3,191 research outputs found
SOAP-GPU code: Efficient Spectral Modelling of Stellar Activity Using Graphical Processing Units
No full textSOAP-GPU is a revised SOAP 2.0 code (Dumusque et al. 2014, ApJ, 796, 132) that simulate spectral time series with the effect of active regions (spot, faculae or both). In addition to the traditional outputs of SOAP 2.0 (the cross-correlation function and extracted parameters: radial velocity, bisector span, full width at half maximum), SOAP-GPU generates the integrated spectra at each phase for given input spectra and spectral resolution
A saga de um clã Xavier
Get PDFThe book brings together historical memories of the Xavier family, of which the author is a member, and includes everything from the heroic episode between members of the Xavier family and Lampião's gang, to a Xavier family tree and tributes to the members of this family, as well as photographic records of known members. The author rescues and preserves important memories of the family, reconstructing facts that, if told orally, could gradually be erased. The story told by Maria do Socorro Cardoso Xavier is also a way of preserving the memory of Ipueira, reporting on the social life and historical setting of the place, using family narrative.O livro reúne registros de memórias históricas da família Xavier, da qual a autora é membro,
e traz desde o episódio heróico entre membros da família Xavier e o bando de Lampião, à
uma árvore genealógica dos Xavier e homenagens aos membros dessa famílias, além de
registros fotográficos dos membros conhecidos. A autora resgata e preserva memórias
importantes da família, reconstituindo fatos que, contados oralmente, poderiam se apagar aos
poucos. A história narrada por Maria do Socorro Cardoso Xavier também é uma forma de
preservar a memória de Ipueira, relatando sobre a vida social e cenário histórico do lugar,
utilizando da narrativa familiar
Stellar noise and planet detection. I. Oscillations, granulation and sun-like spots
No full textAbstractSpectrographs like HARPS can now reach a sub-ms−1 precision in radial-velocity (RV) (Pepe & Lovis 2008). At this level of accuracy, we start to be confronted with stellar noise produced by 3 different physical phenomena: oscillations, granulation phenomena (granulation, meso- and super-granulation) and activity. On solar type stars, these 3 types of perturbation can induce ms−1 RV variation, but on different time scales: 3 to 15 minutes for oscillations, 15 minutes to 1.5 days for granulation phenomena and 10 to 50 days for activity. The high precision observational strategy used on HARPS, 1 measure per night of 15 minutes, on 10 consecutive days each month, is optimized, due to a long exposure time, to average out the noise coming from oscillations (Dumusque et al. 2011a) but not to reduce the noise coming from granulation and activity (Dumusque et al. 2011a and Dumusque et al. 2011b). The smallest planets found with this strategy (Mayor et al. 2009) seems to be at the limit of the actual observational strategy and not at the limit of the instrumental precision. To be able to find Earth mass planets in the habitable zone of solar-type stars (200 days for a K0 dwarf), new observational strategies, averaging out simultaneously all type of stellar noise, are required.</jats:p
Stellar noise and planet detection. I. Oscillations, granulation and sun-like spots
No full textSpectrographs like HARPS can now reach a sub-ms−1 precision in radial-velocity (RV) (Pepe & Lovis 2008). At this level of accuracy, we start to be confronted with stellar noise produced by 3 different physical phenomena: oscillations, granulation phenomena (granulation, meso- and super-granulation) and activity. On solar type stars, these 3 types of perturbation can induce ms−1 RV variation, but on different time scales: 3 to 15 minutes for oscillations, 15 minutes to 1.5 days for granulation phenomena and 10 to 50 days for activity. The high precision observational strategy used on HARPS, 1 measure per night of 15 minutes, on 10 consecutive days each month, is optimized, due to a long exposure time, to average out the noise coming from oscillations (Dumusque et al. 2011a) but not to reduce the noise coming from granulation and activity (Dumusque et al. 2011a and Dumusque et al. 2011b). The smallest planets found with this strategy (Mayor et al. 2009) seems to be at the limit of the actual observational strategy and not at the limit of the instrumental precision. To be able to find Earth mass planets in the habitable zone of solar-type stars (200 days for a K0 dwarf), new observational strategies, averaging out simultaneously all type of stellar noise, are require
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
The mass of Kepler-93b and the composition of terrestrial planets
Get PDFKepler-93b is a 1.478 ± 0.019 R ⊕ planet with a 4.7 day period around a bright (V = 10.2), astroseismically characterized host star with a mass of 0.911 ± 0.033 M ☉ and a radius of 0.919 ± 0.011 R ☉. Based on 86 radial velocity observations obtained with the HARPS-N spectrograph on the Telescopio Nazionale Galileo and 32 archival Keck/HIRES observations, we present a precise mass estimate of 4.02 ± 0.68 M ⊕. The corresponding high density of 6.88 ± 1.18 g cm–3 is consistent with a rocky composition of primarily iron and magnesium silicate. We compare Kepler-93b to other dense planets with well-constrained parameters and find that between 1 and 6 M ⊕, all dense planets including the Earth and Venus are well-described by the same fixed ratio of iron to magnesium silicate. There are as of yet no examples of such planets with masses >6 M ⊕. All known planets in this mass regime have lower densities requiring significant fractions of volatiles or H/He gas. We also constrain the mass and period of the outer companion in the Kepler-93 system from the long-term radial velocity trend and archival adaptive optics images. As the sample of dense planets with well-constrained masses and radii continues to grow, we will be able to test whether the fixed compositional model found for the seven dense planets considered in this paper extends to the full population of 1-6 M ⊕ planets.Peer reviewe
Precise and efficient modeling of stellar-activity-affected solar spectra using SOAP-GPU
No full textContext. One of the main obstacles in exoplanet detection when using the radial velocity (RV) technique is the presence of stellar activity signal induced by magnetic regions. As the most advanced techniques to mitigate this signal are reaching a level better than one meter per second, it is difficult to evaluate their performance: instrumental systematics start to be similar in magnitude, and therefore it is impossible to know the ground truth of the stellar activity signal. In this context, a realistic simulated dataset that can provide photometry and spectroscopic outputs is needed for method development.
