6 research outputs found
The Belgian repository of fundamental atomic data and stellar spectra1
No full textBRASS is an international networking project of the Federal Government of Belgium for the development of a new public database providing accurate fundamental atomic data of vital importance for stellar spectroscopic research. The BRASS database will offer atomic line data that is thoroughly tested by comparing theoretical and observed stellar spectra. We are in the course of performing extensive quality assessments of selected atomic input data with advanced radiative transfer spectrum synthesis calculations that we compare in detail to high-resolution Mercator-HERMES and ESO-VLT-UVES spectra of very high signal-to-noise ratios for about 30 hot and cool bright stars of B, A, F, G, and K spectral types. The new database will provide the tested and validated values of absorption lines we retrieve from various existing atomic repositories, such as NIST and VAMDC. The validated atomic datasets, combined with the observed and theoretical spectra, will be interactively offered online at brass.sdf.org. The combination of these datasets is a novel approach for its development, which will provide a universal reference for advanced stellar spectroscopic research. We present the atmospheric parameter results of a subset of five benchmark stars observed with signal-to-noise ratios of 800-1200. The observed and theoretical spectra of the Sun and 51 Peg between 4000 and 6800 A are offered online in the BRASS Data Interface. It also incorporates a new list of ∼900 metal lines for which we compute blending below 5% of the equivalent width useful for detailed line profile modeling and synthetic spectrum fit quality assessments of atomic line data.SCOPUS: cp.jinfo:eu-repo/semantics/publishe
Herschel SPIRE and PACS observations of the red supergiant VY CMa: analysis of the molecular line spectra
No full textWe present an analysis of the far-infrared and submillimetre molecular emission-line spectrum of the luminous M-supergiant VY CMa, observed with the Spectral and Photometric Imaging Receiver (SPIRE) and Photodetector Array Camera and Spectrometer for Herschel spectrometers aboard the Herschel Space Observatory. Over 260 emission lines were detected in the 190-650 μm SPIRE Fourier Transform Spectrometer spectra, with one-third of the observed lines being attributable to H2O. Other detected species include CO, 13CO, H_2^{18}O, SiO, HCN, SO, SO2, CS, H2S and NH3. Our model fits to the observed 12CO and 13CO line intensities yield a 12C/13C ratio of 5.6 ± 1.8, consistent with measurements of this ratio for other M-supergiants, but significantly lower than previously estimated for VY CMa from observations of lower-J lines. The spectral line energy distribution for 20 SiO rotational lines shows two temperature components: a hot component at ˜1000 K, which we attribute to the stellar atmosphere and inner wind, plus a cooler ˜200 K component, which we attribute to an origin in the outer circumstellar envelope. We fit the line fluxes of 12CO, 13CO, H2O and SiO, using the SMMOL non-local thermodynamic equilibrium (LTE) line transfer code, with a mass-loss rate of 1.85 × 10-4 M⊙ yr-1 between 9R* and 350R*. We also fit the observed line fluxes of 12CO, 13CO, H2O and SiO with SMMOL non-LTE line radiative transfer code, along with a mass-loss rate of 1.85 × 10-4 M⊙ yr-1. To fit the high rotational lines of CO and H2O, the model required a rather flat temperature distribution inside the dust condensation radius, attributed to the high H2O opacity. Beyond the dust condensation radius the gas temperature is fitted best by an r-0.5 radial dependence, consistent with the coolant lines becoming optically thin. Our H2O emission-line fits are consistent with an ortho:para ratio of 3 in the outflow.sponsorship: SPIRE has been developed by a consortium of institutes led by Cardiff University (UK) and including University of Lethbridge (Canada); NAOC (China); CEA, LAM (France); IFSI, University of Padua (Italy); IAC (Spain); Stockholm Observatory (Sweden); Imperial College London, RAL, UCL-MSSL, UKATC, University of Sussex (UK); and Caltech, JPL, NHSC, University of Colorado (USA). This development has been supported by national funding agencies: CSA (Canada); NAOC (China); CEA, CNES, CNRS (France); ASI (Italy); MCINN (Spain); SNSB (Sweden); STFC and UKSA (UK); and NASA (USA). PACS has been developed by a consortium of institutes led by MPE (Germany) and including UVIE (Austria); KU