Michael Castelaz | Brevard College (original) (raw)
Papers by Michael Castelaz
Mapping the Sky, 1988
Ihe Multichannel Astrometric Photometer (MAP) now in use in the Allegheny Observatory astrometric... more Ihe Multichannel Astrometric Photometer (MAP) now in use in the Allegheny Observatory astrometric program is the detector chosen for the strawman design of the Astrometric Telescope Facility (ATF) proposed for the U.S. Space Station. Extrapolation of ground based performance to above atmosphere observing conditions indicates an approximate precision of 0.00001 arc seconds per annual normal point.
Astronomical Journal, 1997
Astronomical Journal, 2000
Spectroscopic measurements of Mira variable stars as a function of phase probe the stellar atmosp... more Spectroscopic measurements of Mira variable stars as a function of phase probe the stellar atmospheres and underlying pulsation mechanisms. For example, measuring variations in TiO, VO, and ZrO with phase can be used to help determine whether these molecular species are produced in an extended region above the layers where Balmer line emission occurs or below this shocked region. Using the same methods, the Balmer line increment, where the strongest Balmer line at phase zero is Hδ and not Hα, can be measured and explanations tested, along with another peculiarity, the absence of the Hɛ line in the spectra of Mira variables when the other Balmer lines are strong. We present new spectra covering the spectral range from 6200 to 9000 Å of 20 Mira variables. A relationship between variations in the Ca II IR triplet and Hα as a function of phase support the hypothesis that Hɛ's observational characteristics result from an interaction of Hɛ photons with the Ca II H line. New periods and epochs of variability are also presented for each star.
Astronomical Journal, 1990
This paper presents the results of spectral type and luminosity classification of reference stars... more This paper presents the results of spectral type and luminosity classification of reference stars in the Allegheny Observatory MAP parallax program, using broadband and intermediate-band photometry. In addition to the use of UBVRI and DDO photometric systems, the uvbyH-beta photometric system was included for classification of blue (B - V less than 0.6) reference stars. The stellar classifications made from the photometry are used to determine spectroscopic parallaxes. The spectroscopic parallaxes are used in turn to adjust the relative parallaxes measured with the MAP to absolute parallaxes. A new method for dereddening stars using more than one photometric system is presented. In the process of dereddening, visual extinctions, spectral types, and luminosity classes are determined, as well as a measure of the goodness of fit. The measure of goodness of fit quantifies confidence in the stellar classifications. It is found that the spectral types are reliable to within 2.5 spectral subclasses.
![Research paper thumbnail of Infrared Light Curves of Mira Variable Stars from [ITAL]COBE[/ITAL] DIRBE Data](https://attachments.academia-assets.com/48423427/thumbnails/1.jpg)
](Astronomical Journal, 2002
We have used the COBE DIRBE database to derive near-and mid-infrared light curves for a well-defi... more We have used the COBE DIRBE database to derive near-and mid-infrared light curves for a well-defined sample of 38 infrared-bright Mira variable stars, and compared with optical data from the AAVSO. In general, the 3.5 µm and 4.9 µm DIRBE bandpasses provide the best S/N light curves, with S/N decreasing with wavelength at longer wavelengths. At 25 µm, good light curves are only available for ∼10% of our stars, and at wavelengths ≥ 60 µm, extracting high quality light curves is not possible. The amplitude of variability is typically less in the near-infrared than in the optical, and less in the mid-infrared than in the near-infrared, with decreasing amplitude with increasing wavelength. On average, there are 0.20 ± 0.01 magnitudes variation at 1.25 µm and 0.14 ± 0.01 magnitudes variation at 4.9 µm for each magnitude variation in V. The observed amplitudes are consistent with results of recent theoretical models of circumstellar dust shells around Mira variables. For a few stars in our sample, we find clear evidence of time lags between the optical and near-infrared maxima of phase ∼ 0.05 − 0.13, with no lags in the minima. For three stars, mid-infrared maximum appears to occur slightly before that in the near-infrared, but after optical maximum. We find three examples of secondary maxima in the rising portions of the DIRBE light curves, all of which have optical counterparts in the AAVSO data, supporting the hypothesis that they are due to shocks rather than newly-formed dust layers. We find no conclusive evidence for rapid (hours to days) variations in the infrared brightnesses of these stars.
