ar X iv : a st ro - p h / 02 08 29 0 v 1 1 5 A ug 2 00 2 O and Ne K absorption edge structures and interstellar abundance towards Cyg X - 2
نویسندگان
چکیده
We have studied the O and Ne absorption features in the X-ray spectrum of Cyg X-2 observed with the Chandra LETG. The O absorption edge is represented by the sum of three absorption-edge components within the limit of the energy resolution and the photon counting statistics. Two of them are due to the atomic O; their energies correspond to two distinct spin states of photo-ionized O atoms. The remaining edge component is considered to represent compound forms of oxide dust grains. Since Cyg X-2 is about 1.4 kpc above the galactic disk, the H column densities can be determined by radio (21 cm and CO emission line) and Hα observations with relatively small uncertainties. Thus the O abundance relative to H can be determined from the absorption edges. We found that the dust scattering can affect the apparent depth of the edge of the compound forms. We determined the amplitude of the effect, which we consider is the largest possible correction factor. The ratio of column densities of O in atomic to compound forms and the O total abundance were respectively determined to be in the range 1.7 −0.9 to 2.8 +5.1 −1.5 (ratio), and 0.63±0.12 solar to 0.74±0.14 solar (total), taking into account the uncertainties in the dust-scattering correction and in the ionized H column density. We also determined the Ne abundance from the absorption edge to be 0.75 ± 0.20 solar. These abundance values are smaller than the widely-used solar values but consistent with the latest estimates of solar abundance.
منابع مشابه
ar X iv : a st ro - p h / 04 08 13 5 v 1 9 A ug 2 00 4 A Determination of the Chemical Composition of α Centauri A from Strong Lines
متن کامل
ar X iv : a st ro - p h / 02 08 26 2 v 1 1 3 A ug 2 00 2 Balmer and He I absorption in the nuclear spectrum of NGC 4151
Spectra taken with the Space Telescope Imaging Spectrograph (STIS) allow accurate location and extraction of the nuclear spectrum of NGC 4151, with minimal contamination by extended line emission and circumnuclear starlight. Spectra since 1997 show that the P Cygni Balmer and He I absorption seen previously in low nuclear states, is present in higher states, with outflow velocity that changes w...
متن کاملar X iv : a st ro - p h / 05 02 36 3 v 4 3 1 A ug 2 00 5 Microlensing optical depth toward the Galactic Bulge using bright sources from OGLE - II
We present a measurement of the microlensing optical depth toward the Galactic Bulge based on 4 years of the OGLE-II survey. We consider only bright sources in the extended Red Clump Giant (RCG) region of the Color
متن کاملar X iv : a st ro - p h / 02 08 18 7 v 1 8 A ug 2 00 2 The Chandra HETGS and RXTE view of GRS 1915 + 105
The Chandra AO1 HETGS observation of the micro-quasar GRS 1915+105 in the low hard state reveals (1) neutral K absorption edges from Fe, Si, Mg, and S in cold gas, and (2) highly ionized (Fe xxv and Fe xxvi) absorption attributed to a hot disk, disk wind, or corona. The neutral edges reveal anomalous Si and Fe abundances which we attribute to surrounding cold material in/near the environment of...
متن کاملar X iv : a st ro - p h / 98 08 01 9 v 1 3 A ug 1 99 8 Magnetic field estimation in Cyg X - 3 ’ s jet
Multi-wavelength photometric observations of Cygnus X-3 were carried out at 18 cm through to 450 μm, complemented by X-ray (2-10 keV) observations. The system was mildly active with cm fluxes at 150 – 250 mJy. We find the spectrum to be flat with a spectral index of zero. Using a modified Wolf-Rayet wind model, and assuming emission is generated in synchrotron emitting jets from the source, we ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره شماره
صفحات -
تاریخ انتشار 2002