Leuven, CSL, IMEC (Belgium); CEA, LAM (France); MPIA (Germany); INAF-IFSI/OAA/OAP/OAT, LENS, SISSA (Italy); IAC (Spain). This development has been supported by the funding agencies BMVIT (Austria), ESA-PRODEX (Belgium), CEA/CNES (France), DLR (Germany), ASI/INAF (Italy) and CICYT/MCYT (Spain). PvH acknowledges support from the Belgian Science Policy office through the ESA PRODEX programme. (CSA (Canada), NAOC (China), CEA (France), CNES (France), CNRS (France), ASI (Italy), MCINN (Spain), SNSB (Sweden), STFC, UKSA (UK), NASA (USA), BMVIT (Austria), ESA-PRODEX (Belgium), CEA/CNES (France), DLR (Germany), ASI/INAF (Italy), CICYT/MCYT (Spain), Belgian Science Policy office through the ESA PRODEX programme, Science and Technology Facilities Council|ST/M006948/1, Science and Technology Facilities Council|ST/M007618/1, Science and Technology Facilities Council|ST/J001511/1, Science and Technology Facilities Council|ST/K000373/1, STFC|ST/K000373/1, STFC|ST/M006948/1, STFC|ST/J001511/1, STFC|ST/M007618/1)status: Publishe
Herschel imaging of the dust in the Helix nebula (NGC 7293)
No full textAims: In our series of papers presenting the Herschel imaging of evolved planetary nebulae, we present images of the dust distribution in the Helix nebula (NGC 7293).
Methods: Images at 70, 160, 250, 350, and 500 μm were obtained with the PACS and SPIRE instruments on board the Herschel satellite.
Results: The broadband maps show the dust distribution over the main Helix nebula to be clumpy and predominantly present in the barrel wall. We determined the spectral energy distribution of the main nebula in a consistent way using Herschel, IRAS, and Planck flux values. The emissivity index of β = 0.99 ± 0.09, in combination with the carbon rich molecular chemistry of the nebula, indicates that the dust consists mainly of amorphous carbon. The dust excess emission from the central star disk is detected at 70 μm and the flux measurement agrees with previous measurement. We present the temperature and dust column density maps. The total dust mass across the Helix nebula (without its halo) is determined to be 3.5 × 10-3 M⊙ at a distance of 216 pc. The temperature map shows dust temperatures between 22 K and 42 K, which is similar to the kinetic temperature of the molecular gas, confirming that the dust and gas co-exist in high density clumps. Archived images are used to compare the location of the dust emission in the far infrared (Herschel) with the ionized (GALEX and Hβ) and molecular (H2) component. The different emission components are consistent with the Helix consisting of a thick walled barrel-like structure inclined to the line of sight. The radiation field decreases rapidly through the barrel wall.sponsorship: Herschel is an ESA space observatory with science instruments provided by European-ledinstruments provided by European-led Principal Investigator consortia and with important participation from NASA. PACS has been developed by a consortium of insitutes led by MPE (Germany) and including UVIE (Austria); KU leuven, CSL, IMEC (Belgium); CEA, LAM (France); MPIA (Germany); INAF-IFSI/OAA/OAP/OAT, LENS, SISSA (Italy); IAC (Spain). This development has been supported by the funding agencies BMVIT (Austria), ESA-PRODEX (Belgium). CEA/CNES (France), DLR (Germany), ASI/INAF (Italy), and CICYT/MCYT (Spain). SPIRE has been developed by a consortium of Institutes led by Cardiff Univeristy (UK) and including Univ. Lethbridge (Canada); NAOC (China); CEA, LAM (France); IFSI, Univ, Padua (Italy); IAC (Spain); Stockholm Observatory (Sweden); Imperial College London. RAL, UCL-MSSL, UKATC, Univ. Sussex (UK); and Caltech, JPL, NHSC, Univ, Colorado (USA). This development has been supported by national funding agencies: CSA (Canada): NAOC (China); CEA, CNES, CNRS (France); ASI (Italy); MCINN (Spain); SNSB (Sweden); STTC (UK); and NASA (USA). HCSS/HSpot/HIPE is a joint development (are joint developments) by the Herschel Science Ground Segment Consortium, consisting of ESA the NASA Herschel Science Center, and the HIFI, PACS and SPIRE consortia. This research made use of tools provided by http://asrometry.net/. Some of the data presented in this paper were obtained from the Multimission Archive at the Space Telescope Science Institute (MAST). STScl is operated by the Association of Univerisites for Research in Astronomy, Inc, under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX09AF08G and by other grants and contracts. P.v.H. and the PACS ICC in Leuven wish to acknowledge support from