
that low-mass G- through M-type T Tauri stars exhibit powerful flaring but
typically at luminosities considerably below the `saturation' level; (d)
confirmation that the presence or absence of a circumstellar disk has no
discernable effect on X-ray emission; (e) evidence that T Tauri plasma
temperatures are often very high with T >= 100 MK, even when luminosities are
modest and flaring is not evident; and (f) detection of the largest sample of
pre-main sequence very low mass objects showing high flaring levels and a
decline in magnetic activity as they evolve into L- and T-type brown dwarfs.Comment: 82 pages, 16 figures, 6 tables. To appear in the Astrophysical
Journal. For a version with high quality images and electronic tables, see
ftp://ftp.astro.psu.edu/pub/edf/orion1
Chandra Orion Ultradeep Project: Observations and Source Lists
We present a description of the data reduction methods and the derived
catalog of more than 1600 X-ray point sources from the exceptionally deep
January 2003 Chandra X-ray Observatory observation of the Orion Nebula Cluster
and embedded populations around OMC-1. The observation was obtained with
Chandra's Advanced CCD Imaging Spectrometer (ACIS) and has been nicknamed the
Chandra Orion Ultradeep Project (COUP). With an 838 ks exposure made over a
continuous period of 13.2 days, the COUP observation provides the most uniform
and comprehensive dataset on the X-ray emission of normal stars ever obtained
in the history of X-ray astronomy.Comment: 52 pages, 11 figures, 12 tables. Accepted for publication in ApJS,
special issue dedicated to Chandra Orion Ultradeep Project. A version with
high quality figures can be found at
http://www.astro.psu.edu/users/gkosta/COUP_Methodology.pd
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Integrated X-ray testing of the electro-optical breadboard model for the XMM reflection grating spectrometer
X-ray calibration of the Electro-Optical Breadboard Model (EOBB) of the XXM Reflection Grating Spectrometer has been carried out at the Panter test facility in Germany. The EOBB prototype optics consisted of a four-shell grazing incidence mirror module followed by an array of eight reflection gratings. The dispersed x-rays were detected by an array of three CCDs. Line profile and efficiency measurements where made at several energies, orders, and geometric configurations for individual gratings and for the grating array as a whole. The x-ray measurements verified that the grating mounting method would meet the stringent tolerances necessary for the flight instrument. Post EOBB metrology of the individual gratings and their mountings confirmed the precision of the grating boxes fabrication. Examination of the individual grating surface`s at micron resolution revealed the cause of anomalously wide line profiles to be scattering due to the crazing of the replica`s surface
Chandra X-Ray Imaging of the Interacting Starburst Galaxy System NGC 7714/5: Tidal ULXs, Emergent Wind, and Resolved HII Regions
We present Chandra X-ray images for the interacting galaxy pair NGC 7714/5.
In addition to the unresolved starburst nucleus, a variable point source with
L(X) ~ 10^40 erg/s was detected 1.5" (270 pc) northwest of the nucleus,
coincident with a blue, extremely optically-luminous (M(V) ~ -14.1) point
source on HST images. Eleven more candidate point-like ultraluminous X-ray
sources (ULXs) are seen, two >= 10^40 erg/s. Ten of these are associated with
interaction-induced features but only two with star formation. We found diffuse
emission with L(X) ~ 3 X 10^40 erg/s extending 11" (1.9 kpc) to the north of
the nucleus. Its spectrum can be fit with a 2-temperature Mekal function (0.6/8
keV) or a 0.6 keV Mekal function plus a power law. The hard component may be
due to high mass X-ray binaries (HMXBs) with contributions from inverse Compton
radiation, while the soft component is likely from a superwind. We also
detected extended X-ray emission from four extra-nuclear HII region complexes.
This emission may be due to HMXBs or to diffuse gas heated by winds from
supernovae, if the X-ray production efficiency L(X)/L(mech) is high (~5%). To
estimate L(X)/L(mech), we collected published data for well-studied HII regions
and superbubbles in nearby galaxies. For young HII regions (<3.5 Myrs), the
median L(X)/L(mech) ~ 0.02%, while for older regions, L(X)/L(mech) ~ 0.2-7%.
Thus gas heating by supernovae may be sufficient to account for the HII region
emission. In galaxies much more distant than NGC 7714, for example, the
Cartwheel galaxy, HII region complexes similar to those in NGC 7714 will be
unresolved by Chandra and will mimick ULXs.Comment: Accepted by the Astronomical Journal. Figures also available at
http://www.etsu.edu/physics/bsmith/research/n7714_chandra.htm
High resolution X-ray spectroscopy of zeta Puppis with the XMM-Newton reflection grating spectrometer
We present the first high resolution X-ray spectrum of the bright O4Ief supergiant star zeta Puppis, obtained with the Reflection Grating Spectrometer on-board XMM-Newton. The spectrum exhibits bright emission lines of hydrogen-like and helium-like ions of nitrogen, oxygen, neon, magnesium, and silicon, as well as neon-like ions of iron. The lines are all significantly resolved, with characteristic velocity widths of order 1000-1500 km s[SUP]-1[/SUP]. The nitrogen lines are especially strong, and indicate that the shocked gas in the wind is mixed with CNO-burned material, as has been previously inferred for the atmosphere of this star from ultraviolet spectra. We find that the forbidden to intercombination line ratios within the helium-like triplets are anomalously low for N VI, O VII, and Ne IX. While this is sometimes indicative of high electron density, we show that in this case, it is instead caused by the intense ultraviolet radiation field of the star. We use this interpretation to derive constraints on the location of the X-ray emitting shocks within the wind that are consistent with current theoretical models for this system