18 results on '"Karl Stapelfeldt"'
Search Results
2. Observations of edge-on protoplanetary disks with ALMA. I. Results from continuum data
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H. Williams, G. van der Plas, Yann Boehler, Geoffroy Lesur, M. Villenave, Schuyler Wolff, François Ménard, F. Louvet, Christophe Pinte, Karl Stapelfeldt, Z. Telkamp, Myriam Benisty, C. Flores, William R. F. Dent, Catherine Dougados, D. Padgett, Gaspard Duchêne, A. Riols, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), NASA Goddard Space Flight Center (GSFC), Monash University [Clayton], Departamento de Astronomia (DAS), Spitzer Science Center, and California Institute of Technology (CALTECH)
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Brightness ,Continuum (design consultancy) ,FOS: Physical sciences ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,circumstellar matter ,01 natural sciences ,0103 physical sciences ,Radiative transfer ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,stars: variables: T Tauri ,Physics ,Earth and Planetary Astrophysics (astro-ph.EP) ,Spectral index ,stars: formation ,010308 nuclear & particles physics ,protoplanetary disks ,Herbig Ae/Be ,Astronomy and Astrophysics ,Scale height ,Astrophysics - Astrophysics of Galaxies ,Wavelength ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Brightness temperature ,Astrophysics of Galaxies (astro-ph.GA) ,Millimeter ,Astrophysics::Earth and Planetary Astrophysics ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,Astrophysics - Earth and Planetary Astrophysics - Abstract
We analyze a sample of 12 HST-selected edge-on protoplanetary disks for which the vertical extent of the emission layers can be constrained directly. We present ALMA high angular resolution continuum images (0.1arcsec) of these disks at two wavelengths, 0.89mm and 2.06mm (respectively ALMA bands 7 and 4), supplemented with archival band 6 data (1.33mm) where available. For most sources, the millimeter continuum emission is more compact than the scattered light, both in the vertical and radial directions. Six sources are resolved along their minor axis in at least one millimeter band, providing direct information on the vertical distribution of the millimeter grains. For the second largest disk of the sample, the significant difference in vertical extent between band 7 and band 4 suggests efficient size-selective vertical settling of large grains. Furthermore, the only Class I object in our sample shows evidence of flaring in the millimeter. Along the major axis, all disks are well resolved. Four of them are larger in band 7 than in band 4 in the radial direction, and three have a similar radial extent in all bands. For all disks, we also derive the millimeter brightness temperature and spectral index maps. We find that the disks are likely optically thick and that the dust emission reveals low brightness temperatures in most cases (, Accepted for publication in Astronomy and Astrophysics Updates: Few typos in the text + Table A.1
- Published
- 2020
3. Investigating the presence of two belts in the HD 15115 system
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Pierre Baudoz, H. M. Schmid, D. Mawet, Th. Henning, Anne-Lise Maire, Jean-Charles Augereau, Markus Feldt, Anne-Marie Lagrange, Henning Avenhaus, Karl Stapelfeldt, Julien Milli, N. Engler, Johan Olofsson, Anthony Boccaletti, C. Perrot, R. Galicher, Johan Mazoyer, Sasha Hinkley, Eric Pantin, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
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Physics ,Earth and Planetary Astrophysics (astro-ph.EP) ,Planetesimal ,Brightness ,010308 nuclear & particles physics ,debris disc ,stars: individual object: HIP 11360, HD 15115 ,Techniques: high angular resolution, polarimetric [planetary systems] ,FOS: Physical sciences ,Astronomy and Astrophysics ,Context (language use) ,Astrophysics ,Radius ,Planetary system ,Position angle ,01 natural sciences ,Exoplanet ,Space and Planetary Science ,Planet ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,010303 astronomy & astrophysics ,ComputingMilieux_MISCELLANEOUS ,Astrophysics::Galaxy Astrophysics ,Astrophysics - Earth and Planetary Astrophysics - Abstract
