José Jesús Castro Caballero - Academia.edu (original) (raw)
Papers by José Jesús Castro Caballero
Free-floating, non-deuterium-burning, substellar objects" are isolated bodies of a few Jupiter ma... more Free-floating, non-deuterium-burning, substellar objects" are isolated bodies of a few Jupiter masses found in very young open clusters and associations, nearby young moving groups and in the immediate vicinity of the Sun. They are neither brown dwarfs nor planets. I look over their nomenclature, history of discovery, sites of detection, formation mechanisms and future directions of research. Most free-floating, non-deuterium-burning, substellar objects share the same formation mechanism as low-mass stars and brown dwarfs, but there are still a few caveats, such as the value of the opacity mass limit, the minimum mass at which an isolated body can form via turbulent fragmentation from a cloud. The least massive free-floating substellar objects found to date have masses of about 0.004 Msol, but current and future surveys should aim at breaking this record. For that, we may need LSST, Euclid and WFIRST.
In spite of its importance for the study of star formation at all mass domains, the nearby young ... more In spite of its importance for the study of star formation at all mass domains, the nearby young sigma Orionis cluster still lacks a comprehensive survey for multiplicity. We try to fill that observational gap by looking for wide resolved binaries with angular separations between 0.4 and 4.0 arcsec. We search for companions to 331 catalogued cluster stellar members and candidates in public K-band UKIDSS images outside the innermost 1 arcmin, which is affected by the glare of the bright, eponymous sigma Ori multiple system, and investigate their cluster membership with colour-magnitude diagrams and previous knowledge of youth features. Of the 18 identified pairs, ten have very low individual probabilities of chance alignment (< 1 here as physical pairs. Four of them are new, while the other six had been discovered previously, but never investigated homogeneously and in detail. Projected physical separations and magnitude differences of the ten probably bound pairs range from 180 t...
We present a deep I,Z photometric survey covering a total area of 1.12 deg^2 of the Sigma Orionis... more We present a deep I,Z photometric survey covering a total area of 1.12 deg^2 of the Sigma Orionis cluster (Icompl=22 and Zcompl=21.5mag). From I, I-Z color-magnitude diagrams we have selected 153 candidates that fit the previously known sequence of the cluster. Using J-band photometry, we find that 124 of the 151 candidates follow the previously known infrared photometric sequence of the cluster and are probably members. We have studied the spatial distribution of these candidates and found that there are objects located at distances greater than 30 arcmin to the north and west of Sigma Orionis that probably belong to different populations of the Orion's Belt. For the 102 bona fide Sigma Orionis cluster member candidates, we find that the radial surface density can be represented by a decreasing exponential function (sigma = sigma_0 e^-r/r_0) with a central density of sigma_0=0.23+/-0.03 object/arcmin^2 and a characteristic radius of r_0=9.5+/-0.7 arcmin. From a statistical comp...
Parallactic distances and proper motions of virtually all stars in the sigma Orionis cluster or: ... more Parallactic distances and proper motions of virtually all stars in the sigma Orionis cluster or: How I learned to get the most out of TOPCAT and love Gaia DR2
Context. Although many studies have been performed so far, there are still dozens of low-mass sta... more Context. Although many studies have been performed so far, there are still dozens of low-mass stars and brown dwarfs in the young sigma Orionis open cluster without detailed spectroscopic characterisation. Aims. We look for unknown strong accretors and disc hosts that were undetected in previous surveys. Methods. We collected low-resolution spectroscopy (R ~ 700) of ten low-mass stars and brown dwarfs in sigma Orionis with OSIRIS at the Gran Telescopio Canarias under very poor weather conditions. These objects display variability in the optical, infrared, Halpha, and/or X-rays on time scales of hours to years. We complemented our spectra with optical and near-/mid-infrared photometry. Results. For seven targets, we detected lithium in absorption, identified Halpha, the calcium doublet, and forbidden lines in emission, and/or determined spectral types for the first time. We characterise in detail a faint, T Tauri-like brown dwarf with an 18 h-period variability in the optical and a l...
