D. C. Hines

Space Telescope Science Institute, Baltimore, Maryland, United States

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Publications (339)1129.45 Total impact

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    ABSTRACT: When giant planets form, they grow by accreting gas and dust. HD 142527 is a young star that offers a scaled-up view of this process. It has a broad, asymmetric ring of gas and dust beyond \about 100 AU and a wide inner gap. Within the gap, a low-mass stellar companion orbits the primary star at just \about 12 AU, and both the primary and secondary are accreting gas. In an attempt to directly detect the dusty counterpart to this accreted gas, we have observed HD 142527 with the Gemini Planet Imager in polarized light at $Y$ band (0.95-1.14 \microns). We clearly detect the companion in total intensity and show that its position and photometry are generally consistent with the expected values. We also detect a point-source in polarized light that may be spatially separated by \about a few AU from the location of the companion in total intensity. This suggests that dust is likely falling onto or orbiting the companion. Given the possible contribution of scattered light from this dust to previously reported photometry of the companion, the current mass limits should be viewed as upper limits only. If the dust near the companion is eventually confirmed to be spatially separated, this system would resemble a scaled-up version of the young planetary system inside the gap of the transition disk around LkCa 15.
    The Astrophysical Journal Letters 07/2014; 791(2). · 6.35 Impact Factor
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    ABSTRACT: Mid-infrared spectral observations Uranus acquired with the Infrared Spectrometer (IRS) on the Spitzer Space Telescope are used to determine the abundances of C2H2, C2H6, CH3C2H, C4H2, CO2, and tentatively CH3 on Uranus at the time of the 2007 equinox. For vertically uniform eddy diffusion coefficients in the range 2200-2600 cm2 s-1, photochemical models that reproduce the observed methane emission also predict C2H6 profiles that compare well with emission in the 11.6-12.5 micron wavelength region, where the nu9 band of C2H6 is prominent. Our nominal model with a uniform eddy diffusion coefficient Kzz = 2430 cm2 sec-1 and a CH4 tropopause mole fraction of 1.6x10-5 provides a good fit to other hydrocarbon emission features, such as those of C2H2 and C4H2, but the model profile for CH3C2H must be scaled by a factor of 0.43, suggesting that improvements are needed in the chemical reaction mechanism for C3Hx species. The nominal model is consistent with a CH3D/CH4 ratio of 3.0+-0.2x10-4. From the best-fit scaling of these photochemical-model profiles, we derive column abundances above the 10-mbar level of 4.5+01.1/-0.8 x 10+19 molecule-cm-2 for CH4, 6.2 +- 1.0 x 10+16 molecule-cm-2 for C2H2 (with a value 24% higher from a different longitudinal sampling), 3.1 +- 0.3 x 10+16 molecule-cm-2 for C2H6, 8.6 +- 2.6 x 10+13 molecule-cm-2 for CH3C2H, 1.8 +- 0.3 x 10+13 molecule-cm-2 for C4H2, and 1.7 +- 0.4 x 10+13 molecule-cm-2 for CO2 on Uranus. Our results have implications with respect to the influx rate of exogenic oxygen species and the production rate of stratospheric hazes on Uranus, as well as the C4H2 vapor pressure over C4H2 ice at low temperatures.
