Stanimir Metchev | University of Western Ontario (original) (raw)
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Papers by Stanimir Metchev
The Astrophysical Journal, 2015
ABSTRACT
The Astronomical Journal, 2015
ABSTRACT We describe digital tracking, a method for asteroid searches that greatly increases the ... more ABSTRACT We describe digital tracking, a method for asteroid searches that greatly increases the sensitivity of a telescope to faint unknown asteroids. It has been previously used to detect faint Kuiper Belt objects using the Hubble Space Telescope and large ground-based instruments, and to find a small, fast-moving asteroid during a close approach to Earth. We complement this earlier work by developing digital tracking methodology for detecting asteroids using large-format CCD imagers. We demonstrate that the technique enables the ground-based detection of large numbers of new faint asteroids. Our methodology resolves or circumvents all major obstacles to the large-scale application of digital tracking for finding main belt and near-Earth asteroids. We find that for both asteroid populations, digital tracking can deliver a factor of ten improvement over conventional searches. Digital tracking has long been standard practice for deep Kuiper Belt surveys, but even there our methodology enables deeper integrations than have yet been attempted. Our search for main belt asteroids using a one-degree imager on the 0.9m WIYN telescope on Kitt Peak validates our methodology, delivers sensitivity to asteroids in a regime previously probed only with 4-meter and larger instruments, and leads to the detection of 156 previously unknown asteroids and 59 known objects in a single field. Digital tracking has the potential to revolutionize searches for faint moving objects ranging from the Kuiper Belt through main belt and near-Earth asteroids, and perhaps even anthropogenic space debris in low Earth orbit.
The Astronomical Journal, 2015
We unveil an on-line database, www.bdcompanions.org, that lists the properties of all published b... more We unveil an on-line database, www.bdcompanions.org, that lists the properties of all published brown dwarf and massive planetary companions to >0.075 solar-mass stars. The database includes substellar secondaries discovered through the radial velocity, direct imaging, astrometry, transit photometry, infrared excess, compound spectroscopy, and eclipse-timing methods. The lower mass limit for the inclusion of a substellar companion in the database is 10 Jupiter masses for most techniques. Companions discovered through direct imaging have been included regardless of their estimated mass. Companions that have been shown to have stellar masses after their discovery, or whose existence is debated or disproven, are noted separately. The database lists the principal properties of each host star (spectral type, measured or estimated parallax, mass, age, etc) and companion (spectral type, mass, semi-major axis, projected orbital separation, etc) where available, and includes the appropriate references. The database is sortable on each of the parameters. Altogether, 125 companions are listed, including 95 with masses between 0.013 and 0.075 times solar. We expect the database to have broad relevance to studies of brown dwarfs, extrasolar planets, and stellar multiplicity.
ABSTRACT We present results from a pilot study to test the viability of precision mid-infrared di... more ABSTRACT We present results from a pilot study to test the viability of precision mid-infrared differential photometry from the ground. We obtained mid-infrared photometry of exozodi candidates in alternating narrow-band filters across the ten-micron silicate feature with T-ReCS on Gemini South. While we did not confirm any of the candidate exozodi, our results demonstrate that we can achieve low photometric uncertainties for faint objects even under sub-median atmospheric conditions. Our analysis shows that we are limited not by the thermal background emission but by the detector readout noise. We are able to push photometric limits and maintain readout-noise dominated uncertainties for faint objects down to magnitudes of 6 mag (0.1 Jy) at 10 micron. As our uncertainties have not yet reached the thermal background-limited regime, there is room for improvement in future mid-infrared instruments, and a potential to observe even fainter objects from the ground with similar or better precision.
The Astrophysical Journal, 2015
ABSTRACT Many brown dwarfs exhibit low-amplitude rotationally modulated variability due to photos... more ABSTRACT Many brown dwarfs exhibit low-amplitude rotationally modulated variability due to photospheric inhomogeneities caused by condensate clouds in their atmospheres. The Spitzer Space Telescope 'Weather on Other Worlds' (WoW) project has monitored 44 brown dwarfs at unprecedented photometric precision from space. We present one of several important new results from WoW: the discovery of brown dwarfs with unexpectedly slow rotation periods. While most brown dwarfs have periods of 2-12 hours, we have identified two with well-constrained periods of 13±1 and >20 hours, respectively, and 2 others that show more tentative evidence of longer than 20-hour periods. By serving as almost non-rotating standards, these objects will allow more accurate calibration of spectroscopic measurements of brown dwarfs' projected rotational velocities. The existence of such slowly-rotating objects also constrains models of brown dwarf formation and angular momentum evolution.
ABSTRACT We unveil an on-line database, www.bdcompanions.org, that lists the properties of all pu... more ABSTRACT We unveil an on-line database, www.bdcompanions.org, that lists the properties of all published brown dwarf and massive planetary companions to >0.075 solar-mass stars. The database includes substellar secondaries discovered through the radial velocity, direct imaging, astrometry, transit photometry, infrared excess, compound spectroscopy, and eclipse-timing methods. The lower mass limit for the inclusion of a substellar companion in the database is 10 Jupiter masses for most techniques. Companions discovered through direct imaging have been included regardless of their estimated mass. Companions that have been shown to have stellar masses after their discovery, or whose existence is debated or disproven, are noted separately. The database lists the principal properties of each host star (spectral type, measured or estimated parallax, mass, age, etc) and companion (spectral type, mass, semi-major axis, projected orbital separation, etc) where available, and includes the appropriate references. The database is sortable on each of the parameters. Altogether, 125 companions are listed, including 95 with masses between 0.013 and 0.075 times solar. We expect the database to have broad relevance to studies of brown dwarfs, extrasolar planets, and stellar multiplicity.