Astronomical Journal, 1991
UBVRI, DDO, and uvby, H-beta photometry of astrometric reference stars is presented. Spectral typ... more UBVRI, DDO, and uvby, H-beta photometry of astrometric reference stars is presented. Spectral types and luminosity classifications made from the colors are used to determine their spectroscopic parallaxes. In this paper, colors for 309 stars in 25 regions are given, and classifications for 210 stars have been made. These stars form reference frames in the Allegheny Observatory Multichannel Astrometric Photometer astrometric program, and in the Praesepe cluster reduced by Russell (1976). It is found that the present photometric spectral types are reliable to within 2.5 spectral subclasses.
Astronomical Journal, 1991
UBVRI, DDO, and uvby, H-beta photometry of astrometric reference stars is presented. Spectral typ... more UBVRI, DDO, and uvby, H-beta photometry of astrometric reference stars is presented. Spectral types and luminosity classifications made from the colors are used to determine their spectroscopic parallaxes. In this paper, colors for 309 stars in 25 regions are given, and classifications for 210 stars have been made. These stars form reference frames in the Allegheny Observatory Multichannel Astrometric Photometer
Native American, Hispanic, African American, and other underrepresented high school students in r... more Native American, Hispanic, African American, and other underrepresented high school students in rural Western North Carolina have unprecedented opportunity as researchers in the Space Science Lab to conduct visible and radio observations of the Sun. The program involves 90 students over a three year period. The students conduct their own research and also interact with scientists around the world. The primary goal is to reach students who otherwise would not have this opportunity and motivate them to develop the critical thinking skills necessary for objective scientific inquiry. Students develop skills in electronics, computer sciences, astronomy, physics and earth sciences. Equally important is the hope that the students will become interested in pursuing careers in research or other science-related areas. The program objectives are aligned with the North Carolina Standard Course of Study for grades 9-12 in the areas of Earth/Environmental Science, Physical Science and Physics. The first group of 27 students spent a week in the Space Science Lab located on the campus of the Pisgah Astronomical Research Institute (PARI) during the Summer 2006. Students constructed their own JOVE radio telescopes that they took home to continue their observations. They share their results during four follow-up sessions throughout the school year. The students also have Internet access to radio telescopes and solar monitoring equipment at PARI. We expect their enthusiasm for science will increase by experiencing research investigations that are fun and relevant to their understanding of the world around them. We gratefully acknowledge support from the Burroughs Wellcome Fund Student Science Enrichment Program.
Pisgah Astronomical Research Institute (PARI) offers summer undergraduate research internships. P... more Pisgah Astronomical Research Institute (PARI) offers summer undergraduate research internships. PARI has received support for the internships from the NC Space Grant Consortium, NSF awards for public science education, private donations, private foundations, and through a collaboration with the Pisgah Astronomical Research and Education Center of the University of North Carolina - Asheville. The internship program began in 2001 with 4 students. This year 9 funded students participated in 2010. Mentors for the interns include PARI's Directors of Science, Education, and Information Technology and visiting faculty who are members of the PARI Research Affiliate Faculty program. Students work with mentors on radio and optical astronomy research, electrical engineering for robotic control of instruments, software development for instrument control and applets for citizen science projects, and science education by developing curricula and multimedia and teaching high school students in summer programs at PARI. At the end of the summer interns write a paper about their research which is published in the PARI Summer Student Proceedings. Several of the students have presented their results at AAS Meetings. We will present a summary of specific research conducted by the students with their mentors, the logistics for hosting the PARI undergraduate internship program, and plans for growth based on the impact of an NSF supported renovation to the Research Building on the PARI campus.
