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Radial velocity measurements showed evidence that the M dwarf GL 581 might host a planet, GL 581d, in the so-called habitable zone of the star. A study of Halpha in GL 581 demonstrated that changes in this activity indicator correlated with radial velocity variations attributed to GL 581d. An exopplanet that was important for studies of planet habitability may be an artifact of stellar activity. Previous investigations analyzing the same activity data have reached different conclusions regarding the existence of GL 581d. We therfore investigated the Halpha variations for GL 581 to assess the nature of the radial velocity variations attributed to the possible planet GL 581d. We performed a Fourier analysis of the published Halpha measurements for GL 581d using a so-called pre-whitening process to isolate the variations at the orbital frequency of GL 581d. The frequency analysis yields five significant frequencies, one of which is associated with the 66.7 d orbital period of the presumed planet Gl 581d. The Halpha variations at this period show sine-like variations that are 180 degrees out-of-phase with the radial velocity variations of GL 581d. This is seen in thefull data set that spans almost 7 years, as well as a subset of the data that had good temporal sampling over 230 days. Furthermore, No significant temporal variations are found in the ratio of the amplitudes of the Halpha index and radial velocity variations. This provides additional evidence that the radial velocity signal attributed to GL 581d is in fact due to stellar activity.
We present new evidence for a problem with cooling rates predicted by substellar evolutionary models that implies model-derived masses in the literature for brown dwarfs and directly imaged planets may be too high. Based on our dynamical mass for Gl
The planetary system around the M star Gliese 581 contains at least three close-in potentially low-mass planets, GL 581 c, d, and e. In order to address the question of the habitability of GL 581 d, we performed detailed atmospheric modeling studies
Recently, new debates about the role of layers of strong shear have emerged in stellar dynamo theory. Further information on the long-term magnetic activity of fully convective stars could help determine whether their underlying dynamo could sustain
Let $phi$ be a Hecke-Maass cusp form for $SL(3, mathbb{Z})$ with Langlands parameters $({bf t}_{i})_{i=1}^{3}$ satisfying $$|{bf t}_{3} - {bf t}_{2}| leq T^{1-xi -epsilon}, quad , {bf t}_{i} approx T, quad , , i=1,2,3$$ with $1/2 < xi <1$ and any $ep
Let $mathsf k$ be a local field. Let $I_ u$ and $I_{ u}$ be smooth principal series representations of $mathrm{GL}_n(mathsf k)$ and $mathrm{GL}_{n-1}(mathsf k)$ respectively. The Rankin-Selberg integrals yield a continuous bilinear map $I_ utimes I_{