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  • 04. Solid Earth::04.08. Volcanology::04.08.01. Gases  (21)
  • 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring  (13)
  • Astronomy
  • J24
  • 2005-2009  (39)
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  • 1
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    Effects of Dust Growth and Settling in T Tauri Disks (2006)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: We presented self-consistent disk models of T Tauri stars that include a parameterized treatment of dust settling and grain growth, building on techniques developed in a series of papers by D'Alessio et al. The models incorporate depleted distributions of dust in upper disk layers along with larger sized particles near the disk midplane, which are expected theoretically and, as we suggested earlier, are necessary to account for millimeter-wave emission, SEDs, scattered light images, and silicate emission features simultaneously. By comparing the models with recent mid- and near-IR observations, we find that the dust-to-gas mass ratio of small grains at the upper layers should be less than 10% of the standard value. The grains that have disappeared from the upper layers increase the dust-to-gas mass ratio of the disk interior; if those grains grow to maximum sizes of the order of millimeters during the settling process, then both the millimeter-wave fluxes and spectral slopes can be consistently explained. Depletion and growth of grains can also enhance the ionization of upper layers, increasing the possibility of the magnetorotational instability for driving disk accretion.
    Schlagwort(e): Astronomy
    Materialart: The Astrophysical Journal; 638; 1; 314-335
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Why Do T Tauri Disks Accrete? (2006)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Observations of T Tauri stars and young brown dwarfs suggest that the accretion rates of their disks scales roughly with the square of the central stellar mass. No dependence of accretion rate on stellar mass is predicted by the simplest version of the Gammie layered disk model, in which nonthermal ionization of upper disk layers allows accretion to occur via the magnetorotational instability. We show that a minor modification of Gaminie's model to include heating by irradiation from the central star yields a modest dependence of accretion on the mass of the central star. A purely viscous disk model could provide a strong dependence of accretion rate on stellar mass if the initial disk radius (before much viscous evolution has occurred) has a strong dependence on stellar mass. However, it is far from clear that at least the most massive pre-main-sequence disks can be totally magnetically activated by X-rays or cosmic rays. We suggest that a combination of effects are responsible for the observed dependence, with the lowest mass stars having the lowest mass disks, which can be thoroughly magnetically active, while the higher mass stars have higher mass disks that have layered accret,ion and relatively inactive or "dead" central zones at some radii. In such dead zones, we suggest that gravitational instabilities may play a role in allowing accretion to proceed. In this connection, we emphasize the uncertainty in disk masses derived from dust emission and argue that T Tauri disk masses have been systematically underestimated by conventional analyses. Furtlier study of accretion rates, especially in the lowest mass stars, would help to clarify the mechanisms of accretion in T Tauri stars.
    Schlagwort(e): Astronomy
    Materialart: The Astrophysical Journal; 648; 1; 484-490
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 3
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    Disks in Transition in the Taurus Population: Spitzer IRS Spectra of GM Aurigae and DM Tauri (2005)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: We presented Spitzer Infrared Spectrograph (IRS) observations of two objects of the Taurus population that show unambiguous signs of clea,ring in their inner disks. In one of the objects, DM Tau, the outer disk is truncated at 3 AU; this object is akin to another recently reported in Taurus, CoKu Tau/4, in that the inner disk region is free of small dust. Unlike CoKu Tau/4, however, this star is still accreting, so optically thin gas should still remain in the inner disk region. The other object, GM Aur, also accreting, has about 0.02 lunar masses of small dust in the inner disk region within about 5 AU, consistent with previous reports. However, the IRS spectrum clearly shows that the optically thick outer disk has an inner truncation at a much larger radius than previously suggested, of order 24 AU. These observations provide strong evidence for the presence of gaps in protoplanetary disks.