    07/2014;
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    ABSTRACT: On 2007 December 16-17, spectra were acquired of the disk of Uranus by the Spitzer Infrared Spectrometer (IRS) when its equator was close to the sub-earth point. This spectrum provides the highest-resolution broad-band spectrum ever obtained for Uranus from space, allowing a determination of the disk-averaged temperature and molecule composition to a greater degree of accuracy than ever before. The temperature profiles derived from the Voyager radio occultation experiments that match these data best are those that assume a high abundance of methane in the deep atmosphere, but none of these models provides a satisfactory fit over the full spectral range. This be the result of spatial differences between global and low-latitudinal regions, changes in time, missing continuum opacity sources such as stratospheric hazes or unknown tropospheric constituents, or undiagnosed systematic problems with either the radio-occultation or the Spitzer IRS data sets. The spectrum is compatible with the stratospheric temperatures derived from the Voyager ultraviolet occultations measurements. Thermospheric temperatures determined from the analysis of the observed H2 quadrupole emission features are colder than those derived by Herbert et al. at pressures less than ~1 microbar. Extrapolation of the nominal model spectrum to far-infrared through millimeter wavelengths shows that the spectrum arising solely from H2 collision-induced absorption is too warm to reproduce observations between wavelengths of 0.8 and 3.3 mm. Adding an additional absorber such as H2S provides a reasonable match to the spectrum, although a unique identification of the responsible absorber is not yet possible with available data. An immediate practical use for the spectrum resulting from this model is to establish a high-precision continuum flux model for use as an absolute radiometric standard for future astronomical observations.
    Icarus 07/2014; · 3.16 Impact Factor
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    ABSTRACT: We are currently conducting a comprehensive and consistent re-processing of archival HST-NICMOS coronagraphic surveys using advanced PSF subtraction methods, entitled the Archival Legacy Investigations of Circumstellar Environments program (ALICE, HST/AR 12652). This virtual campaign of about 400 targets has already produced numerous new detections of previously unidentified point sources and circumstellar structures. We present five newly spatially resolved debris disks revealed in scattered light by our analysis of the archival data. These images provide new views of material around young solar-type stars at ages corresponding to the period of terrestrial planet formation in our solar system. We have also detected several new candidate substellar companions, for which there are ongoing followup campaigns (HST/WFC3 and VLT/SINFONI in ADI mode). Since the methods developed as part of ALICE are directly applicable to future missions (JWST, AFTA coronagraph) we emphasize the importance of devising optimal PSF subtraction methods for upcoming coronagraphic imaging missions. We describe efforts in defining direct imaging high-level science products (HLSP) standards that can be applicable to other coronagraphic campaigns, including ground-based (e.g., Gemini Planet Imager), and future space instruments (e.g., JWST). ALICE will deliver a first release of HLSPs to the community through the MAST archive at STScI in 2014.
    07/2014;
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    ABSTRACT: Spatially resolved scattered-light images of circumstellar (CS) debris in exoplanetary systems constrain the physical properties and orbits of the dust particles in these systems. They also inform on co-orbiting (but unseen) planets, systemic architectures, and forces perturbing starlight-scattering CS material. Using HST/STIS optical coronagraphy, we have completed the observational phase of a program to study the spatial distribution of dust in ten CS debris systems, and one "mature" protoplanetrary disk all with HST pedigree, using PSF-subtracted multi-roll coronagraphy. These observations probe stellocentric distances > 5 AU for the nearest stars, and simultaneously resolve disk substructures well beyond, corresponding to the giant planet and Kuiper belt regions in our Solar System. They also disclose diffuse very low-surface brightness dust at larger stellocentric distances. We present new results inclusive of fainter disks such as HD92945 confirming, and better revealing, the existence of a narrow inner debris ring within a larger diffuse dust disk. Other disks with ring-like sub-structures, significant asymmetries and complex morphologies include: HD181327 with a posited spray of ejecta from a recent massive collision in an exo-Kuiper belt; HD61005 suggested interacting with the local ISM; HD15115 & HD32297, discussed also in the context of environmental interactions. These disks, and HD15745, suggest debris system evolution cannot be treated in isolation. For AU Mic's edge-on disk, out-of-plane surface brightness asymmetries at > 5 AU may implicate one or more planetary perturbers. Time resolved images of the MP Mus proto-planetary disk provide spatially resolved temporal variability in the disk illumination. These and other new images from our program enable direct inter-comparison of the architectures of these exoplanetary debris systems in the context of our own Solar System.
