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Browsing by Author "Hines, DC"

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    Discovery of a nearly edge-on disk around HD 32297
    (IOP Publishing, 2005-08-20) Schneider, G; Silverstone, MD; Hines, DC; University of Arizona; University of Alabama Tuscaloosa
    We report the discovery of a nearly edge-on disk about the A0 star HD 32297 seen in light scattered by the disk grains revealed in NICMOS PSF-subtracted coronagraphic images. The disk extends to a distance of at least 400 AU (3".3) along its major axis with a 1.1 mu m flux density of 4.81 +/- 0.57 mJy beyond a radius of 0".3 from the coronagraphically occulted star. The fraction of 1.1 mu m starlight scattered by the disk, 0.0033 +/- 0.0004, is comparable to its fractional excess emission at 25 + 60 mu m of similar to 0.0027 as measured from IRAS data. The disk appears to be inclined 10 degrees.5 +/- 2 degrees.5 from an edge-on viewing geometry, with its major axis oriented 236 degrees.5 +/- 1 degrees eastward of north. The disk exhibits unequal brightness on opposing sides and a break in the surface brightness profile along the NE-side disk major axis. Such asymmetries might implicate the existence of one or more (unseen) planetary mass companions.
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    The formation and evolution of planetary systems (FEPS): Discovery of an unusual debris system associated with HD 12039
    (IOP Publishing, 2006-02-20) Hines, DC; Backman, DE; Bouwman, J; Hillenbrand, LA; Carpenter, JM; Meyer, MR; Kim, JS; Silverstone, MD; Rodmann, J; Wolf, S; Mamajek, EE; Brooke, TY; Padgett, DL; Henning, T; Moro-Martin, A; Stobie, E; Gordon, KD; Morrison, JE; Muzerolle, J; Su, KYL; National Aeronautics & Space Administration (NASA); Max Planck Society; California Institute of Technology; University of Arizona; Harvard University; Smithsonian Astrophysical Observatory; Smithsonian Institution; Princeton University; University of Alabama Tuscaloosa
    We report the discovery of a debris system associated with the similar to 30 Myr old G3/5V star HD 12039 using Spitzer Space Telescope observations from 3.6-160 mu m. An observed infrared excess (L-IR/L-* = 1 x 10(-4)) above the expected photosphere for lambda greater than or similar to 14 mu m is fit by thermally emitting material with a color temperature of T similar to 110 K, warmer than the majority of debris disks identified to date around Sun-like stars. The object is not detected at 70 mu m with a 3 sigma upper limit 6 times the expected photospheric flux. The spectrum of the infrared excess can be explained by warm, optically thin material comprised of blackbody-like grains of size greater than or similar to 7 mu m that reside in a belt orbiting the star at 4-6 AU. An alternate model dominated by smaller grains, near the blowout size a similar to 0.5 mu m, located at 30-40 AU is also possible but requires the dust to have been produced recently, since such small grains will be expelled from the system by radiation pressure in approximately a few times 10(2) yr.
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    Formation and evolution of planetary systems: Cold outer disks associated with sun-like stars
    (IOP Publishing, 2005-10-10) Kim, JS; Hines, DC; Backman, DE; Hillenbrand, LA; Meyer, MR; Rodmann, J; Moro-Martin, A; Carpenter, JM; Silverstone, MD; Bouwman, J; Mamajek, EE; Wolf, S; Malhotra, R; Pascucci, I; Najita, J; Padgett, DL; Henning, T; Brooke, TY; Cohen, M; Strom, SE; Stobie, EB; Engelbracht, CW; Gordon, KD; Misselt, K; Morrison, JE; Muzerolle, J; Su, KYL; University of Arizona; National Aeronautics & Space Administration (NASA); NASA Ames Research Center; California Institute of Technology; Max Planck Society; Princeton University; Harvard University; Smithsonian Astrophysical Observatory; Smithsonian Institution; National Optical Astronomy Observatory; University of California System; University of California Berkeley; University of Alabama Tuscaloosa
    We present the discovery of debris systems around three Sun-like stars based on observations performed with the Spitzer Space Telescope as part of a Legacy Science Program, "The Formation and Evolution of Planetary Systems'' ( FEPS). We also confirm the presence of debris around two other stars. All the stars exhibit infrared emission in excess of the expected photospheres in the 70 mu m band but are consistent with photospheric emission at <= 33 mu m. This restricts the maximum temperature of debris in equilibrium with the stellar radiation to T < 70 K. We find that these sources are relatively old in the FEPS sample, in the age range 0.7 - 3 Gyr. On the basis of models of the spectral energy distributions, we suggest that these debris systems represent materials generated by collisions of planetesimal belts. We speculate on the nature of these systems through comparisons to our own Kuiper Belt, and on the possible presence of planet( s) responsible for stirring the system and ultimately releasing dust through collisions. We further report observations of a nearby star HD 13974 ( d 11 pc) that are indistinguishable from a bare photosphere at both 24 and 70 mu m. The observations place strong upper limits on the presence of any cold dust in this nearby system (L-IR/L-* < 10 (-5.2)).