Astronomical Journal, 2000
Spectroscopic measurements of Mira variable stars as a function of phase probe the stellar atmosp... more Spectroscopic measurements of Mira variable stars as a function of phase probe the stellar atmospheres and underlying pulsation mechanisms. For example, measuring variations in TiO, VO, and ZrO with phase can be used to help determine whether these molecular species are produced in an extended region above the layers where Balmer line emission occurs or below this shocked region. Using the same methods, the Balmer line increment, where the strongest Balmer line at phase zero is Hd and not Ha, can be measured and explanations tested, along with another peculiarity, the absence of the Hv line in the spectra of Mira variables when the other Balmer lines are strong. We present new spectra covering the spectral range from 6200 to 9000 of 20 Mira variables. A relationship between variations in the Ca II A IR triplet and Ha as a function of phase support the hypothesis that HvÏs observational characteristics result from an interaction of Hv photons with the Ca II H line. New periods and epochs of variability are also presented for each star.
Astrophysical Journal, 1987
Astrophysical Journal, 1988
The Orion proplyds are of astrophysical interest because they offer a unique opportunity to study... more The Orion proplyds are of astrophysical interest because they offer a unique opportunity to study important aspects of protostellar and protoplanetary evolution. Proplyds offer the only opportunity known in which to study the effects of external ionization on this phase of young stellar object disk evolution in an external environment like that of the early Solar System. Most proplyds have central stars or starlike objects visible in HST WFPC V continuum or narrow-band filters. The physical properties of the central stars are of interest in fully understanding these systems. Some of the observable IR SED of the disk comes from reprocessed emission from the central star and thus depends on central star properties. Also, accretion rates and disk lifetimes are affected by the mass of the central star. We obtained one spectrum each of three central stars (218-354, 164-510, and 171-340) using the HST STIS instrument. With a spatial resolution of 0.05 arcsecond per pixel STIS easily resolved the central star in all three objects. The spatial resolution of STIS also permits a much more accurate subtraction of the bright nebular background than is possible with ground-based observations. Nebular contamination can be a significant source of error in performing spectral classification. We have completed our analysis and will report on the spectral types, masses, and luminosities for the three central stars.
The Michigan Objective Prism Blue Survey (e.g. Sowell et al 2007, AJ, 134, 1089) photographic pla... more The Michigan Objective Prism Blue Survey (e.g. Sowell et al 2007, AJ, 134, 1089) photographic plates located in the Astronomical Photographic Data Archive at the Pisgah Astronomical Research Institute hold hundreds of thousands of stellar spectra, many of which have not been classified before. The public is invited to participate in a distributed computing online environment to classify the stars on the objective prism plates. The online environment is called Stellar Classification Online - Public Exploration (SCOPE). Through a website, SCOPE participants are given a tutorial on stellar spectra and their classification, and given the chance to practice their skills at classification. After practice, participants register, login, and select stars for classification from scans of the objective prism plates. Their classifications are recorded in a database where the accumulation of classifications of the same star by many users will be statistically analyzed. The project includes stars with known spectral types to help test the reliability of classifications. The SCOPE webpage and the use of results will be described.
Astrophysical Journal, 1987
ABSTRACT Surface brightness maps at 12, 25, 60, and 100 microns were made of a 2.5 deg x 2.5 deg ... more ABSTRACT Surface brightness maps at 12, 25, 60, and 100 microns were made of a 2.5 deg x 2.5 deg area of the reflection nebulae in the Pleiades by coadding IRAS scans of this region. Emission is seen surrounding 17 Tau, 20 Tau, 23 Tau, and 25 Tau in all four bands, coextensive with the visible reflection nebulosity, and extending as far as 30 arcminutes from the illuminating stars. The infrared energy distributions of the nebulae peak in the 100 micron band, but up to 40 percent of the total infrared power lies in the 12 and 25 micron bands. The brightness of the 12 and 25 micron emission and the absence of temperature gradients at these wavelengths are inconsistent with the predictions of equilibrium thermal emission models. The emission at these wavelengths appears to be the result of micron nonequilibrium emission from very small grains, or from molecules consisting of 10-100 carbon atoms, which have been excited by ultraviolet radiation from the illuminating stars.
