98 research outputs found

    Using a model for telluric absorption in full-spectrum fits

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    The typical approach for removing telluric absorption lines from a science spectrum is to divide it by the spectrum of a standard star of spectral type A or B observed close in time and airmass. We present a new method, where we use a model for the transmission of the Earth's atmosphere in a full-spectrum fit, which determines the parameters for the stellar and Earth's atmosphere simultaneously. This eliminates the need of a standard star completely.Comment: 4 pages, 3 figures, International Workshop on Stellar Spectral Libraries 201

    Obstrucción microvascular derivada de la resonancia margnética cardiaca tras un infarto miocárdico con elevación del ST –asociación con marcadores de necrosis cardiaca y cambios del segmento ST

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    Este trabajo, que se dividió en tres partes, pretendió determinar la asociación entre la obstrucción microvascular (MVO) estimada mediante resonancia magnética cardiaca (RMC) con determinados marcadores ampliamente disponibles en el contexto del infarto agudo de miocardio con elevación del segmento-ST (IAMCEST). La RMC permite una exhaustiva evaluación de los pacientes con IAMCEST. En este sentido, la aparición de MVO ha mostrado ser un factor asociado a episodios cardiovasculares adversos mayores y remodelado negativo tras un IAMCEST. En la primera parte de este trabajo, pretendimos explorar la asociación entre el sumatorio de las derivaciones con ST elevado (sum-ST) y la resolución del segmento ST con la presencia de MVO. Se observó que el sum-ST determinado a los 90 minutos tras la reperfusión mediante angioplastia primaria fue el parámetro más intensamente asociado a la MVO. En una segunda etapa, determinamos la asociación entre la liberación de los marcadores de necrosis miocárdica (troponina, creatin kinasa y mioglobina) con la aparición de MVO tras un IAMCEST. Con respecto a este punto, observamos una mayor liberación plasmática de marcadores de necrosis en los pacientes con MVO; concretamente, la troponina fue el marcador que mas inmensamente asociado a la MVO. Finalmente, pretendimos evaluar el valor de parámetros clínicos habituales determinados al ingreso para predecir MVO. Así, desarrollamos una puntuación simple de riesgo que incluyó variables clínicas y electrocardiográficas, todas ellas de fácil adquisición en el momento del ingreso.This work is divided into 3 parts and assesses the association of cardiovascular magnetic resonance (CMR)-derived microvascular obstruction (MVO) with readily available biomarkers after ST-elevation myocardial infarction (STEMI). CMR allows for a comprehensive assessment of patients with STEMI. Out of a wide range of myocardial infarction parameters especially MVO has emerged as a strong predictor of adverse outcome in terms of major adverse cardiovascular events and adverse remodeling after STEMI. In the first part the association of ST-segment changes, especially the sum of STsegment elevation and ST-segment resolution, with MVO is investigated. There was a strong relationship of ST-segment changes with the presence of MVO. The sum of ST-segment elevation at 90 minutes after reperfusion via primary percutaneous coronary intervention was the ECG parameter most strongly associate with MVO. The second part of this work investigates the association of cardiac necrosis markers, in detail troponin, creatine kinase and myoglobin, with the occurrence of MVO after STEMI. We found a larger release of cardiac necrosis markers in patients with MVO. Troponin was the cardiac necrosis marker, which possessed the strongest predictive capability for MVO. Finally, we sought to determine the predictive value of parameters available on patient admission for the prediction of MVO in STEMI. A simple score was constructed using only clinical and ECG variables, which are the timeliest available variables, on patient admission

    The central dynamics of M3, M13, and M92: Stringent limits on the masses of intermediate-mass black holes

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    We used the PMAS integral field spectrograph to obtain large sets of radial velocities in the central regions of three northern Galactic globular clusters: M3, M13, and M92. By applying the novel technique of crowded field 3D spectroscopy, we measured radial velocities for about 80 stars within the central ~ 10 arcsec of each cluster. These are by far the largest spectroscopic datasets obtained in the innermost parts of these clusters up to now. To obtain kinematical data across the whole extent of the clusters, we complement our data with measurements available in the literature. We combine our velocity measurements with surface brightness profiles to analyse the internal dynamics of each cluster using spherical Jeans models, and investigate whether our data provide evidence for an intermediate-mass black hole in any of the clusters. The surface brightness profiles reveal that all three clusters are consistent with a core profile, although shallow cusps cannot be excluded. We find that spherical Jeans models with a constant mass-to-light ratio provide a good overall representation of the kinematical data. A massive black hole is required in none of the three clusters to explain the observed kinematics. Our 1sigma (3sigma) upper limits are 5300 M_sun (12000 M_sun) for M3, 8600 M_sun (13000 M_sun) for M13, and 980 M_sun (2700 M_sun) for M92. A puzzling circumstance is the existence of several potential high velocity stars in M3 and M13, as their presence can account for the majority of the discrepancies that we find in our mass limits compared to M92.Comment: accepted for publication in A&A, 20 pages, 15 figures, tables D1 to D6 only available at CD