the Belgian Science Policy office through the ESA PRODEX programme. M.E. J.R.G and J.C thank the Spanish MINECO for funding support from grants CSD2009-00038, AYA2009-07304 and AYA2012-32032. (BMVIT (Austria), ESA-PRODEX (Belgium), CEA/CNES (France), DLR (Germany), ASI/INAF (Italy), CICYT/MCYT (Spain), CSA (Canada), NAOC (China), CEA, (France), CNES, (France), CNRS (France), ASI (Italy), MCINN (Spain), SNSB (Sweden), STTC (UK), NASA (USA), NASA|NAS5-26555, NASA Office of Space Science|NNX09AF08G, Belgian Science Policy office through the ESA PRODEX programme, Spanish MINECO|CSD2009-00038, Spanish MINECO|AYA2009-07304, Spanish MINECO|AYA2012-32032, STFC|ST/J001449/1, STFC|ST/M001334/1, STFC|ST/K000926/1, STFC|ST/N005856/1, STFC|ST/M007634/1, STFC|ST/M003019/1, STFC|ST/M001083/1, STFC|ST/J001511/1, STFC|ST/L003597/1, Science and Technology Facilities Council|ST/K000926/1, Science and Technology Facilities Council|ST/M007634/1, Science and Technology Facilities Council|ST/N005856/1, Science and Technology Facilities Council|ST/M003019/1, Science and Technology Facilities Council|ST/M001083/1, Science and Technology Facilities Council|ST/J001511/1, Science and Technology Facilities Council|ST/M001229/1, Science and Technology Facilities Council|ST/M001334/1, Science and Technology Facilities Council|ST/J001449/1)status: Publishe
Carbon monoxide in the cold debris of supernova 1987A
No full textWe report spectroscopic and imaging observations of rotational transitions of cold CO and SiO in the ejecta of SN1987A, the first such emission detected in a supernova remnant. In addition to line luminosities for the CO J = 1-0, 2-1, 6-5, and 7-6 transitions, we present upper limits for all other transitions up to J = 13-12, collectively measured from the Atacama Large Millimeter Array, the Atacama Pathfinder EXperiment, and the Herschel Spectral and Photometric Imaging REceiver. Simple models show the lines are emitted from at least 0.01 M-circle dot of CO at a temperature >14 K, confined within at most 35% of a spherical volume expanding at similar to 2000 km s(-1). Moreover, we locate the emission within 1 '' of the central debris. These observations, along with a partial observation of SiO, confirm the presence of cold molecular gas within supernova remnants and provide insight into the physical conditions and chemical processes in the ejecta. Furthermore, we demonstrate the powerful new window into supernova ejecta offered by submillimeter observations
A <i>Herschel</i> study of NGC 650
No full textAs part of the Herschel guaranteed time key project Mass loss of Evolved StarS (MESS) we have imaged a sample of planetary nebulae. In this paper we present the Photodetector Array Camera and Spectrometer (PACS) and Spectral and Photometric Imaging Receiver (SPIRE) images of the classical bipolar planetary nebula NGC 650. We used these images to derive a temperature map of the dust. We also constructed a photoionization and dust radiative transfer model using the spectral synthesis code Cloudy. To constrain this model, we used the PACS and SPIRE fluxes and combined them with hitherto unpublished International Ultraviolet Explorer (IUE) and Spitzer InfraRed Spectrograph (IRS) spectra as well as various other data from the literature. A temperature map combined with a photoionization model were used to study various aspects of the central star, the nebula, and in particular the dust grains in the nebula. The central star parameters are determined to be Teff = 208 kK and L = 261 L⊙ assuming a distance of 1200 pc. The stellar temperature is much higher than previously published values. We confirm that the nebula is carbon-rich with a C/O ratio of 2.1. The nebular abundances are typical for a type IIa planetary nebula. With the photoionization model we determined that the grains in the ionized nebula are large (assuming single-sized grains, they would have a radius of 0.15 μm). Most likely these large grains were inherited from the asymptotic giant branch phase. The PACS 70/160 μm temperature map shows evidence of two radiation components heating the grains. The first component is direct emission from the central star, while the second component is diffuse emission from the ionized gas (mainly Lyα). We show that previous suggestions of a photo-dissociation region surrounding the ionized region are incorrect. The neutral material resides in dense clumps inside the ionized region. These may also harbor stochastically heated very small grains in addition to the large grains.
Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Tables 2-5 are available in electronic form at http://www.aanda.orgsponsorship: We kindly thank Gerardo Ramos-Larios for making the H beta image of NGC 650 available to us. We thank Nicholas Lee for his invaluable help in interpreting the Chandra data and we thank the referee for his helpful comments. P. v. H. and the PACS ICC in Leuven wish to acknowledge support from the Belgian Science Policy office through the ESA PRODEX programme. PACS has been developed by a consortium of institutes led by MPE (Germany) and including UVIE (Austria); KU Leuven, CSL, IMEC (Belgium); CEA, LAM (France); MPIA (Germany); INAFIFSI /OAA /OAP /OAT, LENS, SISSA (Italy); IAC (Spain). This development has been supported by the funding agencies BMVIT (Austria), ESA-PRODEX (Belgium), CEA /CNES (France), DLR (Germany), ASI /INAF (Italy), and CICYT /MCYT (Spain). SPIRE has been developed by a consortium of institutes led by Cardiff Univ. (UK) and including: Univ. Lethbridge (Canada); NAOC (China); CEA, LAM (France); IFSI, Univ. Padua (Italy); IAC (Spain); Stockholm Observatory (Sweden); Imperial College London, RAL, UCL-MSSL, UKATC, Univ. Sussex (UK); and Caltech, JPL, NHSC, Univ. Colorado (USA). This development has been supported by national funding agencies: CSA (Canada); NAOC (China); CEA, CNES, CNRS (France); ASI (Italy); MCINN (Spain); SNSB (Sweden); STFC, UKSA (UK); and NASA (USA). Some of the data presented in this paper were obtained from the Multimission Archive at the Space Telescope Science Institute (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX09AF08G and by other grants and contracts. The IRS was a collaborative venture between Cornell University and Ball Aerospace Corporation funded by NASA through the Jet Propulsion Laboratory and Ames Research Center. This publication makes use of data products from theWide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. Data presented in this paper were analyzed using HIPE, a joint development by the Herschel Science Ground Segment Consortium, consisting of ESA, the NASA Herschel Science Center, and the HIFI, PACS, and SPIRE consortia. This research made use of tools provided by Astrometry.net. This research made use of the Atomic Line List available at http://www.pa.uky.edu/similar to peter/atomic. (Belgian Science Policy office through the ESA PRODEX programme, NASA|NAS5-26555, NASA Office of Space Science|NNX09AF08G, NASA through the Jet Propulsion Laboratory and Ames Research Center, National Aeronautics and Space Administration, STFC|ST/G002827/1, STFC|ST/J001511/1, STFC|ST/K000926/1, STFC|ST/J001449/1)status: Publishe
A Stubbornly Large Mass of Cold Dust in the Ejecta of Supernova 1987A
No full textWe present new Herschel photometric and spectroscopic observations of Supernova 1987A, carried out in 2012. Our dedicated photometric measurements provide new 70 mu m data and improved imaging quality at 100 and 160 mu m compared to previous observations in 2010. Our Herschel spectra show only weak CO line emission, and provide an upper limit for the 63 mu m [O-I] line flux, eliminating the possibility that line contaminations distort the previously estimated dustmass. The far-infrared spectral energy distribution (SED) is well fitted by thermal emission from cold dust. The newly measured 70 mu m flux constrains the dust temperature, limiting it to nearly a single temperature. The far-infrared emission can be fitted by 0.5 +/- 0.1M(circle dot) of amorphous carbon, about a factor of two larger than the current nucleosynthetic mass prediction for carbon. The observation of SiO molecules at early and late phases suggests that silicates may also have formed and we could fit the SED with a combination of 0.3M(circle dot) of amorphous carbon and 0.5M(circle dot) of silicates, totalling 0.8M(circle dot) of dust. Our analysis thus supports the presence of a large dust reservoir in the ejecta of SN 1987A. The inferred dust mass suggests that supernovae can be an important source of dust in the interstellar medium, from local to high-redshift galaxies.</p
