DOCSLIB.ORG

Coronography at La Silla: High Resolution Imaging of Faint Features Near Bright Objects F

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Coronography at La Silla: High Resolution Imaging of Faint Features Near Bright Objects F Coronography at La Silla: High Resolution Imaging of Faint Features Near Bright Objects F. PARESCE and c. BURROWS, Space Telescope Science Institute, Baltimore, USA, and Astrophysics Division, Space Science Dept. of ESA Introduction of this article and available from the sponds to 5.10-3 square arcseconds in authors. the sky with a total rectangular field of Some of the more interesting as­ view of 22.5 by 35.9 arcseconds. tronomical sources happen to lie very The optical and detector system just close to bright objects. If the source is Experimental Setup described was calibrated absolutely us­ very faint, it becomes extremely difficult ing bright, stable stars as calibration to discern it against the glare of the The optical configuration of our ob­ sources. Using standard Johnson S, V, bright object. This situation arises, for servational setup at La Silla is shown and Rand Cousins I filters available at example, when attempting to image the schematically in Figure 1. Light from the La Silla (ESO filter numbers 445, 446, ionized tori around satellites such as 10, object under investigation is gathered 447 and 465), we obtained overall peak protoplanetary or circumstellar systems and focused by the f/8 MPI 2.2-metre counting efficiencies between 4,000 and of nearby stars, accretion disks within Cassegrain telescope onto a blackened 8,000 Aof 0.2 to 0.4 CCO counts per close binaries, faint emission photoetched mask located in the focal photon depending on bandpass. The nebulosities in the vicinity of old novae plane. This occulting mask is shaped in transmission of the achromatic doublet and possible fuzz around bright the form of a long thin wedge which can decreases rapidly below 4000 Aand is quasars. In all these cases, it is impera­ be moved longitudinally by a microme­ essentially opaque below 3500 A. Thus tive to reduce dramatically the scattered ter in order to vary its projected width in for U band measurements the lens light in the wings of the bright object the sky from 2 to 10 arcseconds de­ should be replaced by a singlet of fused seeing disk and/or to prevent the bright pending on seeing conditions, source quartz or silica and the detector object from saturating the detector and brightness, etc. It can also be moved changed to the UV sensitive GEC CCO thereby disabling it in the adjacent transversely to occult any desired por­ available at the 2.2 metre. areas. The latter effect can be important tion of the field of view. Following the even for relatively faint objects such as mask, an achromatic doublet reimages 15th magnitude quasars if long integra­ the telescope focal plane with a magnifi­ tion times are required. cation of 5 onto the detector so that the Observing Methodology Accomplishing this objective would effective focal ratio of the system be­ First, the coronograph is focused by open up a very fertile field of inquiry; one comes f/40. adjusting the position of the lens mount that is ideally suited to the performance An apodizing mask especially de­ until the image of the occulting wedge characteristics of modern high resolu­ signed to reduce diffracted stellar light under flat field illumination comes into tion, large aperture telescopes and de­ from the 2.2-metre telescope pupil is sharp focus. The coronograph comes tectors. Success requires a well-de­ located in the exit pupil and is rigidly equipped with internat LEOs to provide signed coronograph coupled to a high attached to the lens mount to ensure such illumination so that the focusing quality photon collecting device located that it remains there as the coronograph can be carried out even when the tele­ on a site with excellent seeing condi­ is focused. The mask obscures 30 per scope is not in operation. Second, a tions. This note briefly describes the cent of the exit pupil close to the images suitable star is made to fall somewhere techniques we have devised in our first of the entrance pupil edges. After this on the unocculted area of the detector attempts with a simple coronograph mask, the light passes through optical through a broad band filter and the re­ mated to the 2.2-metre MPI Cassegrain filters in a rotating commandable two­ sultant image is used to focus the tele­ telescope at La Silla and some of the wheel assembly mounted just in front of scope secondary. The coronograph results obtained in the first year of oper­ the detector. In our two runs of Sep­ need not be refocused if a filter is ation. A more complete description of tember and November 1986 at La Silla, changed since the filters are in an f/40 the experimental and data analysis we employed the 512 x 320 30 micron beam. Third, a suitably opaque