Aims. The goal of this paper is to describe two realistic simulations of solar activity obtained from SOAP-GPU and to compare them with real data obtained from the HARPS-N solar telescope. For this purpose, both simulated spectral time series cover the time window of HARPS-N solar observation, but nothing prevents SOAP-GPU from modeling the data over different time spans.
Methods. We describe two different methods of modeling solar activity using SOAP-GPU. The first models the evolution of active regions based on the spot number as a function of time. Other physical parameters are either drawn from observed solar distributions or modeled with empirical relations. The second method relies on the extraction of active regions from the Solar Dynamics Observatory (SDO) data. The location of spots and faculae on the solar disk at each timestamp are derived from the magnetogram and intensity maps and are fed into SOAP-GPU to simulate the corresponding spectra.
Results. The simulated spectral time series generated with the first method shows a long-term RV behavior similar to that seen in the HARPS-N solar observations. The effect of stellar activity induced by stellar rotation is also well modeled with prominent periodicities at the stellar rotation period and its first harmonic. The comparison between the simulated spectral time series generated using SDO images and the HARPS-N solar spectra shows that SOAP-GPU can precisely model the RV time series of the Sun to a precision better than 0.9 m/s. By studying the width and depth variations of each spectral line in the HARPS-N solar and SOAP-GPU data, we find a strong correlation between the observation and the simulation for strong spectral lines, therefore supporting the modeling of the stellar activity effect at the spectral level. The correlations are weaker for shallow lines, although it is likely that their lower signal-to-noise ratio does not allow a meaningful comparison.
Conclusions. We introduce two methods for modeling solar activity using SOAP-GPU. With only sunspot numbers as input, we accurately capture the long-term magnetic cycle and rotational features. Additionally, we effectively model shift and depth variations at the spectral line level by using data from SDO. These simulated solar spectral time series serve as a useful test bed for evaluating spectral-level stellar activity mitigation techniques
Sir William Collins and Xavier Herbert
No full textSir William Collins, publisher and Xavier Herbert, author. Hand written comment about the photograph by Xavier Herbert on verso. [Gift of David Rowbotham
San Xavier District pedestrian access and safety study : final report
Get PDFabstract: The San Xavier District of the Tohono O’odham Nation is home to approximately 2,000 people. Numerous others come to the District to visit the San Xavier del Bac Mission Church. The San Xavier District Pedestrian Access and Safety Study is being prepared to improve the walking and bicycling environment on the San Xavier District for Community members and visitors alike. The study is being funded by the Arizona Department of Transportation Multimodal Planning Division’s Planning Assistance for Rural Areas program.Includes bibliographical references
Interview with Xavier Aldana Reyes
Get PDFXavier Aldana Reyes is Reader in English Literature and Film in Manchester, a founding member of the Manchester Centre for Gothic Studies, and the author of Spanish Gothic: National Identity, Collaboration and Cultural Adaptation (2017) and Gothic Cinema (2019). His publications in Gothic and horror studies include Twenty-First-Century Gothic: An Edinburgh Companion (with Maisha Wester; 2019), Horror: A Literary History (2016) and Digital Horror: Haunted Technologies, Network Panic and the Found Footage Phenomenon (with Linnie Blake; 2015). Aldana Reyes also edited fiction anthologies for the British Library series, Tales of the Weird, including the following titles: The Gothic Tales of H.P. Lovecraft (2018), The Weird Tales of William Hope Hodgson (2019), Promethean Horrors: Classic Tales of Mad Science (2019) and Roarings from Further Out: Four Weird Novellas, by Algernon Blackwood (2019)
- …