We present new observations of the edge-on debris disk around HD 15115 (F star at 48.2 pc) obtained in the near-IR. We search for observational evidence for a second inner planetesimal ring in the system. We obtained total intensity and polarimetric data in the broad bands J and H and processed the data with differential imaging techniques achieving an angular resolution of about 40 mas. We observe an axisymmetric planetesimal belt with a radius of $\sim$2$''$, an inclination of $85.8^{\circ} \pm 0.7^{\circ}$ and position angle of 278.9$^{\circ} \pm 0.1^{\circ}$. A grid of models describing the spatial distribution of the grains in the disk is generated to constrain the geometric parameters of the disk and to explore the presence of a second belt. We perform a photometric analysis of the data and compare disk brightness in two bands in scattered and in polarized light. The analysis shows that the west side is $\sim$2.5 times brighter in total intensity than the east side in both bands, while for polarized light in the J band this ratio is only 1.25. The maximum polarization fraction is 15--20% at $r\sim$2.5$''$. We also find that the J - H color of the disk appears to be red for the radial separations $r\lesssim2''$ and is getting bluer for the larger separations. This apparent change of disk color from red to blue with an increasing radial separation could be explained by the decreasing average grain size with distance. The presence of an additional inner belt slightly inclined with respect to the main planetesimal belt is suspected from the polarized intensity image but the analysis and modeling presented here cannot establish a firm conclusion due to the faintness of the disk and its high inclination., 23 pages, 21 figures typos corrected
- Published
- 2019
4. PANCHROMATIC OBSERVATIONS AND MODELING OF THE HV TAU C EDGE-ON DISK
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Gaspard Duchêne, Maria Morales-Calderon, Timothy Y. Brooke, Christophe Pinte, Andrea M. Ghez, H. Maness, Hervé Bouy, D. Padgett, Alberto Noriega-Crespo, C. McCabe, Karl Stapelfeldt, François Ménard, Gilles Duvert, D. Barrado y Navascués, and Sebastian Wolf
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Physics ,010504 meteorology & atmospheric sciences ,Opacity ,FOS: Physical sciences ,Astronomy and Astrophysics ,Orbital eccentricity ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Protoplanetary disk ,Position angle ,01 natural sciences ,Radial velocity ,Wavelength ,Atmospheric radiative transfer codes ,Astrophysics - Solar and Stellar Astrophysics ,13. Climate action ,Space and Planetary Science ,0103 physical sciences ,Spectral energy distribution ,Astrophysics::Earth and Planetary Astrophysics ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,0105 earth and related environmental sciences - Abstract
We present new high spatial resolution (, Comment: 26 pages, 11 figures, editorially accepted for publication in ApJ
- Published
- 2010
5. Probing dust grain evolution in IM Lupi's circumstellar disc
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Geoffrey A. Blake, Glenn Schneider, Carol A. Grady, Sebastian Wolf, E. F. van Dishoeck, Thomas Henning, John Krist, Christophe Pinte, Jacqueline E. Kessler-Silacci, O. Panić, Deborah Padgett, Gaspard Duchêne, Klaus M. Pontoppidan, Murray D. Silverstone, Marshall D. Perrin, Bringfried Stecklum, Dean C. Hines, Karl Stapelfeldt, Jean-Charles Augereau, Dave Lommen, Johan Olofsson, François Ménard, Laboratoire d'Astrophysique de Grenoble (LAOG), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
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Physics ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,01 natural sciences ,Photometry (optics) ,T Tauri star ,Wavelength ,Interferometry ,13. Climate action ,Space and Planetary Science ,0103 physical sciences ,Radiative transfer ,Spectral energy distribution ,Millimeter ,Astrophysics::Earth and Planetary Astrophysics ,010306 general physics ,Spectroscopy ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
We present a panchromatic study, involving a multiple technique approach, of the circumstellar disc surrounding the T Tauri star IM Lupi (Sz 82). We have undertaken a comprehensive observational study of IM Lupi using photometry, spectroscopy, millimetre interferometry and multi-wavelength imaging. For the first time, the disc is resolved from optical and near-infrared wavelengths in scattered light, to the millimetre regime in thermal emission. Our data-set, in conjunction with existing photometric data, provides an extensive coverage of the spectral energy distribution, including a detailed spectrum of the silicate emission bands. We have performed a simultaneous modelling of the various observations, using the radiative transfer code MCFOST, and analysed a grid of models over a large fraction of the parameter space via Bayesian