Determinación de la masa y la distancia en cuarenta nebulosas planetarias

Se desarrolla una expresión matemática para calcular la masa de nebulosas planetarias ópticamen te delgadas en el continuo de Lyman Se adopta una ecuación directa para encontrar las distancias. Se discute la determinación del factor de porosidad. Finalmenre, se calculan las masas, distancias y radios de cuarenta nebulosas planetarias seleccionadas. Se hacen comparaciones con otros autores

Masa, distancia y radio de la nebulosa planetaria NGC 6302.

NGC 6302 es una nebulosa planetaria ópticamente delgada en el continuo de Lyman. La temperatura y densidad de electrones fU eron calculadas por Danziger et al. (1973) y Faúndez (1981), respectivamente. La masa nebular promedio determinada es M = 0.013 M0 , y la distancia promedio es D = O. 34 Bpc, para є = 1.0. El factor de porosidad adoptado para los cálculos fue є = 1.0 y є = 0.5. El radio de NGC 6302, calculado usando el método de O'Dell (1962) fue R = 0.039 pc, para є = 1.0

Testing the no-hair theorem with GW150914

We analyze gravitational-wave data from the first LIGO detection of a binary black-hole merger (GW150914) in search of the ringdown of the remnant black hole. Using observations beginning at the peak of the signal, we find evidence of the fundamental quasinormal mode and at least one overtone, both associated with the dominant angular mode ($\ell=m=2$), with $3.6\sigma$ confidence. A ringdown model including overtones allows us to measure the final mass and spin magnitude of the remnant exclusively from postinspiral data, obtaining an estimate in agreement with the values inferred from the full signal. The mass and spin values we measure from the ringdown agree with those obtained using solely the fundamental mode at a later time, but have smaller uncertainties. Agreement between the postinspiral measurements of mass and spin and those using the full waveform supports the hypothesis that the GW150914 merger produced a Kerr black hole, as predicted by general relativity, and provides a test of the no-hair theorem at the ${\sim}10\%$ level. An independent measurement of the frequency of the first overtone yields agreement with the no-hair hypothesis at the ${\sim 20}\%$ level. As the detector sensitivity improves and the detected population of black hole mergers grows, we can expect that using overtones will provide even stronger tests.Comment: v2: journal versio

Proper motions of Local Group dwarf spheroidal galaxies I: First ground-based results for Fornax

In this paper we present in detail the methodology and the first results of a ground-based program to determine the absolute proper motion of the Fornax dwarf spheroidal galaxy. The proper motion was determined using bona-fide Fornax star members measured with respect to a fiducial at-rest background spectroscopically confirmed Quasar, \qso. Our homogeneous measurements, based on this one Quasar gives a value of (\mua,\mud)$= (0.64 \pm 0.08, -0.01 \pm 0.11)$ \masy. There are only two other (astrometric) determinations for the transverse motion of Fornax: one based on a combination of plates and HST data, and another (of higher internal precision) based on HST data. We show that our proper motion errors are similar to those derived from HST measurements on individual QSOs. We provide evidence that, as far as we can determine it, our motion is not affected by magnitude, color, or other potential systematic effects. Last epoch measurements and reductions are underway for other four Quasar fields of this galaxy, which, when combined, should yield proper motions with a weighted mean error of $\sim50\,\mu$as y$^{-1}$, allowing us to place important constraints on the orbit of Fornax.Comment: Accepted for publication in Publications of the Astronomical Society of the Pacific, PASP. To appear in July issue. 64 pages, 18 figure

Temperatura y densidad de electrones en la región HII compacta Sh 288

Se ha hecho obsetvaciones de Sh 288, una región HII compacta, desde Λ 3728 hasta Λ 7326 A°. Se ha determinado un valor de la constante C de enrojecimiento interestelar igual a 1.1 ± 0. 1. Se calculó una temperatura de electrones de Te = 8990 K, y una densidad de electrones Ne = 322 cm-3

Effect of Charged Scalar Loops on Photonic Decays of a Fermiophobic Higgs

Higgs bosons with very suppressed couplings to fermions ("Fermiophobic Higgs bosons", h_f) can decay to two photons (\gamma\gamma) with a branching ratio significantly larger than that expected for the Standard Model Higgs boson for m_{h_f}<150 GeV. Such a particle would give a clear signal at the LHC and can arise in the Two Higgs Doublet Model (type I) in which h_f -> \gamma\gamma is mediated by W^+ and charged Higgs boson (H^+) loops. We show that the H^+ loops can cause both constructive and destructive contributions with a magnitude considerably larger than the anticipated precision in the measurement of the photonic decay channel at future hadron and lepton colliders.Comment: 18 pages, 5 figures, clarifications added, one reference added, accepted by Physical Review

Automorphisms of Generalized Fermat manifolds

Let $d \geq 1$, $k \geq 2$ and $n \geq d+1$ be integers. A compact complex manifold $M$ of dimension $d$ is a generalized Fermat manifold of type $(d;k,n)$ if it admits a group $H \cong {\mathbb Z}_{k}^{n}$ of holomorphic automorphisms such that there is a Galois holomorphic branched covering $\pi:M \to {\mathbb P}^{d}$, with $H$ as its deck group, whose branch locus consists of $n+1$ hyperplanes in general position (each one of branch order $k$); we also say that $H$ is a generalized Fermat group of type $(d;k,n)$. It is well known from the general theory that, for $d \leq 2$, $M$ is algebraic. If $d=1$, then $M$ a suitable fiber product of classical Fermat curves of degree $k$ and, for $(k-1)(n-1)>2$, it has a unique generalized Fermat group of type $(1;k,n)$. In this paper we generalize the above for $d\geq 2$. More precisely, (i) we note that $M$ is algebraic and we provide explicit equations, in terms of the branch hyperplanes, being a suitable fiber product of Fermat hypersurfaces of degree $k$ and dimension $d$ and (ii) we prove that $M$ has a unique generalized Fermat group of type $(d;k,n)$, for $(d;k,n) \notin \{(2;2,5), (2;4,3)\}$. This also permits us to describe the (coarse) moduli space as a complex orbifold, this is of dimension $d(n-d-1)$ given as a quotient $X_{n}/{\mathfrak S}_{n+1}$, where $X_{n}$ is a domain in ${\mathbb C}^{d(n-d-1)}$.Comment: minor corrections from previous versio

Nuclear pore complex-mediated modulation of TCR signaling is required for naïve CD4+ T cell homeostasis.

Nuclear pore complexes (NPCs) are channels connecting the nucleus with the cytoplasm. We report that loss of the tissue-specific NPC component Nup210 causes a severe deficit of naïve CD4+ T cells. Nup210-deficient CD4+ T lymphocytes develop normally but fail to survive in the periphery. The decreased survival results from both an impaired ability to transmit tonic T cell receptor (TCR) signals and increased levels of Fas, which sensitize Nup210-/- naïve CD4+ T cells to Fas-mediated cell death. Mechanistically, Nup210 regulates these processes by modulating the expression of Cav2 (encoding Caveolin-2) and Jun at the nuclear periphery. Whereas the TCR-dependent and CD4+ T cell-specific upregulation of Cav2 is critical for proximal TCR signaling, cJun expression is required for STAT3-dependent repression of Fas. Our results uncover an unexpected role for Nup210 as a cell-intrinsic regulator of TCR signaling and T cell homeostasis and expose NPCs as key players in the adaptive immune system