    06/2014;
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    ABSTRACT: We have spatially resolved five debris disks (HD 30447, HD 35841, HD 141943, HD 191089, and HD 202917) for the first time in near-infrared scattered light by reanalyzing archival Hubble Space Telescope (HST)/NICMOS coronagraphic images obtained between 1999 and 2006. One of these disks (HD 202917) was previously resolved at visible wavelengths using HST/Advanced Camera for Surveys. To obtain these new disk images, we performed advanced point-spread function subtraction based on the Karhunen-Loeve Image Projection (KLIP) algorithm on recently reprocessed NICMOS data with improved detector artifact removal (Legacy Archive PSF Library And Circumstellar Environments Legacy program). Three of the disks (HD 30447, HD 35841, and HD 141943) appear edge-on, while the other two (HD 191089 and HD 202917) appear inclined. The inclined disks have been sculpted into rings; in particular, the disk around HD 202917 exhibits strong asymmetries. All five host stars are young (8-40 Myr), nearby (40-100 pc) F and G stars, and one (HD 141943) is a close analog to the young sun during the epoch of terrestrial planet formation. Our discoveries increase the number of debris disks resolved in scattered light from 19 to 23 (a 21% increase). Given their youth, proximity, and brightness (V = 7.2 to 8.5), these targets are excellent candidates for follow-up investigations of planet formation at visible wavelengths using the HST/STIS coronagraph, at near-infrared wavelengths with the Gemini Planet Imager (GPI) and Very Large Telescope (VLT)/SPHERE, and at thermal infrared wavelengths with the James Webb Space Telescope NIRCam and MIRI coronagraphs.
    04/2014; 786(2).
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    ABSTRACT: The James Webb Space Telescope will enable a wealth of new scientific investigations in the near- and mid-infrared, with sensitivity and spatial/spectral resolution greatly surpassing its predecessors. In this paper, we focus upon Solar System science facilitated by JWST, discussing the most current information available concerning JWST instrument properties and observing techniques relevant to planetary science. We also present numerous example observing scenarios for a wide variety of Solar System targets to illustrate the potential of JWST science to the Solar System community. This paper updates and supersedes the Solar System white paper published by the JWST Project in 2010 (Lunine et al., 2010). It is based both on that paper and on a workshop held at the annual meeting of the Division for Planetary Sciences in Reno, NV in 2012.
    03/2014;
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    ABSTRACT: We have carried out a study to examine the spatial structure and composition of dust in the Diffuse Interstellar Medium, using Spitzer IRAC and MIPS observations of the Lockman Hole and Taurus. Models of the infrared background include three components: scattered light and thermal emission from zodiacal dust, diffuse emission from dust in the Milky Way, and the Cosmic Infrared Background. The Background Model Generator (BMG) developed by IPAC to model the Spitzer background includes all three components (Reach 2000), and it assumes that: 1) the spatial distribution of the diffuse interstellar dust is well-traced out by the emission observed in the COBE DIRBE + IRAS 100 micron all sky map; 2) that the Spectral Energy Distribution of the dust is well-described using the Schlegel, Finkbeiner, & Davis (1998) template. We compare the Spitzer data for these regions to this background model to determine how fine scale structure that is not spatially resolved by COBE and the observed, relative contribution from various emission features from dust, impact our understanding of the diffuse interstellar emission. This in turn enables us to evaluate the efficacy of models based only on the averaged SEDs and low spatial resolution data.