    Schlagwort(e): Astronomy
    Materialart: The Astrophysical Journal; 630; 2; L185 - L188
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 4
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    The Accretion Disk of the Lithium-Depleted Young Binary St 34 (2005)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: We presented the infrared spectrum of the young binary system St 34 obtained with the Infrared Spectrograph (IRS) on the Spitzer Space Telescope. The IRS spectrum clearly shows excess dust emission, consistent with the suggestion of White & Hillenbrand that St 34 is accreting from a circumbinary disk. The disk emission of St 34 is low in comparison with the levels observed in typical T Tauri stars; silicate features at 10 and 20 microns are much weaker than typically seen in T Tauri stars; and excess emission is nearly absent at the shortest wavelengths observed. These features of the infrared spectrum suggest substantial grain growth (to eliminate silicate features) and possible settling of dust to the disk midplane (to reduce the continuum excess emission levels), along with a relatively evacuated inner disk, as expected due to gravitational perturbations by the binary system. Although the position of St 34 in the H-R diagram suggests an age of 8f Myr, assuming that it lies at the distance of the Taurus-Auriga molecular clouds, White & Hillenbrand could not detect any Li I absorption, which would indicate a Li depletion age of roughly 25 Myr or more. We suggest that St 34 is closer than the Taurus clouds by about 30-40 pc and has an age roughly consistent with Li depletion models. Such an advanced age would make St 34 the oldest known low-mass pre-main-sequence object with a dusty accretion disk. The persistence of optically thick dust emission well outside the binary orbit may indicate a failure to make giant planets that could effectively remove dust particles.
    Schlagwort(e): Astronomy
    Materialart: The Astrophysical Journal; 628; 2; L147 - L150
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 5
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    Disk Evolution in Cep OB2: Results from the Spitzer Space Telescope (2006)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: We presented the results of an infrared imaging survey of Tr 37 and NGC 7160 using the IRAC and MIPS instruments on board the Spitzer Space Telescope. Our observations cover the wavelength range from 3.6 to 24 microns, allowing us to detect disk emission over a typical range of radii 0.1 to 20 AU from the central star. In Tr 37, with an age of about 4 Myr, about 48% of the low-mass stars exhibit detectable disk emission in the IRAC bands. Roughly 10% of the stars with disks may be "transition" objects, with essentially photospheric fluxes at wavelengths i 4.5 microns but with excesses at longer wavelengths, indicating an optically thin inner disk. The median optically thick disk emission in Tr 37 is lower than the corresponding median for stars in the younger Taurus region; the decrease in infrared excess is larger at 6-8 microns than at 24 microns, suggesting that grain growth and/or dust settling has proceeded faster at smaller disk radii, as expected on general theoretical grounds. Only about 4% of the low-mass stars in the 10 Myr old cluster NGC 7160 show detectable infrared disk emission. We also find evidence for 24 micron excesses around a few intermediate-mass stars, which may represent so-called "debris disk" systems. Our observations provided new constraints on disk evolution through an important age range.
    Schlagwort(e): Astronomy
    Materialart: The Astrophysical Journal; 638; 897-919
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 6
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    INGV Broad Band Ocean Bottom Seismometers deployed in the Ionian Sea (2008)
    Details
    Publikationsdatum: 2017-04-04
    Beschreibung: In May 2007, within the monitoring activities carried out in cooperation with the Italian National Civil Protection Department (DPC) and European NERIES project (activity NA6), INGV has deployed three Broad Band Ocean Bottom Seismometers in the southern Ionian Sea at 3500/4000 meters of depth. The OBS’s are equipped with a Nanometrics Trillium 120p seismometer, a Cox-Webb Differential Pressure Gauge and a 21 bits SEND Geolon-MLS digitizer. The three OBS’s, entirely developed at the Gibilmanna Geophysical Observatory of the INGV National Earthquake Center (CNT), are part of a pool of eight ready to deploy instruments and they are the first Italian OBS’s taking part in a long term experiment: two of them will be recovered by February 2008, whereas the third, in the deep Ionian Sea, will be replaced every year, until May 2010, to accomplish the continuous long-term seismic monitoring task of the EU NERIES project. The area selected for the deployment is a region of high scientific interest for several reasons: i) there are no seismological data on the structure of the Ionian lithosphere; ii) the level and features of the seismicity of the area between the Hyblean-Malta fault system and the accretionary prism of the Calabrian Arc are unknown. This experiment allows us to test the pressure waves detection system that will be implemented in the Tsunami Warning System INGV is developing within the IOC-UNESCO “NEAMTWS” (North-East Atlantic, Mediterranean and connected seas Tsunami Warning System). In this poster we describe the technical features and the performance of the OBS’s, the deployment campaign, and some seismic data recorded.