With the new Tycho-Gaia Astrometric Solution, I derive a new parallactic distance to the young si... more With the new Tycho-Gaia Astrometric Solution, I derive a new parallactic distance to the young sigma Orionis open cluster, which is a cornerstone region for studying the formation and evolution of stars and substellar objects from tens of solar masses to a few Jupiter masses. I started with the list of the 46 brightest cluster stars of Caballero (2007). After identifying the 24 TGAS stars in the 30 arcmin-radius survey area and accounting for 11 FGKM-type dwarfs and giants in the fore- and background, I got a list of 13 cluster members and candidates with new parallaxes. Of them, I discarded five cluster member candidates with questionable features of youth and/or discordant parallaxes and proper motions, including a distant Herbig Ae/Be star, and proceeded with the remaining eight stars. The sigma Orionis mean heliocentric distance is d =360^+44_-35 pc, which is consistent with a contemporaneous interferometric determination that concludes a two-decade dispute on the cluster distan...
Aims: We investigated the X-ray emission from young stars and brown dwarfs in the sigma Orionis c... more Aims: We investigated the X-ray emission from young stars and brown dwarfs in the sigma Orionis cluster (tau~3 Ma, d~385 pc) and its relation to mass, presence of circumstellar discs, and separation to the cluster centre by taking advantage of the superb spatial resolution of the Chandra X-ray Observatory. Methods: We used public HRC-I/Chandra data from a 97.6 ks pointing towards the cluster centre and complemented them with X-ray data from IPC/Einstein, HRI/ROSAT, EPIC/XMM-Newton, and ACIS-S/Chandra together with optical and infrared photometry and spectroscopy from the literature and public catalogues. On our HRC-I/Chandra data, we measured count rates, estimated X-ray fluxes, and searched for short-term variability. We also looked for long-term variability by comparing with previous X-ray observations. Results: Among the 107 detected X-ray sources, there were 70 cluster stars with known signposts of youth, two young brown dwarfs, 12 cluster member candidates, four field dwarfs, a...
The boundary between professional and amateur astronomers gets narrower and narrower. We present ... more The boundary between professional and amateur astronomers gets narrower and narrower. We present several real examples, most of them published in refereed journals, of works resulting from fruitful collaborations between key amateur astronomers in Spain and pro-fessional colleagues. The common denominator of these works is the search for binaries, mostly nearby, wide, common proper-motion pairs with low-mass stellar components, in-cluding some of the most fragile systems ever found. 1 Today: in media res In the 17th century some good practices for scientific writing were already established, and since then scientists have given more importance to plain and accurate description than rhetorical flourishes. However, authors in that epoch also emphasised the importance of not boring the reader. Here we present the results of several professional-amateur collaborations on low-mass stars in fragile multiple systems using in media res (“into the midst of things”), the literary and artistic...
arXiv: Solar and Stellar Astrophysics, 2014
Gaia will not observe 50000 brown dwarfs, but about 100 times less. However, these <~ 500 brow... more Gaia will not observe 50000 brown dwarfs, but about 100 times less. However, these <~ 500 brown dwarfs will be benchmarks for many substellar topics. It is possible to identify them in advance and make the list public to all astronomers worldwide through a virtual observatory-compliant "Gaia brown dwarf" catalogue. This M-, L- and T-dwarf Archive of Interest for Astrophysics would tabulate precise Gaia astrometry, multiband photometry, high- and low-resolution spectroscopy and homogeneously derived astrophysical parameters. Spanish observatories may play a key role in the catalogue preparation.
The wide variety in descriptions, implementations, and accessibility of scientific models poses a... more The wide variety in descriptions, implementations, and accessibility of scientific models poses a huge challenge for model interoperability. Model interoperability is key in the automation of tasks including model integration, seamless access to distributed models, data reuse and repurpose. Current approaches for model interoperability include the creation of generic standards and vocabularies to describe models, their inputs and outputs. These domain-agnostic standards often do not provide the fine-grained level required to describe a specific domain or task, and extending such standards requires a considerable amount of effort and time that is deviated from the purpose of producing scientific breakthrough and results. This paper presents a semi-structured, knowledge-based framework implemented with a service-driven architecture: The Sustainable Water through Integrated Modelling Framework (SWIM). SWIM is part of an ongoing effort to expose water sustainability models on the Web wi...