    01/2014;
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    ABSTRACT: The Mid-Infrared Instrument (MIRI) on JWST is equipped with four-quadrant phase mask coronagraphs (4QPM) that will enable cutting-edge science at small inner working angles. The effectiveness of these phase masks relies on accurate target acquisition and positioning at the apex of the four quadrants. In order to optimize MIRI target acquisition as well as coronagraphy operations in general, we have run optical simulations to derive contrast performances of all three MIRI 4QPM for various slew accuracy models. Our simulations include full Fourier propagation from the pupil entrance to MIRI focal plane, including intervening masks, realistic wavefront error, transmission profiles for filters and Germanium coating, as well as detector efficiency. We also include photon noise from the star and background as well as detector noise (readout, pixel-to-pixel variations). Here, we discuss the use of the CCC mechanism and the impact of latent images on science. Our results suggest that operations of MIRI coronagraphs should be modified to allow for cases where the CCC is not to be used. This work will also tie in the implementation of coronagraphy in the JWST Exposure time Calculator. ___________________________
    01/2014;
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    ABSTRACT: We have spatially resolved four new debris disks in scattered light for the first time through the analysis of archival HST NICMOS coronagraphic images. These disks around 12-30-Myr-old main-sequence F or G stars were revealed by reprocessing recalibrated archival images (HST AR program LAPLACE; PI Schneider) with a novel pipeline that improves the subtraction of the PSF (ALICE; Soummer et al. 2012). Three of these disks (HD 30447, HD 35841, and HD 141943) appear to be edge-on, and the fourth (HD 191089) appears to be an asymmetric inclined ring. We describe our modeling efforts so far that take into account all available photometry and resolved images for these sources. We employ the 3D radiative transfer code MCFOST (Pinte et al. 2008), which enables the reconstruction of SEDs and images according to the specified dust composition and disk morphology.
    01/2014;
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    ABSTRACT: We have obtain WFC3/IR observations of 15 carefully selected stars with the immediate objective of establishing their Absolute Physical Flux (ABF), and an ultimate goal of achieving the sub-1% absolute photometric accuracies required by Dark Energy science with JWST and other facilities. Even with the best data available, the current determination of ABFs is plagued by the reliance on the Vega photometric system, which is known to be problematic primarily due to the fact that Vega is a pole-on rapid rotator with an infrared excess from its circumstellar disk! which makes it difficult to model. Vega is also far too bright for large aperture telescopes. In an effort to remedy these difficulties, teams from the National Institute of Standards (NIST), the University of New Mexico, Johns Hopkins University and STScI have begun to develop a catalog of stars that have spectral energy distributions that are tied directly to NIST (diode) standards with very precisely determined physical characteristics. A key element in this pursuit has been the efforts at STScI to measure the spectra of many of these objects with STIS. We discuss our program to extend this effort into the near-IR which is crucial to reliably extend the SEDs to longer wavelengths, including the mid IR.
    01/2014;
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    ABSTRACT: We present new Hubble Space Telescope (HST) observations of the HD 181327 debris disk using the Space Telescope Imaging Spectrograph (STIS). Our multi-roll coronagraphic image, combined with new multi-roll image processing techniques, reveals the outer debris ring in its entirety at high SNR. The disk exhibits several significant asymmetries that, at first glance, appear to suggest the presence of a planet. We use new image deprojection methods to constrain the true disk geometry, measure an empirical scattering phase function, and show that the majority of these asymmetries are consistent with scattering and line-of-sight projection effects. One asymmetry, a "post-pericenter glow," appears to be a true density enhancement and we speculate on the origin of this density asymmetry.
    01/2014;
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    ABSTRACT: The solar system furnishes a suite of natural laboratories for studying topics ranging from comparative climatology to astrophysical disks. Furthermore, the solar system is our only source of ground truth for the increasingly diverse array of known exoplanets. The James Webb Space Telescope (JWST) will be capable of observing objects in the solar system with unprecedented detail and sensitivity. We will highlight several case studies for solar system observations with JWST, extracted from a white paper in preparation; the list of applications discussed here is far from comprehensive. The upcoming white paper updates and supersedes the solar system white paper published by the JWST Project in 2010 (Lunine et al., 2010).
    01/2014;
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    ABSTRACT: The Archival Legacy Investigation of Circumstellar Environments (ALICE) project (HST/AR program 12652; PI Soummer) is currently conducting a comprehensive and consistent reprocessing of HST-NICMOS coronagraphic survey data to search for point sources and disks using advanced PSF subtraction. The Karhunen-Loeve Image Projection (KLIP) algorithm based on principal component analysis was developed for this project. We present the main concept for the pipeline, reduction strategy, and PSF subtraction implementation and performance. The ALICE pipeline was designed to process automatically approximately 400 targets in the NICMOS coronagraphic archive, and to deliver High-Level Science Products (HLSPs) back to the MAST archive at STScI. The HLSPs are defined in collaboration with other similar projects to define a standard format for high-contrast imaging. We present and discuss the ALICE point source candidates detected in the NICMOS archive together with a statistical analysis of the population of background objects.
    01/2014;
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    ABSTRACT: We have spatially resolved the debris disk around the young 30 Myr) G dwarf HD 202917 through the analysis of archival HST/NICMOS coronagraphic images. The disk was revealed by reprocessing the images (HST/AR program 11279; PI Schneider) through a novel pipeline that improves the subtraction of the coronagraphic PSF (HST/AR program 12652; PI Soummer). The NICMOS scattered light image confirms an earlier, formally unpublished detection of the disk at optical wavelengths from HST/ACS coronagraph images. Together, the images show a highly inclined disk extending ~200 AU from the star. We describe preliminary disk models obtained from available photometry and resolved images of the system and the 3D radiative transfer code MCFOST (Pinte et al. 2008), which enables the reconstruction of SEDs and images according to specified dust composition and disk morphology.
    01/2014;
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    ABSTRACT: By reprocessing the NICMOS coronagraphic archive using improved PSF subtraction methods, we have obtained new images of 5 debris disks, all previously unseen using classical PSF subtractions. Three of the disks are edge on and two appear to be ring like, one of which is extremely asymmetric. Their stellar hosts are nearby, young F and G type stars (40-90 pc, 12-30 Myr), including one that is a close analog to the young sun at roughly the age at which terrestrial planets were assembling. This is a 25% increase in the sample of debris disks seen in scattered light. Analysis and modeling of the disk geometries is in process. Given these systems' youth, proximity, and brightness (V = 7.2 to 8.5), these will be superb targets for investigating planet formation, and are perfect targets for studies with GPI, SPHERE and JWST.
    Proceedings of the International Astronomical Union 01/2014;
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    ABSTRACT: We present high contrast visible light imaging of the highly unusual circumstellar debris disk around HD 15745 with the Space Telescope Imaging Spectrograph (STIS) instrument on the Hubble Space Telescope (HST). The combination of two coronagraphic wedges and three separate spacecraft orientations provides unprecedented signal-to-noise and inner working angle for this disk. We detect the disk to as close as ~0.4" (26 AU) and as far as 6" (380 AU). We confirm the presence of disk emission that extends further to the west as well as evidence for a second, inner disk. Additionally, HD 15745's motion on the sky is parallel to the extended nebulosity observed, raising the possibility that ISM interactions could play a part in its unusual structure. We investigate the plausibility of this scenario. We acknowledge support from STScI for program (GO12228) and its observations.
    01/2014;
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    ABSTRACT: The James Webb Space Telescope (JWST) will provide important new capabilities to study our Solar System. JWST is a large aperture, cryogenic, infrared-optimized space observatory under construction by NASA, ESA, and CSA for launch in 2018 into a L2 orbit. Imaging, spectroscopy, and coronography covers 0.6-29 microns. Integral-field spectroscopy is performed with apertures 3 to 7 arcsec square (spatial slices of 0.1 to 0.6 arcsec). JWST is designed to observe Solar System objects having apparent rates of motion up to 0.030 arcseconds/second. This tracking capability includes the planets, satellites, asteroids, Trans-Neptunian Objects, and comets beyond Earth’s orbit. JWST will observe in the solar elongation range of 85 to 135 degrees, and a roll range of +/-5 degrees about the telescope’s optical axis. During an observation of a moving target, the science target is held fixed in the desired science aperture by controlling the guide star to follow the inverse of the target’s trajectory. The pointing control software uses polynomial ephemerides for the target generated using data from JPL’s HORIZON system. The JWST guider field of view (2.2x2.2 arcmin) is located in the telescope focal plane several arcmin from the science apertures. The instrument apertures are fixed with respect to the telescope focal plane. For targets near the ecliptic, those apertures also have a nearly fixed orientation relative to the ecliptic. This results from the fact that the Observatory's sunshield and solar panels must always be between the telescope and the Sun. On-board scripts autonomously control the execution of the JWST science timeline. The event-driven scripts respond to actual slew and on-board command execution, making operations more efficient. Visits are scheduled with overlapping windows to provide execution flexibility and to avoid lost time. An observing plan covering about ten days will be uplinked weekly. Updates could be more frequent if necessary (for example, to accommodate a Target of Opportunity - TOO). The event-driven operations system supports time-critical observations and TOOs. The minimum response time for TOOs is 48 hours (observation approval to execution).
