We present IRAC (3.6, 4.5, 5.8, and 8.0 micron) observations of the Chamaeleon II molecular cloud... more We present IRAC (3.6, 4.5, 5.8, and 8.0 micron) observations of the Chamaeleon II molecular cloud. The observed area covers about 1 square degree defined by A_V >2. Analysis of the data in the 2005 c2d catalogs reveals a small number of sources (40) with properties similar to those of young stellaror substellar objects (YSOs). The surface density of these YSO candidates is low, and contamination by background galaxies appears to be substantial, especially for sources classified as Class I or flat SED. We discuss this problem in some detail and conclude that very few of the candidate YSOs in early evolutionary stages are actually in the Cha II cloud. Using a refined set of criteria, we define a smaller, but more reliable, set of 24 YSO candidates.
Using the Spitzer Space Telescope, we have observed 90 weak-line and classical T Tauri stars in t... more Using the Spitzer Space Telescope, we have observed 90 weak-line and classical T Tauri stars in the vicinity of the Ophiuchus, Lupus, Chamaeleon, and Taurus star-forming regions as part of the Cores to Disks (c2d) Spitzer Legacy project. In addition to the Spitzer data, we have obtained contemporaneous optical photometry to assist in constructing spectral energy distributions. These objects were specifically chosen as solar-type young stars with low levels of Hα emission, strong X-ray emission, and lithium absorption i.e. weak-line T Tauri stars, most of which were undetected in the mid-to-far IR by the IRAS survey. Weak-line T Tauri stars are potentially extremely important objects in determining the timescale over which disk evolution may take place. Our objective is to determine whether these young stars are diskless or have remnant disks which are below the detection threshold of previous infrared missions. We find that only 5/83 weak-line T Tauri stars have detectable excess em...
While the baseline for the Next Generation Space Telescope (NGST) is the 1 to 5 um wavelenght int... more While the baseline for the Next Generation Space Telescope (NGST) is the 1 to 5 um wavelenght interval, compelling astronomical observations become possible at longer wavelenghts.
Using the Spitzer Space Telescope, we have observed 90 weak-line and classical T Tauri stars in t... more Using the Spitzer Space Telescope, we have observed 90 weak-line and classical T Tauri stars in the vicinity of the Ophiuchus, Lupus, Chamaeleon, and Taurus star-forming regions as part of the Cores to Disks (c2d) Spitzer Legacy project. In addition to the Spitzer data, we have obtained contemporaneous optical photometry to assist in constructing spectral energy distributions. These objects were specifically chosen as solar-type young stars with low levels of H alpha emission, strong X-ray emission, and lithium absorption i.e. weak-line T Tauri stars, most of which were undetected in the mid-to-far IR by the IRAS survey. Weak-line T Tauri stars are potentially extremely important objects in determining the timescale over which disk evolution may take place. Our objective is to determine whether these young stars are diskless or have remnant disks which are below the detection threshold of previous infrared missions. We find that only 5/83 weak-line T Tauri stars have detectable exce...
We present models for the GM Auriga circumstellar disk based upon its spectral energy distributio... more We present models for the GM Auriga circumstellar disk based upon its spectral energy distribution and high-resolution HST imaging obtained with WFPC-2 (F555W) and NICMOS at 1.1 and 1.6 microns in its coronagraphic imaging mode. Our circumstellar geometry comprises a passively heated flared disk of mass Md=0.06M_sun, radius Rd=300AU, viewed at inclination i=45o. Fitting the SED in the range 1 to 12 microns constrains the inner disk truncation radius to be Rin ~ 4AU. Modeling additional SIRTF data in this regime will provide tighter constraints on the disk truncation radius. Our Monte Carlo radiative equilibrium code calculates accurate disk temperature structures and SEDs in only a few minutes on current Linux boxes. We will show model SEDs and disk temperature distributions for a range of different disk structures and inner disk truncation radii. We acknowledge support from a UK/PPARC Advanced Fellowship, NASA's LTSA program, NSF Stellar Astronomy, and the Hubble Fellowship program. This work is based, in part, on observations with the NASA/ESA Hubble Space Telescope, obtained at the STScI, which is operated by the AURA, Inc. under NASA contract NAS5-26555 and supported by NASA grant NAG5-3042 to the NICMOS IDT.