    Discovery of an old nova remnant in the Galactic globular cluster M 22

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    A nova is a cataclysmic event on the surface of a white dwarf in a binary system that increases the overall brightness by several orders of magnitude. Although binary systems with a white dwarf are expected to be overabundant in globular clusters (GCs) compared to the Galaxy, only two novae from Galactic globular clusters have been observed. We present the discovery of an emission nebula in the Galactic globular cluster M 22 (NGC 6656) in observations made with the integral-field spectrograph MUSE. We extract the spectrum of the nebula and use the radial velocity determined from the emission lines to confirm that the nebula is part of NGC 6656. Emission-line ratios are used to determine the electron temperature and density. It is estimated to have a mass of 1 to 17×10517 \times 10^{-5} solar masses. This mass and the emission-line ratios indicate that the nebula is a nova remnant. Its position coincides with the reported location of a 'guest star', an ancient Chinese term for transients, observed in May 48 BCE. With this discovery, this nova may be one of the oldest confirmed extrasolar events recorded in human history.Comment: 7 pages, 3 figures; accepted for publication in Astronomy & Astrophysic

    Kinematic differences between multiple populations in Galactic globular clusters

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    The formation process of multiple populations in globular clusters is still up for debate. Kinematic differences between the populations are particularly interesting in this respect, because they allow us to distinguish between single-epoch formation scenarios and multi-epoch formation scenarios. We analyze the kinematics of 25 globular clusters and aim to find kinematic differences between multiple populations to constrain their formation process. We split red-giant branch (RGB) stars in each cluster into three populations (P1, P2, P3) for the type-II clusters and two populations (P1 and P2) otherwise using Hubble photometry. We derive the rotation and dispersion profiles for each cluster and its populations by using all stars with radial velocity measurements obtained from MUSE spectroscopy. Based on these profiles, we calculate the rotation strength in terms of ordered-over-random motion (v/σ)HL\left(v/\sigma\right)_\mathrm{HL} evaluated at the half-light radius of the cluster. We detect rotation in all but four clusters. For NGC~104, NGC~1851, NGC~2808, NGC~5286, NGC~5904, NGC~6093, NGC~6388, NGC~6541, NGC~7078 and NGC~7089 we also detect rotation for P1 and/or P2 stars. For NGC~2808, NGC~6093 and NGC~7078 we find differences in (v/σ)HL\left(v/\sigma\right)_\mathrm{HL} between P1 and P2 that are larger than 1σ1\sigma. Whereas we find that P2 rotates faster than P1 for NGC~6093 and NGC~7078, the opposite is true for NGC~2808. However, even for these three clusters, the differences are still of low significance. We find that the strength of rotation of a cluster generally scales with its median relaxation time. For P1 and P2, the corresponding relation is very weak at best. We observe no correlation between the difference in rotation strength between P1 and P2 and cluster relaxation time. The MUSE stellar radial velocities that this analysis is based on are made publicly available

    Hazy with a chance of star spots: constraining the atmosphere of the young planet, K2-33b

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    Although all-sky surveys have led to the discovery of dozens of young planets, little is known about their atmospheres. Here, we present multi-wavelength transit data for the super Neptune-sized exoplanet, K2-33b -- the youngest (~10 Myr) transiting exoplanet to-date. We combined photometric observations of K2-33 covering a total of 33 transits spanning >2 years, taken from K2, MEarth, Hubble, and Spitzer. The transit photometry spanned from the optical to the near-infrared (0.6-4.5μ\mum), enabling us to construct a transmission spectrum of the planet. We find that the optical transit depths are nearly a factor of two deeper than those from the near-infrared. This difference holds across multiple datasets taken over years, ruling out issues of data analysis and unconstrained systematics. Surface inhomogeneities on the young star can reproduce some of the difference, but required spot coverage fractions (>60%) are ruled out by the observed stellar spectrum(<20%). We find a better fit to the transmission spectrum using photochemical hazes, which were predicted to be strong in young, moderate-temperature, and large-radius planets like K2-33b. A tholin haze with CO as the dominant gaseous carbon carrier in the atmosphere can reasonably reproduce the data with small or no stellar surface inhomogeneities, consistent with the stellar spectrum. The HST data quality is insufficient for the detection of any molecular features. More observations would be required to fully characterize the hazes and spot properties and confirm the presence of CO suggested by current data.Comment: Accepted to AJ. 26 pages, 14 figures, 6 table
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