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dc.contributor.authorUeda, Yoshihiro
dc.contributor.authorYamaoka, Kazutaka
dc.contributor.authorRemillard, Ronald A
dc.date.accessioned2015-03-20T15:06:14Z
dc.date.available2015-03-20T15:06:14Z
dc.date.issued2009-04
dc.date.submitted2008-10
dc.identifier.issn0004-637X
dc.identifier.issn1538-4357
dc.identifier.urihttp://hdl.handle.net/1721.1/96116
dc.description.abstractWe present the results from simultaneous Chandra HETGS and Rossi X-ray Timing Explorer (RXTE) observations of the microquasar GRS 1915+105 in its quasi-stable "soft state" (or State A) performed on 2007 August 14, several days after the state transition from "hard state" (State C). The X-ray flux increased with spectral hardening around the middle of the Chandra observation, after which the 67 Hz quasi-periodic oscillation (QPO) became significant. The HETGS spectra reveal at least 32 narrow absorption lines from highly ionized ions including Ne, Mg, Si, S, Ar, Ca, Cr, Mn, Fe, whose features are the deepest among those ever observed with Chandra from this source. By fitting to the absorption-line profiles by Voigt functions, we find that the absorber has outflow velocities of ≈150 and ≈500 km s–1 with a line-of-sight velocity dispersion of ≈70 and ≈200 km s[superscript –1] for the Si XIV and Fe XXVI ions, respectively. The larger velocity and its dispersion in heavier ions indicate that the wind has a nonuniform dynamical structure along the line of sight. The location of the absorber is estimated at ~(1-3) × 10[superscript 5] r [subscript g] (where r[subscript g] is the gravitational radius) from the source, consistent with thermally and/or radiation-driven winds. By taking into account narrow spectral features detected with Chandra, the continuum spectra obtained with RXTE in the 3-25 keV band can be well described with a thermal Comptonization with an electron temperature of ≈4 keV and an optical depth of ≈5 from seed photons from the standard disk extending down to (4-7)r [subscript g]. In this interpretation, most of the radiation energy is produced in the Comptonization corona, which completely covers the inner part of the disk. A broad (1σ width of ≈0.2 keV) iron-K emission line and a smeared edge feature are detected, which can be explained by reflection from the accretion disk at radii larger than 400r [subscript g] when an emissivity power law index of –3 is assumed.en_US
dc.description.sponsorshipJapan. Ministry of Education, Culture, Sports, Science and Technology (Grants-in-Aid for Scientific Research 20540230, Global COE Program “The Next Generation of Physics, Spun from Universality and Emergence”)en_US
dc.language.isoen_US
dc.publisherInstitute of Physics/American Astronomical Societyen_US
dc.relation.isversionofhttp://dx.doi.org/10.1088/0004-637x/695/2/888en_US
dc.rightsArticle is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.en_US
dc.sourceAmerican Astronomical Societyen_US
dc.titleGRS 1915+105 IN “SOFT STATE”: NATURE OF ACCRETION DISK WIND AND ORIGIN OF X-RAY EMISSIONen_US
dc.typeArticleen_US
dc.identifier.citationUeda, Yoshihiro, Kazutaka Yamaoka, and Ronald Remillard. “GRS 1915+105 IN ‘SOFT STATE’: NATURE OF ACCRETION DISK WIND AND ORIGIN OF X-RAY EMISSION.” The Astrophysical Journal 695, no. 2 (April 3, 2009): 888–899. © 2009 American Astronomical Society.en_US
dc.contributor.departmentMassachusetts Institute of Technology. Department of Physicsen_US
dc.contributor.departmentMIT Kavli Institute for Astrophysics and Space Researchen_US
dc.contributor.mitauthorRemillard, Ronald Alanen_US
dc.relation.journalAstrophysical Journalen_US
dc.eprint.versionFinal published versionen_US
dc.type.urihttp://purl.org/eprint/type/JournalArticleen_US
eprint.statushttp://purl.org/eprint/status/PeerRevieweden_US
dspace.orderedauthorsUeda, Yoshihiro; Yamaoka, Kazutaka; Remillard, Ronalden_US
mit.licensePUBLISHER_POLICYen_US
mit.metadata.statusComplete


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