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    The formation and evolution of planetary systems: First results from a Spitzer Legacy Science Program
    (University of Chicago Press, 2004-09) Meyer, MR; Hillenbrand, LA; Backman, DE; Beckwith, SVW; Bouwman, J; Brooke, TY; Carpenter, JM; Cohen, M; Gorti, U; Henning, T; Hines, DC; Hollenbach, D; Kim, JS; Lunine, J; Malhotra, R; Mamajek, EE; Metchev, S; Moro-Martin, A; Morris, P; Najita, J; Padgett, DL; Rodmann, J; Silverstone, MD; Soderblom, DR; Stauffer, JR; Stobie, EB; Strom, SE; Watson, DM; Weidenschilling, SJ; Wolf, S; Young, E; Engelbracht, CW; Gordon, KD; Misselt, K; Morrison, J; Muzerolle, J; Su, K; University of Arizona; California Institute of Technology; National Aeronautics & Space Administration (NASA); NASA Ames Research Center; Space Telescope Science Institute; Johns Hopkins University; Max Planck Society; University of California System; University of California Berkeley; National Optical Astronomy Observatory; University of Rochester; University of Alabama Tuscaloosa
    We present 3-160 mum photometry obtained with the Infrared Array Camera (IRAC) and Multiband Imaging Photometer for Spitzer (MIPS) instruments for the first five targets from the Spitzer Space Telescope Legacy Science Program "Formation and Evolution of Planetary Systems'' and 4-35 mum spectrophotometry obtained with the Infrared Spectrograph (IRS) for two sources. We discuss in detail our observations of the debris disks surrounding HD 105 (G0 V, 30+/-10 Myr) and HD 150706 (G3 V, similar to700+/-300 Myr). For HD 105, possible interpretations include large bodies clearing the dust inside of 45 AU or a reservoir of gas capable of sculpting the dust distribution. The disk surrounding HD 150706 also exhibits evidence of a large inner hole in its dust distribution. Of the four survey targets without previously detected IR excess, spanning ages 30 Myr to 3 Gyr, the new detection of excess in just one system of intermediate age suggests a variety of initial conditions or divergent evolutionary paths for debris disk systems orbiting solar-type stars.
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    Infrared views of the TW Hydra disk
    (University of Chicago Press, 2002) Weinberger, AJ; Becklin, EE; Schneider, G; Chiang, EI; Lowrance, PJ; Silverstone, M; Zuckerman, B; Hines, DC; Smith, BA; University of California System; University of California Los Angeles; Carnegie Institution for Science; University of Arizona; University of California Berkeley; California Institute of Technology; University of Hawaii System; University of Alabama Tuscaloosa
    The face-on disk around TW Hya is imaged in scattered light at 1.1 and 1.6 mum using the coronagraph in the Near Infrared Camera and Multi Object Spectrometer aboard the Hubble Space Telescope. Stellar light scattered from the optically thick dust disk is seen from 20 to 230 AU. The surface brightness declines as a power law of r(-2.6+/-0.1) between 45 and 150 AU. The scattering profile indicates that the disk is flared, not geometrically flat. The disk, while spatially unresolved in thermal radiation at 12 and 18 mum in observations from the W. M. Keck Observatory, shows amorphous and crystalline silicate emission in its spectrum. A disk with silicate grains of a radius similar to1 mum in size in its surface layers can explain the color of the scattered light and the shape of the mid-infrared spectrum. Much larger grains in the disk interior are necessary to fit the millimeter-wave spectral energy distribution, and hence grain growth from an original interstellar size population may have occurred.
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    NICMOS coronagraphic observations of 55 Cancri
    (University of Chicago Press, 2001) Schneider, G; Becklin, EE; Smith, BA; Weinberger, AJ; Silverstone, M; Hines, DC; University of Arizona; University of California System; University of California Los Angeles; University of Hawaii System; University of Alabama Tuscaloosa
    We present new near-infrared (1.1 mum) observations of the circumstellar environment of the planet-bearing star 55 Cancri. With these Hubble Space Telescope (HST) images we are unable to confirm the observation of bright scattered radiation at longer NIR wavelengths previously reported by Trilling and coworkers. NICMOS coronagraphic images with detection sensitivities to similar to 100 mu Jy arcsec(-2) at 1.1 mum in the region 28-60 AU from the star fail to reveal any significant excess flux in point-spread function (PSF) subtracted images taken in two HST orbits. These new observations place flux densities in the 19-28 AU zone at a factor of 10 or more below the reported ground-based observations. Applying a suite of a dozen well-matched coronagraphic reference PSFs, including one obtained in the same orbits as the observations of 55 Cnc, yielded consistently null results in detecting a disk. We also searched for and failed to find a suggested flux-excess anisotropy in the ratio of similar to1.7:1 in the circumstellar background along and orthogonal to the plane of the putative disk. We suggest that, if such a disk does exist, then the total 1.1 km spectral flux density in an annular zone 28-42 AU from the star must be no more than similar to0.4 mJy, at least 10 times smaller than suggested by Trilling and Brown, upon which their very large estimate for the total dust mass (0.4 M+) was based. Based on the far-infrared and submillimeter flux of this system and observations of scattered light and thermal emission from other debris disks, we also expect the intensity of the scattered light to be at least an order of magnitude below our upper limits.