inference. We have constructed a model that can reproduce all of the observations of the disc. Our analysis illustrates the importance of combining a wide range of observations in order to fully constrain the disc model, with each observation providing a strong constraint only on some aspects of the disc structure and dust content. Quantitative evidence of dust evolution in the disc is obtained: grain growth up to millimetre-sized particles, vertical stratification of dust grains with micrometric grains close to the disc surface and larger grains which have settled towards the disc midplane, and possibly the formation of fluffy aggregates and/or ice mantles around grains., 20 pages, 13 figures. Accepted for publication in A&A
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- 2008
6. Visions of Nature's Planet Foundry: Images of Circumstellar Disks
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Karl Stapelfeldt
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Physics ,Planetesimal ,Solar System ,Extant taxon ,Planet ,Hubble space telescope ,Young stellar object ,Astronomy ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics ,Planetary system ,Circumstellar disk ,Astrophysics::Galaxy Astrophysics - Abstract
As the number of detected extrasolar planetary systems has steadily grown over the past five years, so too has the number of circumstellar disks with resolved images. In this contribution, I take stock of the current inventory of disk images at various wavelengths; summarize the results of a new disk imaging survey conducted with the Hubble Space Telescope; review the major inferences that can be drawn about disk structure from the extant images; and suggest areas for future progress.
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- 2004
7. Future Opportunities in Young Binary Star Research with Space Observatories
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Karl Stapelfeldt
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Physics ,Binary star ,Astronomy ,Astrophysics ,Space observatory - Abstract
Ambitious infrared and astrometric space observatories are planned by both NASA and ESA for the first decade of the new millenium. I present a brief overview of their capabilities and suggest some of their likely contributions to research on young binary stars.
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- 2001
8. HERSCHEL-RESOLVED OUTER BELTS OF TWO-BELT DEBRIS DISKS—EVIDENCE OF ICY GRAINS
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Geoffrey Bryden, Michael W. Werner, Karl Stapelfeldt, and Farisa Y. Morales
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Physics ,010504 meteorology & atmospheric sciences ,Space and Planetary Science ,0103 physical sciences ,Astronomy and Astrophysics ,010303 astronomy & astrophysics ,01 natural sciences ,Debris ,0105 earth and related environmental sciences ,Astrobiology - Published
- 2016
9. WFPC2 Studies of the Disk and Jet of HH 30
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Karl Stapelfeldt, Chris Burrows, John Krist, and Alan Watson
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Physics ,Jet (fluid) ,Hubble Deep Field ,Young stellar object ,Hubble Deep Field South ,Astronomy ,Astrophysics ,Collimated light ,Stars ,Perpendicular ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Absorption (electromagnetic radiation) ,Astrophysics::Galaxy Astrophysics - Abstract
Hubble Space Telescope imaging of HH 30 has revealed this object to be a prototype young stellar object (YSO) accretion disk system. An optically thick circumstellar absorption disk, 450 AU in diameter, is seen extending perpendicular to highly collimated bipolar jets. The jet width is resolved in the transverse direction and increases with distance from the central star. The size and age of the disk compare well to the early solar nebula during planet formation. HH 30 is the first YSO disk ever observed at 14 AU resolution, and the first viewed close enough to edge-on that the vertical structure of the disk is clearly visible. These HST images of HH 30 offer the first-ever opportunity to directly measure the flaring profile of an astrophysical accretion disk. We have compared the images to model nebulosities calculated in both multiple and single scattering regimes, in the latter case via chi-squared minimization. This analysis constrains the circumstellar density distribution and grain scattering properties. A brief summary of the results is presented here; full details and references appear in Burrows et al., Ap.J. (1996).