arXiv: Solar and Stellar Astrophysics, 2012
The boundary between professional and amateur astronomers gets narrower and narrower. We present ... more The boundary between professional and amateur astronomers gets narrower and narrower. We present several real examples, most of them published in refereed journals, of works resulting from fruitful collaborations between key amateur astronomers in Spain and professional colleagues. The common denominator of these works is the search for binaries, mostly nearby, wide, common proper-motion pairs with low-mass stellar components, including some of the most fragile systems ever found.
Ante la ausencia de un kit de Tc–IgG para radiodiagnóstico de inflamación e infección ocultas, a ... more Ante la ausencia de un kit de Tc–IgG para radiodiagnóstico de inflamación e infección ocultas, a fines de 1998 se capacitó personal en preparación y control de calidad de dicho radiofármaco en un país de la región. La técnica de producción del Kit de IgG que se utilizó está basada en el protocolo de producción validado en CNEA-Argentina. Se redujo la proteína, se colectaron fracciones y donde se obtuvo la proteína se utilizó para elaborar el kit liofilizado.
Aims. We investigated the X-ray emission from young stars and brown dwarfs in the σ Orionis clust... more Aims. We investigated the X-ray emission from young stars and brown dwarfs in the σ Orionis cluster (τ ∼ 3 Ma, d ∼ 385 pc) and its relation to mass, the presence of circumstellar discs, and separation to the cluster centre by taking advantage of the superb spatial resolution of the Chandra X-ray Observatory. Methods. We used public HRC-I/Chandra data from a 97.6 ks pointing towards the cluster centre and complemented them with X-ray data from IPC/Einstein, HRI/ROSAT, EPIC/XMM-Newton, and ACIS-S/Chandra together with optical and infrared photometry and spectroscopy from the literature and public catalogues. On our HRC-I/Chandra data, we measured count rates, estimated X-ray fluxes, and searched for short-term variability. We also looked for long-term variability by comparing with previous X-ray observations. Results. Among the 107 detected X-ray sources, there were 70 cluster stars with known signposts of youth, two young brown dwarfs, 12 cluster member candidates, four field dwarfs,...
Resumen El CEA es una glicoproteína que se encuentra muy concentrada en el propio tejido tumoral,... more Resumen El CEA es una glicoproteína que se encuentra muy concentrada en el propio tejido tumoral, pero escasamente elevada en el suero. Este marcador es útil en casos de cáncer colorectal, aumentado la concentración del antígeno con relación al estadio de la enfermedad. Una vez estandarizada la técnica de marcación, obteniendo una pureza radioquímica (PRQ) 97.57% con una estabilidad de seis días post-marcación, se procedió a realizar las evaluaciones biológicas de este anticuerpo (distribución biológica (DB), toxicidad aguda, esterilidad y pirógenos) en ratones sanos de la variedad Balb/c. Para las pruebas de DB, después de 24 horas de la inyección del anticuerpo Monoclonal (AcMo), se aloja en mayor concentración en los órganos específicos (intestino, hígado y estómago), siendo el mejor momento para realizar la toma de imágenes. Con respecto a las demás pruebas biológicas se concluye que tenemos un producto estéril, no tóxico y libre de pirógenos.
Research Notes of the AAS, 2018
Astronomy & Astrophysics, 2019
Context. Only a few open clusters are as important for the study of stellar and substellar object... more Context. Only a few open clusters are as important for the study of stellar and substellar objects, and their formation and evolution, as the young σ Orionis cluster. However, a complete spectroscopic characterisation of its whole stellar population is still missing. Aims. We filled most of that gap with a large spectroscopic and astrometric survey of targets towards σ Orionis. Eventually, it will be one of the open clusters with the lowest proportion of interlopers and the largest proportion of confirmed cluster members with known uncontrovertible youth features. Methods. We acquired 317 low-resolution optical spectra with the Intermediate Dispersion Spectrograph (IDS) at the 2.5 m Isaac Newton Telescope (INT) and the Optical System for Imaging and low Resolution Integrated Spectroscopy (OSIRIS) at the 10.4 m Gran Telescopio Canarias (GTC). We measured equivalent widths of Li I, Hα, and other key lines from these spectra, and determined spectral types. We complemented this informat...
