Stellar Populations in Bulges of Spiral Galaxies     

Pascale Jablonka  Javier Gorgas  Paul Goudfrooij 《Astrophysics and Space Science》2002,281(1-2):367-370

We present a few results of a work in progress tackling the radial spectroscopic properties of bulges of spiral galaxies. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献   

Exoplanet atmospheres with EChO: spectral retrievals using EChOSim     

Joanna K. Barstow  Neil E. Bowles  Suzanne Aigrain  Leigh N. Fletcher  Patrick G. J. Irwin  Ryan Varley  Enzo Pascale 《Experimental Astronomy》2015,40(2-3):545-561

We demonstrate the effectiveness of the Exoplanet Characterisation Observatory mission concept for constraining the atmospheric properties of hot and warm gas giants and super Earths. Synthetic primary and secondary transit spectra for a range of planets are passed through EChOSim [13] to obtain the expected level of noise for different observational scenarios; these are then used as inputs for the NEMESIS atmospheric retrieval code and the retrieved atmospheric properties (temperature structure, composition and cloud properties) compared with the known input values, following the method of [1]. To correctly retrieve the temperature structure and composition of the atmosphere to within 2 σ, we find that we require: a single transit or eclipse of a hot Jupiter orbiting a sun-like (G2) star at 35 pc to constrain the terminator and dayside atmospheres; 20 transits or eclipses of a warm Jupiter orbiting a similar star; 10 transits/eclipses of a hot Neptune orbiting an M dwarf at 6 pc; and 30 transits or eclipses of a GJ1214b-like planet.  相似文献   

Scheduling the EChO survey with known exoplanets     

J. C. Morales  J.-P. Beaulieu  V. Coudé du Foresto  M. Ollivier  I. Ortega Castello  R. Clédassou  J. Jaubert  P. Van-Troostenberghe  R. Varley  I. P. Waldmann  E. Pascale  M. Tessenyi 《Experimental Astronomy》2015,40(2-3):655-670

The Exoplanet Characterization Observatory (EChO) is a concept of a dedicated space telescope optimized for low-resolution transit and occultation spectroscopy to study the exoplanet diversity through the composition of their atmospheres. The scope of this paper is to answer the following question: Can we schedule a nominal EChO mission, with targets known today (in mid 2013), given the science requirements, realistic performances and operational constraints? We examine this issue from the point of view of duration of the mission and the scheduling restrictions with a sample of exoplanet systems known nowadays. We choose different scheduling algorithms taking into account the science and operational constraints and we verified that it is fairly straightforward to schedule a mission scenario over the lifetime of EChO compliant with the science requirements. We identified agility as a critical constraint that reduces significantly the efficiency of the survey. We conclude that even with known targets today the EChO science objectives can be reached in the 4.5 years duration of the mission. We also show that it is possible to use gaps between exoplanet observations, to fit the required calibration observations, data downlinks and station keeping operations or even to observe more exoplanet targets to be discovered in the coming years.  相似文献   

EChOSim: The Exoplanet Characterisation Observatory software simulator     

E. Pascale  I. P. Waldmann  C. J. MacTavish  A. Papageorgiou  A. Amaral-Rogers  R. Varley  V. Coudé du Foresto  M. J. Griffin  M. Ollivier  S. Sarkar  L. Spencer  B. M. Swinyard  M. Tessenyi  G. Tinetti 《Experimental Astronomy》2015,40(2-3):601-619

EChOSim is the end-to-end time-domain simulator of the Exoplanet Characterisation Observatory (EChO) space mission. EChOSim has been developed to assess the capability of the EChO mission concept to detect and characterise the atmospheres of transiting exoplanets. Here we discuss the details of the EChOSim implementation and describe the models used to represent the instrument and to simulate the detection. Software simulators have assumed a central role in the design of new instrumentation and in assessing the level of systematics affecting the measurements of existing experiments. Thanks to its high modularity, EChOSim can simulate basic aspects of several existing and proposed spectrometers including instruments on the Hubble Space Telescope and Spitzer, ground-based and balloon-borne experiments. A discussion of different uses of EChOSim is given, including examples of simulations performed to assess the EChO mission.  相似文献   

Triggering of El Niño by westerly wind events in a coupled general circulation model     

Matthieu?LengaigneEmail author  Eric?Guilyardi  Jean-Philippe?Boulanger  Christophe?Menkes  Pascale?Delecluse  Pete?Inness  Jeff?Cole  Julia?Slingo 《Climate Dynamics》2004,23(6):601-620