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- 1997
10. Zodiac II: debris disk science from a balloon
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Geoffrey Bryden, Wesley Traub, Lewis C. Roberts, Jr., Robin Bruno, Stephen Unwin, Stan Backovsky, Paul Brugarolas, Supriya Chakrabarti, Pin Chen, Lynne Hillenbrand, John Krist, Charles Lillie, Bruce Macintosh, Dimitri Mawet, Bertrand Mennesson, Dwight Moody, Zahidul Rahman, Justin Rey, Karl Stapelfeldt, David Stuchlik, John Trauger, Gautam Vaischt, and Shaklan, Stuart
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Physics ,Telescope ,Debris disk ,Zodiac ,law ,Astronomy ,Planetary system ,Debris ,Coronagraph ,Exoplanet ,Space debris ,Astrobiology ,law.invention - Abstract
Zodiac II is a proposed balloon-borne science investigation of debris disks around nearby stars. Debris disks are analogs of the Asteroid Belt (mainly rocky) and Kuiper Belt (mainly icy) in our Solar System. Zodiac II will measure the size, shape, brightness, and color of a statistically significant sample of disks. These measurements will enable us to probe these fundamental questions: what do debris disks tell us about the evolution of planetary systems; how are debris disks produced; how are debris disks shaped by planets; what materials are debris disks made of; how much dust do debris disks make as they grind down; and how long do debris disks live? In addition, Zodiac II will observe hot, young exoplanets as targets of opportunity. The Zodiac II instrument is a 1.1-m diameter SiC telescope and an imaging coronagraph on a gondola carried by a stratospheric balloon. Its data product is a set of images of each targeted debris disk in four broad visiblewavelength bands. Zodiac II will address its science questions by taking high-resolution, multi-wavelength images of the debris disks around tens of nearby stars. Mid-latitude flights are considered: overnight test flights within the United States followed by half-global flights in the Southern Hemisphere. These longer flights are required to fully explore the set of known debris disks accessible only to Zodiac II. On these targets, it will be 100 times more sensitive than the Hubble Space Telescope's Advanced Camera for Surveys (HST/ACS); no existing telescope can match the Zodiac II contrast and resolution performance. A second objective of Zodiac II is to use the near-space environment to raise the Technology Readiness Level (TRL) of SiC mirrors, internal coronagraphs, deformable mirrors, and wavefront sensing and control, all potentially needed for a future space-based telescope for high-contrast exoplanet imaging.
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- 2011
11. Microwave Observations of Edge-on Protoplanetary Disks: Program Overview and First Results
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Sarah T. Maddison, Christophe Pinte, Patrick Palmer, Gilles Duvert, Carl Melis, François Ménard, Laura Chomiuk, Gaspard Duchêne, Marshall D. Perrin, and Karl Stapelfeldt
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Physics ,Very large array ,Line-of-sight ,010504 meteorology & atmospheric sciences ,Wavelength range ,Stratification (water) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Protoplanetary disk ,01 natural sciences ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Planet ,0103 physical sciences ,010303 astronomy & astrophysics ,Microwave ,Solar and Stellar Astrophysics (astro-ph.SR) ,0105 earth and related environmental sciences - Abstract
We are undertaking a multi-frequency Expanded Very Large Array (EVLA) survey of edge-on protoplanetary disks to probe the growth of solids in each disk, sedimentation of such material into the disk midplane, and the connection of these phenomena to the planet formation process. The projection of edge-on disk systems along our line of sight enables a study of the vertical stratification of large grains with fewer model dependencies than would be required for disks that are more face-on. Robust studies of the spatial distribution of grains up to ~1 cm in size are possible with the wavelength range and sensitivity of the EVLA. In this contribution we describe target selection and observational strategies. First results concerning the Class 0 source IRAS04368+2557 (L1527 IRS) are presented, including a study of this source's 8.46 GHz continuum variability over short and long time baselines and an indication that its protoplanetary disk may have a dearth of pebble-sized grains., 17 pages, 2 tables, 3 figures. Accepted for ApJ Letters EVLA special issue. Updated affiliations
- Published
- 2011
12. The circumstellar disc in the Bok globule CB 26: Multi-wavelength observations and modelling of the dust disc and envelope
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Tyler L. Bourke, Christophe Pinte, Gaspard Duchêne, Ralf Launhardt, J. Sauter, J. H. Chen, Sebastian Wolf, C. McCabe, Klaus M. Pontoppidan, Mike Dunham, Deborah Padgett, Karl Stapelfeldt, François Ménard, Laboratoire d'Astrophysique de Grenoble (LAOG), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
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FOS: Physical sciences ,Context (language use) ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,symbols.namesake ,Spitzer Space Telescope ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,Envelope (waves) ,Earth and Planetary Astrophysics (astro-ph.EP) ,Physics ,Spectral index ,010308 nuclear & particles physics ,Bok globule ,Star formation ,Astronomy and Astrophysics ,Planetary system ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,symbols ,Spectral energy distribution ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics - Earth and Planetary Astrophysics - Abstract
