We describe a search for an optical pulsar in the remnant of Supernova 1987A. We have performed over one hundred separate observations of the supernova, covering wavelengths from 3500 angstroms to 1.8 microns, with sensitivity to pulsations as faint as magnitude 22.7. As of September 26, 1990, we have not seen evidence for pulsations due to a pulsar in the supernova. We discuss the implications of this result on predictions of pulsar optical luminosity. We have constructed for the search two photodiode detectors and a data system. We describe their design, calibration and performance. These detectors have allowed us to increase our sensitivity as much as a factor of 5 over standard photomultiplier tubes, and extend this search to near infrared wavelengths. 59 refs., 10 figs., 1 tab.
{"title":"An optical and near infrared search for a pulsar in Supernova 1987A","authors":"T. Sasseen","doi":"10.2172/6223782","DOIUrl":"https://doi.org/10.2172/6223782","url":null,"abstract":"We describe a search for an optical pulsar in the remnant of Supernova 1987A. We have performed over one hundred separate observations of the supernova, covering wavelengths from 3500 angstroms to 1.8 microns, with sensitivity to pulsations as faint as magnitude 22.7. As of September 26, 1990, we have not seen evidence for pulsations due to a pulsar in the supernova. We discuss the implications of this result on predictions of pulsar optical luminosity. We have constructed for the search two photodiode detectors and a data system. We describe their design, calibration and performance. These detectors have allowed us to increase our sensitivity as much as a factor of 5 over standard photomultiplier tubes, and extend this search to near infrared wavelengths. 59 refs., 10 figs., 1 tab.","PeriodicalId":9423,"journal":{"name":"Bulletin of the American Astronomical Society","volume":"32 1","pages":"842"},"PeriodicalIF":0.0,"publicationDate":"1990-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87867495","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 : 1990-09-01DOI: 10.1007/978-3-642-77566-6_58
B. Grossan, R. Remillard, H. Bradt, T. Ohashi, K. Hayashida, F. Makino, Yasuo Tanaka
{"title":"A Thermal Model of the Continuum Variability of GQ Comae (PG1202+281)","authors":"B. Grossan, R. Remillard, H. Bradt, T. Ohashi, K. Hayashida, F. Makino, Yasuo Tanaka","doi":"10.1007/978-3-642-77566-6_58","DOIUrl":"https://doi.org/10.1007/978-3-642-77566-6_58","url":null,"abstract":"","PeriodicalId":9423,"journal":{"name":"Bulletin of the American Astronomical Society","volume":"61 1","pages":"1194"},"PeriodicalIF":0.0,"publicationDate":"1990-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77968794","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 : 1990-03-01DOI: 10.1017/cbo9780511564833.010
P. R. Wilson, P. McIntosh
{"title":"The Origin of the Large-Scale Fields","authors":"P. R. Wilson, P. McIntosh","doi":"10.1017/cbo9780511564833.010","DOIUrl":"https://doi.org/10.1017/cbo9780511564833.010","url":null,"abstract":"","PeriodicalId":9423,"journal":{"name":"Bulletin of the American Astronomical Society","volume":"28 1","pages":"872"},"PeriodicalIF":0.0,"publicationDate":"1990-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85846197","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 evolution and p-mode oscillation frequencies of several solar models are presented, highlighting the effects of uncertainties in the opacity and equation of state. The Dappen, Mihalas, Hummer, and Mihalas ('MHD') equation of state tables are incorporated into the evolution and oscillation calculations, and the results are compared with those of models calculated using the analytical Iben equation of state. The nonadiabatic low-degree p-mode oscillation frequencies derived from models using either of these equations of state agree with observations to within a few microhertz. The MHD equation of state, with more detailed treatment of envelope ionization regions, improves agreement with observations for p-modes of degree l = 40-300. For higher degree p-modes, observational uncertainties make it difficult to determine how much improvement the MHD equation of state provides over the analytical Iben procedure. Calculated p-mode oscillation frequencies favor the higher Ross-Aller opacities, which include molecular effects and more iron lines, over the older Cox-Tabor opacities in the solar envelope at temperatures below 9000 K. Thus, solar oscillations can be effectively used to constrain opacities at the solar surface and below the convection zone. 32 refs.
