* Astronomy

Members Login

Post Info

TOPIC: 51 Ophiuchus

Blobrana

L

Posts: 131433

Date: Apr 25 00:43 2013

RE: 51 Ophiuchus	Permalink

Title: Nature of the gas and dust around 51 Oph Authors: W. F. Thi (1), F. Ménard (2 and 1), G. Meeus (3), A. Carmona (1), P. Riviere-Marichalar (4 and 3), J.-C. Augereau (1), I. Kamp (5), P. Woitke (6), C. Pinte (1), I. Mendigutía (7), C. Eiroa (3), B. Montesinos (3), S. Britain (7), W. Dent (8) ((1) UJF-Grenoble 1 / CNRS-INSU, IPAG, France, (2) UMI-LFCA, Universidad de Chile, Chile, (3) Dep Fisica Teorica, UAM, Spain, (4) CAB, Spain, (5) Kapteyn Astronomical Institute, NL, (6) SUPA, University of St-Andrews, UK, (7) Clemson University, USA, (8) ALMA, Chile) Circumstellar disc evolution is paramount for the understanding of planet formation. The GASPS program aims at determining the circumstellar gas and solid mass around ~250 pre-main-sequence Herbig Ae and TTauri stars. We aim to understand the origin and nature of the circumstellar matter orbiting 51 Oph, a young (<1 Myr) luminous B9.5 star. We obtained continuum and line observations with the PACS instrument on board the Herschel Space Observatory and continuum data at 1.2 mm with the IRAM 30m telescope. The SED and line fluxes were modelled using the physico-chemo radiative transfer code ProDiMo. We detected a strong emission by OI at 63 microns using the Herschel Space Observatory. The [OI] emission at 145 microns, the [CII] emission at 158 microns, the high-J CO emissions, and the warm water emissions were not detected. Continuum emission was detected at 1.2 mm. The continuum from the near- to the far-infrared and the [OI] emission are well explained by the emission from a compact hydrostatic disc model with a gas mass of 5E-6 solar masses, 100 times that of the solid mass. However, this model fails to match the continuum millimeter flux, which hints at a cold outer disc with a mass in solids of 1E-6 solar masses or free-free emission from a photoevaporative disc wind. This outer disc can either be devoid of gas and/or is to cold to emit in the [OI] line. A very flat extended disc model (Rout=400 AU) with a fixed vertical structure and dust settling matches all photometric points and most of the [O I] flux. The observations can be explained by an extended flat disc where dust grains have settled. However, a flat gas disc cannot be reproduced by hydrostatic disc models. The low mass of the 51 Oph inner disc in gas and dust may be explained either by the fast dissipation of an initial massive disc or by a very small initial disc mass. Read more (337kb, PDF) __________________

Blobrana

L

Posts: 131433

Date: Sep 24 22:33 2009

RE: 51 Ophiuchi	Permalink

Keck Interferometer Nuller Spots Double Dust Cloud Linking the twin, 10-meter telescopes in Hawaii, astronomers at the W. M. Keck Observatory discovered an extended, double-layered dust disk orbiting 51 Ophiuchi, a star that is 410 light-years from Earth. It is the first time the Keck Interferometer Nuller instrument has identified such a compact cloud around a star so far away. The new data suggest that 51 Ophiuchi is a protoplanetary system with a dust cloud that orbits extremely close to its parent star, said University of Maryland astronomer Christopher Stark, who led the research team. Read more __________________

Blobrana

L

Posts: 131433

Date: Sep 11 21:51 2009

51 Ophiuchus	Permalink

Title: 51 Ophiuchus: A Possible Beta Pictoris Analog Measured with the Keck Interferometer Nuller Authors: Christopher C. Stark, Marc J. Kuchner, Wesley A. Traub, John D. Monnier, Eugene Serabyn, Mark Colavita, Chris Koresko, Bertrand Mennesson, Luke D. Keller We present observations of the 51 Ophiuchi circumstellar disk made with the Keck interferometer operating in nulling mode at N-band. We model these data simultaneously with VLTI-MIDI visibility data and a Spitzer IRS spectrum using a variety of optically-thin dust cloud models and an edge-on optically-thick disk model. We find that single-component optically-thin disk models and optically-thick disk models are inadequate to reproduce the observations, but an optically-thin two-component disk model can reproduce all of the major spectral and interferometric features. Our preferred disk model consists of an inner disk of blackbody grains extending to ~4 AU and an outer disk of small silicate grains extending out to ~1200 AU. Our model is consistent with an inner "birth" disk of continually colliding parent bodies producing an extended envelope of ejected small grains. This picture resembles the disks around Vega, AU Microscopii, and Beta Pictoris, supporting the idea that 51 Ophiuchius may be a Beta Pictoris analogy. Read more (189kb, PDF) __________________

Blobrana

L

Posts: 131433

Date: Aug 3 16:05 2005

51 Ophiuchi	Permalink

Title: Observations of 51 Ophiuchi with MIDI at the VLTI Authors: C. Gil, F. Malbet, M. Schoeller, O. Chesneau and Ch. Leinert Researchers present interferometric observations of the Be star 51 Ophiuchi. These observations were obtained during the science demonstration phase of the MIDI instrument at the Very Large Telescope Interferometer (VLTI). Using MIDI, a Michelson 2 beam combiner that operates at the N band (8 - 13 microns), they obtained for the first time observations of 51 Ophiuchi in the mid-infrared at high-angular resolution. It is currently known that this object presents a circumstellar dust and gas disk that shows a very different composition from other Herbig Ae disks. The nature of the 51 Ophiuchi system is still a mystery to be solved. Does it have a companion? Is it a protoplanetary system? We still don't know. Observations with MIDI at the VLTI allowed them to reach high-angular resolution (20 mas). They report they have several uv points that allowed them to constrain the disk model. Theye have modelled 51 Oph visibilities and were able to constrain the size and geometry of the 51 Oph circumstellar disk. 51 Oph disk visibility model. The five visibility points (marked as crosses on the uv-track) were obtained in 2 different nights. The object 51 Ophiuchi (B9.5Ve) is often considered as a close analogue to Beta Pictoris. Its infrared excess is larger than that of Beta Pictoris. The optical spectrum reveals ionised circumstellar gas, and Ca, K lines suggest the presence of in falling bodies Read More (PDF, 121kb) __________________

Page 1 of 1 sorted by

Create your own FREE Forum
Report Abuse