Circumstellar discs are expected to be the nursery of planets. Grain growth within such discs is the first step in the planet formation process. The Bok globule CB 26 harbours such a young disc. We present a detailed model of the edge-on circumstellar disc and its envelope in the Bok globule CB 26. The model is based on HST near-infrared maps in the I, J, H, and K bands, OVRO and SMA radio maps at 1.1mm, 1.3mm and 2.7mm, and the spectral energy distribution (SED) from 0.9 microns to 3mm. New photometric and spectroscopic data from the Spitzer Space Telescope and the Caltech Submilimeter Observatory have been obtained and are part of our analysis. Using the self-consistent radiative transfer code MC3D, the model we construct is able to discriminate parameter sets and dust properties of both its parts, namely envelope and disc. We find that the disc has an inner hole with a radius of 45 +/- 5 AU. Based on a dust model including silicate and graphite the maximum grain size needed to reproduce the spectral millimetre index is 2.5 microns. Features seen in the near-infrared images, dominated by scattered light, can be described as a result of a rotating envelope. Successful employment of ISM dust in both the disc and envelope hint that grain growth may not yet play a significant role for the appearance of this system. A larger inner hole gives rise to the assumption that CB 26 is a circumbinary disc., 18 pages, 15 figures, Accepted for publication in A&A
- Published
- 2009
13. The Peculiar Periodic YSO WL 4 in ρ Ophiuchus
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Peter Plavchan, Alan H. Gee, Karl Stapelfeldt, Andrew Becker, Eric Stempels, and Stempels, Eric
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Physics ,T Tauri star ,Star formation ,Stellar rotation ,Ophiuchus ,Astronomy ,Stellar structure ,Astrophysics ,Light curve ,Orbital period ,Eclipse - Abstract
We present the discovery of 130.87 day periodic near-infrared flux variability for the Class II T Tauri star WL 4 (= 2MASS J16271848-2429059, ISO-Oph 128). Our data are from the 2MASS Calibration Point Source Working Database, and constitute 1580 observations in J, H and K_s of a field in ρ Ophiuchus used to calibrate the 2MASS All-Sky Survey. We identify a light curve for WL 4 with eclipse amplitudes of ~0.4 mag lasting more than one-quarter the period, and color variations in J-H and H-K_s, of ~0.1 mag. The long period cannot be explained by stellar rotation. We propose that WL 4 is a triple YSO system, with an inner binary orbital period of 130.87 days. We posulate that we are observing each component of the inner binary alternately being eclipsed by a circum-binary disk with respect to our line of sight. This system will be useful in investigating terrestrial zone YSO disk properties and dynamics at ~1 Myr.
- Published
- 2009
14. Detection of the Tip of the Red Giant Branch in NGC 5128
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David Crisp, J. A. Holtzman, J. Jeff Hester, J. R. Mould, Stefano Casertano, Karl Stapelfeldt, John S. Gallagher, Roberto Soria, Richard E. Griffiths, Alan M. Watson, James A. Westphal, Christopher J. Burrows, John Clarke, Gilda E. Ballester, John G. Hoessel, John T. Trauger, and Paul A. Scowen
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Physics ,Astrophysics::High Energy Astrophysical Phenomena ,Astronomy ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Horizontal branch ,Hubble sequence ,Red-giant branch ,symbols.namesake ,Space and Planetary Science ,Globular cluster ,symbols ,Asymptotic giant branch ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Dwarf elliptical galaxy ,Astrophysics::Galaxy Astrophysics ,Dwarf galaxy ,Luminosity function (astronomy) - Abstract
We present a color-magnitude diagram of more than 10,000 stars in the halo of the galaxy NGC 5128 (Centaurus A), based on WFPC2 images through V-band and I-band filters. The position of the red giant branch (RGB) stars is compared with the loci of the red giant branch in six well-studied globular clusters and in the dwarf elliptical galaxy NGC 185; the tip of the RGB is signalled by an observed turn-up in the luminosity function at I≃24.1 ± 0.1 mag; this yields a distance modulus (m - M)_0 = 27.8 ± 0.2 for NGC 5128 (i.e., a distance of 3.6 ± 0.2 Mpc), in agreement with previous determinations based on the planetary nebulae luminosity function and on the surface brightness fluctuations technique. The presence of an intermediate-age stellar population (~5 Gyr) is suggested by the luminosity function of the asymptotic giant branch stars, extending up to I= 22.6 mag (for V - I > 2) and M_(bot) ~ -5 mag; however, the number of these stars constrains the intermediate-age stellar population in the halo of NGC 5128 to be less than ~ 10% of the total. The color distribution at constant I magnitude, albeit affected by the completeness level of our sample, strongly suggests a mean value of [Fe/H] > -0.9 dex, possibly similar to the value found in M31 and higher than that observed in NGC 185. Like the M31 halo, the halo of NGC 5128 exhibits a broad range of levels of chemical enrichment.