neutral techniques and the scientific results can square pixels RCA CCO. In this particu­ density filter (N03 or 4) is moved into be found in the references at the end lar configuration, each pixel corre- the beam and the bright primary source acquired. Using the telescope TV autoguiding system described by Ouchateau and Tele~cope Coronagraph ~---- 1\ Ziebell in the Messenger No. 45, 1986, \ ( the source is placed behind the occult­ ing wedge in aseries of short acquisi­ tion exposures. With aseries of increas­ ingly smaller offsets, the source is pre­ ---- cisely centred behind the occulting wedge. This is accomplished by making the spillover light distribution above and below the wedge obtained with progres­ -- - sively less ND attenuation as symmetri­ cal as possible. Finally, any ND filter remaining is removed and the long ex­ 1: Optical-------configuration. Figure posure in the specified bandpass be- 43 set mainly by the time necessary to read ing. Gosmic ray events and local GGO out, process, and display the relevant defects are also located by comparison GGO acquisition images. A detector with neighbouring pixels using standard with real time display capabilities or a statistical tests and iterating to avoid faster data handling system for the GGO including bad pixels in the averaging would obviously shorten considerably process. Finally, the edges of the this set up period and allow a faster turn occulting mask are defined interactively around. This is a critical factor for a and stored in a file associated with the lengthy survey programme. image. No further user interaction is re­ quired in the subsequent processing which can proceed automatically. Data Analysis and Results The results of this process are shown All the raw images are processed in a in Figures 2 and 3 that represent images standard way to prepare them for scien­ of Beta and Alpha Pictoris, respectively, tific analysis. The GGO bias level and the taken with the system we have just de­ variations in response across the detec­ scribed with the R band filter on the tor area are removed by subtracting a night of November 27, 1986. Beta Pic­ constant bias level and dividing by an toris is a star suspected of having a appropriate flat field. Overclocked, satu­ giant protoplanetary system seen edge­ Figure 2: Image of Alpha Pictoris. The image rated pixels, and bad columns are easily on in emission surrounding the central has been flat fielded, and minor blemishes located and masked out so that they will star while Alpha Pictoris is used as the have been removed. The horizontal bar is the not contribute to the rest of the process- reference star. Both images are mainly occulting mask and has been masked black. The masked circular area in the centre with triangular appendages is due to saturated and bleeding pixels. The deviations from cir­ cular symmetry are due to instrumental scat­ tering and diffraction effects. The image is truncated at 5,000 counts, and has been displayed with the image greyscale changed to give equal numbers of pixels at any given intensity. (Histogram equalization.) gun. If a faint feature is expected to be lost in the light from the wings of the bright object seeing profile, the tele­ scope is moved to a control star nearby and the procedure just described re­ peated. After some practice, the over­ head time used to acquire and precisely register the source can be kept within approximately 20 minutes. This time is Figure 3: An image of Beta Pictoris with trun­ Figure 4: R band image of Beta Pictoris circumstellar disk .obtained as a difference image of cation at 3,000 counts. It is otherwise treated Figures 2 and 1. North is up and East is to the left. The image displayed is about 23 arcsec in identically to that of Figure 1. All instrumental width. The disk extr:mds diagonally from NE to Sw. The dWk portions of the image are due to effects are similar but there is an additional saturated pixels or the focal plane mask. The bright line rUlining vertically through the frame bulge in the image at bottom left (NE) through centre, and light close to the mask particularly to the right of centre are due to residual top right, due to the circumstellar disko diffractive scattering. 44 composed of the stellar seeing disk with small contributions due to scattering within the instrument and, of course, for Beta Pictoris, the circumstellar disko This feature, however, is almost lost in the image shown in Figure 2 without benefit of a direct comparison with the reference image shown in Figure 3. Although a feature running in a rough­ Iy NE to SW direction through the Beta Pic image, without a corresponding one to be discerned in the control image, stands out rather clearly in the image shown in Figure 2, considerably more analysis effort has to be expended in order to generate a photometrically true or correct image of the immediate surroundings of Beta Pictoris.