We have used the COBE DIRBE database to derive near- and mid-infrared light curves for a well-def... more We have used the COBE DIRBE database to derive near- and mid-infrared light curves for a well-defined sample of 38 infrared-bright Mira variable stars, and compared with optical data from the AAVSO. In general, the 3.5 micron and 4.9 micron DIRBE bandpasses provide the best S/N light curves, with S/N decreasing with wavelength at longer wavelengths. At 25 microns, good light curves are only available for ~10 percent of our stars, and at wavelengths >= 60 microns, extracting high quality light curves is not possible. The amplitude of variability is typically less in the near-infrared than in the optical, and less in the mid-infrared than in the near-infrared, with decreasing amplitude with increasing wavelength. On average, there are 0.20 +/- 0.01 magnitudes variation at 1.25 microns and 0.14 +/- 0.01 magnitudes variation at 4.9 micron for each magnitude variation in V. The observed amplitudes are consistent with results of recent theoretical models of circumstellar dust shells around Mira variables. For a few stars in our sample, we find clear evidence of time lags between the optical and maxima of phase ~ 0.05 - 0.13, with no lags in the minima. For three stars, mid-infrared maximum appears to occur slightly before that in the near-infrared,but after optical maximum. We find three examples of secondary maxima in the rising portions of the DIRBE light curves, all of which have optical counterparts in the AAVSO data, supporting the hypothesis that they are due to shocks rather than newly-formed dust layers. We find no conclusive evidence for rapid (hours to days) variations in the infrared brightnesses of these stars.
Astrophysical Journal, 1986
Astrophysical Journal, 2000
As a preliminary step in deducing and log (g) of Mira variables as a function of phase, a compari... more As a preliminary step in deducing and log (g) of Mira variables as a function of phase, a compari-T eff son is made between spectra synthesized from LTE stellar atmosphere models and observed spectra. The observed spectra show obvious vanadium oxide (VO) absorption bands. However, the molecular line list used to produce the synthetic spectra does not include the bound-bound VO opacities. The wavenumbers, line oscillator strengths, and lowest energy levels are needed to calculate these opacities. The equations, constants, and experimentally determined factors required to calculate the line oscillator strengths and lowest energy levels from experimentally determined wavenumbers are presented. The e †ect of including the wavenumbers, line oscillator strengths, and lowest energy levels of the VO BÈX (0, 0) band are calculated and show the expected absorption features observed in the spectra of Mira variables. In the VO BÈX (0, 0) band the line oscillator strengths range from about 0.05 to 3.
Astronomy & Astrophysics Supplement Series, 1996
Native American, Hispanic, African American, and other underrepresented high school students in r... more Native American, Hispanic, African American, and other underrepresented high school students in rural Western North Carolina have the unprecedented opportunity as researchers in the Space Science Lab to conduct visible and radio observations of the Sun. The program involves 90 students over a three year period. The primary goal is to reach students who otherwise would not have this opportunity, and motivate them to develop the critical thinking skills necessary for objective scientific inquiry. Students develop skills in electronics, computer sciences, astronomy, physics and earth sciences. Equally important is the hope that the students will become interested in pursuing careers in research or other science-related areas. We expect their enthusiasm for science will increase by experiencing research investigations that are fun and relevant to their understanding of the world around them. The students conduct their own research, and also interact with scientists around the world. A total of 54 students have spent a week at the Space Science Lab located on the campus of the Pisgah Astronomical Research Institute (PARI) during the Summers of 2006 and 2007. Students construct their own JOVE radio telescopes that they bring home to continue their observations during the academic year. They share their results during four follow-up sessions throughout the school year. The students also have Internet access to radio telescopes and solar monitoring equipment at PARI. We report on results from student evaluations from the first year in 2006 and current session student experiences. We gratefully acknowledge support from the Burroughs Wellcome Fund - Student Science Enrichment Program
Mapping the Sky, 1988
Ihe Multichannel Astrometric Photometer (MAP) now in use in the Allegheny Observatory astrometric... more Ihe Multichannel Astrometric Photometer (MAP) now in use in the Allegheny Observatory astrometric program is the detector chosen for the strawman design of the Astrometric Telescope Facility (ATF) proposed for the U.S. Space Station. Extrapolation of ground based performance to above atmosphere observing conditions indicates an approximate precision of 0.00001 arc seconds per annual normal point.
