1,721,047 research outputs found
Discovery of a hot, transiting, Earth-sized planet and a second temperate, non-transiting planet around the M4 dwarf GJ 3473 (TOI-488)
No full textDiscovery of a hot, transiting, Earth-sized planet and a second temperate, non-transiting planet around the M4 dwarf GJ 3473 (TOI-488)
No full textWe present the confirmation and characterisation of GJ 3473 b (G 50–16, TOI-488.01), a hot Earth-sized planet orbiting an M4 dwarf star, whose transiting signal ( P = 1.1980035 ± 0.0000018 d) was first detected by the Transiting Exoplanet Survey Satellite (TESS). Through a joint modelling of follow-up radial velocity observations with CARMENES, IRD, and HARPS together with extensive ground-based photometric follow-up observations with LCOGT, MuSCAT, and MuSCAT2, we determined a precise planetary mass, M b = 1.86 ± 0.30 M ⊕ , and radius, R b = 1.264 ± 0.050 R ⊕ . Additionally, we report the discovery of a second, temperate, non-transiting planet in the system, GJ 3473 c, which has a minimum mass, M c sin i = 7.41 ± 0.91 M ⊕ , and orbital period, P c = 15.509 ± 0.033 d. The inner planet of the system, GJ 3473 b, is one of the hottest transiting Earth-sized planets known thus far, accompanied by a dynamical mass measurement, which makes it a particularly attractive target for thermal emission spectroscopy
Reassessment of the putative habitable zone planet GJ 832c
No full textContext.
Gliese-832 (GJ 832) is an M2V star hosting a massive planet on a decade-long orbit, GJ 832b, discovered by radial velocity (RV). Later, a super Earth or mini-Neptune orbiting within the stellar habitable zone was reported (GJ 832c). The recently determined stellar rotation period (45.7 ± 9.3 days) is close to the orbital period of putative planet c (35.68 ± 0.03 days).
Aims.
We aim to confirm or dismiss the planetary nature of the RV signature attributed to GJ 832c, by adding 119 new RV data points, new photometric data, and an analysis of the spectroscopic stellar activity indicators. Additionally, we update the orbital parameters of the planetary system and search for additional signals.
Methods.
We performed a frequency content analysis of the RVs to search for periodic and stable signals. Radial velocity time series were modelled with Keplerians and Gaussian process (GP) regressions alongside activity indicators to subsequently compare them within a Bayesian framework.
Results.
We updated the stellar rotational period of GJ 832 from activity indicators, obtaining 37.5
+1.4
-1.5
days, improving the precision by a factor of 6. The new photometric data are in agreement with this value. We detected an RV signal near 18 days (FAP < 4.6%), which is half of the stellar rotation period. Two Keplerians alone fail at modelling GJ 832b and a second planet with a 35-day orbital period. Moreover, the Bayesian evidence from the GP analysis of the RV data with simultaneous activity indices prefers a model without a second Keplerian, therefore negating the existence of planet c
Discovery of a hot, transiting, Earth-sized planet and a second temperate, non-transiting planet around the M4 dwarf GJ 3473 (TOI-488)
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Stellar Activity or a Planet? Revisiting dubious planetary signals in M-dwarf systems
Full text linkGJ581, una estrella M3V, inicialmente se pensaba que albergaba seis planetas. Sin embargo, el periodo de rotación estelar recientemente determinado (132.3 ± 6.3 días), que es el doble y el cuádruple de los periodos orbitales de los dudosos planetas d (Porb : 66.8 días) y g (Porb: 36.5 días), respectivamente, introduce una incertidumbre respecto al origen de estas señales periódicas. Nuestro objetivo es confirmar o refutar la naturaleza planetaria de las señales de velocidad radial (RV) atribuidas a estos planetas analizando 718 puntos de datos de RV, que constituyen el conjunto de datos más extenso hasta la fecha, y los indicadores espectroscópicos de actividad estelar. Identificamos 4 señales periódicas mediante un análisis de frecuencias de las series temporales de: 5.37 d(planeta b), 12.9 d(planeta c), 66.3 d(planeta d), and 3.15 ¿(planeta e), que se modelan utilizando modelos Keplerianos, seguido de un análisis de estabilidad temporal que indica la presencia de una señal inducida por la actividad estelar con un período de 66.3 días. Para confirmar la naturaleza de esta señal periódica, debemos emplear un modelo kepleriano junto con procesos Gaussianos (GP) de manera simultánea. Adicionalmente, actualizamos el periodo de rotación estelar de GJ581 mediante un análisis de indicadores de actividad, empleando un modelo de GP, obteniendo un valor de Prot = 132 +1.82 -1.71 días, mejorando la precisión respecto al valor de la literatura.GJ581, an M3V star, was initially thought to harbor six planets.However, the recently determined stellar rotation period (132.3 ± 6.3 days), being twice and four times the orbital periods of putative planets d (Porb : 66.8 days) and g (Porb : 36.5 days), respectively, introduces uncertainty regarding the origin of these periodic signals. Our aim is to confirm or refute the planetary nature of the radial velocity (RV) signals attributed to these planets by analyzing 718 RV data points, constituting the most extensive dataset to date, and the spectroscopic stellar activity indicators. We identify four periodic signals by performing a frequency analysis on the RV timeseries: 5.37 d(planet b), 12.9 d(planet c), 66.3 d(planet d), and 3.15 d(planet e). The RVs are modeled using Keplerian models, followed by a temporal stability analysis, which indicates the 66.3 d signal is induced by stellar activity. To confirm the nature of this periodic signal, we must employ a simultaneous Keplerian and Gaussian Process (GP) model. Additionally, we update the stellar rotation period of GJ581 through an analysis of activity indicators, employing GP regression modeling, obtaining a value of Prot = 132 +1.82 -1.71 days, improving the accuracy compared to the literature value.Asociación Argentina de Astronomí
Variations on the Author
Full text link“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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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