Load more

Recommended publications
  • Mathématiques Et Espace
    Atelier disciplinaire AD 5 Mathématiques et Espace Anne-Cécile DHERS, Education Nationale (mathématiques) Peggy THILLET, Education Nationale (mathématiques) Yann BARSAMIAN, Education Nationale (mathématiques) Olivier BONNETON, Sciences - U (mathématiques) Cahier d'activités Activité 1 : L'HORIZON TERRESTRE ET SPATIAL Activité 2 : DENOMBREMENT D'ETOILES DANS LE CIEL ET L'UNIVERS Activité 3 : D'HIPPARCOS A BENFORD Activité 4 : OBSERVATION STATISTIQUE DES CRATERES LUNAIRES Activité 5 : DIAMETRE DES CRATERES D'IMPACT Activité 6 : LOI DE TITIUS-BODE Activité 7 : MODELISER UNE CONSTELLATION EN 3D Crédits photo : NASA / CNES L'HORIZON TERRESTRE ET SPATIAL (3 ème / 2 nde ) __________________________________________________ OBJECTIF : Détermination de la ligne d'horizon à une altitude donnée. COMPETENCES : ● Utilisation du théorème de Pythagore ● Utilisation de Google Earth pour évaluer des distances à vol d'oiseau ● Recherche personnelle de données REALISATION : Il s'agit ici de mettre en application le théorème de Pythagore mais avec une vision terrestre dans un premier temps suite à un questionnement de l'élève puis dans un second temps de réutiliser la même démarche dans le cadre spatial de la visibilité d'un satellite. Fiche élève ____________________________________________________________________________ 1. Victor Hugo a écrit dans Les Châtiments : "Les horizons aux horizons succèdent […] : on avance toujours, on n’arrive jamais ". Face à la mer, vous voyez l'horizon à perte de vue. Mais "est-ce loin, l'horizon ?". D'après toi, jusqu'à quelle distance peux-tu voir si le temps est clair ? Réponse 1 : " Sans instrument, je peux voir jusqu'à .................. km " Réponse 2 : " Avec une paire de jumelles, je peux voir jusqu'à ............... km " 2. Nous allons maintenant calculer à l'aide du théorème de Pythagore la ligne d'horizon pour une hauteur H donnée.
    [Show full text]
  • Lurking in the Shadows: Wide-Separation Gas Giants As Tracers of Planet Formation
    Lurking in the Shadows: Wide-Separation Gas Giants as Tracers of Planet Formation Thesis by Marta Levesque Bryan In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy CALIFORNIA INSTITUTE OF TECHNOLOGY Pasadena, California 2018 Defended May 1, 2018 ii © 2018 Marta Levesque Bryan ORCID: [0000-0002-6076-5967] All rights reserved iii ACKNOWLEDGEMENTS First and foremost I would like to thank Heather Knutson, who I had the great privilege of working with as my thesis advisor. Her encouragement, guidance, and perspective helped me navigate many a challenging problem, and my conversations with her were a consistent source of positivity and learning throughout my time at Caltech. I leave graduate school a better scientist and person for having her as a role model. Heather fostered a wonderfully positive and supportive environment for her students, giving us the space to explore and grow - I could not have asked for a better advisor or research experience. I would also like to thank Konstantin Batygin for enthusiastic and illuminating discussions that always left me more excited to explore the result at hand. Thank you as well to Dimitri Mawet for providing both expertise and contagious optimism for some of my latest direct imaging endeavors. Thank you to the rest of my thesis committee, namely Geoff Blake, Evan Kirby, and Chuck Steidel for their support, helpful conversations, and insightful questions. I am grateful to have had the opportunity to collaborate with Brendan Bowler. His talk at Caltech my second year of graduate school introduced me to an unexpected population of massive wide-separation planetary-mass companions, and lead to a long-running collaboration from which several of my thesis projects were born.
    [Show full text]
  • Correlations Between the Stellar, Planetary, and Debris Components of Exoplanet Systems Observed by Herschel⋆
    A&A 565, A15 (2014) Astronomy DOI: 10.1051/0004-6361/201323058 & c ESO 2014 Astrophysics Correlations between the stellar, planetary, and debris components of exoplanet systems observed by Herschel J. P. Marshall1,2, A. Moro-Martín3,4, C. Eiroa1, G. Kennedy5,A.Mora6, B. Sibthorpe7, J.-F. Lestrade8, J. Maldonado1,9, J. Sanz-Forcada10,M.C.Wyatt5,B.Matthews11,12,J.Horner2,13,14, B. Montesinos10,G.Bryden15, C. del Burgo16,J.S.Greaves17,R.J.Ivison18,19, G. Meeus1, G. Olofsson20, G. L. Pilbratt21, and G. J. White22,23 (Affiliations can be found after the references) Received 15 November 2013 / Accepted 6 March 2014 ABSTRACT Context. Stars form surrounded by gas- and dust-rich protoplanetary discs. Generally, these discs dissipate over a few (3–10) Myr, leaving a faint tenuous debris disc composed of second-generation dust produced by the attrition of larger bodies formed in the protoplanetary disc. Giant planets detected in radial velocity and transit surveys of main-sequence stars also form within the protoplanetary disc, whilst super-Earths now detectable may form once the gas has dissipated. Our own solar system, with its eight planets and two debris belts, is a prime example of an end state of this process. Aims. The Herschel DEBRIS, DUNES, and GT programmes observed 37 exoplanet host stars within 25 pc at 70, 100, and 160 μm with the sensitiv- ity to detect far-infrared excess emission at flux density levels only an order of magnitude greater than that of the solar system’s Edgeworth-Kuiper belt. Here we present an analysis of that sample, using it to more accurately determine the (possible) level of dust emission from these exoplanet host stars and thereafter determine the links between the various components of these exoplanetary systems through statistical analysis.