Two ten-members ensemble experiments using a coupled ocean-atmosphere general circulation model are performed to study the dynamical response to a strong westerly wind event (WWE) when the tropical Pacific has initial conditions favourable to the development of a warm event. In the reference ensemble (CREF), no wind perturbation is introduced, whereas a strong westerly wind event anomaly is introduced in boreal winter over the western Pacific in the perturbed ensemble (CWWE). Our results demonstrate that an intense WWE is capable of establishing the conditions under which a strong El Niño event can occur. First, it generates a strong downwelling Kelvin wave that generates a positive sea surface temperature (SST) anomaly in the central-eastern Pacific amplified through a coupled ocean-atmosphere interaction. This anomaly can be as large as 2.5°C 60 days after the WWE. Secondly, this WWE also initiates an eastward displacement of the warm-pool that promotes the occurrence of subsequent WWEs in the following months. These events reinforce the initial warming through the generation of additional Kelvin waves and generate intense surface jets at the eastern edge of the warm-pool that act to further shift warm waters eastward. The use of a ten-members ensemble however reveals substantial differences in the coupled response to a WWE. Whereas four members of CWWE ensemble develop into intense El Niño warming as described above, four others display a moderate warming and two remains in neutral conditions. This diversity between the members appears to be due to the internal atmospheric variability during and following the inserted WWE. In the four moderate warm cases, the warm-pool is initially shifted eastward following the inserted WWE, but the subsequent weak WWE activity (when compared to the strong warming cases) prevents to further shift the warm-pool eastwards. The seasonal strengthening of trade winds in June–July can therefore act to shift warm waters back into the western Pacific, reducing the central-eastern Pacific warming. This strong sensitivity of the coupled response to WWEs may therefore limit the predictability of El Niño events, as the high frequency wind variability over the warm pool region remains largely unpredictable even at short time lead.  相似文献   

Defining organominerals: Comment on ‘Defining biominerals and organominerals: Direct and indirect indicators of life’ by Perry et al. (2007, Sedimentary Geology, 201, 157–179)     

Christian Défarge  Pascale Gautret  Joachim Reitner  Jean Trichet 《Sedimentary Geology》2009,213(3-4):152-155

The paper by Perry et al. (2007, Defining biominerals and organominerals: Direct and indirect indicators of life, Sedimentary Geology, 201, 157–179) proposes to introduce “the new term ‘organomineral’” to describe mineral products whose formation is induced by by-products of biological activity, dead and decaying organisms, or nonbiological organic compounds, to be distinguished from the biomineral components of living organisms. The substantive ‘organomineral’, however, is not new: it was first introduced in 1993, with basically the same definition and distinction from biominerals, at the 7th International Symposium on Biomineralization (Défarge and Trichet, 1995, From biominerals to ‘organominerals’: The example of the modern lacustrine calcareous stromatolites from Polynesian atolls, Bulletin de l'Institut Océanographique de Monaco, n° spéc. 14, vol. 2, pp. 265–271). Thereafter, more than twenty-five papers by various authors have been devoted to organominerals and organomineral formation (‘organomineralization’) processes. Only two of these papers are cited by Perry et al., and without any reference to the definitions, or even the terms ‘organomineral’ or ‘organomineralization’, which they included. Moreover, Perry et al. tend to enlarge the original concept of organomineral to encompass all minerals containing organic matter, whether these organic compounds are active or passive in the mineralization, which introduces ambiguities detrimental to a fine understanding of present and past geobiological processes. Finally, Perry et al. propose to consider organominerals as indirect biosignatures that could be used in the search for evidence of life in the geological record and extraterrestrial bodies. This latter proposition also is problematical, in that organominerals may be formed in association with prebiotic or abiotic organic matter.  相似文献   

Ab initio quantum mechanical study of γ-AlOOH boehmite: structure and vibrational spectrum     

Yves Noel  Raffaella Demichelis  Fabien Pascale  Piero Ugliengo  Roberto Orlando  Roberto Dovesi 《Physics and Chemistry of Minerals》2009,36(1):47-59

The structure and vibrational spectrum of boehmite have been investigated at the quantum-mechanical level with the CRYSTAL code, using a Gaussian-type basis set and the B3LYP Hamiltonian. Three space groups are considered in this study: Cmcm, Cmc2₁, P2₁/c. Cmcm turns out to correspond to a transition state, whereas Cmc2₁ and P2₁/c are minimum energy structures. The difference among them is the position of H atoms only, the Al-O frame being essentially the same. Harmonic frequencies at the Γ point have been computed. The comparison between calculated and experimental frequencies shows a good agreement for the Al-O part of the spectrum (under 790 cm⁻¹). For the Al-OH bending modes (800–1,300 cm⁻¹) an absolute differences of 50–100 cm⁻¹ is observed; for the OH stretching modes (3,200–3,500 cm⁻¹) it increases to 120–200 cm⁻¹: anharmonicity is large because OH groups are involved in strong hydrogen bonds.  相似文献   