We present Keck mid-infrared observations of the disk around beta Pictoris. Extended emission is ... more We present Keck mid-infrared observations of the disk around beta Pictoris. Extended emission is evident in images obtained with the MIRLIN camera at 12.5 and 17.9 mu m. Emission is unresolved at 8.8 mu m. At 17.9 mu m, the disk is detected out to a distance of 5'' (100 AU) from the star. Interior to this, the SW lobe
American Astronomical Society Meeting Abstracts 221, 2013
ABSTRACT Since 1994, RECONS (www.recons.org, REsearch Consortium On Nearby Stars) has been discov... more ABSTRACT Since 1994, RECONS (www.recons.org, REsearch Consortium On Nearby Stars) has been discovering and characterizing the Sun's neighbors. Nearby stars provide increased fluxes, larger astrometric perturbations, and higher probabilities for eventual resolution and detailed study of planets than similar stars at larger distances. Examination of the nearby stellar sample will reveal the prevalence and structure of solar systems, as well as the balance of Jovian and terrestrial worlds. These are the stars and planets that will ultimately be key in our search for life elsewhere. Here we outline what we know ... and what we don't know ... about the population of the nearest stars. We have expanded the original RECONS 10 pc horizon to 25 pc and are constructing a database that currently includes 2124 systems. By using the CTIO 0.9m telescope --- now operated by RECONS as part of the SMARTS Consortium --- we have published the first accurate parallaxes for 149 systems within 25 pc and currently have an additional 213 unpublished systems to add. Still, we predict that roughly two-thirds of the systems within 25 pc do not yet have accurate distance measurements. In addition to revealing the Sun's stellar neighbors, we have been using astrometric techniques to search for massive planets orbiting roughly 200 of the nearest red dwarfs. Unlike radial velocity searches, our astrometric effort is most sensitive to Jovian planets in Jovian orbits, i.e. those that span decades. We have now been monitoring stars for up to 13 years with positional accuracies of a few milliarcseconds per night. We have detected stellar and brown dwarf companions, as well as enigmatic, unseen secondaries, but have yet to reveal a single super-Jupiter ... a somewhat surprising result. In total, only 3% of stars within 25 pc are known to possess planets. It seems clear that we have a great deal of work to do to map out the stars, planets, and perhaps life in the solar neighborhood. This effort is supported by the NSF through grant AST-0908402 and via observations made possible by the SMARTS Consortium.
Bulletin of the American Astronomical Society, May 1, 1998
Title: A Circumstellar Disk around HR 4796. Authors: Koerner, David W.; Backman, Dana; Ressler, M... more Title: A Circumstellar Disk around HR 4796. Authors: Koerner, David W.; Backman, Dana; Ressler, Michael; Werner, Michael. ... Abstract. We report the discovery of a circumstellar disk around the young A0 star, HR 4796, in thermal infrared images obtained at the Keck telescope. ...
We propose to complete a medium-scale MIPS 24 and 70 micron census of Sun-like stars in order to ... more We propose to complete a medium-scale MIPS 24 and 70 micron census of Sun-like stars in order to identify additional dust systems for detailed follow-up within the Spitzer mission lifetime. Our sample builds upon results from disparate GTO and GO programs to establish a truly volume-limited survey of K,G, and F dwarfs (0.7 msun < M* < 1.7 msun) within
We present IRAC (3.6, 4.5, 5.8, and 8.0 micron) observations of the Chamaeleon II molecular cloud... more We present IRAC (3.6, 4.5, 5.8, and 8.0 micron) observations of the Chamaeleon II molecular cloud. The observed area covers about 1 square degree defined by A_V >2. Analysis of the data in the 2005 c2d catalogs reveals a small number of sources (40) with properties similar to those of young stellaror substellar objects (YSOs). The surface density of these YSO candidates is low, and contamination by background galaxies appears to be substantial, especially for sources classified as Class I or flat SED. We discuss this problem in some detail and conclude that very few of the candidate YSOs in early evolutionary stages are actually in the Cha II cloud. Using a refined set of criteria, we define a smaller, but more reliable, set of 24 YSO candidates.
Using the Spitzer Space Telescope, we have observed 90 weak-line and classical T Tauri stars in t... more Using the Spitzer Space Telescope, we have observed 90 weak-line and classical T Tauri stars in the vicinity of the Ophiuchus, Lupus, Chamaeleon, and Taurus star-forming regions as part of the Cores to Disks (c2d) Spitzer Legacy project. In addition to the Spitzer data, we have obtained contemporaneous optical photometry to assist in constructing spectral energy distributions. These objects were specifically chosen as solar-type young stars with low levels of Hα emission, strong X-ray emission, and lithium absorption i.e. weak-line T Tauri stars, most of which were undetected in the mid-to-far IR by the IRAS survey. Weak-line T Tauri stars are potentially extremely important objects in determining the timescale over which disk evolution may take place. Our objective is to determine whether these young stars are diskless or have remnant disks which are below the detection threshold of previous infrared missions. We find that only 5/83 weak-line T Tauri stars have detectable excess em...
While the baseline for the Next Generation Space Telescope (NGST) is the 1 to 5 um wavelenght int... more While the baseline for the Next Generation Space Telescope (NGST) is the 1 to 5 um wavelenght interval, compelling astronomical observations become possible at longer wavelenghts.
Using the Spitzer Space Telescope, we have observed 90 weak-line and classical T Tauri stars in t... more Using the Spitzer Space Telescope, we have observed 90 weak-line and classical T Tauri stars in the vicinity of the Ophiuchus, Lupus, Chamaeleon, and Taurus star-forming regions as part of the Cores to Disks (c2d) Spitzer Legacy project. In addition to the Spitzer data, we have obtained contemporaneous optical photometry to assist in constructing spectral energy distributions. These objects were specifically chosen as solar-type young stars with low levels of H alpha emission, strong X-ray emission, and lithium absorption i.e. weak-line T Tauri stars, most of which were undetected in the mid-to-far IR by the IRAS survey. Weak-line T Tauri stars are potentially extremely important objects in determining the timescale over which disk evolution may take place. Our objective is to determine whether these young stars are diskless or have remnant disks which are below the detection threshold of previous infrared missions. We find that only 5/83 weak-line T Tauri stars have detectable exce...