    [Show full text]
  • The Brightest Stars Seite 1 Von 9
    The Brightest Stars Seite 1 von 9 The Brightest Stars This is a list of the 300 brightest stars made using data from the Hipparcos catalogue. The stellar distances are only fairly accurate for stars well within 1000 light years. 1 2 3 4 5 6 7 8 9 10 11 12 13 No. Star Names Equatorial Galactic Spectral Vis Abs Prllx Err Dist Coordinates Coordinates Type Mag Mag ly RA Dec l° b° 1. Alpha Canis Majoris Sirius 06 45 -16.7 227.2 -8.9 A1V -1.44 1.45 379.21 1.58 9 2. Alpha Carinae Canopus 06 24 -52.7 261.2 -25.3 F0Ib -0.62 -5.53 10.43 0.53 310 3. Alpha Centauri Rigil Kentaurus 14 40 -60.8 315.8 -0.7 G2V+K1V -0.27 4.08 742.12 1.40 4 4. Alpha Boötis Arcturus 14 16 +19.2 15.2 +69.0 K2III -0.05 -0.31 88.85 0.74 37 5. Alpha Lyrae Vega 18 37 +38.8 67.5 +19.2 A0V 0.03 0.58 128.93 0.55 25 6. Alpha Aurigae Capella 05 17 +46.0 162.6 +4.6 G5III+G0III 0.08 -0.48 77.29 0.89 42 7. Beta Orionis Rigel 05 15 -8.2 209.3 -25.1 B8Ia 0.18 -6.69 4.22 0.81 770 8. Alpha Canis Minoris Procyon 07 39 +5.2 213.7 +13.0 F5IV-V 0.40 2.68 285.93 0.88 11 9. Alpha Eridani Achernar 01 38 -57.2 290.7 -58.8 B3V 0.45 -2.77 22.68 0.57 144 10.
    [Show full text]
  • Assaj V1 N6 1925-Nov
    ~he dournal of tbe .astronomical Societ~ of South .africa. Vol. l. NOVEMBER, 1925. No.6. PRESENT.DAY PROBLEMS OF ASTRONOMY . • (PRESIDENTIAL ADDRESS, SESSION 1924-25.) By J. K. E. HALM, PH.D., F.R.A.S., F.R.S.E. The history of Astronomv during- the last three centuries is a record of continuous progress. Since the clays of Kepler and Newton no period can be pointed out when advance in one or other of its branches was entirelv suspended. But the centre of most rapid progress has shiftecl fronl time to time. It was natural, for instance, that the discovery of the law of gravita­ tion and its fundamental bearing on the motions of the bodies governed by the attractive force of the sun should lead. in the earlier days, to a concentration of efforts in the direction of establishing the dynamics of our solar system. Here was an inexhaustible field for the mathematician who by ever-increasing­ refinements in his analytical methods endeavoured ancl succeeded to account for the complex motions of the constituent members of our system as the manifestations of tnat one. still mys.terious, force called gravitation. This branch of astronomical science, as you know, held its sway predominantly up to the middle of last century. .... As an illustration of the state of astronomy in those early days, an introductory address circulated prior to the first meeting of the Royal Astronomical Society in 1820 contains the following paragraph :- "Beyond the limits of our svstem all at present is in obscurity. Some vast and general views on the con;;truc­ tion of the heaven and the laws which mav regulate the formation of sidereal systems have, it is true.