- Published
- 1996
15. Surveying the Solar Neighborhood for Brown Dwarf Companions with the ECLIPSE Discovery Mission
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Karl Stapelfeldt
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Physics ,Brown dwarf ,Astronomy ,Circumbinary planet ,Astrobiology ,Eclipse - Abstract
The proposed Eclipse Discovery mission is an optical space telescope designed to provide a thousandfold reduction in scattered light near bright stars in comparison to any Hubble Space Telescope instrument. A survey of 500 single stars within 15 pc can detect companions with absolute z magnitude of 22 at separations > 10 AU in most of the targets. Spectrophotometry of CH4 and H2O bands between 0.8-1.0 μm can be used to derive the effective temperatures of the objects. The ECLIPSE brown dwarf survey would directly measure the luminosity function of brown dwarf companions down to ~20 Jupiter masses, providing a crucial comparison with field objects.
- Published
- 2003
16. THE NORTH AMERICAN AND PELICAN NEBULAE. II. MIPS OBSERVATIONS AND ANALYSIS
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S. Guieu, Alberto Noriega-Crespo, John R. Stauffer, John M. Carpenter, D. M. Cole, S. C. Wolff, D. Padgett, S. E. Strom, Luisa Rebull, Sean Carey, Karl Stapelfeldt, and Lynne A. Hillenbrand
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Physics ,biology ,Young stellar object ,Extinction (astronomy) ,FOS: Physical sciences ,Astronomy ,Astronomy and Astrophysics ,Stars ,Pelican ,Astrophysics - Solar and Stellar Astrophysics ,Spitzer Space Telescope ,Space and Planetary Science ,biology.animal ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
We present observations of ~7 square degrees of the North American and Pelican Nebulae region at 24, 70, and 160 microns with the Spitzer Space Telescope Multiband Imaging Photometer for Spitzer (MIPS). We incorporate the MIPS observations with earlier Spitzer Infrared Array Camera (IRAC) observations, as well as archival near-infrared (IR) and optical data. We use the MIPS data to identify 1286 young stellar object (YSO) candidates. IRAC data alone can identify 806 more YSO candidates, for a total of 2076 YSO candidates. Prior to the Spitzer observations, there were only ~200 YSOs known in this region. Three subregions within the complex are highlighted as clusters: the Gulf of Mexico, the Pelican, and the Pelican's Hat. The Gulf of Mexico cluster is subject to the highest extinction (Av at least ~30) and has the widest range of infrared colors of the three clusters, including the largest excesses and by far the most point-source detections at 70 microns. Just 3% of the cluster members were previously identified; we have redefined this cluster as about 10-100 times larger (in projected area) than was previously realized., Accepted to ApJS. Full data tables available at http://web.ipac.caltech.edu/staff/rebull/research.html
- Published
- 2011
17. Hubble Space Telescope Far-Ultraviolet Imaging of Jupiter During the Impacts of Comet Shoemaker-Levy 9
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John T. Trauger, L. Ben Jaffel, Wing-Huen Ip, Alex D. Storrs, Karl Stapelfeldt, F. Paresce, W. M. Harris, H. B. Hammel, C. Emerich, Mihaly Horanyi, Renée Prangé, John Clarke, David Crisp, D. Rego, Steve Miller, Robin W. Evans, J. L. Bertaux, Jean-Claude Gérard, M. Ballav, Harold A. Weaver, and Gilda E. Ballester
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Physics ,Jupiter ,Far ultraviolet ,Hubble space telescope ,Comet ,Astronomy - Published
- 1995
18. WFPC2 Studies of the Crab Nebula. III. Magnetic Rayleigh-Taylor Instabilities and the Origin of the Filaments
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Byung Il Jun, Paul A. Scowen, John Krist, Christopher J. Burrows, J. J. Hester, Alan M. Watson, Richard E. Griffiths, John S. Gallagher, Michael L. Norman, Karl Stapelfeldt, David Crisp, Stefano Casertano, Ravi Sankrit, J. A. Holtzman, John G. Hoessel, John T. Trauger, Gilda E. Ballester, James M. Stone, J. A. Westphal, Jeremy Mould, and John Clarke