    Beschreibung: Published
    Beschreibung: Vienna
    Beschreibung: 2.5. Laboratorio per lo sviluppo di sistemi di rilevamento sottomarini
    Beschreibung: open
    Schlagwort(e): Ocean Bottom Seismometer ; OBS ; OBS/H ; Ionian Sea ; Greece ; Seismic monitoring ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: Poster session
    Standort Signatur Erwartet Verfügbarkeit
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    ARTIKEL (OA)
  • 7
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    Task 4 - Garda - Deliverables D14-D15: Stima degli effetti di sito (2007)
    Details
    Publikationsdatum: 2021-01-27
    Beschreibung: Nell’area del Garda, gli effetti di sito sono stati valutati in modo speditivo, utilizzando le informazioni geologiche e geomorfologiche di superficie insieme a misure di rumore ambientale. Dove possibile, sono stati utilizzati anche dati e informazioni disponibili dagli studi di rischio sismico della Regione Lombardia-CNR (1996). Le misure di rumore sono state effettuate nei quattro comuni prescelti: Vobarno, Salò, Toscolano Maderno e Gardone Riviera. Inoltre è stata condotta una campagna di misure lungo la Val Sabbia, dove sono stati rilevati i maggiori danni. Nel comune di Gardone Riviera è stata selezionata un’area rappresentativa dell’intero versante che va da questo comune fino a Gargnano, caratterizzato da depositi eluviali sovrastanti calcari stratificati. Come area rappresentativa dei conoidi detritici, presenti in vari comuni del lago, deposti lungo il fronte del sovrascorrimento e immergenti nel lago di Garda, è stato selezionato l’abitato di Toscolano Maderno. L’area di Vobarno si trova su depositi alluvionali recenti e terrazzati del fiume Chiese, mentre Salò è ubicatosu depositi morenici di spessore significativo (massimo un centinaio di metri) su cui poggiano depositi alluvioniali recenti. Lo scopo di questo studio è la classificazione dei suoli secondo la normativa italiana (Ordinanza PCM 3274; 2003 e Norme tecniche per le costruzioni; D.M. 14/09/05) attraverso l’utilizzo congiunto delle informazioni geologiche e della frequenza di risonanza dei depositi, calcolata attraverso i rapporti spettrali della componente orizzontale e verticale del rumore ambientale. Inoltre si è verificato se esistesse una correlazione fra dati di intensità risentita durante l’evento del 24 Novembre 2004 e le condizioni di sito, individuate utlizzando informazioni geologiche.
    Beschreibung: Progetto INGV-DPC S3 “Scenari di scuotimento in aree di interesse prioritario e/o strategico” (coord. F.Pacor e M.Mucciarelli).