Long-term groundwater resource observatory for Southwestern Madagascar     

Simon D. Carrière  Thomas Health  Pascale F. M. Rakotomandrindra  Chloé Ollivier  Riva E. Rajaomahefasoa  Heritiana A. Rakoto  Jean Lapègue  Yves E. Rakotoarison  Marie Mangin  Jean Kempf  Théodore Razakamanana  Konstantinos Chalikakis 《水文研究》2021,35(3):e14108

Madagascar has one of the highest poverty rates in the world and consequently the long-term monitoring of groundwater resources is not a priority for the authorities. However, groundwater is often the only sustainable resource that has a satisfactory quality to supply the population. This is especially true in the south-west of the country, which is a semi-arid region and a global change hot spot (intense land use and climate changes). In response to the lack of data, the Groundwater Resource Observatory for Southwestern Madagascar (GROSoM) was established to monitor piezometry and meteorology over the longer term as part of a humanitarian response. The first site was setup in 2014 in a catchment located over a carbonate plateau; in 2018, a second site was installed in an alluvial setting within a crystalline basement catchment and a third site will be installed in 2020 to monitor groundwater dynamics in a coastal setting. The three sites, located between Toliara and Taolagnaro cities, are complementary and representative of various hydrogeological systems in Southwestern Madagascar. Each site includes a weather station and between 3 and 6 piezometric probes. The monitoring data indicate a strong inter-annual variability in precipitation, which induces a strong variability in aquifers recharge. One of the driest years in 2016 seems to be consistent with strong El Niño – Southern Oscillation (ENSO) effects observed at the global scale, while years with higher recharge appear to be related to cyclones such as Fundi in 2015 and Eketsang in 2019. Preliminary results of cross-disciplinary studies demonstrated a link between groundwater and health issues (i.e., admissions to basic health centres). This observatory aims to produce long-term data and has two objectives: (i) strengthening the early warning system for humanitarian crises in Madagascar; (ii) contributing to a better understanding of the effects of climate change on groundwater resources in this semi-arid region.  相似文献   

Critical evaluation of the customisation process of the UNDRR disaster resilience scorecard for cities to earthquake-induced soil liquefaction disaster events     

Jones  Keith  Pascale  Federica  Wanigarathna  Nadeeshani  Morga  Mariantonietta  Sargin  Sinan 《Bulletin of Earthquake Engineering》2021,19(10):4115-4143

Bulletin of Earthquake Engineering - As cities become larger and more densely populated the impacts of major earthquake events on city communities become more severe. Improving community resilience...  相似文献   

Time and Frequency Transfer Using GPS Codes and Carrier Phases: Onsite Experiments     

Carine Bruyninx  Pascale Defraigne  Jean-Marie Sleewaegen 《GPS Solutions》1999,3(2):1-10

Recent studies have shown the capabilities of Global Positioning System (GPS) carrier phases for frequency transfer based on the observations from geodetic GPS receivers driven by stable atomic clocks. This kind of receiver configuration is the kind primarily used within the framework of the International GPS Service (IGS). The International GPS Service/Bureau International des Poids et Mesures (IGS/BIPM) pilot project aims at taking advantage of these GPS receivers to enlarge the network of Time Laboratories contributing to the realization of the International Atomic Time (TAI). In this article, we outline the theory necessary to describe the abilities and limitations of time and frequency transfer using the GPS code and carrier phase observations. We report on several onsite tests and evaluate the present setup of our 12-channel IGS receiver (BRUS), which uses a hydrogen maser as an external frequency reference, to contribute to the IGS/BIPM pilot project. In the initial experimental setup, the receivers had a common external frequency reference; in the second setup, separate external frequency references were used. Independent external clock monitoring provided the necessary information to validate the results. Using two receivers with a common frequency reference and connected to the same antenna, a zero baseline, we were able to use the carrier phase data to derive a frequency stability of 6 × 10⁻¹⁶ for averaging times of one day. The main limitation in the technique originates from small ambient temperature variations of a few degrees Celsius. While these temperature variations have no effect on the functioning of the GPS receiver within the IGS network, they reduce the capacities of the frequency transfer results based on the carrier phase data. We demonstrate that the synchronization offset at the initial measurement epoch can be estimated from a combined use of the code and carrier phase observations. In our test, the discontinuity between two consecutive days was about 140 ps. ? 1999 John Wiley & Sons, Inc.  相似文献