Limits on the density of neutral gas within 100 parsecs from observations of the soft X-ray background
Observations are presented in two soft X-ray bands, the Be band (0.077-0.111 keV) and the B-prime (0.105-0.188 keV), for nine directions in the sky. The ratio of count rates in these two bands remains constant as the rates vary by a factor of three, even though the effective interstellar absorption...
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| Veröffentlicht in: | The Astrophysical journal 1991-01, Vol.367 (1), p.182-185 |
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| container_title | The Astrophysical journal |
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| creator | Juda, M. Bloch, J. J. Edwards, B. C. Mccammon, D. Sanders, W. T. |
| description | Observations are presented in two soft X-ray bands, the Be band (0.077-0.111 keV) and the B-prime (0.105-0.188 keV), for nine directions in the sky. The ratio of count rates in these two bands remains constant as the rates vary by a factor of three, even though the effective interstellar absorption cross sections in the bands differ by a factor of about 3.5. For a model in which the bulk of the observed soft X-ray emission originates in a uniform low-density region surrounding the sun, the constant ratio between the band rates places an upper limit on the amount of neutral material that can be homogeneously mixed with the X-ray-emitting gas. The 2 sigma upper limit on the H I column density over an average path through the local emitting region is 6.6 x 10 to the 18th/sq cm. If the average path length is about 100 pc, then clouds similar to the one in which the sun is embedded could still have a filling factor as large as 25 percent. |
| doi_str_mv | 10.1086/169615 |
| format | Article |
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The 2 sigma upper limit on the H I column density over an average path through the local emitting region is 6.6 x 10 to the 18th/sq cm. 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T.</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-c263t-29060083411c528db18251d4472f5b090955e3e4dc9b7aa00947242b21762f4a3</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>1991</creationdate><topic>640105 - Astrophysics & Cosmology- Galaxies</topic><topic>ABSORPTION</topic><topic>ASTRONOMY</topic><topic>Astrophysics</topic><topic>BACKGROUND RADIATION</topic><topic>CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS</topic><topic>COSMIC GASES</topic><topic>COSMIC RADIO SOURCES</topic><topic>CROSS SECTIONS</topic><topic>DENSITY</topic><topic>Earth, ocean, space</topic><topic>ELECTROMAGNETIC RADIATION</topic><topic>Exact sciences and technology</topic><topic>FLUIDS</topic><topic>GASES</topic><topic>H1 REGIONS</topic><topic>Interstellar medium (ism) and nebulae in external galaxies</topic><topic>INTERSTELLAR SPACE</topic><topic>IONIZING RADIATIONS</topic><topic>LIMITING VALUES</topic><topic>PHYSICAL PROPERTIES</topic><topic>RADIATIONS</topic><topic>SOFT X RADIATION</topic><topic>SPACE</topic><topic>Stellar systems. Galactic and extragalactic objects and systems. The universe</topic><topic>X RADIATION</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Juda, M.</creatorcontrib><creatorcontrib>Bloch, J. J.</creatorcontrib><creatorcontrib>Edwards, B. C.</creatorcontrib><creatorcontrib>Mccammon, D.</creatorcontrib><creatorcontrib>Sanders, W. T.</creatorcontrib><collection>NASA Scientific and Technical Information</collection><collection>NASA Technical Reports Server</collection><collection>Pascal-Francis</collection><collection>CrossRef</collection><collection>OSTI.GOV</collection><jtitle>The Astrophysical journal</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Juda, M.</au><au>Bloch, J. J.</au><au>Edwards, B. C.</au><au>Mccammon, D.</au><au>Sanders, W. T.</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Limits on the density of neutral gas within 100 parsecs from observations of the soft X-ray background</atitle><jtitle>The Astrophysical journal</jtitle><date>1991-01-20</date><risdate>1991</risdate><volume>367</volume><issue>1</issue><spage>182</spage><epage>185</epage><pages>182-185</pages><issn>0004-637X</issn><eissn>1538-4357</eissn><coden>ASJOAB</coden><abstract>Observations are presented in two soft X-ray bands, the Be band (0.077-0.111 keV) and the B-prime (0.105-0.188 keV), for nine directions in the sky. The ratio of count rates in these two bands remains constant as the rates vary by a factor of three, even though the effective interstellar absorption cross sections in the bands differ by a factor of about 3.5. 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| source | NASA Technical Reports Server; Alma/SFX Local Collection |
| subjects | 640105 - Astrophysics & Cosmology- Galaxies ABSORPTION ASTRONOMY Astrophysics BACKGROUND RADIATION CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS COSMIC GASES COSMIC RADIO SOURCES CROSS SECTIONS DENSITY Earth, ocean, space ELECTROMAGNETIC RADIATION Exact sciences and technology FLUIDS GASES H1 REGIONS Interstellar medium (ism) and nebulae in external galaxies INTERSTELLAR SPACE IONIZING RADIATIONS LIMITING VALUES PHYSICAL PROPERTIES RADIATIONS SOFT X RADIATION SPACE Stellar systems. Galactic and extragalactic objects and systems. The universe X RADIATION |
| title | Limits on the density of neutral gas within 100 parsecs from observations of the soft X-ray background |
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