We present models for the GM Auriga circumstellar disk based upon its spectral energy distributio... more We present models for the GM Auriga circumstellar disk based upon its spectral energy distribution and high-resolution HST imaging obtained with WFPC-2 (F555W) and NICMOS at 1.1 and 1.6 microns in its coronagraphic imaging mode. Our circumstellar geometry comprises a passively heated flared disk of mass Md=0.06M_sun, radius Rd=300AU, viewed at inclination i=45o. Fitting the SED in the range 1 to 12 microns constrains the inner disk truncation radius to be Rin ~ 4AU. Modeling additional SIRTF data in this regime will provide tighter constraints on the disk truncation radius. Our Monte Carlo radiative equilibrium code calculates accurate disk temperature structures and SEDs in only a few minutes on current Linux boxes. We will show model SEDs and disk temperature distributions for a range of different disk structures and inner disk truncation radii. We acknowledge support from a UK/PPARC Advanced Fellowship, NASA's LTSA program, NSF Stellar Astronomy, and the Hubble Fellowship program. This work is based, in part, on observations with the NASA/ESA Hubble Space Telescope, obtained at the STScI, which is operated by the AURA, Inc. under NASA contract NAS5-26555 and supported by NASA grant NAG5-3042 to the NICMOS IDT.
We present Keck mid-infrared observations of the disk around beta Pictoris. Extended emission is ... more We present Keck mid-infrared observations of the disk around beta Pictoris. Extended emission is evident in images obtained with the MIRLIN camera at 12.5 and 17.9 mu m. Emission is unresolved at 8.8 mu m. At 17.9 mu m, the disk is detected out to a distance of 5'' (100 AU) from the star. Interior to this, the SW lobe
American Astronomical Society Meeting Abstracts 221, 2013
ABSTRACT Since 1994, RECONS (www.recons.org, REsearch Consortium On Nearby Stars) has been discov... more ABSTRACT Since 1994, RECONS (www.recons.org, REsearch Consortium On Nearby Stars) has been discovering and characterizing the Sun's neighbors. Nearby stars provide increased fluxes, larger astrometric perturbations, and higher probabilities for eventual resolution and detailed study of planets than similar stars at larger distances. Examination of the nearby stellar sample will reveal the prevalence and structure of solar systems, as well as the balance of Jovian and terrestrial worlds. These are the stars and planets that will ultimately be key in our search for life elsewhere. Here we outline what we know ... and what we don't know ... about the population of the nearest stars. We have expanded the original RECONS 10 pc horizon to 25 pc and are constructing a database that currently includes 2124 systems. By using the CTIO 0.9m telescope --- now operated by RECONS as part of the SMARTS Consortium --- we have published the first accurate parallaxes for 149 systems within 25 pc and currently have an additional 213 unpublished systems to add. Still, we predict that roughly two-thirds of the systems within 25 pc do not yet have accurate distance measurements. In addition to revealing the Sun's stellar neighbors, we have been using astrometric techniques to search for massive planets orbiting roughly 200 of the nearest red dwarfs. Unlike radial velocity searches, our astrometric effort is most sensitive to Jovian planets in Jovian orbits, i.e. those that span decades. We have now been monitoring stars for up to 13 years with positional accuracies of a few milliarcseconds per night. We have detected stellar and brown dwarf companions, as well as enigmatic, unseen secondaries, but have yet to reveal a single super-Jupiter ... a somewhat surprising result. In total, only 3% of stars within 25 pc are known to possess planets. It seems clear that we have a great deal of work to do to map out the stars, planets, and perhaps life in the solar neighborhood. This effort is supported by the NSF through grant AST-0908402 and via observations made possible by the SMARTS Consortium.
Bulletin of the American Astronomical Society, May 1, 1998
Title: A Circumstellar Disk around HR 4796. Authors: Koerner, David W.; Backman, Dana; Ressler, M... more Title: A Circumstellar Disk around HR 4796. Authors: Koerner, David W.; Backman, Dana; Ressler, Michael; Werner, Michael. ... Abstract. We report the discovery of a circumstellar disk around the young A0 star, HR 4796, in thermal infrared images obtained at the Keck telescope. ...
We propose to complete a medium-scale MIPS 24 and 70 micron census of Sun-like stars in order to ... more We propose to complete a medium-scale MIPS 24 and 70 micron census of Sun-like stars in order to identify additional dust systems for detailed follow-up within the Spitzer mission lifetime. Our sample builds upon results from disparate GTO and GO programs to establish a truly volume-limited survey of K,G, and F dwarfs (0.7 msun < M* < 1.7 msun) within
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