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    NICMOS coronagraphic observations of the GM Aurigae circumstellar disk
    (IOP Publishing, 2003-03) Schneider, G; Wood, K; Silverstone, MD; Hines, DC; Koerner, DW; Whitney, BA; Bjorkman, JE; Lowrance, PJ; University of Arizona; University of St Andrews; Northern Arizona University; University System of Ohio; University of Toledo; California Institute of Technology; University of Alabama Tuscaloosa
    We present Hubble Space Telescope Near Infrared Camera and Multi-Object Spectrometer (NICMOS) coronagraphic observations of the environment in the region of the young star-disk system GM Aurigae. Scattered near-infrared light in two spectral bands (F110W = 1.1 mum and F160W = 1.6 mum) trace the morphology of circumstellar dust to a distance of similar to700 AU from the star. An similar to300 AU radius outwardly flared disk inclined 50degrees-55degrees to the plane of the sky surrounded by a tenuous envelope is seen in the NICMOS images, confirming the size and suspected flared nature of the disk suggested by earlier CO and optical observations. The NICMOS images probe the disk region with spatial resolutions of similar to0."1 at radial distances of 0."35 to similar to4."5-5."0 from the largely unobscured (A(v) < 0.5) central star. The midplane of the disk 1.'' 3 from GM Aurigae is revealed in silhouette against the previously unseen lower portion of the illuminated disk along its minor axis ( as projected onto the sky). We comment on surface brightness profiles along the disk major and minor axes, as well as isophotal maps of the disk. From these photometric data we have measured the integrated flux density of the disk, beyond the instrumental inner radius of 0.'' 35, as 8.0 and 9.3 mJy (+/-20%) at F110W and F160W, respectively, corresponding to disk scattering fractions of L-disk/L* = 0.025 (+/-20%) in both bands. By fitting the photometric properties of the disk to a scattered-light model, we estimate the disk mass to be similar to 0.04 M-.. Additionally, we find two diffuse red polar lobes along the disk minor axis, likely the result of a bipolar outflow, at distances of +/-3.'' 8 from GM Aurigae (similar to 900 AU with our inferred inclination) with peak H-band surface brightnesses of similar to 14 mu Jy arcsec(-2). We also note the existence of a broad (similar to 3 '' wide) band of blue material within the NICMOS field of view, spatially coincident with and extending at least 12 '' from the northeast outer region of the disk major axis.
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    Spitzer Space Telescope observations of G dwarfs in the Pleiades: Circumstellar debris disks at 100 Myr age
    (University of Chicago Press, 2005-10) Stauffer, JR; Rebull, LM; Carpenter, J; Hillenbrand, L; Backman, D; Hines, DC; Soderblom, DR; Mamajek, E; Morris, P; Bouwman, J; Strom, SE; California Institute of Technology; National Aeronautics & Space Administration (NASA); NASA Ames Research Center; University of Arizona; Space Telescope Science Institute; Max Planck Society; National Optical Astronomy Observatory; University of Alabama Tuscaloosa
    Fluxes and upper limits in the wavelength range from 3.6 to 70 mu m from the Spitzer Space Telescope are provided for 20 solar-mass Pleiades members. One of these stars shows a probable mid-IR excess, and two others have possible excesses, presumably due to circumstellar debris disks. For the star with the largest, most secure excess flux at MIPS (Multiband Imaging Photometer for Spitzer) wavelengths, HII 1101, we derive log (L-dust/L-*) similar to -3.8 and an estimated debris disk mass of 4.2 x 10(-5) M-circle plus for an assumed uniform dust grain size of 10 mu m. If the stars with detected excesses are interpreted as stars with relatively recent, large collisional events producing a transient excess of small dust particles, the frequency of such disk transients is similar to 10% for our similar to 100 Myr, Pleiades G dwarf sample. For the stars without detected 24-70 mu m excesses, the upper limits to their fluxes correspond to approximate 3 sigma upper limits to their disk masses of 6 x 10(-6) M-circle plus using the MIPS 24 mu m upper limit or 2 x 10(-4) M-circle plus using the MIPS 70 mu m limit. These upper limit disk masses (for "warm" and "cold" dust, respectively) are roughly consistent with, but somewhat lower than, predictions of a heuristic model for the evolution of an "average" solar-mass star's debris disk based on extrapolation backward in time from current properties of the Sun's Kuiper Belt.