GRS 1915+105 IN “SOFT STATE”: NATURE OF ACCRETION DISK WIND AND ORIGIN OF X-RAY EMISSION
We 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...
| Main Authors: | , , |
|---|---|
| Other Authors: | |
| Format: | Article |
| Language: | en_US |
| Published: |
Institute of Physics/American Astronomical Society
2015
|
| Online Access: | http://hdl.handle.net/1721.1/96116 |
| _version_ | 1826208935084818432 |
|---|---|
| author | Ueda, Yoshihiro Yamaoka, Kazutaka Remillard, Ronald A |
| author2 | Massachusetts Institute of Technology. Department of Physics |
| author_facet | Massachusetts Institute of Technology. Department of Physics Ueda, Yoshihiro Yamaoka, Kazutaka Remillard, Ronald A |
| author_sort | Ueda, Yoshihiro |
| collection | MIT |
| description | We 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. |
| first_indexed | 2024-09-23T14:15:04Z |
| format | Article |
| id | mit-1721.1/96116 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T14:15:04Z |
| publishDate | 2015 |
| publisher | Institute of Physics/American Astronomical Society |
| record_format | dspace |
| spelling | mit-1721.1/961162022-09-28T19:28:04Z GRS 1915+105 IN “SOFT STATE”: NATURE OF ACCRETION DISK WIND AND ORIGIN OF X-RAY EMISSION Ueda, Yoshihiro Yamaoka, Kazutaka Remillard, Ronald A Massachusetts Institute of Technology. Department of Physics MIT Kavli Institute for Astrophysics and Space Research Remillard, Ronald Alan We 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. Japan. 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”) 2015-03-20T15:06:14Z 2015-03-20T15:06:14Z 2009-04 2008-10 Article http://purl.org/eprint/type/JournalArticle 0004-637X 1538-4357 http://hdl.handle.net/1721.1/96116 Ueda, 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 http://dx.doi.org/10.1088/0004-637x/695/2/888 Astrophysical Journal Article 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. application/pdf Institute of Physics/American Astronomical Society American Astronomical Society |
| spellingShingle | Ueda, Yoshihiro Yamaoka, Kazutaka Remillard, Ronald A GRS 1915+105 IN “SOFT STATE”: NATURE OF ACCRETION DISK WIND AND ORIGIN OF X-RAY EMISSION |
| title | GRS 1915+105 IN “SOFT STATE”: NATURE OF ACCRETION DISK WIND AND ORIGIN OF X-RAY EMISSION |
| title_full | GRS 1915+105 IN “SOFT STATE”: NATURE OF ACCRETION DISK WIND AND ORIGIN OF X-RAY EMISSION |
| title_fullStr | GRS 1915+105 IN “SOFT STATE”: NATURE OF ACCRETION DISK WIND AND ORIGIN OF X-RAY EMISSION |
| title_full_unstemmed | GRS 1915+105 IN “SOFT STATE”: NATURE OF ACCRETION DISK WIND AND ORIGIN OF X-RAY EMISSION |
| title_short | GRS 1915+105 IN “SOFT STATE”: NATURE OF ACCRETION DISK WIND AND ORIGIN OF X-RAY EMISSION |
| title_sort | grs 1915 105 in soft state nature of accretion disk wind and origin of x ray emission |
| url | http://hdl.handle.net/1721.1/96116 |
| work_keys_str_mv | AT uedayoshihiro grs1915105insoftstatenatureofaccretiondiskwindandoriginofxrayemission AT yamaokakazutaka grs1915105insoftstatenatureofaccretiondiskwindandoriginofxrayemission AT remillardronalda grs1915105insoftstatenatureofaccretiondiskwindandoriginofxrayemission |