Members of Centaurus OB1 and NGC 4755: new spectroscopic and astrometric studies

Context. An OB association is a gravitationally unbound group of stars. The identification of the members of the association is an important aspect of its study. There are few astrometric membership studies for OB associations, but the combination of these studies with astrophysical techniques becomes a very powerful tool for this type of research. Aims. We perform new spectroscopic and astrometric studies of the members of the association Centaurus OB1 (Cen OB1) and the open cluster NGC 4755. Methods. To carry out this study we used new spectroscopic optical observations obtained at CASLEO, and proper motion and photometric data from the Tycho-2 Catalogue and other databases available via the Internet. Results. With this investigation we found 52 members of Cen OB1 (l = 303º.7, b = 0º.4) and four members of NGC 4755 (l = 303º.2, b = 2º.5), an open cluster integrated into the Cen OB1 stellar association. The distance, heliocentric radial velocity, proper motion, and age of Cen OB1 are 2.6 ± 0.5 kpc, ~-20 km s-1, μαcosδ = -4.78 ± 0.10 mas yr-1, μδ = -0.93 ± 0.10 mas yr-1, and ~20 × 106 years old, respectively. The same parameters found for NGC 4755 are 1.9 ± 0.5 kpc, -18 ± 2 km s-1, μαcosδ = -4.14 ± 0.19 mas yr-1, μδ = -1.09 ± 0.12 mas yr-1, and ~15 × 106 years old. The pulsars PSR J1253-5820 and PSR J1254-6150 could have been born as the result of supernovae explosions that occurred in the past by massive members of Cen OB1. We have seen Infrared Astronomical Satellite (IRAS) sources near Cen OB1, that show that star formation is still occurring. The age gradient observed between the different members of Cen OB1 makes it likely that the stellar association and IRAS sources represent different stages of a sequential formation process.Facultad de Ciencias Astronómicas y GeofísicasInstituto Argentino de RadioastronomíaInstituto de Astrofísica de La Plat

Members of Centaurus OB1 and NGC 4755: new spectroscopic and astrometric studies

Context. An OB association is a gravitationally unbound group of stars. The identification of the members of the association is an important aspect of its study. There are few astrometric membership studies for OB associations, but the combination of these studies with astrophysical techniques becomes a very powerful tool for this type of research. Aims. We perform new spectroscopic and astrometric studies of the members of the association Centaurus OB1 (Cen OB1) and the open cluster NGC 4755. Methods. To carry out this study we used new spectroscopic optical observations obtained at CASLEO, and proper motion and photometric data from the Tycho-2 Catalogue and other databases available via the Internet. Results. With this investigation we found 52 members of Cen OB1 (l = 303º.7, b = 0º.4) and four members of NGC 4755 (l = 303º.2, b = 2º.5), an open cluster integrated into the Cen OB1 stellar association. The distance, heliocentric radial velocity, proper motion, and age of Cen OB1 are 2.6 ± 0.5 kpc, ~-20 km s-1, μαcosδ = -4.78 ± 0.10 mas yr-1, μδ = -0.93 ± 0.10 mas yr-1, and ~20 × 106 years old, respectively. The same parameters found for NGC 4755 are 1.9 ± 0.5 kpc, -18 ± 2 km s-1, μαcosδ = -4.14 ± 0.19 mas yr-1, μδ = -1.09 ± 0.12 mas yr-1, and ~15 × 106 years old. The pulsars PSR J1253-5820 and PSR J1254-6150 could have been born as the result of supernovae explosions that occurred in the past by massive members of Cen OB1. We have seen Infrared Astronomical Satellite (IRAS) sources near Cen OB1, that show that star formation is still occurring. The age gradient observed between the different members of Cen OB1 makes it likely that the stellar association and IRAS sources represent different stages of a sequential formation process.Facultad de Ciencias Astronómicas y GeofísicasInstituto Argentino de RadioastronomíaInstituto de Astrofísica de La Plat

Clustering dinámico para tiempo de encendido mínimo en redes de sensores inalámbricas (CLUDITEM)

La medición de variables del medio es fundamental para la supervisión y control de ambientes y actividades de la más diversa índole. Resulta de gran utilidad en aplicaciones industriales, médicas, agrícolas, de preservación del medio natural o creación de ambientes inteligentes, entre otras. En muchas de las aplicaciones mencionadas, el seguimiento de las variables de interés debe realizarse en locaciones distantes u hostiles que hacen muy difícil el cableado y la atención periódica de los dispositivos de medición. Por estos motivos se utilizan las redes inalámbricas de sensores inteligentes (RISI) para obtener los datos necesarios.Facultad de Informátic

SWEET - User manual (version 2.0)