    01/2014;
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    ABSTRACT: The Archival Legacy Investigation of Circumstellar Environments (ALICE) project (AR-12652) is currently conducting a comprehensive and consistent reprocessing of HST-NICMOS coronagraphic survey data to search for point sources and disks using advanced PSF subtraction. The KLIP algorithm (Karhunen-Loève Image Projection) was developed for this project, and has proven very effective at processing the hundreds of selected archival images. This project has already been very successful with numerous detections of previously unseen point sources and several resolved debris disks that we are currently following up by multiple avenues. We give an overview of the project including preliminary scientific results with companion candidates and improved images of known disks
    Proceedings of the International Astronomical Union 01/2014;
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    ABSTRACT: We present polarization images of Comet ISON (C/2012 S1) taken with the Hubble Space Telescope (HST) on UTC 2013 May 8 (rh = 3.81 AU, Delta = 4.34 AU), when the phase angle was alpha = 12.16 degrees. This phase angle is approximately centered in the negative polarization branch for cometary dust. The region beyond 1000 km from the nucleus shows a negative polarization amplitude of p% -1.6%. Within 1000 km of the nucleus, the polarization position angle rotates to be approximately perpendicular to the scattering plane, with an amplitude p% +2.5%. Such positive polarization has been observed previously as a characteristic feature of cometary jets, and we show that Comet ISON does indeed harbor a jet-like feature. These HST observations of Comet ISON represent the first visible light, imaging polarimetry with sub-arcsecond spatial resolution of a Nearly Isotropic Comet (NIC) beyond 3.8 AU from the Sun at a small phase angle. The observations provide an early glimpse of the properties of the cometary dust preserved in this Oort-cloud comet.
    The Astrophysical Journal 11/2013; 780(2). · 6.73 Impact Factor

Publication Stats

5k Citations
1,129.45 Total Impact Points

Institutions

  • 2011–2014
    • Space Telescope Science Institute
      Baltimore, Maryland, United States
  • 1999–2014
    • The University of Arizona
      • • Department of Astronomy
      • • Department of Planetary Sciences
      Tucson, Arizona, United States
  • 2013
    • University of Concepción
      • Departamento de Astronomía
      Ciudad de Concepcion, Biobío, Chile
  • 2012
    • University of Oklahoma
      • Homer L. Dodge Department of Physics and Astronomy
      Norman, Oklahoma, United States
  • 2006–2010
    • The Space Science Institute
      Boulder, Colorado, United States
  • 2009
    • University of Texas at Austin
      • Department of Astronomy
      Austin, Texas, United States
    • University of Illinois, Urbana-Champaign
      • Department of Astronomy
      Urbana, Illinois, United States
  • 2007
    • University of California, Los Angeles
      • Department of Physics and Astronomy
      Los Angeles, California, United States
    • California State University, Los Angeles
      • Department of Physics and Astronomy
      Los Angeles, California, United States
    • Princeton University
      Princeton, New Jersey, United States
  • 2003
    • Arizona State University
      Phoenix, Arizona, United States
  • 1998
    • William Penn University
      Penn Hills, Pennsylvania, United States