Astronomical Journal, 1997
Astronomical Journal, 2000
Spectroscopic measurements of Mira variable stars as a function of phase probe the stellar atmosp... more Spectroscopic measurements of Mira variable stars as a function of phase probe the stellar atmospheres and underlying pulsation mechanisms. For example, measuring variations in TiO, VO, and ZrO with phase can be used to help determine whether these molecular species are produced in an extended region above the layers where Balmer line emission occurs or below this shocked region. Using the same methods, the Balmer line increment, where the strongest Balmer line at phase zero is Hδ and not Hα, can be measured and explanations tested, along with another peculiarity, the absence of the Hɛ line in the spectra of Mira variables when the other Balmer lines are strong. We present new spectra covering the spectral range from 6200 to 9000 Å of 20 Mira variables. A relationship between variations in the Ca II IR triplet and Hα as a function of phase support the hypothesis that Hɛ's observational characteristics result from an interaction of Hɛ photons with the Ca II H line. New periods and epochs of variability are also presented for each star.
Astronomical Journal, 1990
This paper presents the results of spectral type and luminosity classification of reference stars... more This paper presents the results of spectral type and luminosity classification of reference stars in the Allegheny Observatory MAP parallax program, using broadband and intermediate-band photometry. In addition to the use of UBVRI and DDO photometric systems, the uvbyH-beta photometric system was included for classification of blue (B - V less than 0.6) reference stars. The stellar classifications made from the photometry are used to determine spectroscopic parallaxes. The spectroscopic parallaxes are used in turn to adjust the relative parallaxes measured with the MAP to absolute parallaxes. A new method for dereddening stars using more than one photometric system is presented. In the process of dereddening, visual extinctions, spectral types, and luminosity classes are determined, as well as a measure of the goodness of fit. The measure of goodness of fit quantifies confidence in the stellar classifications. It is found that the spectral types are reliable to within 2.5 spectral subclasses.
Astronomical Journal, 2002
We have used the COBE DIRBE database to derive near-and mid-infrared light curves for a well-defi... more We have used the COBE DIRBE database to derive near-and mid-infrared light curves for a well-defined sample of 38 infrared-bright Mira variable stars, and compared with optical data from the AAVSO. In general, the 3.5 µm and 4.9 µm DIRBE bandpasses provide the best S/N light curves, with S/N decreasing with wavelength at longer wavelengths. At 25 µm, good light curves are only available for ∼10% of our stars, and at wavelengths ≥ 60 µm, extracting high quality light curves is not possible. The amplitude of variability is typically less in the near-infrared than in the optical, and less in the mid-infrared than in the near-infrared, with decreasing amplitude with increasing wavelength. On average, there are 0.20 ± 0.01 magnitudes variation at 1.25 µm and 0.14 ± 0.01 magnitudes variation at 4.9 µm for each magnitude variation in V. The observed amplitudes are consistent with results of recent theoretical models of circumstellar dust shells around Mira variables. For a few stars in our sample, we find clear evidence of time lags between the optical and near-infrared maxima of phase ∼ 0.05 − 0.13, with no lags in the minima. For three stars, mid-infrared maximum appears to occur slightly before that in the near-infrared, but after optical maximum. We find three examples of secondary maxima in the rising portions of the DIRBE light curves, all of which have optical counterparts in the AAVSO data, supporting the hypothesis that they are due to shocks rather than newly-formed dust layers. We find no conclusive evidence for rapid (hours to days) variations in the infrared brightnesses of these stars.