Monthly Notices of the Royal Astronomical Society, 2017
Astronomische Nachrichten, 2017
In spite of its importance for the study of star formation at all mass domains, the nearby young ... more In spite of its importance for the study of star formation at all mass domains, the nearby young σ Orionis cluster still lacks a comprehensive survey for multiplicity. We try to fill that observational gap by looking for wide resolved binaries with angular separations between 0.4 and 4.0 arcsec. We search for companions to 331 catalogued cluster stellar members and candidates in public K-band UKIDSS images outside the innermost 1 arcmin, which is affected by the glare of the bright, eponymous σ Ori multiple system, and investigate their cluster membership with colour-magnitude diagrams and previous knowledge of youth features. Of the 18 identified pairs, ten have very low individual probabilities of chance alignment (< 1 %) and are considered here as physical pairs. Four of them are new, while the other six had been discovered previously, but never investigated homogeneously and in detail. Projected physical separations and magnitude differences of the ten probably bound pairs range from 180 to 1220 au, and from 0.0 to 3.4 mag in K, respectively. Besides, we identify two cluster stars with elongated point spread functions. We determine the minimum frequency of wide multiplicity in the interval of projected physical separations s = 160-1600 au in σ Orionis at 3.0 +1.2 −1.1 %. We discover a new Lindroos system, find that massive and X-ray stars tend to be in pairs or trios, conclude that multiplicity truncates circumstellar discs and enhances X-ray emission, and ascribe a reported lithium depletion in a young star to unresolved binarity in spectra of moderate resolution. When accounting for all know multiples, including spectroscopic binaries, the minimum frequency of multiplicity increases to about 10 %, which implies that of the order of 80-100 unknown multiple systems still await discovery in σ Orionis.
Astronomische Nachrichten, 2017
Astronomy & Astrophysics, 2014
Free-floating, non-deuterium-burning, substellar objects" are isolated bodies of a few Jupiter ma... more Free-floating, non-deuterium-burning, substellar objects" are isolated bodies of a few Jupiter masses found in very young open clusters and associations, nearby young moving groups and in the immediate vicinity of the Sun. They are neither brown dwarfs nor planets. I look over their nomenclature, history of discovery, sites of detection, formation mechanisms and future directions of research. Most free-floating, non-deuterium-burning, substellar objects share the same formation mechanism as low-mass stars and brown dwarfs, but there are still a few caveats, such as the value of the opacity mass limit, the minimum mass at which an isolated body can form via turbulent fragmentation from a cloud. The least massive free-floating substellar objects found to date have masses of about 0.004 Msol, but current and future surveys should aim at breaking this record. For that, we may need LSST, Euclid and WFIRST.
In spite of its importance for the study of star formation at all mass domains, the nearby young ... more In spite of its importance for the study of star formation at all mass domains, the nearby young sigma Orionis cluster still lacks a comprehensive survey for multiplicity. We try to fill that observational gap by looking for wide resolved binaries with angular separations between 0.4 and 4.0 arcsec. We search for companions to 331 catalogued cluster stellar members and candidates in public K-band UKIDSS images outside the innermost 1 arcmin, which is affected by the glare of the bright, eponymous sigma Ori multiple system, and investigate their cluster membership with colour-magnitude diagrams and previous knowledge of youth features. Of the 18 identified pairs, ten have very low individual probabilities of chance alignment (< 1 here as physical pairs. Four of them are new, while the other six had been discovered previously, but never investigated homogeneously and in detail. Projected physical separations and magnitude differences of the ten probably bound pairs range from 180 t...
