Brian Espey - Academia.edu (original) (raw)
Papers by Brian Espey
The Astrophysical Journal, 2008
arXiv (Cornell University), Apr 23, 2004
Using satellite imagery, the light output from towns and cities across Europe and beyond will be ... more Using satellite imagery, the light output from towns and cities across Europe and beyond will be compared to estimate light use/waste per capita for different countries with the aim of identifying best practice in this regard. It is known that the US as a whole produces more light per capita on a national basis and some European cities produce much less, but the situation in Ireland has not been examined in detail. The project work will involve using the R shareware package with georeferenced data such as CSO and European shapefiles and databases. https://www.jessesadler.com/post/gis-with-r-intro/
Remote Sensing, 2021
Study of light at night has increased in recent decades due to the recognition of its impact on t... more Study of light at night has increased in recent decades due to the recognition of its impact on the environment, potential health concerns, as well as both the financial and carbon cost of energy waste. The advent of more extensive and improved ground-based measurements together with quantifiable satellite data has revolutionised the field, and provided data to test improved theoretical models. However, “closing the loop” and finding a detailed connection between these measurements requires knowledge of the “city emission function”, the angular distribution of upwelling radiation with zenith distance. Simplified analytical functions have been superseded by more complex models involving statistical approximation of emission sources and obstructions and inversion techniques now permit the estimation of emission functions from the observed sky brightness measurements. In this paper, we present an efficient GIS-based method to model public lighting using real-world photometric data and ...
![Research paper thumbnail of Far-Ultraviolet Observations of NGC 4151 during the [ITAL]ORFEUS-SPAS II[/ITAL] Mission](https://attachments.academia-assets.com/117755818/thumbnails/1.jpg)
](The Astrophysical Journal, 1998
We observed the Seyfert 1 galaxy NGC 4151 on 11 occasions at 1-2 day intervals using the Berkeley... more We observed the Seyfert 1 galaxy NGC 4151 on 11 occasions at 1-2 day intervals using the Berkeley spectrometer during the ORFEUS-SPAS II mission in 1996 November. The mean spectrum covers 912-1220 Å at ∼0.3 Å resolution with a total exposure of 15,658 s. The mean flux at 1000 Å was ergs cm Ϫ2 s Ϫ1 Ϫ13
The Astrophysical Journal, 2006
The Astrophysical Journal, 1995
The Astrophysical Journal, 1999
The Astrophysical Journal, 1990
< The Astrophysical Journal, 342:666-676,1989 July 15 © 1989. The American Astronomica... more < The Astrophysical Journal, 342:666-676,1989 July 15 © 1989. The American Astronomical Society. All rights reserved. Printed in USA Ha EMISSION LINES IN HIGH-REDSHIFT QUASARS BR Espey AND RF Carswell Institute of Astronomy, Cambridge JA Bailey ...
The Astrophysical Journal, 1998
The Astronomical Journal, 2000
Monthly Notices of the Royal Astronomical Society, 1996
The Astrophysical Journal Supplement Series, 1999
Symbiotic stars are binary systems consisting of a hot star, typically a white dwarf, and a cool ... more Symbiotic stars are binary systems consisting of a hot star, typically a white dwarf, and a cool giant companion. The wind from the cool star is ionized by the radiation from the hot star, resulting in the characteristic combination of sharp nebular emission lines and stellar molecular absorption bands in the optical spectrum. Most of the emission lines are readily identifiable with common ions. However, two strong, broad emission lines at λλ6825 and 7082 defied identification with known atoms and ions. In 1989, Schmid made the case that these long unidentified emission lines resulted from the Raman scattering of the O VI resonance photons at λλ1032, 1038 by neutral hydrogen. We present contemporaneous far-UV and optical observations of direct and Raman scattered O VI lines for nine symbiotic stars obtained with the Hopkins Ultraviolet Telescope (Astro-2) and various ground-based optical telescopes. The O VI emission lines are present in every instance in which the λλ6825, 7082 lines are present, in support of the Schmid Raman scattering model. We calculate the scattering efficiencies and discuss the results in terms of the Raman scattering model. Additionally, we measure the flux of the Fe II fluorescence line at λ1776, which is excited by the O VI line at λ 1032, and calculate the first estimates of the conversion efficiencies for this process.