    Beschreibung: Published
    Beschreibung: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Beschreibung: open
    Schlagwort(e): site effects ; microtremor analysis ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: report
    Standort Signatur Erwartet Verfügbarkeit
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    ARTIKEL (OA)
  • 8
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    Terremoti con effetti macrosismici in Sicilia orientale nel periodo Gennaio 2002 - Dicembre 2005 (2007)
    Istituto Nazionale di Geofisica e Vulcanologia
    Details
    Publikationsdatum: 2020-11-20
    Beschreibung: Il presente lavoro è costituito dalla raccolta sistematica delle indagini macrosismiche eseguite in occasione dei terremoti più energetici verificatisi in Sicilia orientale dal Gennaio 2002 al Dicembre 2005. Esso rappresenta l’estensione, agli anni più recenti, della compilazione effettuata per il periodo 1999-2001 [Azzaro et al., 2002], e più in generale è inserita nel contesto delle attività di pronto intervento macrosismico effettuate regolarmente in ambito regionale dal 1988. L’esecuzione di rilievi in occasione di eventi sismici significativi è una prassi ormai consolidata nelle attività di monitoraggio dell’INGV, che recentemente ha istituito a tal fine il gruppo di lavoro denominato QUEST (QUick Earthquake Survey Team, DP n° 44 del 25/02/2004). I dati raccolti assolvono ad una duplice funzione: 1) nell’immediatezza di un evento sismico, a definire il quadro degli effetti a supporto degli interventi di Protezione Civile e della Comunità Scientifica; 2) a risolvere lacune e problemi interpretativi dei terremoti del passato attraverso il confronto con gli effetti macrosismici degli eventi attuali. La raccolta sistematica di dati macrosismici anche nel caso di eventi di bassa magnitudo, che interessano estensioni areali limitate come quelle etnee, è comunque importante per l’implementazione di banche dati e cataloghi macrosismici sia a livello locale che nazionale. Nel primo caso è stato aggiornato il catalogo macrosismico dei terremoti etnei [Azzaro et al., 2000], recentemente reso disponibile anche su Internet. Nel secondo caso, la più recente versione del catalogo parametrico dei terremoti italiani [Gruppo di Lavoro CPTI, 2004] utilizzata per la redazione della nuova mappa di pericolosità sismica del territorio nazionale (Ordinanza PCM 3274 del 20/03/2003), incorpora i dati dei terremoti siciliani al di sopra della soglia del danno pubblicati in Azzaro et al. [2002, 2003]. I rilievi macrosismici di seguito riportati sono relativi a tutti i terremoti oltre la soglia del danno verificatisi nel periodo considerato, ovvero a quegli eventi che sono stati avvertiti in modo significativo dalla popolazione (Figura 1). In larga parte si tratta di eventi di area etnea che, soprattutto nel corso del 2002, hanno provocato effetti macrosismici di rilievo. Tra i terremoti regionali riportati, non è incluso il terremoto di Palermo del 2002 per il quale è disponibile uno studio specifico [Azzaro et al., 2003].
    Beschreibung: Published
    Beschreibung: 1-62
    Beschreibung: 1.11. TTC - Osservazioni e monitoraggio macrosismico del territorio nazionale
    Beschreibung: N/A or not JCR
    Beschreibung: open
    Schlagwort(e): NONE ; Sicilia ; terremoti ; macrosismica ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring ; 05. General::05.02. Data dissemination::05.02.02. Seismological data
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
    Format: 4332185 bytes
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    ARTIKEL (OA)
  • 9
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    MACROMAP: Una Utility per MAPINFO™ per la georeferenziazione di dati macrosismici e la loro rappresentazione cartografica (2008)
    INGV
    Details
    Publikationsdatum: 2021-03-01
    Beschreibung: Questo lavoro presenta una utility per il GIS MapInfo™ sviluppata per l'archiviazione ed elaborazione dei dati macrosismici dalla fase di georeferenziazione fino al plottaggio finale su mappa. L'identificazione della località associata con un'osservazione macrosismica è un'operazione che talvolta può causare errori ed in seguito problemi nell'analisi ed interpretazione dei dati. La routine MacroMap fornisce uno strumento che in modo semplice e veloce aiuti nell'identificazione della corretta località a cui attribuire l'informazione macrosismica durante lo studio di un terremoto. L'utility è strutturata per utilizzare il formato della directory geografica DIR04 e le procedure adottate nella compilazione del DataBase Macrosismico Italiano DBMI04. MacroMap è stata sperimentata "sul campo" durante alcune indagini macrosismiche e tiene conto dell'esperienza e dei suggerimenti degli operatori del Gruppo QUEST (QUick Earthquake Survey Team). I campi di utilizzo di MacroMap vanno dalla realizzazione speditiva di mappe e tabelle per la produzione di report macrosismici per la Protezione Civile, alla revisione di terremoti storici, grazie all'avanzato sistema di query disponibile per la selezione dei toponimi del database geografico.