We present a deep I,Z photometric survey covering a total area of 1.12 deg^2 of the Sigma Orionis... more We present a deep I,Z photometric survey covering a total area of 1.12 deg^2 of the Sigma Orionis cluster (Icompl=22 and Zcompl=21.5mag). From I, I-Z color-magnitude diagrams we have selected 153 candidates that fit the previously known sequence of the cluster. Using J-band photometry, we find that 124 of the 151 candidates follow the previously known infrared photometric sequence of the cluster and are probably members. We have studied the spatial distribution of these candidates and found that there are objects located at distances greater than 30 arcmin to the north and west of Sigma Orionis that probably belong to different populations of the Orion's Belt. For the 102 bona fide Sigma Orionis cluster member candidates, we find that the radial surface density can be represented by a decreasing exponential function (sigma = sigma_0 e^-r/r_0) with a central density of sigma_0=0.23+/-0.03 object/arcmin^2 and a characteristic radius of r_0=9.5+/-0.7 arcmin. From a statistical comp...
Parallactic distances and proper motions of virtually all stars in the sigma Orionis cluster or: ... more Parallactic distances and proper motions of virtually all stars in the sigma Orionis cluster or: How I learned to get the most out of TOPCAT and love Gaia DR2
Context. Although many studies have been performed so far, there are still dozens of low-mass sta... more Context. Although many studies have been performed so far, there are still dozens of low-mass stars and brown dwarfs in the young sigma Orionis open cluster without detailed spectroscopic characterisation. Aims. We look for unknown strong accretors and disc hosts that were undetected in previous surveys. Methods. We collected low-resolution spectroscopy (R ~ 700) of ten low-mass stars and brown dwarfs in sigma Orionis with OSIRIS at the Gran Telescopio Canarias under very poor weather conditions. These objects display variability in the optical, infrared, Halpha, and/or X-rays on time scales of hours to years. We complemented our spectra with optical and near-/mid-infrared photometry. Results. For seven targets, we detected lithium in absorption, identified Halpha, the calcium doublet, and forbidden lines in emission, and/or determined spectral types for the first time. We characterise in detail a faint, T Tauri-like brown dwarf with an 18 h-period variability in the optical and a l...
With the new Tycho-Gaia Astrometric Solution, I derive a new parallactic distance to the young si... more With the new Tycho-Gaia Astrometric Solution, I derive a new parallactic distance to the young sigma Orionis open cluster, which is a cornerstone region for studying the formation and evolution of stars and substellar objects from tens of solar masses to a few Jupiter masses. I started with the list of the 46 brightest cluster stars of Caballero (2007). After identifying the 24 TGAS stars in the 30 arcmin-radius survey area and accounting for 11 FGKM-type dwarfs and giants in the fore- and background, I got a list of 13 cluster members and candidates with new parallaxes. Of them, I discarded five cluster member candidates with questionable features of youth and/or discordant parallaxes and proper motions, including a distant Herbig Ae/Be star, and proceeded with the remaining eight stars. The sigma Orionis mean heliocentric distance is d =360^+44_-35 pc, which is consistent with a contemporaneous interferometric determination that concludes a two-decade dispute on the cluster distan...
Aims: We investigated the X-ray emission from young stars and brown dwarfs in the sigma Orionis c... more Aims: We investigated the X-ray emission from young stars and brown dwarfs in the sigma Orionis cluster (tau~3 Ma, d~385 pc) and its relation to mass, presence of circumstellar discs, and separation to the cluster centre by taking advantage of the superb spatial resolution of the Chandra X-ray Observatory. Methods: We used public HRC-I/Chandra data from a 97.6 ks pointing towards the cluster centre and complemented them with X-ray data from IPC/Einstein, HRI/ROSAT, EPIC/XMM-Newton, and ACIS-S/Chandra together with optical and infrared photometry and spectroscopy from the literature and public catalogues. On our HRC-I/Chandra data, we measured count rates, estimated X-ray fluxes, and searched for short-term variability. We also looked for long-term variability by comparing with previous X-ray observations. Results: Among the 107 detected X-ray sources, there were 70 cluster stars with known signposts of youth, two young brown dwarfs, 12 cluster member candidates, four field dwarfs, a...