- Subjects
Physics ,Nebula ,Field line ,Astrophysics::High Energy Astrophysical Phenomena ,Magnetic confinement fusion ,Astronomy and Astrophysics ,Astrophysics ,Instability ,Magnetic field ,Protein filament ,Crab Nebula ,Space and Planetary Science ,Ejecta ,Astrophysics::Galaxy Astrophysics - Abstract
Recently obtained Hubble Space Telescope WFPC2 images of the Crab Nebula show that the emission-line filaments are dominated by structures that morphologically appear to be the result of magnetic Rayleigh Taylor (R-T) instabilities at the interface between the pulsar-driven synchrotron nebula and a shell of swept up ejecta. We replace this morphological argument with a quantitative treatment of the growth rate and characteristic wavelength of such instabilities. Using published data on the rate of expansion of the synchrotron nebula and the density of the ejecta, together with a wavelength for the instability measured from the WFPC2 images, we calculate a magnetic field strength of ~540 µG. This is within a factor of 2 of the canonical minimum energy equipartition field of 300 µG, and probably closer than that to a more realistic estimate of the field at the edge of the Crab. Comparison of the detailed morphology and ionization structure of the R-T fingers in the Crab with recent magnetohydrodynamical simulations which follow the development of magnetic R-T instabilities into the nonlinear regime is used to establish a sequence of filament properties which are determined by the density of the shell of swept-up ejecta at the edge of the synchrotron nebula. When the density is below a critical value, the interface is stable. For somewhat higher densities R-T instabilities grow, but the field, which becomes aligned along the length of the R-T fingers, is strong enough to prevent the development of secondary Kelvin Helmholtz (K-H) instabilities as the finger falls through the lighter medium. At higher densities these K-H instabilities develop, but the field is still strong enough to maintain a long streamer-like connection between the head of the filament and the shell. In a few cases, the density of the shell is high enough that the magnetic field is unable to prevent the fragmentation of R-T fingers, and the structure becomes more characteristic of a nonmagnetic R-T instability. The magnetic field is oriented along the length of an R-T finger, so material is free to "pour" into the finger from above. In equilibrium, gradients in thermal pressure and effective gravity must balance along field lines. As a result, loss of pressure support in the fingers due to cooling enhances the flow of material into the fingers, "siphoning" gas into the finger from above. If an extended remnant of ejecta surrounds the visible extent of the Crab, as has been suggested frequently, then the synchrotron nebula is expanding through this extended remnant, sweeping up ejecta as it goes. R-T instabilities channel this swept-up ejecta into the hierarchy of dense visible filaments. It seems likely that the current system of filaments originated as a result of R-T instabilities as the synchrotron nebula expanded out through more uniformly distributed ejecta. If an extended remnant remains today, then filament formation is an ongoing process. The ionization structure of filaments is also found to change in a systematic way as a function of the relative importance of the magnetic field and the mass density. Filaments which are dominated by the magnetic field are confined by the field and have sharp, well defined edges. Filaments in which the magnetic field is less dominant consist of high-density, low-ionization cores embedded within more extended high-ionization material. This confirms a previous suggestion that variations in magnetic confinement are an important caveat to published interpretations of spectra of Crab filaments.
- Published
- 1996
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