The equation of state of cold dense matter in strong magnetic fields is calculated in the Thomas-Fermi and Thomas-Fermi-Dirac approximations. For use in the latter calculation, a new expression is derived for the exchange energy of the uniform electron gas in a strong magnetic field. Detailed calculations of the density profile in the surface region of a neutron star are described for a variety of equations of state, and these show that the surface density profile is strongly affected by the magnetic field, irrespective of whether or not matter in a magnetic field has a condensed state bound with respect to isolated atoms. It is also shown that, as a consequence of the field dependence of the screening potential, magnetic fields can significantly increase nuclear reaction rates.
{"title":"Surface structure of neutron stars with high magnetic fields","authors":"I. Fushiki, E. Gudmundsson, C. Pethick","doi":"10.1086/167653","DOIUrl":"https://doi.org/10.1086/167653","url":null,"abstract":"The equation of state of cold dense matter in strong magnetic fields is calculated in the Thomas-Fermi and Thomas-Fermi-Dirac approximations. For use in the latter calculation, a new expression is derived for the exchange energy of the uniform electron gas in a strong magnetic field. Detailed calculations of the density profile in the surface region of a neutron star are described for a variety of equations of state, and these show that the surface density profile is strongly affected by the magnetic field, irrespective of whether or not matter in a magnetic field has a condensed state bound with respect to isolated atoms. It is also shown that, as a consequence of the field dependence of the screening potential, magnetic fields can significantly increase nuclear reaction rates.","PeriodicalId":9423,"journal":{"name":"Bulletin of the American Astronomical Society","volume":"27 1","pages":"720"},"PeriodicalIF":0.0,"publicationDate":"1989-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78933956","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A CCD spectroscopic survey of Mg II and Mg I absorption lines in a C IV selected sample of 35 metal systems, observed toward 12 QSOs between z = 1.1 and z = 2.1, is reported. Six Mg I and 10 Mg II absorption lines are detected in 33 C IV clouds, and some peculiarities are noted. The complex or asymmetric line profiles reveal that multiple components are present and that variations in the C IV/Mg II and Mg II/Mg I ratio may occur often from one component to another with a velocity separation less than the velocity resolution of about 100 km/s. Comparison with the Mg II absorption-line statistics at z-bar = 0.5 implies that, at z-bar = 1.6, there are more strong absorbers per unit z with W(2796) greater than 0.6 A and fewer weak absorbers. The evolutionary parameter gamma appears to depend on W(min): its value drops as W(min) is reduced and is negative at W(min) = 0.15 A. This suggests a different redshift evolution for the population of weak and strong Mg II absorbers.
{"title":"The Evolution of Low Ionization QSO Absorption Systems","authors":"A. Caulet","doi":"10.1086/167378","DOIUrl":"https://doi.org/10.1086/167378","url":null,"abstract":"A CCD spectroscopic survey of Mg II and Mg I absorption lines in a C IV selected sample of 35 metal systems, observed toward 12 QSOs between z = 1.1 and z = 2.1, is reported. Six Mg I and 10 Mg II absorption lines are detected in 33 C IV clouds, and some peculiarities are noted. The complex or asymmetric line profiles reveal that multiple components are present and that variations in the C IV/Mg II and Mg II/Mg I ratio may occur often from one component to another with a velocity separation less than the velocity resolution of about 100 km/s. Comparison with the Mg II absorption-line statistics at z-bar = 0.5 implies that, at z-bar = 1.6, there are more strong absorbers per unit z with W(2796) greater than 0.6 A and fewer weak absorbers. The evolutionary parameter gamma appears to depend on W(min): its value drops as W(min) is reduced and is negative at W(min) = 0.15 A. This suggests a different redshift evolution for the population of weak and strong Mg II absorbers.","PeriodicalId":9423,"journal":{"name":"Bulletin of the American Astronomical Society","volume":"39 1","pages":"1126"},"PeriodicalIF":0.0,"publicationDate":"1989-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76684612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
New values for the Haser model scale lengths of NH are derived from extensive narrow-band photometry of comet P/Halley. The observations require a parent scale length which is 5-10 times larger than previously published values. It is shown that the newly determined scale lengths also give better agreement with recent observations of two other comets: P/Borrelly and Liller. When combined with fluorescence efficiency calculations by others, the present results indicate that NH production in typical comets, relative to that of other molecular species, is about 20 times greater than previously believed.
{"title":"Revised scale lengths for cometary NH","authors":"D. Schleicher, R. Millis","doi":"10.1086/167365","DOIUrl":"https://doi.org/10.1086/167365","url":null,"abstract":"New values for the Haser model scale lengths of NH are derived from extensive narrow-band photometry of comet P/Halley. The observations require a parent scale length which is 5-10 times larger than previously published values. It is shown that the newly determined scale lengths also give better agreement with recent observations of two other comets: P/Borrelly and Liller. When combined with fluorescence efficiency calculations by others, the present results indicate that NH production in typical comets, relative to that of other molecular species, is about 20 times greater than previously believed.","PeriodicalId":9423,"journal":{"name":"Bulletin of the American Astronomical Society","volume":"81 1","pages":"821"},"PeriodicalIF":0.0,"publicationDate":"1989-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85965310","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
It has been suggested that the solar corona is heated by the dissipation of electric currents. The low value of the resistivity requires the magnetic field to have structure at very small length scales if this mechanism is to work. In this paper it is demonstrated that the coronal magnetic field acquires small-scale structure through the braiding produced by smooth, randomly phased, photospheric flows. The current density develops a filamentary structure and grows exponentially in time. Nonlinear processes in the ideal magnetohydrodynamic equations produce a cascade effect, in which the structure introduced by the flow at large length scales is transferred to smaller scales. If this process continues down to the resistive dissipation length scale, it would provide an effective mechanism for coronal heating.