SWEET (Shallow Water Equations Evolving in Time) is a code for the solution of the 2D de Saint Venant equations, written in their conservative form. The code adopts a Finite Differences scheme to advance in time, with a fractional step procedure. The space discretization is realized through Finite Elements, with a linear representation of the water elevation and a quadratic representation of the unit- width discharge. In this document, the physical model and the numerical schemes used for solving the resulting equations are extensively described. The accuracy of the scheme is verified in different test cases. The sequential algorithm has been ported in the parallel computing framework by using the domain decomposition approach. The Schwarz algorithm has been added to the scheme for preconditioning the iterative solution of the elliptic equation modeling the dynamics of the elevation of the water level. The performance of the parallel code are evaluated on a large size computational test case. The structure of the code is explained by a description of the role of each sub- routine and by a flowchart of the program. The input and output files are described in detail, as they constitute the user interface of the code. Both input and output files have a simple structure, and any effort has been made to simplify the procedure of the input setup for the parallel code, and to manage the output results. The PVM message passing library has been used to perform the communications in the parallel version of SWEET. A short introduction to PVM is added at the end of the present report. The SWEET package is the results of a joint work between CRS4 and Enel - Polo Idraulico e Strutturale. The authors of this document kindly acknowledge the valuable contributions of Vincenzo Pennati, from Enel - Polo Idraulico e Strutturale, and of Luca Formaggia, Alfio Quarteroni and Alan Scheinine, from CRS4. This manual is an extension and revision of the SWEET User Manual Version 1.0, 1996. The author of the former document, as well as of the largest part of the SWEET code, is Davide Ambrosi, currently at Politecnico di Torino. To him, not only our sincere thank is due, but mainly the recognizance that SWEET is and will remain a work of his

GS305+04-26: Revisiting the interstellar medium around the Centaurus OB1 stellar association

Context. Massive stars deeply modify their surrounding interstellar medium (ISM) via their high throughput of ionizing photons and their strong stellar winds. In this way, they may create large expanding structures of neutral gas. Aims. We study a new large neutral hydrogen (Hi) shell, labelled GS305+04-26, and its relationship with the OB association Cen OB1. Methods. To carry out this study, we have used a multi-wavelength approach. We analyse both Hi line data retrieved from the Leiden-Argentina-Bonn (LAB) survey and new spectroscopic optical observations obtained at CASLEO, as well as make use of proper motion databases available from CDS. Results. The analysis of the Hi data reveals a large expanding structure GS305+04-26 centred at (l,b) = (305°, + 4°) in the velocity range from-33 to-17 km s -1. Based on its central velocity of-26 km s -1 and using standard galactic rotation models, a distance of 2.5 ± 0.9 kpc is inferred. This structure, elliptical in shape, has a major and minor axis of 440 and 270 pc, respectively. Its expansion velocity, total gaseous mass, and kinetic energy are ~8 km s -1, (2.4 ± 0.5) × 10 5 M âŠ(tm), and (1.6 ± 0.4) × 10 50 erg, respectively. Several stars of the OB-association Cen OB1 are seen projected onto, and within, the boundaries of GS305+04-26. Based on an analysis of proper motions, new members of Cen OB1 are identified. The mechanical energy injected by these stars could have been the origin of this Hi structure.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Unusual Methylobacterium fujisawaense Infection in a Patient with Acute Leukaemia Undergoing Hematopoietic Stem Cell Transplantation: First Case Report

Microorganisms of the genus Methylobacterium are facultative methylotrophic, gram-negative rods that are ubiquitous in nature and rarely cause human disease, mostly in subjects with preexisting causes of immune depression. Methylobacterium fujisawaense, first proposed as a new species in 1988, has never been reported as a bacterial agent of human infections so far. Here we describe a case of M. fujisawaense infection in a relapsed acute leukaemia undergoing unrelated allogeneic hematopoietic stem cell transplantation. Molecular identification of an M. fujisawaense strain was obtained from multiple mycobacterial blood cultures

Members of Centaurus OB1 and NGC 4755: new spectroscopic and astrometric studies

Context. An OB association is a gravitationally unbound group of stars. The identification of the members of the association is an important aspect of its study. There are few astrometric membership studies for OB associations, but the combination of these studies with astrophysical techniques becomes a very powerful tool for this type of research. Aims. We perform new spectroscopic and astrometric studies of the members of the association Centaurus OB1 (Cen OB1) and the open cluster NGC 4755. Methods. To carry out this study we used new spectroscopic optical observations obtained at CASLEO, and proper motion and photometric data from the Tycho-2 Catalogue and other databases available via the Internet. Results. With this investigation we found 52 members of Cen OB1 (l = 303º.7, b = 0º.4) and four members of NGC 4755 (l = 303º.2, b = 2º.5), an open cluster integrated into the Cen OB1 stellar association. The distance, heliocentric radial velocity, proper motion, and age of Cen OB1 are 2.6 ± 0.5 kpc, ~-20 km s-1, μαcosδ = -4.78 ± 0.10 mas yr-1, μδ = -0.93 ± 0.10 mas yr-1, and ~20 × 106 years old, respectively. The same parameters found for NGC 4755 are 1.9 ± 0.5 kpc, -18 ± 2 km s-1, μαcosδ = -4.14 ± 0.19 mas yr-1, μδ = -1.09 ± 0.12 mas yr-1, and ~15 × 106 years old. The pulsars PSR J1253-5820 and PSR J1254-6150 could have been born as the result of supernovae explosions that occurred in the past by massive members of Cen OB1. We have seen Infrared Astronomical Satellite (IRAS) sources near Cen OB1, that show that star formation is still occurring. The age gradient observed between the different members of Cen OB1 makes it likely that the stellar association and IRAS sources represent different stages of a sequential formation process.Facultad de Ciencias Astronómicas y GeofísicasInstituto Argentino de RadioastronomíaInstituto de Astrofísica de La Plat