Astronomical Journal, 1991
UBVRI, DDO, and uvby, H-beta photometry of astrometric reference stars is presented. Spectral typ... more UBVRI, DDO, and uvby, H-beta photometry of astrometric reference stars is presented. Spectral types and luminosity classifications made from the colors are used to determine their spectroscopic parallaxes. In this paper, colors for 309 stars in 25 regions are given, and classifications for 210 stars have been made. These stars form reference frames in the Allegheny Observatory Multichannel Astrometric Photometer astrometric program, and in the Praesepe cluster reduced by Russell (1976). It is found that the present photometric spectral types are reliable to within 2.5 spectral subclasses.
Astronomical Journal, 1991
UBVRI, DDO, and uvby, H-beta photometry of astrometric reference stars is presented. Spectral typ... more UBVRI, DDO, and uvby, H-beta photometry of astrometric reference stars is presented. Spectral types and luminosity classifications made from the colors are used to determine their spectroscopic parallaxes. In this paper, colors for 309 stars in 25 regions are given, and classifications for 210 stars have been made. These stars form reference frames in the Allegheny Observatory Multichannel Astrometric Photometer
Native American, Hispanic, African American, and other underrepresented high school students in r... more Native American, Hispanic, African American, and other underrepresented high school students in rural Western North Carolina have unprecedented opportunity as researchers in the Space Science Lab to conduct visible and radio observations of the Sun. The program involves 90 students over a three year period. The students conduct their own research and also interact with scientists around the world. The primary goal is to reach students who otherwise would not have this opportunity and motivate them to develop the critical thinking skills necessary for objective scientific inquiry. Students develop skills in electronics, computer sciences, astronomy, physics and earth sciences. Equally important is the hope that the students will become interested in pursuing careers in research or other science-related areas. The program objectives are aligned with the North Carolina Standard Course of Study for grades 9-12 in the areas of Earth/Environmental Science, Physical Science and Physics. The first group of 27 students spent a week in the Space Science Lab located on the campus of the Pisgah Astronomical Research Institute (PARI) during the Summer 2006. Students constructed their own JOVE radio telescopes that they took home to continue their observations. They share their results during four follow-up sessions throughout the school year. The students also have Internet access to radio telescopes and solar monitoring equipment at PARI. We expect their enthusiasm for science will increase by experiencing research investigations that are fun and relevant to their understanding of the world around them. We gratefully acknowledge support from the Burroughs Wellcome Fund Student Science Enrichment Program.
Pisgah Astronomical Research Institute (PARI) offers summer undergraduate research internships. P... more Pisgah Astronomical Research Institute (PARI) offers summer undergraduate research internships. PARI has received support for the internships from the NC Space Grant Consortium, NSF awards for public science education, private donations, private foundations, and through a collaboration with the Pisgah Astronomical Research and Education Center of the University of North Carolina - Asheville. The internship program began in 2001 with 4 students. This year 9 funded students participated in 2010. Mentors for the interns include PARI's Directors of Science, Education, and Information Technology and visiting faculty who are members of the PARI Research Affiliate Faculty program. Students work with mentors on radio and optical astronomy research, electrical engineering for robotic control of instruments, software development for instrument control and applets for citizen science projects, and science education by developing curricula and multimedia and teaching high school students in summer programs at PARI. At the end of the summer interns write a paper about their research which is published in the PARI Summer Student Proceedings. Several of the students have presented their results at AAS Meetings. We will present a summary of specific research conducted by the students with their mentors, the logistics for hosting the PARI undergraduate internship program, and plans for growth based on the impact of an NSF supported renovation to the Research Building on the PARI campus.