    Beschreibung: Published
    Beschreibung: 1-21
    Beschreibung: 5.1. TTC - Banche dati e metodi macrosismici
    Beschreibung: N/A or not JCR
    Beschreibung: open
    Schlagwort(e): Osservazioni macrosismiche ; 04. Solid Earth::04.06. Seismology::04.06.05. Historical seismology ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring ; 05. General::05.02. Data dissemination::05.02.02. Seismological data
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    ARTIKEL (OA)
  • 10
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    Changes in eruptive style during the A.D. 1538 Monte Nuovo eruption (Phlegrean Fields, Italy): the role of syn-eruptive crystallization (2005)
    Springer
    Details
    Publikationsdatum: 2017-04-04
    Beschreibung: The Monte Nuovo eruption is the most recent event that occurred at Phlegrean Fields (Italy) and lasted from 29 September to 6 October 1538. It was characterized by 2 days of quasi-sustained phreatomagmatic activity generating pumice-bearing pyroclastic density currents and forming a 130-m-high tuff cone (Lower Member deposits). The activity resumed after a pause of 2 days with two discrete Vulcanian explosions that emplaced radially distributed, scoria-bearing pyroclastic flows (Upper Member deposits). The juvenile products of Lower and Upper Members are, respectively, phenocryst-poor, light-coloured pumice and dark scoria fragments with K-phonolitic bulk compositions, identical in terms of both major and trace elements. Groundmass is formed by variable proportions of K-feldspar and glass, along with minor sodalite and Fe-Ti oxide present in the most crystallized samples. Investigations of groundmass compositions and textures were performed to assess the mechanisms of magma ascent, degassing and fragmentation along the conduit and implications for the eruptive dynamics. In pumice of the Lower Member groundmass crystal content increases from 13 to 28 vol% from the base to the top of the sequence. Products of the Upper Member consist of clasts with a groundmass crystal content between 30 and 40 vol% and of totally crystallized fragments. Crystal size distributions of groundmass feldspars shift from a single population at the base of the Lower Member to a double population in the remaining part of the sequence. The average size of both populations regularly increases from the Lower to the Upper Member. Crystal number density increases by two orders of magnitude from the Lower to the Upper Member, suggesting that nucleation dominated during the second phase of the eruption. The overall morphological, compositional and textural data suggest that the juvenile components of the Monte Nuovo eruption are likely to record variations of the magma properties within the conduit. The different textures of pumice clasts from the Lower Member possibly reflect horizontal gradients of the physical properties (P, T) of the ascending magma column, while scoriae from the second phase are thought to result from the disruption of a slowly rising plug crystallizing in response to degassing. In particular, crystal size distribution data point to syn-eruptive degassing-induced crystallization as responsible for the transition in eruptive style from the first to the second phase of the eruption. This mechanism not only has been proved to profoundly affect the dynamics of dome-forming calc-alkaline eruptions, but may also have a strong influence in driving the eruption dynamics of alkaline magmas of intermediate to evolved compositions.
    Beschreibung: Published
    Beschreibung: 601-621
    Beschreibung: reserved
    Schlagwort(e): Phlegrean Fields ; Vulcanian explosion ; Degassing ; Groundmass crystallization ; Eruption dynamics ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.02. Experimental volcanism ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
    Format: 1175329 bytes
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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    ARTIKEL (OA)
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