    [Show full text]
  • The 10 Parsec Sample in the Gaia Era?,?? C
    A&A 650, A201 (2021) Astronomy https://doi.org/10.1051/0004-6361/202140985 & c C. Reylé et al. 2021 Astrophysics The 10 parsec sample in the Gaia era?,?? C. Reylé1 , K. Jardine2 , P. Fouqué3 , J. A. Caballero4 , R. L. Smart5 , and A. Sozzetti5 1 Institut UTINAM, CNRS UMR6213, Univ. Bourgogne Franche-Comté, OSU THETA Franche-Comté-Bourgogne, Observatoire de Besançon, BP 1615, 25010 Besançon Cedex, France e-mail: [email protected] 2 Radagast Solutions, Simon Vestdijkpad 24, 2321 WD Leiden, The Netherlands 3 IRAP, Université de Toulouse, CNRS, 14 av. E. Belin, 31400 Toulouse, France 4 Centro de Astrobiología (CSIC-INTA), ESAC, Camino bajo del castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain 5 INAF – Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025 Pino Torinese (TO), Italy Received 2 April 2021 / Accepted 23 April 2021 ABSTRACT Context. The nearest stars provide a fundamental constraint for our understanding of stellar physics and the Galaxy. The nearby sample serves as an anchor where all objects can be seen and understood with precise data. This work is triggered by the most recent data release of the astrometric space mission Gaia and uses its unprecedented high precision parallax measurements to review the census of objects within 10 pc. Aims. The first aim of this work was to compile all stars and brown dwarfs within 10 pc observable by Gaia and compare it with the Gaia Catalogue of Nearby Stars as a quality assurance test. We complement the list to get a full 10 pc census, including bright stars, brown dwarfs, and exoplanets.
    [Show full text]
  • Seeing the Light: the Art and Science of Astronomy
    Chapter 1 Seeing the Light: The Art and Science of Astronomy In This Chapter ▶ Understanding the observational nature of astronomy ▶ Focusing on astronomy’s language of light ▶ Weighing in on gravity ▶ Recognizing the movements of objects in space tep outside on a clear night and look at the sky. If you’re a city dweller Sor live in a cramped suburb, you see dozens, maybe hundreds, of twin- kling stars. Depending on the time of the month, you may also see a full Moon and up to five of the eight planets that revolve around the Sun. A shooting star or “meteor” may appear overhead. What you actually see is the flash of light from a tiny piece of comet dust streaking through the upper atmosphere. Another pinpoint of light moves slowly and steadily across the sky. Is it a space satellite, such as the Hubble Space Telescope, or just a high-altitude airliner? If you have a pair of binoculars, you may be able to see the difference. Most air- liners have running lights, and their shapes may be perceptible. If you liveCOPYRIGHTED in the country — on the seashore MATERIAL away from resorts and develop- ments, on the plains, or in the mountains far from any floodlit ski slope — you can see thousands of stars. The Milky Way appears as a beautiful pearly swath across the heavens. What you’re seeing is the cumulative glow from millions of faint stars, individually indistinguishable with the naked eye. At a great observation place, such as Cerro Tololo in the Chilean Andes, you can see even more stars.
    [Show full text]
  • 1411 (Created: Wednesday, June 24, 2020 at 12:00:37 AM Eastern Standard Time) - Overview
