1,725,551 research outputs found
6441. Canal de La Viga
No full textI.O. Anverso: "6441. Canal de la viga". Reverso: "2865". V.F. 450309
[Raritan River., Engine Drawing Card, Sketch No. 6441]
No full textThis engine drawing card was created for the Raritan River Railroad Company, Class 12-34 1/4D. Section N-12 1/4D. Sketch 6441. Copy Spec. C-3737
Hunting for intermediate-mass black holes in globular clusters: An astrometric study of NGC 6441
Get PDFWe present an astrometric study of the proper motions (PMs) in the core of the globular cluster NGC 6441. The core of this cluster has a high density and observations with current instrumentation are very challenging. We combine ground-based, high-angular-resolution NACO@VLT images with Hubble Space Telescope ACS/HRC data and measure PMs with a temporal baseline of 15 yr for about 1400 stars in the centremost 15 arcsec of the cluster. We reach a PM precision of ∼30 μas yr-1 for bright, well-measured stars. Our results for the velocity dispersion are in good agreement with other studies and extend already existing analyses of the stellar kinematics of NGC 6441 to its centremost region never probed before. In the innermost arcsecond of the cluster, we measure a velocity dispersion of (19.1 ± 2.0) km s-1 for evolved stars. Because of its high mass, NGC 6441 is a promising candidate for harbouring an intermediate-mass black hole (IMBH). We combine our measurements with additional data from the literature and compute dynamical models of the cluster. We find an upper limit of M IMBH < 1.32 × 104 M but we can neither confirm nor rule out its presence. We also refine the dynamical distance of the cluster to $12.74+0.16-0.15 kpc. Although the hunt for an IMBH in NGC 6441 is not yet concluded, our results show how future observations with extremely large telescopes will benefit from the long temporal baseline offered by existing high-angular-resolution data
Variable Stars in the Unusual, Metal-Rich Globular Cluster NGC-6441
No full textWe have undertaken a search for variable stars in the metal-rich globular cluster NGC 6441 using time-series BV photometry. The total number of variables found near NGC 6441 has been increased to approx. 104, with 48 new variables being found in this survey. A significant number of the variables are RR Lyrae stars (approx. 46), most of which are probable cluster members. As was noted by Layden et al. (1999), the periods of the fundamental mode RR Lyrae are unusually long compared to field stars of similar metallicity. The existence of these long period RRab stars is consistent with Sweigart & Catelan's (1998) prediction that the horizontal branch of NGC 6441 is unusually bright. This result implies that the metallicity-luminosity relationship for RR Lyrae stars is not universal. We discuss the difficulty in determining the Oosterhoff classification of NGC 6441 due to the unusual nature of its RR Lyrae. A number of ab-type RR Lyrae are found to be both brighter and redder than the other probable RRab found along the horizontal branch, which may be a result of blending with stars of redder color. A smaller than usual gap is found between the shortest period fundamental mode and the longest period first-overtone mode RR Lyrae. We determine the reddening of the cluster to be E(B - V) = 0.51 +/- 0.02 mag, with substantial differential reddening across the face of the cluster. The mean V magnitude of the RR Lyrae is found to be 17.51 +/- 0.02 resulting in a distance of 10.4 to 11.9 kpc, for a range of assumed values of for RR Lyrae stars. The possibility that stars in NGC 6441 may span a range in [Fe/H] is also discussed
Near-Infrared photometry of the Galactic Globular Cluster NGC 6441
No full textWe present new near-infrared Ks photometry of the interesting Galactic globular cluster NGC 6441. The optical-NIR color-magnitude diagram shows evolutionary features that seem to agree with a canonical evolutionary framework. The K-band Period-LuminosityMetallicity relation of RR Lyrae stars gives a distance estimate of 15.51 \ub1 0.07 that is slightly larger previous estimates.Peer reviewed: YesNRC publication: Ye
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Near-infrared observations of RR Lyrae and Type II Cepheid variables in the metal-rich bulge globular cluster NGC 6441
Get PDFNGC 6441 is a bulge globular cluster with an unusual horizontal branch
morphology and a rich population of RR Lyrae (RRL) and Type II Cepheid (T2C)
variables that is unexpected for its relatively high metallicity. We present
near-infrared (NIR, ) time-series observations of 42 RRL, 8 T2Cs, and 10
eclipsing binary candidate variables in NGC 6441. The multi-epoch observations
were obtained using the FLAMINGOS-2 instrument on the 8-m Gemini South
telescope. Multi-band data are used to investigate pulsation properties of RRL
and T2C variables including their light curves, instability strip,
period--amplitude diagrams, and period--luminosity and period--wesenheit
relations (PLRs and PWRs) in filters. NIR pulsation properties of RRL
variables are well fitted with theoretical models that have canonical helium
content and mean-metallicity of NGC 6441 ([Fe/H]~dex). The
helium-enhanced RRL models predict brighter NIR magnitudes and bluer colors
than the observations of RRL in the cluster. This suggests that these RRL
variables in NGC 6441 are either not significantly helium enhanced as
previously thought or the impact of such enhancement is smaller in NIR than the
predictions of the pulsation models. We also use theoretical calibrations of
RRL period--luminosity--metallicity (PLZ) relations to simultaneously estimate
the mean reddening, ~mag, and the distance,
~kpc, to NGC 6441. Our mean reddening value and the distance
are consistent with the independent estimates from the bulge reddening map
based on red clump stars and the latest Gaia data, respectively. Our distance
and reddening values provide a very good agreement between the PLRs of T2Cs in
NGC 6441 and those for RRL and T2Cs in Galactic globular clusters that span a
broad range of metallicity.Comment: 17 pages, 14 figures, accepted in A&A, abridged abstrac
Variations on the Author
Get PDF“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
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