The boundary between professional and amateur astronomers gets narrower and narrower. We present ... more The boundary between professional and amateur astronomers gets narrower and narrower. We present several real examples, most of them published in refereed journals, of works resulting from fruitful collaborations between key amateur astronomers in Spain and pro-fessional colleagues. The common denominator of these works is the search for binaries, mostly nearby, wide, common proper-motion pairs with low-mass stellar components, in-cluding some of the most fragile systems ever found. 1 Today: in media res In the 17th century some good practices for scientific writing were already established, and since then scientists have given more importance to plain and accurate description than rhetorical flourishes. However, authors in that epoch also emphasised the importance of not boring the reader. Here we present the results of several professional-amateur collaborations on low-mass stars in fragile multiple systems using in media res (“into the midst of things”), the literary and artistic...
arXiv: Solar and Stellar Astrophysics, 2014
Gaia will not observe 50000 brown dwarfs, but about 100 times less. However, these <~ 500 brow... more Gaia will not observe 50000 brown dwarfs, but about 100 times less. However, these <~ 500 brown dwarfs will be benchmarks for many substellar topics. It is possible to identify them in advance and make the list public to all astronomers worldwide through a virtual observatory-compliant "Gaia brown dwarf" catalogue. This M-, L- and T-dwarf Archive of Interest for Astrophysics would tabulate precise Gaia astrometry, multiband photometry, high- and low-resolution spectroscopy and homogeneously derived astrophysical parameters. Spanish observatories may play a key role in the catalogue preparation.
The wide variety in descriptions, implementations, and accessibility of scientific models poses a... more The wide variety in descriptions, implementations, and accessibility of scientific models poses a huge challenge for model interoperability. Model interoperability is key in the automation of tasks including model integration, seamless access to distributed models, data reuse and repurpose. Current approaches for model interoperability include the creation of generic standards and vocabularies to describe models, their inputs and outputs. These domain-agnostic standards often do not provide the fine-grained level required to describe a specific domain or task, and extending such standards requires a considerable amount of effort and time that is deviated from the purpose of producing scientific breakthrough and results. This paper presents a semi-structured, knowledge-based framework implemented with a service-driven architecture: The Sustainable Water through Integrated Modelling Framework (SWIM). SWIM is part of an ongoing effort to expose water sustainability models on the Web wi...
arXiv: Solar and Stellar Astrophysics, 2012
The boundary between professional and amateur astronomers gets narrower and narrower. We present ... more The boundary between professional and amateur astronomers gets narrower and narrower. We present several real examples, most of them published in refereed journals, of works resulting from fruitful collaborations between key amateur astronomers in Spain and professional colleagues. The common denominator of these works is the search for binaries, mostly nearby, wide, common proper-motion pairs with low-mass stellar components, including some of the most fragile systems ever found.
Ante la ausencia de un kit de Tc–IgG para radiodiagnóstico de inflamación e infección ocultas, a ... more Ante la ausencia de un kit de Tc–IgG para radiodiagnóstico de inflamación e infección ocultas, a fines de 1998 se capacitó personal en preparación y control de calidad de dicho radiofármaco en un país de la región. La técnica de producción del Kit de IgG que se utilizó está basada en el protocolo de producción validado en CNEA-Argentina. Se redujo la proteína, se colectaron fracciones y donde se obtuvo la proteína se utilizó para elaborar el kit liofilizado.
Aims. We investigated the X-ray emission from young stars and brown dwarfs in the σ Orionis clust... more Aims. We investigated the X-ray emission from young stars and brown dwarfs in the σ Orionis cluster (τ ∼ 3 Ma, d ∼ 385 pc) and its relation to mass, the presence of circumstellar discs, and separation to the cluster centre by taking advantage of the superb spatial resolution of the Chandra X-ray Observatory. Methods. We used public HRC-I/Chandra data from a 97.6 ks pointing towards the cluster centre and complemented them with X-ray data from IPC/Einstein, HRI/ROSAT, EPIC/XMM-Newton, and ACIS-S/Chandra together with optical and infrared photometry and spectroscopy from the literature and public catalogues. On our HRC-I/Chandra data, we measured count rates, estimated X-ray fluxes, and searched for short-term variability. We also looked for long-term variability by comparing with previous X-ray observations. Results. Among the 107 detected X-ray sources, there were 70 cluster stars with known signposts of youth, two young brown dwarfs, 12 cluster member candidates, four field dwarfs,...