The Astrophysical Journal, 2015
ABSTRACT
The Astronomical Journal, 2015
ABSTRACT We describe digital tracking, a method for asteroid searches that greatly increases the ... more ABSTRACT We describe digital tracking, a method for asteroid searches that greatly increases the sensitivity of a telescope to faint unknown asteroids. It has been previously used to detect faint Kuiper Belt objects using the Hubble Space Telescope and large ground-based instruments, and to find a small, fast-moving asteroid during a close approach to Earth. We complement this earlier work by developing digital tracking methodology for detecting asteroids using large-format CCD imagers. We demonstrate that the technique enables the ground-based detection of large numbers of new faint asteroids. Our methodology resolves or circumvents all major obstacles to the large-scale application of digital tracking for finding main belt and near-Earth asteroids. We find that for both asteroid populations, digital tracking can deliver a factor of ten improvement over conventional searches. Digital tracking has long been standard practice for deep Kuiper Belt surveys, but even there our methodology enables deeper integrations than have yet been attempted. Our search for main belt asteroids using a one-degree imager on the 0.9m WIYN telescope on Kitt Peak validates our methodology, delivers sensitivity to asteroids in a regime previously probed only with 4-meter and larger instruments, and leads to the detection of 156 previously unknown asteroids and 59 known objects in a single field. Digital tracking has the potential to revolutionize searches for faint moving objects ranging from the Kuiper Belt through main belt and near-Earth asteroids, and perhaps even anthropogenic space debris in low Earth orbit.
The Astronomical Journal, 2015
We unveil an on-line database, www.bdcompanions.org, that lists the properties of all published b... more We unveil an on-line database, www.bdcompanions.org, that lists the properties of all published brown dwarf and massive planetary companions to >0.075 solar-mass stars. The database includes substellar secondaries discovered through the radial velocity, direct imaging, astrometry, transit photometry, infrared excess, compound spectroscopy, and eclipse-timing methods. The lower mass limit for the inclusion of a substellar companion in the database is 10 Jupiter masses for most techniques. Companions discovered through direct imaging have been included regardless of their estimated mass. Companions that have been shown to have stellar masses after their discovery, or whose existence is debated or disproven, are noted separately. The database lists the principal properties of each host star (spectral type, measured or estimated parallax, mass, age, etc) and companion (spectral type, mass, semi-major axis, projected orbital separation, etc) where available, and includes the appropriate references. The database is sortable on each of the parameters. Altogether, 125 companions are listed, including 95 with masses between 0.013 and 0.075 times solar. We expect the database to have broad relevance to studies of brown dwarfs, extrasolar planets, and stellar multiplicity.
ABSTRACT We present results from a pilot study to test the viability of precision mid-infrared di... more ABSTRACT We present results from a pilot study to test the viability of precision mid-infrared differential photometry from the ground. We obtained mid-infrared photometry of exozodi candidates in alternating narrow-band filters across the ten-micron silicate feature with T-ReCS on Gemini South. While we did not confirm any of the candidate exozodi, our results demonstrate that we can achieve low photometric uncertainties for faint objects even under sub-median atmospheric conditions. Our analysis shows that we are limited not by the thermal background emission but by the detector readout noise. We are able to push photometric limits and maintain readout-noise dominated uncertainties for faint objects down to magnitudes of 6 mag (0.1 Jy) at 10 micron. As our uncertainties have not yet reached the thermal background-limited regime, there is room for improvement in future mid-infrared instruments, and a potential to observe even fainter objects from the ground with similar or better precision.
The Astrophysical Journal, 2015
ABSTRACT Many brown dwarfs exhibit low-amplitude rotationally modulated variability due to photos... more ABSTRACT Many brown dwarfs exhibit low-amplitude rotationally modulated variability due to photospheric inhomogeneities caused by condensate clouds in their atmospheres. The Spitzer Space Telescope 'Weather on Other Worlds' (WoW) project has monitored 44 brown dwarfs at unprecedented photometric precision from space. We present one of several important new results from WoW: the discovery of brown dwarfs with unexpectedly slow rotation periods. While most brown dwarfs have periods of 2-12 hours, we have identified two with well-constrained periods of 13±1 and >20 hours, respectively, and 2 others that show more tentative evidence of longer than 20-hour periods. By serving as almost non-rotating standards, these objects will allow more accurate calibration of spectroscopic measurements of brown dwarfs' projected rotational velocities. The existence of such slowly-rotating objects also constrains models of brown dwarf formation and angular momentum evolution.
ABSTRACT We unveil an on-line database, www.bdcompanions.org, that lists the properties of all pu... more ABSTRACT We unveil an on-line database, www.bdcompanions.org, that lists the properties of all published brown dwarf and massive planetary companions to >0.075 solar-mass stars. The database includes substellar secondaries discovered through the radial velocity, direct imaging, astrometry, transit photometry, infrared excess, compound spectroscopy, and eclipse-timing methods. The lower mass limit for the inclusion of a substellar companion in the database is 10 Jupiter masses for most techniques. Companions discovered through direct imaging have been included regardless of their estimated mass. Companions that have been shown to have stellar masses after their discovery, or whose existence is debated or disproven, are noted separately. The database lists the principal properties of each host star (spectral type, measured or estimated parallax, mass, age, etc) and companion (spectral type, mass, semi-major axis, projected orbital separation, etc) where available, and includes the appropriate references. The database is sortable on each of the parameters. Altogether, 125 companions are listed, including 95 with masses between 0.013 and 0.075 times solar. We expect the database to have broad relevance to studies of brown dwarfs, extrasolar planets, and stellar multiplicity.