Lower Crustal Earthquakes in the March 2018 Sequence Along the Western Margin of Afar

During the evolution of continental rift systems, extension is thought to progressively focus in-rift to the future breakup boundary while faults along the rift margins progressively deactivate. However, observational constraints on how strain is partitioned between rift axis and rift margins are still lacking. The Afar rift records the latest stages of rifting and incipient continental breakup. Here, we analyzed the recent MW 5.2 earthquake on the Western Afar Margin on March 24, 2018 and the associated seismic sequence of >500 earthquakes using 24 temporary seismic stations deployed during 2017–2018. We show seismicity occurring at lower crustal depths, from ∼15 to ∼30 km, with focal mechanisms and relocated earthquakes highlighting both west-dipping and east-dipping normal faults. We tested earthquake depth using InSAR by processing six independent interferograms using Sentinel-1 data acquired from both ascending and descending tracks. None of them shows evidence of surface deformation. We tested possible ranges of depth by producing forward models for a fault located at progressively increasing depths. Models show that surface deformation is not significant for fault slip at depths greater than 15 km, in agreement with the hypocentral depth of 19 km derived from seismic data for the largest earthquake. Due to the localized nature of deep earthquakes near hot springs coupled with subsurface evidence for magmatism, we favor an interpretation of seismicity induced by migrating fluids such as magma or CO2. We suggest that deep fluid migration can occur at the rifted-margin influencing seismicity during incipient continental rupture

Lower Crustal Earthquakes in the March 2018 Sequence Along the Western Margin of Afar

During the evolution of continental rift systems, extension is thought to progressively focus in-rift to the future breakup boundary while faults along the rift margins progressively deactivate. However, observational constraints on how strain is partitioned between rift axis and rift margins are still lacking. The Afar rift records the latest stages of rifting and incipient continental breakup. Here, we analyzed the recent M W 5.2 earthquake on the Western Afar Margin on March 24, 2018 and the associated seismic sequence of &gt;500 earthquakes using 24 temporary seismic stations deployed during 2017–2018. We show seismicity occurring at lower crustal depths, from ∼15 to ∼30 km, with focal mechanisms and relocated earthquakes highlighting both west-dipping and east-dipping normal faults. We tested earthquake depth using InSAR by processing six independent interferograms using Sentinel-1 data acquired from both ascending and descending tracks. None of them shows evidence of surface deformation. We tested possible ranges of depth by producing forward models for a fault located at progressively increasing depths. Models show that surface deformation is not significant for fault slip at depths greater than 15 km, in agreement with the hypocentral depth of 19 km derived from seismic data for the largest earthquake. Due to the localized nature of deep earthquakes near hot springs coupled with subsurface evidence for magmatism, we favor an interpretation of seismicity induced by migrating fluids such as magma or CO 2. We suggest that deep fluid migration can occur at the rifted-margin influencing seismicity during incipient continental rupture. </p

GS305+04-26: Revisiting the interstellar medium around the Centaurus OB1 stellar association

Context. Massive stars deeply modify their surrounding interstellar medium (ISM) via their high throughput of ionizing photons and their strong stellar winds. In this way, they may create large expanding structures of neutral gas. Aims. We study a new large neutral hydrogen (Hi) shell, labelled GS305+04-26, and its relationship with the OB association Cen OB1. Methods. To carry out this study, we have used a multi-wavelength approach. We analyse both Hi line data retrieved from the Leiden-Argentina-Bonn (LAB) survey and new spectroscopic optical observations obtained at CASLEO, as well as make use of proper motion databases available from CDS. Results. The analysis of the Hi data reveals a large expanding structure GS305+04-26 centred at (l,b) = (305°, + 4°) in the velocity range from-33 to-17 km s -1. Based on its central velocity of-26 km s -1 and using standard galactic rotation models, a distance of 2.5 ± 0.9 kpc is inferred. This structure, elliptical in shape, has a major and minor axis of 440 and 270 pc, respectively. Its expansion velocity, total gaseous mass, and kinetic energy are ~8 km s -1, (2.4 ± 0.5) × 10 5 M âŠ(tm), and (1.6 ± 0.4) × 10 50 erg, respectively. Several stars of the OB-association Cen OB1 are seen projected onto, and within, the boundaries of GS305+04-26. Based on an analysis of proper motions, new members of Cen OB1 are identified. The mechanical energy injected by these stars could have been the origin of this Hi structure.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat