Publications (8)4.59 Total impact
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Article: Observations of Herbig Ae/Be stars with Herschel/PACS. The atomic and molecular contents of their protoplanetary discs
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ABSTRACT: We observed a sample of 20 representative Herbig Ae/Be stars and 5 A-type debris discs with PACS onboard Herschel, as part of the GAS in Protoplanetary Systems (GASPS) project. The observations were done in spectroscopic mode, and cover the far-infrared lines of [O i], [C ii], CO, CH + , H 2 O, and OH. We have a [O i] 63 μm detection rate of 100% for the Herbig Ae/Be and 0% for the debris discs. The [O i] 145 μm line is only detected in 25% and CO J = 18–17 in 45% (and fewer cases for higher J transitions) of the Herbig Ae/Be stars, while for [C ii] 157 μm, we often find spatially variable background contamination. We show the first detection of water in a Herbig Ae disc, HD 163296, which has a settled disc. Hydroxyl is detected as well in this disc. First seen in HD 100546, CH + emission is now detected for the second time in a Herbig Ae star, HD 97048. We report fluxes for each line and use the observations as line diagnostics of the gas properties. Furthermore, we look for correlations between the strength of the emission lines and either the stellar or disc parameters, such as stellar luminosity, ultraviolet and X-ray flux, accretion rate, polycyclic aromatic hydrocarbon (PAH) band strength, and flaring. We find that the stellar ultraviolet flux is the dominant excitation mechanism of [O i] 63 μm, with the highest line fluxes being found in objects with a large amount of flaring and among the largest PAH strengths. Neither the amount of accretion nor the X-ray luminosity has an influence on the line strength. We find correlations between the line flux of [O i] 63 μm and [O i] 145 μm, CO J = 18–17 and [O i] 6300 Å, and between the continuum flux at 63 μm and at 1.3 mm, while we find weak correlations between the line flux of [O i] 63 μm and the PAH luminosity, the line flux of CO J = 3–2, the continuum flux at 63 μm, the stellar effective temperature, and the Brγ luminosity. Finally, we use a combination of the [O i] 63 μm and 12 CO J = 2–1 line fluxes to obtain order of magnitude estimates of the disc gas masses, in agreement with the values that we find from detailed modelling of two Herbig Ae/Be stars, HD 163296 and HD 169142.Astronomy and Astrophysics 07/2012; 544(78). · 4.59 Impact Factor -
Article: Herschel-PACS observation of the 10 Myr old T Tauri disk TW Hya: Constraining the disk gas mass
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ABSTRACT: Planets are formed in disks around young stars. With an age of ~10 Myr, TW Hya is one of the nearest T Tauri stars that is still surrounded by a relatively massive disk. In addition a large number of molecules has been found in the TW Hya disk, making TW Hya the perfect test case in a large survey of disks with Herschel-PACS to directly study their gaseous component. We aim to constrain the gas and dust mass of the circumstellar disk around TW Hya. We observed the fine-structure lines of [OI] and [CII] as part of the Open-time large program GASPS. We complement this with continuum data and ground-based 12CO 3-2 and 13CO 3-2 observations. We simultaneously model the continuum and the line fluxes with the 3D Monte-Carlo code MCFOST and the thermo-chemical code ProDiMo to derive the gas and dust masses. We detect the [OI] line at 63 micron. The other lines that were observed, [OI] at 145 micron and [CII] at 157 micron, are not detected. No extended emission has been found. Preliminary modeling of the photometric and line data assuming [12CO]/[13CO]=69 suggests a dust mass for grains with radius < 1 mm of ~1.9 times 10^-4 Msun (total solid mass of 3 times 10^-3 Msun) and a gas mass of (0.5--5) times 10^-3 Msun. The gas-to-dust mass may be lower than the standard interstellar value of 100. Comment: 6 pages, 6 figures, accepted for publication in the A&A Herschel special issue05/2010; -
Article: Herschel-PACS observation of the 10 Myr old T Tauri disk TW Hya. Constraining the disk gas mass
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ABSTRACT: Planets are formed in disks around young stars. With an age of ~10 MyrAstronomy and Astrophysics, v.518, id.L125 (2010). -
Article: The
http://dx.doi.org/10.1051/0004-6361/201014591. -
Article: ensuremath Herschelensuremath<?iensuremath>-PACS observation of the 10 Myr old T Tauri disk TW Hya
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ABSTRACT: Planets are formed in disks around young stars. With an age of textttchar12610 Myr, TW Hya is one of the nearest T Tauri stars that is still surrounded by a relatively massive disk. In addition a large number of molecules has been found in the TW Hya disk, making TW Hya the perfect test case in a large survey of disks with ensuremath Herschelensuremath<?iensuremath>?PACS to directly study their gaseous component. We aim to constrain the gas and dust mass of the circumstellar disk around TW Hya. We observed the fine-structure lines of ?O I? and ?C II? as part of the open-time large program GASPS. We complement this with continuum data and ground-based ensuremath 12ensuremath<?supensuremath>CO 3?2 and ensuremath 13ensuremath<?supensuremath>CO 3?2 observations. We simultaneously model the continuum and the line fluxes with the 3D Monte-Carlo code ensuremath MCFOSTensuremath<?iensuremath> and the thermo-chemical code ensuremath ProDiMoensuremath<?iensuremath> to derive the gas and dust masses. We detect the ?O I? line at 63 ensuremathmum. The other lines that were observed, ?O I? at 145 ensuremathmum and ?C II? at 157 ensuremathmum, are not detected. No extended emission has been found. Preliminary modeling of the photometric and line data assuming ?ensuremath 12ensuremath<?supensuremath>CO? ??ensuremath 13ensuremath<?supensuremath>CO? = 69 suggests a dust mass for grains with radius ensuremath<1 mm of textttchar1261.9 $times$ 10ensuremath -4ensuremath<?supensuremath> Mensuremath ?ensuremath<?subensuremath> (total solid mass of 3 $times$ 10ensuremath -3ensuremath<?supensuremath> Mensuremath ?ensuremath<?subensuremath>) and a gas mass of (0.5?5) $times$ 10ensuremath -3ensuremath<?supensuremath> Mensuremath ?ensuremath<?subensuremath>. The gas-to-dust mass may be lower than the standard interstellar value of 100.Astronomy and Astrophysics. 518:L125?1-L125?6. -
Article: The Herschel view of GAS in Protoplanetary Systems (GASPS) First comparisons with a large grid of models
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Article: Herschel-PACS observation of the 10 Myr old T Tauri disk TW Hya Constraining the disk gas mass
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Article: The Herschel view of GAS in Protoplanetary Systems (GASPS). First comparisons with a large grid of models
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ABSTRACT: The Herschel GASPS key program is a survey of the gas phase of protoplanetary discs, targeting 240 objects which cover a large range of ages, spectral types, and disc properties. To interpret this large quantity of data and initiate self-consistent analyses of the gas and dust properties of protoplanetary discs, we have combined the capabilities of the radiative transfer code MCFOST with the gas thermal balance and chemistry code ProDiMo to compute a grid of ââ°Ë300 000 disc models (DENT). We present a comparison of the first Herschel/GASPS line and continuum data with the predictions from the DENT grid of models. Our objective is to test some of the main trends already identified in the DENT grid, as well as to define better empirical diagnostics to estimate the total gas mass of protoplanetary discs. Photospheric UV radiation appears to be the dominant gas-heating mechanism for Herbig stars, whereas UV excess and/or X-rays emission dominates for T Tauri stars. The DENT grid reveals the complexity in the analysis of far-IR lines and the difficulty to invert these observations into physical quantities. The combination of Herschel line observations with continuum data and/or with rotational lines in the (sub-)millimetre regime, in particular CO lines, is required for a detailed characterisation of the physical and chemical properties of circumstellar discs. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Astronomy and Astrophysics, v.518, id.L126 (2010).
