Abstract
LTT 1445 is a hierarchical triple M-dwarf star system located at a distance of 6.86 pc. The primary star LTT 1445A (0.257
M
⊙
) is known to host the transiting planet LTT 1445Ab with an ...orbital period of 5.36 days, making it the second-closest known transiting exoplanet system, and the closest one for which the host is an M dwarf. Using Transiting Exoplanet Survey Satellite data, we present the discovery of a second planet in the LTT 1445 system, with an orbital period of 3.12 days. We combine radial-velocity measurements obtained from the five spectrographs, Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations, High Accuracy Radial Velocity Planet Searcher, High-Resolution Echelle Spectrometer, MAROON-X, and Planet Finder Spectrograph to establish that the new world also orbits LTT 1445A. We determine the mass and radius of LTT 1445Ab to be 2.87 ± 0.25
M
⊕
and
1.304
−
0.060
+
0.067
R
⊕
, consistent with an Earth-like composition. For the newly discovered LTT 1445Ac, we measure a mass of
1.54
−
0.19
+
0.20
M
⊕
and a minimum radius of 1.15
R
⊕
, but we cannot determine the radius directly as the signal-to-noise ratio of our light curve permits both grazing and nongrazing configurations. Using MEarth photometry and ground-based spectroscopy, we establish that star C (0.161
M
⊙
) is likely the source of the 1.4 day rotation period, and star B (0.215
M
⊙
) has a likely rotation period of 6.7 days. We estimate a probable rotation period of 85 days for LTT 1445A. Thus, this triple M-dwarf system appears to be in a special evolutionary stage where the most massive M dwarf has spun down, the intermediate mass M dwarf is in the process of spinning down, while the least massive stellar component has not yet begun to spin down.
2021 ApJ 922 30 We present the discovery of 32 new double periodic variables (DPVs) located
toward the Galactic bulge. We found these objects among the nearly half a
million binary stars published by ...the Optical Gravitational Lensing Experiment
project. With this discovery, we increase the number of known DPVs in the Milky
Way by a factor of 2. The new set of DPVs contains 31 eclipsing binaries and
one ellipsoidal variable star. The orbital periods cover the range from 1.6 to
26 days, while long periods are detected between 47 and 1144 days. Our analysis
confirms a known correlation between orbital and long periods that is also
observed in similar systems in the Magellanic Clouds.
Abridged: We measured photometric and spectroscopic \(P_{\rm rot}\) for a large sample of nearby bright M dwarfs with spectral types from M0 to M9, as part of our continual effort to fully ...characterize the Guaranteed Time Observation programme stars of the CARMENES survey. We determine \(P_{\rm rot}\) for 129 stars. Combined with the literature, we tabulate \(P_{\rm rot}\) for 261 stars, or 75% of our sample. We evaluate the plausibility of all periods available for this sample by comparing them with activity signatures and checking for consistency between multiple measurements. We find that 166 of these stars have independent evidence that confirmed their \(P_{\rm rot}\). There are inconsistencies in 27 periods, which we classify as debated. A further 68 periods are identified as provisional detections that could benefit from independent verification. We provide an empirical relation for the \(P_{\rm rot}\) uncertainty as a function of the \(P_{\rm rot}\) value, based on the dispersion of the measurements. We show that published formal errors seem to be often underestimated for periods \(\gtrsim 10\) d. We highlight the importance of independent verification on \(P_{\rm rot}\) measurements, especially for inactive M dwarfs. We examine rotation-activity relations with emission in X-rays, H\(\alpha\), Ca II H & K, and surface magnetic field strengths. We find overall agreement with previous works, as well as tentative differences in the partially versus fully convective subsamples. We show \(P_{\rm rot}\) as a function of stellar mass, age, and galactic kinematics. With the notable exception of three transiting planet systems and TZ Ari, all known planet hosts in this sample have \(P_{\rm rot} \gtrsim 15\) d. This indicates that important limitations need to be overcome before the radial velocity technique can be routinely used to detect and study planets around young and active stars.
We present the discovery of 32 new double periodic variables (DPVs) located toward the Galactic bulge. We found these objects among the nearly half a million binary stars published by the Optical ...Gravitational Lensing Experiment project. With this discovery, we increase the number of known DPVs in the Milky Way by a factor of 2. The new set of DPVs contains 31 eclipsing binaries and one ellipsoidal variable star. The orbital periods cover the range from 1.6 to 26 days, while long periods are detected between 47 and 1144 days. Our analysis confirms a known correlation between orbital and long periods that is also observed in similar systems in the Magellanic Clouds.
Introducción: La peritonitis es una de las complicaciones más frecuentes y graves asociadas a la diálisis peritoneal (DP), siendo la primera causa de pérdida de catéter y de finalización de la ...técnica. La incidencia y etiología de cada episodio varía en función de cada región y evoluciona a lo largo del tiempo. Por esta razón, es de vital importancia conocer los factores de riesgo y pronósticos de peritonitis en cada momento. Métodos: Se realizó un estudio observacional de cohorte, multicéntrico, prospectivo, con un seguimiento máximo de 7 años (2003-2010) que incluyó 1177 pacientes, con 476 episodios de primera peritonitis (total: 1091 peritonitis). Resultados: Se presenta la descripción de las características del primer episodio de peritonitis en una serie amplia y actual. Los factores que se asociaron a un menor tiempo hasta la primera peritonitis en análisis multivariante fueron la comorbilidad cardiovascular previa (hazard ratio HR 1,25 1,04-1,58), la procedencia de hemodiálisis (HR 1,39 1,10-1,76) o trasplante renal previo (HR 1,38 1,10-1,93), iniciar DP con técnica manual (HR 1,39 1,13-1,73) y la edad de inicio > 70 años (HR 1,53 1,23-1,90). El primer episodio de peritonitis presenta una tasa de recidiva del 7,8 %, retirada de catéter del 11,7 % y una mortalidad en el primer mes tras el episodio del 1,3 %. La evolución de la peritonitis depende fundamentalmente del tipo de germen. Se estima un riesgo mayor para gramnegativos (odds ratio OR 5,31 2,26-12,48) y el agregado de peritonitis polimicrobianas, por hongos o por micobacterias (OR 38,24 13,84-105,63), comparados con la referencia de grampositivos. Conclusión: El desarrollo del primer episodio de peritonitis depende de las características del paciente al inicio de diálisis, la comorbilidad y la técnica utilizada. Los pacientes que presentan mayor riesgo deben recibir una atención especial en los procesos de entrenamiento y seguimiento.