    JWST Proposal 1411 (Created: Wednesday, June 24, 2020 at 12:00:37 AM Eastern Standard Time) - Overview 1411 - Coronagraphy of the Debris Disk Archetype Beta Pictoris Cycle: 1, Proposal Category: GTO INVESTIGATORS Name Institution E-Mail Dr. Christopher C. Stark (PI) Space Telescope Science Institute [email protected] Dr. Laurent Pueyo (CoI) Space Telescope Science Institute [email protected] Dr. Marshall Perrin (CoI) Space Telescope Science Institute [email protected] Dr. Remi Soummer (CoI) Space Telescope Science Institute [email protected] Dr. Matt Mountain (CoI) Space Telescope Science Institute [email protected] Abhijith Rajan (CoI) Space Telescope Science Institute [email protected] Dr. Mark Clampin (CoI) NASA Goddard Space Flight Center [email protected] OBSERVATIONS Folder Observation Label Observing Template Science Target Beta Pic with MIRI coronagraphs 1 Beta Pic - 2300 Lyot R MIRI Coronagraphic Imaging (1) BETA-PIC oll 1 2 Beta Pic - 1550 4QPM MIRI Coronagraphic Imaging (1) BETA-PIC Roll 1 3 Beta Pic - 1550 4QPM MIRI Coronagraphic Imaging (1) BETA-PIC Roll 2 4 Beta Pic - 2300 Lyot R MIRI Coronagraphic Imaging (1) BETA-PIC oll 2 5 Alpha Pic - 2300 Lyot MIRI Coronagraphic Imaging (2) ALPHA-PIC PSF 6 Alpha Pic - 1550 4QP MIRI Coronagraphic Imaging (2) ALPHA-PIC M PSF Beta Pic with NIRCam Coronagraphs 7 Alpha Pic - LW PSF NIRCam Coronagraphic Imaging (2) ALPHA-PIC 1 JWST Proposal 1411 (Created: Wednesday, June 24, 2020 at 12:00:37 AM Eastern Standard Time) - Overview Folder Observation Label Observing Template Science Target 8 Alpha Pic - SW PSF NIRCam Coronagraphic Imaging (2) ALPHA-PIC 10 Beta Pic - SW Roll 1 NIRCam Coronagraphic Imaging (1) BETA-PIC 11 Beta Pic - SW Roll 2 NIRCam Coronagraphic Imaging (1) BETA-PIC 12 Beta Pic - LW Roll 2 NIRCam Coronagraphic Imaging (1) BETA-PIC 13 Beta Pic - LW Roll 1 NIRCam Coronagraphic Imaging (1) BETA-PIC ABSTRACT The famous debris disk around Beta Pic was the first circumstellar disk to be spatially resolved.
    [Show full text]
  • An Unusually Large Gaseous Transit in a Debris Disc
    MNRAS 000,1{11 (2019) Preprint 11 October 2019 Compiled using MNRAS LATEX style file v3.0 An unusually large gaseous transit in a debris disc Daniela P. Iglesias1;2?, Johan Olofsson1;2, Amelia Bayo1;2, Sebastian Zieba3, Mat´ıas Montesinos1;2;4, Jonathan Smoker5, Grant M. Kennedy6, Nicol´as Godoy1;2, Blake Pantoja7, Geert Jan Talens8, Zahed Wahhaj5, and Catalina Zamora1;2 1Instituto de F´ısica y Astronom´ıa, Facultad de Ciencias, Universidad de Valpara´ıso, Av. Gran Breta~na 1111, 5030 Casilla, Valpara´ıso, Chile 2N´ucleo Milenio de Formaci´on Planetaria - NPF, Universidad de Valpara´ıso, Av. Gran Breta~na 1111, Valpara´ıso, Chile 3Universit¨at Innsbruck, Institut fur¨ Astro- und Teilchenphysik, Technikerstraße 25, 6020 Innsbruck, Austria 4Chinese Academy of Sciences South America Center for Astronomy, National Astronomical Observatories, CAS, Beijing 100012, China, 5European Southern Observatory, Alonso de C´ordova 3107, Vitacura, Santiago, Chile 6Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK 7Departamento de Astronom´ıa, Universidad de Chile, Camino el Observatorio 1515, Las Condes, Santiago, Chile, Casilla 36-D 8Institut de Recherche sur les Exoplan`etes, D´epartement de Physique, Universit´ede Montr´eal, Montr´eal, QC H3C 3J7, Canada Accepted XXX. Received YYY; in original form ZZZ ABSTRACT We present the detection of an unusually large transient gas absorption in several ionized species in the debris disc star HD 37306 using high-resolution optical spectra. We have been analysing a large sample of debris discs searching for circumstellar gas absorptions aiming to determine the frequency of gas in debris discs.