Astronomical Journal, 2000
Spectroscopic measurements of Mira variable stars as a function of phase probe the stellar atmosp... more Spectroscopic measurements of Mira variable stars as a function of phase probe the stellar atmospheres and underlying pulsation mechanisms. For example, measuring variations in TiO, VO, and ZrO with phase can be used to help determine whether these molecular species are produced in an extended region above the layers where Balmer line emission occurs or below this shocked region. Using the same methods, the Balmer line increment, where the strongest Balmer line at phase zero is Hd and not Ha, can be measured and explanations tested, along with another peculiarity, the absence of the Hv line in the spectra of Mira variables when the other Balmer lines are strong. We present new spectra covering the spectral range from 6200 to 9000 of 20 Mira variables. A relationship between variations in the Ca II A IR triplet and Ha as a function of phase support the hypothesis that HvÏs observational characteristics result from an interaction of Hv photons with the Ca II H line. New periods and epochs of variability are also presented for each star.
Astrophysical Journal, 1987
Astrophysical Journal, 1988
The Orion proplyds are of astrophysical interest because they offer a unique opportunity to study... more The Orion proplyds are of astrophysical interest because they offer a unique opportunity to study important aspects of protostellar and protoplanetary evolution. Proplyds offer the only opportunity known in which to study the effects of external ionization on this phase of young stellar object disk evolution in an external environment like that of the early Solar System. Most proplyds have central stars or starlike objects visible in HST WFPC V continuum or narrow-band filters. The physical properties of the central stars are of interest in fully understanding these systems. Some of the observable IR SED of the disk comes from reprocessed emission from the central star and thus depends on central star properties. Also, accretion rates and disk lifetimes are affected by the mass of the central star. We obtained one spectrum each of three central stars (218-354, 164-510, and 171-340) using the HST STIS instrument. With a spatial resolution of 0.05 arcsecond per pixel STIS easily resolved the central star in all three objects. The spatial resolution of STIS also permits a much more accurate subtraction of the bright nebular background than is possible with ground-based observations. Nebular contamination can be a significant source of error in performing spectral classification. We have completed our analysis and will report on the spectral types, masses, and luminosities for the three central stars.
The Michigan Objective Prism Blue Survey (e.g. Sowell et al 2007, AJ, 134, 1089) photographic pla... more The Michigan Objective Prism Blue Survey (e.g. Sowell et al 2007, AJ, 134, 1089) photographic plates located in the Astronomical Photographic Data Archive at the Pisgah Astronomical Research Institute hold hundreds of thousands of stellar spectra, many of which have not been classified before. The public is invited to participate in a distributed computing online environment to classify the stars on the objective prism plates. The online environment is called Stellar Classification Online - Public Exploration (SCOPE). Through a website, SCOPE participants are given a tutorial on stellar spectra and their classification, and given the chance to practice their skills at classification. After practice, participants register, login, and select stars for classification from scans of the objective prism plates. Their classifications are recorded in a database where the accumulation of classifications of the same star by many users will be statistically analyzed. The project includes stars with known spectral types to help test the reliability of classifications. The SCOPE webpage and the use of results will be described.
Astrophysical Journal, 1987
ABSTRACT Surface brightness maps at 12, 25, 60, and 100 microns were made of a 2.5 deg x 2.5 deg ... more ABSTRACT Surface brightness maps at 12, 25, 60, and 100 microns were made of a 2.5 deg x 2.5 deg area of the reflection nebulae in the Pleiades by coadding IRAS scans of this region. Emission is seen surrounding 17 Tau, 20 Tau, 23 Tau, and 25 Tau in all four bands, coextensive with the visible reflection nebulosity, and extending as far as 30 arcminutes from the illuminating stars. The infrared energy distributions of the nebulae peak in the 100 micron band, but up to 40 percent of the total infrared power lies in the 12 and 25 micron bands. The brightness of the 12 and 25 micron emission and the absence of temperature gradients at these wavelengths are inconsistent with the predictions of equilibrium thermal emission models. The emission at these wavelengths appears to be the result of micron nonequilibrium emission from very small grains, or from molecules consisting of 10-100 carbon atoms, which have been excited by ultraviolet radiation from the illuminating stars.