The Astrophysical Journal, 2008
arXiv (Cornell University), Apr 23, 2004
Using satellite imagery, the light output from towns and cities across Europe and beyond will be ... more Using satellite imagery, the light output from towns and cities across Europe and beyond will be compared to estimate light use/waste per capita for different countries with the aim of identifying best practice in this regard. It is known that the US as a whole produces more light per capita on a national basis and some European cities produce much less, but the situation in Ireland has not been examined in detail. The project work will involve using the R shareware package with georeferenced data such as CSO and European shapefiles and databases. https://www.jessesadler.com/post/gis-with-r-intro/
Remote Sensing, 2021
Study of light at night has increased in recent decades due to the recognition of its impact on t... more Study of light at night has increased in recent decades due to the recognition of its impact on the environment, potential health concerns, as well as both the financial and carbon cost of energy waste. The advent of more extensive and improved ground-based measurements together with quantifiable satellite data has revolutionised the field, and provided data to test improved theoretical models. However, “closing the loop” and finding a detailed connection between these measurements requires knowledge of the “city emission function”, the angular distribution of upwelling radiation with zenith distance. Simplified analytical functions have been superseded by more complex models involving statistical approximation of emission sources and obstructions and inversion techniques now permit the estimation of emission functions from the observed sky brightness measurements. In this paper, we present an efficient GIS-based method to model public lighting using real-world photometric data and ...
The Astrophysical Journal, 1998
We observed the Seyfert 1 galaxy NGC 4151 on 11 occasions at 1-2 day intervals using the Berkeley... more We observed the Seyfert 1 galaxy NGC 4151 on 11 occasions at 1-2 day intervals using the Berkeley spectrometer during the ORFEUS-SPAS II mission in 1996 November. The mean spectrum covers 912-1220 Å at ∼0.3 Å resolution with a total exposure of 15,658 s. The mean flux at 1000 Å was ergs cm Ϫ2 s Ϫ1 Ϫ13
The Astrophysical Journal, 2006
The Astrophysical Journal, 1995
The Astrophysical Journal, 1999
The Astrophysical Journal, 1990
< The Astrophysical Journal, 342:666-676,1989 July 15 © 1989. The American Astronomica... more < The Astrophysical Journal, 342:666-676,1989 July 15 © 1989. The American Astronomical Society. All rights reserved. Printed in USA Ha EMISSION LINES IN HIGH-REDSHIFT QUASARS BR Espey AND RF Carswell Institute of Astronomy, Cambridge JA Bailey ...
The Astrophysical Journal, 1998
The Astronomical Journal, 2000
Monthly Notices of the Royal Astronomical Society, 1996
The Astrophysical Journal Supplement Series, 1999
Symbiotic stars are binary systems consisting of a hot star, typically a white dwarf, and a cool ... more Symbiotic stars are binary systems consisting of a hot star, typically a white dwarf, and a cool giant companion. The wind from the cool star is ionized by the radiation from the hot star, resulting in the characteristic combination of sharp nebular emission lines and stellar molecular absorption bands in the optical spectrum. Most of the emission lines are readily identifiable with common ions. However, two strong, broad emission lines at λλ6825 and 7082 defied identification with known atoms and ions. In 1989, Schmid made the case that these long unidentified emission lines resulted from the Raman scattering of the O VI resonance photons at λλ1032, 1038 by neutral hydrogen. We present contemporaneous far-UV and optical observations of direct and Raman scattered O VI lines for nine symbiotic stars obtained with the Hopkins Ultraviolet Telescope (Astro-2) and various ground-based optical telescopes. The O VI emission lines are present in every instance in which the λλ6825, 7082 lines are present, in support of the Schmid Raman scattering model. We calculate the scattering efficiencies and discuss the results in terms of the Raman scattering model. Additionally, we measure the flux of the Fe II fluorescence line at λ1776, which is excited by the O VI line at λ 1032, and calculate the first estimates of the conversion efficiencies for this process.