{"title":"Effects of Opacity and Equation of State on Solar Structure and Oscillations","authors":"J. Guzik, A. N. Cox","doi":"10.1086/170655","DOIUrl":"https://doi.org/10.1086/170655","url":null,"abstract":"The evolution and p-mode oscillation frequencies of several solar models are presented, highlighting the effects of uncertainties in the opacity and equation of state. The Dappen, Mihalas, Hummer, and Mihalas ('MHD') equation of state tables are incorporated into the evolution and oscillation calculations, and the results are compared with those of models calculated using the analytical Iben equation of state. The nonadiabatic low-degree p-mode oscillation frequencies derived from models using either of these equations of state agree with observations to within a few microhertz. The MHD equation of state, with more detailed treatment of envelope ionization regions, improves agreement with observations for p-modes of degree l = 40-300. For higher degree p-modes, observational uncertainties make it difficult to determine how much improvement the MHD equation of state provides over the analytical Iben procedure. Calculated p-mode oscillation frequencies favor the higher Ross-Aller opacities, which include molecular effects and more iron lines, over the older Cox-Tabor opacities in the solar envelope at temperatures below 9000 K. Thus, solar oscillations can be effectively used to constrain opacities at the solar surface and below the convection zone. 32 refs.","PeriodicalId":9423,"journal":{"name":"Bulletin of the American Astronomical Society","volume":"30 1","pages":"896"},"PeriodicalIF":0.0,"publicationDate":"1990-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78915947","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 : 1990-01-01DOI: 10.1007/978-3-642-75273-5_24
G. Byrd, S. Howard
{"title":"M51’s Material Arms and Density Waves","authors":"G. Byrd, S. Howard","doi":"10.1007/978-3-642-75273-5_24","DOIUrl":"https://doi.org/10.1007/978-3-642-75273-5_24","url":null,"abstract":"","PeriodicalId":9423,"journal":{"name":"Bulletin of the American Astronomical Society","volume":"36 1","pages":"128-130"},"PeriodicalIF":0.0,"publicationDate":"1990-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86775258","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 : 1990-01-01DOI: 10.1007/978-3-642-75273-5_94
H. Levison, M. Duncan, B. F. Smith
{"title":"The Stability of Highly Flattened Isothermal Oblate Elliptical Galaxies","authors":"H. Levison, M. Duncan, B. F. Smith","doi":"10.1007/978-3-642-75273-5_94","DOIUrl":"https://doi.org/10.1007/978-3-642-75273-5_94","url":null,"abstract":"","PeriodicalId":9423,"journal":{"name":"Bulletin of the American Astronomical Society","volume":"16 1","pages":"371-372"},"PeriodicalIF":0.0,"publicationDate":"1990-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85451985","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}
Solar Maximum Mission soft X-ray spectra and National Solar Observatory (Sacramento Peak) H-alpha spectra were combined in a study of high-speed flows during the impulsive phase of four solar flares. In all events, a blue asymmetry (indicative of upflows) was observed in the coronal Ca XIX line during the soft X-ray rise phase. In all events a red asymmetry (indicative of downflows) was observed simultaneously in chromospheric H-alpha. These oppositely directed flows were concurrent with impulsive hard X-ray emission. Combining the velocity data with estimates of the density based on emission measurements and volume estimates, it is shown that for the impulsive phase as a whole the total momentum of upflowing soft X-ray plasma equaled that of the downflowing H-alpha plasma, to within an order of magnitude, in all four events. Only the chromospheric evaporation model predicts equal total momentum in the upflowing soft X-ray-emitting and downflowing H-alphba-emitting materials.