Resumen El CEA es una glicoproteína que se encuentra muy concentrada en el propio tejido tumoral,... more Resumen El CEA es una glicoproteína que se encuentra muy concentrada en el propio tejido tumoral, pero escasamente elevada en el suero. Este marcador es útil en casos de cáncer colorectal, aumentado la concentración del antígeno con relación al estadio de la enfermedad. Una vez estandarizada la técnica de marcación, obteniendo una pureza radioquímica (PRQ) 97.57% con una estabilidad de seis días post-marcación, se procedió a realizar las evaluaciones biológicas de este anticuerpo (distribución biológica (DB), toxicidad aguda, esterilidad y pirógenos) en ratones sanos de la variedad Balb/c. Para las pruebas de DB, después de 24 horas de la inyección del anticuerpo Monoclonal (AcMo), se aloja en mayor concentración en los órganos específicos (intestino, hígado y estómago), siendo el mejor momento para realizar la toma de imágenes. Con respecto a las demás pruebas biológicas se concluye que tenemos un producto estéril, no tóxico y libre de pirógenos.
Research Notes of the AAS, 2018
Astronomy & Astrophysics, 2019
Context. Only a few open clusters are as important for the study of stellar and substellar object... more Context. Only a few open clusters are as important for the study of stellar and substellar objects, and their formation and evolution, as the young σ Orionis cluster. However, a complete spectroscopic characterisation of its whole stellar population is still missing. Aims. We filled most of that gap with a large spectroscopic and astrometric survey of targets towards σ Orionis. Eventually, it will be one of the open clusters with the lowest proportion of interlopers and the largest proportion of confirmed cluster members with known uncontrovertible youth features. Methods. We acquired 317 low-resolution optical spectra with the Intermediate Dispersion Spectrograph (IDS) at the 2.5 m Isaac Newton Telescope (INT) and the Optical System for Imaging and low Resolution Integrated Spectroscopy (OSIRIS) at the 10.4 m Gran Telescopio Canarias (GTC). We measured equivalent widths of Li I, Hα, and other key lines from these spectra, and determined spectral types. We complemented this informat...
Monthly Notices of the Royal Astronomical Society, 2017
Astronomische Nachrichten, 2017
In spite of its importance for the study of star formation at all mass domains, the nearby young ... more In spite of its importance for the study of star formation at all mass domains, the nearby young σ Orionis cluster still lacks a comprehensive survey for multiplicity. We try to fill that observational gap by looking for wide resolved binaries with angular separations between 0.4 and 4.0 arcsec. We search for companions to 331 catalogued cluster stellar members and candidates in public K-band UKIDSS images outside the innermost 1 arcmin, which is affected by the glare of the bright, eponymous σ Ori multiple system, and investigate their cluster membership with colour-magnitude diagrams and previous knowledge of youth features. Of the 18 identified pairs, ten have very low individual probabilities of chance alignment (< 1 %) and are considered here as physical pairs. Four of them are new, while the other six had been discovered previously, but never investigated homogeneously and in detail. Projected physical separations and magnitude differences of the ten probably bound pairs range from 180 to 1220 au, and from 0.0 to 3.4 mag in K, respectively. Besides, we identify two cluster stars with elongated point spread functions. We determine the minimum frequency of wide multiplicity in the interval of projected physical separations s = 160-1600 au in σ Orionis at 3.0 +1.2 −1.1 %. We discover a new Lindroos system, find that massive and X-ray stars tend to be in pairs or trios, conclude that multiplicity truncates circumstellar discs and enhances X-ray emission, and ascribe a reported lithium depletion in a young star to unresolved binarity in spectra of moderate resolution. When accounting for all know multiples, including spectroscopic binaries, the minimum frequency of multiplicity increases to about 10 %, which implies that of the order of 80-100 unknown multiple systems still await discovery in σ Orionis.
Astronomische Nachrichten, 2017
Astronomy & Astrophysics, 2014