    [Show full text]
  • Correlations Between the Stellar, Planetary and Debris Components Of
    Astronomy & Astrophysics manuscript no. dunes˙debris˙exoplanets˙v18 c ESO 2018 September 3, 2018 Correlations between the stellar, planetary and debris components of exoplanet systems observed by Herschel Jonathan P. Marshall1,2,⋆, A. Moro-Mart´ın3,4, C. Eiroa1, G. Kennedy5, A. Mora6, B. Sibthorpe7, J.-F. Lestrade8, J. Maldonado1,9, J. Sanz-Forcada10, M.C. Wyatt5, B. Matthews11,12, J. Horner2,13,14, B. Montesinos10, G. Bryden15, C. del Burgo16, J.S. Greaves17, R.J. Ivison18,19, G. Meeus1, G. Olofsson20, G.L. Pilbratt21, and G.J. White22,23 (Affiliations can be found after the references) Received —; accepted — ABSTRACT Context. Stars form surrounded by gas and dust rich protoplanetary discs. Generally, these discs dissipate over a few (3–10) Myr, leaving a faint tenuous debris disc composed of second generation dust produced by the attrition of larger bodies formed in the protoplanetary disc. Giant planets detected in radial velocity and transit surveys of main sequence stars also form within the protoplanetary disc, whilst super-Earths now detectable may form once the gas has dissipated. Our own Solar system, with its eight planets and two debris belts is a prime example of an end state of this process. Aims. The Herschel DEBRIS, DUNES and GT programmes observed 37 exoplanet host stars within 25 pc at 70, 100 and 160 µm with the sensitiv- ity to detect far-infrared excess emission at flux density levels only an order of magnitude greater than that of the Solar system’s Edgeworth-Kuiper belt. Here we present an analysis of that sample, using it to more accurately determine the (possible) level of dust emission from these exoplanet host stars and thereafter determine the links between the various components of these exoplanetary systems through statistical analysis.
    [Show full text]
  • The Messenger
    THE MESSENGER ( , New Meteorite Finds At Imilac No. 47 - March 1987 H. PEDERSEN, ESO, and F. GARe/A, elo ESO Introduction hand, depend more on the preserving some 7,500 meteorites were recovered Stones falling from the sky have been conditions of the terrain, and the extent by Japanese and American expeditions. collected since prehistoric times. They to which it allows meteorites to be spot­ They come from a smaller, but yet un­ were, until recently, the only source of ted. Most meteorites are found by known number of independent falls. The extraterrestrial material available for chance. Active searching is, in general, meteorites appear where glaciers are laboratory studies and they remain, too time consuming to be of interest. pressed up towards a mountain range, even in our space age, a valuable However, the blue-ice fields of Antarctis allowing the ice to evaporate. Some source for investigation of the solar sys­ have proven to be a happy hunting have been Iying in the ice for as much as tem's early history. ground. During the last two decades 700,000 years. It is estimated that, on the average, each square kilometre of the Earth's surface is hit once every million years by a meteorite heavier than 500 grammes. Most are lost in the oceans, or fall in sparsely populated regions. As a result, museums around the world receive as few as about 6 meteorites annually from witnessed falls. Others are due to acci­ dental finds. These have most often fallen in prehistoric times. Each of the two groups, 'falls' and 'finds', consists of material from about one thousand catalogued, individual meteorites.
    [Show full text]
  • Spectrally Resolved Helium Absorption from the Extended Atmosphere of a Warm Neptune-Mass Exoplanet
    Title: Spectrally resolved helium absorption from the extended atmosphere of a warm Neptune-mass exoplanet Authors: R. Allart1*, V. Bourrier1, C. Lovis1, D. Ehrenreich1, J.J. Spake2, A. Wyttenbach1,3, L. Pino1,4,5, F. Pepe1, D.K. Sing2,6, A. Lecavelier des Etangs7 Affiliations: 1Observatoire Astronomique de l’Université de Genève, Université de Genève, Chemin des Maillettes 51, 1290 Versoix, SwitZerland. 2 Astrophysics Group, School of Physics, University of Exeter, Stocker Road, Exeter, EX4 4QL, UK. 3 Leiden Observatory, Leiden University, Postbus 9513, 2300 RA Leiden, The Netherlands 4 Dipartimento di Fisica e Astronomia ‘Galileo Galilei’, Univ. di Padova, Vicolo dell’Osservatorio 3, Padova I-35122, Italy 5 Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands 6Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD, USA. 7Institut d’Astrophysique de Paris, CNRS, UMR 7095, Sorbonne Université, 98 bis boulevard Arago, F-75014, Paris, France *[email protected] 1 Abstract: Stellar heating causes atmospheres of close-in exoplanets to expand and escape. These extended atmospheres are difficult to observe because their main spectral signature – neutral hydrogen at ultraviolet wavelengths – is strongly absorbed by interstellar medium. We report the detection of the near-infrared triplet of neutral helium in the transiting warm Neptune-mass exoplanet HAT-P-11b using ground-based, high-resolution observations. The helium feature is repeatable over two independent transits, with an average absorption depth of 1.08±0.05%. Interpreting absorption spectra with 3D simulations of the planet’s upper atmosphere suggests it extends beyond 5 planetary radii, with a large scale height and a helium mass loss rate ≲ 3´105 g‧s−1.
    [Show full text]