{"title":"Momentum balance in four solar flares","authors":"R. Canfield, T. Metcalf, D. Zarro, J. Lemen","doi":"10.1086/168240","DOIUrl":"https://doi.org/10.1086/168240","url":null,"abstract":"Solar Maximum Mission soft X-ray spectra and National Solar Observatory (Sacramento Peak) H-alpha spectra were combined in a study of high-speed flows during the impulsive phase of four solar flares. In all events, a blue asymmetry (indicative of upflows) was observed in the coronal Ca XIX line during the soft X-ray rise phase. In all events a red asymmetry (indicative of downflows) was observed simultaneously in chromospheric H-alpha. These oppositely directed flows were concurrent with impulsive hard X-ray emission. Combining the velocity data with estimates of the density based on emission measurements and volume estimates, it is shown that for the impulsive phase as a whole the total momentum of upflowing soft X-ray plasma equaled that of the downflowing H-alpha plasma, to within an order of magnitude, in all four events. Only the chromospheric evaporation model predicts equal total momentum in the upflowing soft X-ray-emitting and downflowing H-alphba-emitting materials.","PeriodicalId":9423,"journal":{"name":"Bulletin of the American Astronomical Society","volume":"21 1","pages":"688"},"PeriodicalIF":0.0,"publicationDate":"1990-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88612451","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 one-dimensional radiation-hydrodynamics code is used to numerically investigate the structure and evolution of shocks in the winds of hot stars. Results are presented for the specific case of Tau Sco, a well-studied main-sequence B star for which there are X-ray data from the Einstien satellite's Solid State Spectrometer. A phenomenological radiative acceleration term and a mass-loss rate consistent with UV observations, are used to determine the time dependence of the temperatures within and X-ray emission from an isolated shock region. The driving acceleration leads to the formation of a two-component shock zone with 'forward' and 'reverse' shocks, each with their own characteristic temperature. A denser cold region forms between the two shocks, which could potentially account for the presence of narrow absorption features that are observed in the UV P Cygni profiles of many hot stars. The X-ray emission spectra from the shocks in the calculations are in good general agreement with two-temperature model fits to Einstein X-ray observations.
{"title":"Shock-Generated X-ray Emission in Radiatively-Driven Winds: A Model for Tau Scorpii","authors":"J. Macfarlane, J. Cassinelli","doi":"10.1086/168197","DOIUrl":"https://doi.org/10.1086/168197","url":null,"abstract":"A one-dimensional radiation-hydrodynamics code is used to numerically investigate the structure and evolution of shocks in the winds of hot stars. Results are presented for the specific case of Tau Sco, a well-studied main-sequence B star for which there are X-ray data from the Einstien satellite's Solid State Spectrometer. A phenomenological radiative acceleration term and a mass-loss rate consistent with UV observations, are used to determine the time dependence of the temperatures within and X-ray emission from an isolated shock region. The driving acceleration leads to the formation of a two-component shock zone with 'forward' and 'reverse' shocks, each with their own characteristic temperature. A denser cold region forms between the two shocks, which could potentially account for the presence of narrow absorption features that are observed in the UV P Cygni profiles of many hot stars. The X-ray emission spectra from the shocks in the calculations are in good general agreement with two-temperature model fits to Einstein X-ray observations.","PeriodicalId":9423,"journal":{"name":"Bulletin of the American Astronomical Society","volume":"20 1","pages":"1014"},"PeriodicalIF":0.0,"publicationDate":"1989-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82406950","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}
S. Kumagai, T. Shigeyama, K. Nomoto, M. Itoh, J. Nishimura
Recent developments in modeling the X-ray and gamma-ray emission from SN 1987A are discussed by taking into account both the decaying cobalt and the buried neutron star. The light curve and the spectra evolution of X-rays and gamma-rays are well modeled up to day of about 300 if mixing of Co-56 into hydrogen-rich envelope is assumed. However, the 16-28 keV flux observed by Ginga declines very slowly, whereas the spherical mixing model predicts that the flux should have decreased by a large factor at t greater than 300d. It is shown that this problem can be solved if the photoelectric absorption of X-rays is effectively reduced as a result of the formation of chemically inhomogeneous clumps. Based on the adopted hydrodynamical model and the abundance distribution, predictions are offered for future optical, X-ray, and gamma-ray light curves by taking into account other radioactive sources and various types of the central source, e.g., a buried neutron star accreting the reinfalling material or an isolated pulsar.