{"title":"Creation of current filaments in the solar corona","authors":"Z. Mikić, D. Schnack, G. Hoven","doi":"10.1086/167265","DOIUrl":"https://doi.org/10.1086/167265","url":null,"abstract":"It has been suggested that the solar corona is heated by the dissipation of electric currents. The low value of the resistivity requires the magnetic field to have structure at very small length scales if this mechanism is to work. In this paper it is demonstrated that the coronal magnetic field acquires small-scale structure through the braiding produced by smooth, randomly phased, photospheric flows. The current density develops a filamentary structure and grows exponentially in time. Nonlinear processes in the ideal magnetohydrodynamic equations produce a cascade effect, in which the structure introduced by the flow at large length scales is transferred to smaller scales. If this process continues down to the resistive dissipation length scale, it would provide an effective mechanism for coronal heating.","PeriodicalId":9423,"journal":{"name":"Bulletin of the American Astronomical Society","volume":"16 1","pages":"682"},"PeriodicalIF":0.0,"publicationDate":"1989-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84478009","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The characteristics of flashes from 24 normal stars are presented and discussed. Rate estimates are made for the flashes and possible mechanisms for them are considered. The consequences for the earth of solar flashes of varying intensities are examined.
{"title":"Flashes from normal stars","authors":"B. Schaefer","doi":"10.1086/167162","DOIUrl":"https://doi.org/10.1086/167162","url":null,"abstract":"The characteristics of flashes from 24 normal stars are presented and discussed. Rate estimates are made for the flashes and possible mechanisms for them are considered. The consequences for the earth of solar flashes of varying intensities are examined.","PeriodicalId":9423,"journal":{"name":"Bulletin of the American Astronomical Society","volume":"211 1","pages":"1023"},"PeriodicalIF":0.0,"publicationDate":"1989-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72784932","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The results are reported of an Einstein Observatory imaging proportional counter investigation of the X-ray halos of the four brightest young Galactic supernova remnants: the Crab Nebula, Cas A, Tycho's, and Kepler's supernova remnant. It is found that the size, shape, and rough intensity of each of these sources are consistent with the measured properties of the X-ray halos of compact Galactic X-ray sources, and as such are consistent with an origin due solely to the scattering of X-rays by interstellar grains.
{"title":"X-ray halos around supernova remnants","authors":"C. Mauche, P. Gorenstein","doi":"10.1086/167055","DOIUrl":"https://doi.org/10.1086/167055","url":null,"abstract":"The results are reported of an Einstein Observatory imaging proportional counter investigation of the X-ray halos of the four brightest young Galactic supernova remnants: the Crab Nebula, Cas A, Tycho's, and Kepler's supernova remnant. It is found that the size, shape, and rough intensity of each of these sources are consistent with the measured properties of the X-ray halos of compact Galactic X-ray sources, and as such are consistent with an origin due solely to the scattering of X-rays by interstellar grains.","PeriodicalId":9423,"journal":{"name":"Bulletin of the American Astronomical Society","volume":"29 1","pages":"926"},"PeriodicalIF":0.0,"publicationDate":"1989-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78003287","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1989-01-01DOI: 10.1007/978-1-4613-9356-6_15
S. Odewahn
{"title":"Photometry and Kinematics of the Magellanic Type Galaxy NGC 4618","authors":"S. Odewahn","doi":"10.1007/978-1-4613-9356-6_15","DOIUrl":"https://doi.org/10.1007/978-1-4613-9356-6_15","url":null,"abstract":"","PeriodicalId":9423,"journal":{"name":"Bulletin of the American Astronomical Society","volume":"69 1","pages":"116-117"},"PeriodicalIF":0.0,"publicationDate":"1989-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88210376","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1989-01-01DOI: 10.1007/978-94-009-2273-0_24
A. Parmar, N. White, L. Stella
{"title":"The Luminosity Dependence of the Pulse Period and Profile of the Transient X-ray Pulsar EXO 2030+375","authors":"A. Parmar, N. White, L. Stella","doi":"10.1007/978-94-009-2273-0_24","DOIUrl":"https://doi.org/10.1007/978-94-009-2273-0_24","url":null,"abstract":"","PeriodicalId":9423,"journal":{"name":"Bulletin of the American Astronomical Society","volume":"18 1","pages":"283-293"},"PeriodicalIF":0.0,"publicationDate":"1989-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79740915","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1989-01-01DOI: 10.1007/978-94-009-0977-9_67
J. Trauger
{"title":"Wide Field / Planetary Camera-II for the Hubble Space Telescope","authors":"J. Trauger","doi":"10.1007/978-94-009-0977-9_67","DOIUrl":"https://doi.org/10.1007/978-94-009-0977-9_67","url":null,"abstract":"","PeriodicalId":9423,"journal":{"name":"Bulletin of the American Astronomical Society","volume":"15 1","pages":"443-444"},"PeriodicalIF":0.0,"publicationDate":"1989-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84781830","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1989-01-01DOI: 10.1007/978-94-009-0865-9_150
K. Volk, S. Kwok
{"title":"Proto-Planetary Nebulae: Models and Iras Observations","authors":"K. Volk, S. Kwok","doi":"10.1007/978-94-009-0865-9_150","DOIUrl":"https://doi.org/10.1007/978-94-009-0865-9_150","url":null,"abstract":"","PeriodicalId":9423,"journal":{"name":"Bulletin of the American Astronomical Society","volume":"57 1","pages":"452-452"},"PeriodicalIF":0.0,"publicationDate":"1989-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86282191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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