We have used the COBE DIRBE database to derive near- and mid-infrared light curves for a well-def... more We have used the COBE DIRBE database to derive near- and mid-infrared light curves for a well-defined sample of 38 infrared-bright Mira variable stars, and compared with optical data from the AAVSO. In general, the 3.5 micron and 4.9 micron DIRBE bandpasses provide the best S/N light curves, with S/N decreasing with wavelength at longer wavelengths. At 25 microns, good light curves are only available for ~10 percent of our stars, and at wavelengths >= 60 microns, extracting high quality light curves is not possible. The amplitude of variability is typically less in the near-infrared than in the optical, and less in the mid-infrared than in the near-infrared, with decreasing amplitude with increasing wavelength. On average, there are 0.20 +/- 0.01 magnitudes variation at 1.25 microns and 0.14 +/- 0.01 magnitudes variation at 4.9 micron for each magnitude variation in V. The observed amplitudes are consistent with results of recent theoretical models of circumstellar dust shells around Mira variables. For a few stars in our sample, we find clear evidence of time lags between the optical and maxima of phase ~ 0.05 - 0.13, with no lags in the minima. For three stars, mid-infrared maximum appears to occur slightly before that in the near-infrared,but after optical maximum. We find three examples of secondary maxima in the rising portions of the DIRBE light curves, all of which have optical counterparts in the AAVSO data, supporting the hypothesis that they are due to shocks rather than newly-formed dust layers. We find no conclusive evidence for rapid (hours to days) variations in the infrared brightnesses of these stars.
Astrophysical Journal, 1986
Astrophysical Journal, 2000
As a preliminary step in deducing and log (g) of Mira variables as a function of phase, a compari... more As a preliminary step in deducing and log (g) of Mira variables as a function of phase, a compari-T eff son is made between spectra synthesized from LTE stellar atmosphere models and observed spectra. The observed spectra show obvious vanadium oxide (VO) absorption bands. However, the molecular line list used to produce the synthetic spectra does not include the bound-bound VO opacities. The wavenumbers, line oscillator strengths, and lowest energy levels are needed to calculate these opacities. The equations, constants, and experimentally determined factors required to calculate the line oscillator strengths and lowest energy levels from experimentally determined wavenumbers are presented. The e †ect of including the wavenumbers, line oscillator strengths, and lowest energy levels of the VO BÈX (0, 0) band are calculated and show the expected absorption features observed in the spectra of Mira variables. In the VO BÈX (0, 0) band the line oscillator strengths range from about 0.05 to 3.
Astronomy & Astrophysics Supplement Series, 1996
Native American, Hispanic, African American, and other underrepresented high school students in r... more Native American, Hispanic, African American, and other underrepresented high school students in rural Western North Carolina have the unprecedented opportunity as researchers in the Space Science Lab to conduct visible and radio observations of the Sun. The program involves 90 students over a three year period. The primary goal is to reach students who otherwise would not have this opportunity, and motivate them to develop the critical thinking skills necessary for objective scientific inquiry. Students develop skills in electronics, computer sciences, astronomy, physics and earth sciences. Equally important is the hope that the students will become interested in pursuing careers in research or other science-related areas. We expect their enthusiasm for science will increase by experiencing research investigations that are fun and relevant to their understanding of the world around them. The students conduct their own research, and also interact with scientists around the world. A total of 54 students have spent a week at the Space Science Lab located on the campus of the Pisgah Astronomical Research Institute (PARI) during the Summers of 2006 and 2007. Students construct their own JOVE radio telescopes that they bring home to continue their observations during the academic year. They share their results during four follow-up sessions throughout the school year. The students also have Internet access to radio telescopes and solar monitoring equipment at PARI. We report on results from student evaluations from the first year in 2006 and current session student experiences. We gratefully acknowledge support from the Burroughs Wellcome Fund - Student Science Enrichment Program