{"title":"Gamma rays, X-rays, and optical light from the cobalt and the neutron star in SN 1987A","authors":"S. Kumagai, T. Shigeyama, K. Nomoto, M. Itoh, J. Nishimura","doi":"10.1086/167915","DOIUrl":"https://doi.org/10.1086/167915","url":null,"abstract":"Recent developments in modeling the X-ray and gamma-ray emission from SN 1987A are discussed by taking into account both the decaying cobalt and the buried neutron star. The light curve and the spectra evolution of X-rays and gamma-rays are well modeled up to day of about 300 if mixing of Co-56 into hydrogen-rich envelope is assumed. However, the 16-28 keV flux observed by Ginga declines very slowly, whereas the spherical mixing model predicts that the flux should have decreased by a large factor at t greater than 300d. It is shown that this problem can be solved if the photoelectric absorption of X-rays is effectively reduced as a result of the formation of chemically inhomogeneous clumps. Based on the adopted hydrodynamical model and the abundance distribution, predictions are offered for future optical, X-ray, and gamma-ray light curves by taking into account other radioactive sources and various types of the central source, e.g., a buried neutron star accreting the reinfalling material or an isolated pulsar.","PeriodicalId":9423,"journal":{"name":"Bulletin of the American Astronomical Society","volume":"419 1","pages":"714"},"PeriodicalIF":0.0,"publicationDate":"1989-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74378864","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}
L. Mundy, B. Wilking, G. Blake, A. Sargent, H. Wootten
We present 4".5 x 2".5 resolution millimeter wavelength observations of the young far-infrared source IRAS 16293-2422 which resolve the continuum emission into two sources, MM 1 and MM 2. These sources coincide with known radio continuum sources and may constitute a very young binary system with a projected separation of 840 AU. Flux measurements from 18 cm to 25 μm show that the majority of the millimeter wavelength emission arises from dust within 300 AU of the individual central objects. The total dynamical mass of 1.1-1.3 M_⊙, coupled with our mass estimates for MM 1 and MM 2, suggests that the mass in circumstellar material is comparable to that of the central stellar cores. Since the stellar masses are constrained to be ≤ 0.5 M_⊙ each, it is likely that the bolometric luminosity of 30-40 L_⊙ is derived mainly from accretion of the observed circumstellar material. Maps of the J = 2, 3-1, 2 transition of SO obtained simultaneously show that this emission is centered on MM 1, with weaker emission in a clumpy distribution to the east and west. No SO emission is detected toward MM 2, indicating an upper limit to the fractional abundance which is a factor of 10 below that toward MM 1. We propose that the SO emission toward MM 1 is a result of the outflow activity associated with this source and that the outlying emission clumps trace regions of mild interaction between the outflow and the ambient cloud.
{"title":"IRAS 16293-2422: A Very Young Binary System","authors":"L. Mundy, B. Wilking, G. Blake, A. Sargent, H. Wootten","doi":"10.1086/170939","DOIUrl":"https://doi.org/10.1086/170939","url":null,"abstract":"We present 4\".5 x 2\".5 resolution millimeter wavelength observations of the young far-infrared source IRAS \u000016293-2422 which resolve the continuum emission into two sources, MM 1 and MM 2. These sources coincide with known radio continuum sources and may constitute a very young binary system with a projected separation of 840 AU. Flux measurements from 18 cm to 25 μm show that the majority of the millimeter wavelength emission arises from dust within 300 AU of the individual central objects. The total dynamical mass of 1.1-1.3 M_⊙, coupled with our mass estimates for MM 1 and MM 2, suggests that the mass in circumstellar material is comparable to that of the central stellar cores. Since the stellar masses are constrained to be ≤ 0.5 M_⊙ each, it is likely that the bolometric luminosity of 30-40 L_⊙ is derived mainly from accretion of the observed circumstellar material. Maps of the J = 2, 3-1, 2 transition of SO obtained simultaneously show that this emission is centered on MM 1, with weaker emission in a clumpy distribution to the east and west. No SO emission is detected toward MM 2, indicating an upper limit to the fractional abundance which is a factor of 10 below that toward MM 1. We propose that the SO emission toward MM 1 is a result of the outflow activity associated with this source and that the outlying emission clumps trace regions of mild interaction between the outflow and the ambient cloud.","PeriodicalId":9423,"journal":{"name":"Bulletin of the American Astronomical Society","volume":"10 1","pages":"1223"},"PeriodicalIF":0.0,"publicationDate":"1989-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87499934","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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