Artículos de revista, ponencias, capítulos de libro y otros http://sedici.unlp.edu.ar:80/handle/10915/17 2026-11-14T22:59:03Z 2026-11-14T22:59:03Z Guarracino, Luis Jougnot, D. Soldi, Mariangeles http://sedici.unlp.edu.ar:80/handle/10915/200606 2026-10-29T04:15:42Z 2023-01-01T00:00:00Z

Articulo Workshop: “Gestión del recurso hídrico en áreas continentales y costeras: casos de estudio sobre la interacción cuali-cuantitativa del agua subterránea y superficial en Italia Y Argentina” (La Plata, 3 de mayo de 2023); Revista del Museo de La Plata; vol. 8, no. 1, suplemento resúmenes El método del potencial espontáneo es una técnica geofísica relativamente simple y económica utilizada usualmente para la prospección de recursos minerales y el sondeo de pozos de exploración. Sin embargo, este método también puede ser utilizado para analizar en flujo de aguas subterráneas de manera pasiva y no invasiva. De hecho, constituye una de las pocas técnicas geofísicas que es directamente sensible al flujo de aguas subterráneas. El método se basa en la medición y el análisis de la diferencia de potencial eléctrico que se genera de manera espontánea en el subsuelo, utilizando un voltímetro y electrodos impolarizables. El potencial eléctrico generado por el flujo de aguas subterráneas se denomina potencial electrocinético y es originado por el desbalance entre la cantidad de cargas eléctricas presente en la superficie de los poros de la roca y los iones de signo contrario que son arrastrados por el flujo de agua. Existen en la literatura numerosos ejemplos donde se han observado señales de potencial electrocinético, entre ellas se destacan los ensayos de bombeo, procesos de infiltración, flujo hidrotermal, actividad sísmica y ensayos de fracturación hidráulica. Para poder determinar los parámetros hidráulicos a partir de las mediciones del potencial espontáneo es imprescindible contar con modelos petrofísicos que relacionen las variaciones de presión de agua con las diferencias de potencial electrocinético. Estos modelos de naturaleza macroscópica pueden obtenerse a partir de la descripción del flujo y de la densidad de carga eléctrica a escala poral. En este trabajo se presentan las bases del modelado electrocinético para medios porosos sedimentarios y fracturados desarrollados por el grupo de trabajo

2023-01-01T00:00:00Z El método del potencial espontáneo es una técnica geofísica relativamente simple y económica utilizada usualmente para la prospección de recursos minerales y el sondeo de pozos de exploración. Sin embargo, este método también puede ser utilizado para analizar en flujo de aguas subterráneas de manera pasiva y no invasiva. De hecho, constituye una de las pocas técnicas geofísicas que es directamente sensible al flujo de aguas subterráneas. El método se basa en la medición y el análisis de la diferencia de potencial eléctrico que se genera de manera espontánea en el subsuelo, utilizando un voltímetro y electrodos impolarizables. El potencial eléctrico generado por el flujo de aguas subterráneas se denomina potencial electrocinético y es originado por el desbalance entre la cantidad de cargas eléctricas presente en la superficie de los poros de la roca y los iones de signo contrario que son arrastrados por el flujo de agua. Existen en la literatura numerosos ejemplos donde se han observado señales de potencial electrocinético, entre ellas se destacan los ensayos de bombeo, procesos de infiltración, flujo hidrotermal, actividad sísmica y ensayos de fracturación hidráulica. Para poder determinar los parámetros hidráulicos a partir de las mediciones del potencial espontáneo es imprescindible contar con modelos petrofísicos que relacionen las variaciones de presión de agua con las diferencias de potencial electrocinético. Estos modelos de naturaleza macroscópica pueden obtenerse a partir de la descripción del flujo y de la densidad de carga eléctrica a escala poral. En este trabajo se presentan las bases del modelado electrocinético para medios porosos sedimentarios y fracturados desarrollados por el grupo de trabajo Pendiuk, Jonatan Emmanuel Guarracino, Luis http://sedici.unlp.edu.ar:80/handle/10915/200604 2026-10-29T04:15:43Z 2023-01-01T00:00:00Z

Articulo Workshop: “Gestión del recurso hídrico en áreas continentales y costeras: casos de estudio sobre la interacción cuali-cuantitativa del agua subterránea y superficial en Italia Y Argentina” (La Plata, 3 de mayo de 2023); Revista del Museo de La Plata; vol. 8, no. 1, suplemento resúmenes En la llanura de la Provincia de Buenos Aires, la evapotranspiración (ET) es el principal mecanismo de pérdida de agua ya que el sistema de drenaje superficial está pobremente desarrollado. En este ambiente hidrogeológico, los cambios en el patrón de ET están fuertemente relacionados con los eventos de inundación y sequía que afectan periódicamente a la región. El objetivo de este estudio es presentar una nueva técnica para estimar la ET utilizando mediciones de gravedad proporcionados por un gravímetro superconductor. Este dispositivo mide las variaciones temporales de la gravedad con muy alta resolución (décimas de nm/s2) en un radio de unos cientos de metros alrededor del instrumento. Al igual que los lisímetros, los gravímetros proporcionan estimaciones directas de las variaciones de las reservas de agua en el orden del milímetro, pero a escalas espaciales mayores y sin perturbar el perfil del suelo.

2023-01-01T00:00:00Z En la llanura de la Provincia de Buenos Aires, la evapotranspiración (ET) es el principal mecanismo de pérdida de agua ya que el sistema de drenaje superficial está pobremente desarrollado. En este ambiente hidrogeológico, los cambios en el patrón de ET están fuertemente relacionados con los eventos de inundación y sequía que afectan periódicamente a la región. El objetivo de este estudio es presentar una nueva técnica para estimar la ET utilizando mediciones de gravedad proporcionados por un gravímetro superconductor. Este dispositivo mide las variaciones temporales de la gravedad con muy alta resolución (décimas de nm/s2) en un radio de unos cientos de metros alrededor del instrumento. Al igual que los lisímetros, los gravímetros proporcionan estimaciones directas de las variaciones de las reservas de agua en el orden del milímetro, pero a escalas espaciales mayores y sin perturbar el perfil del suelo. Cuello, Julián Eduardo Guarracino, Luis http://sedici.unlp.edu.ar:80/handle/10915/200596 2026-10-29T04:15:43Z 2023-01-01T00:00:00Z

Articulo Workshop: “Gestión del recurso hídrico en áreas continentales y costeras: casos de estudio sobre la interacción cuali-cuantitativa del agua subterránea y superficial en Italia Y Argentina” (La Plata, 3 de mayo de 2023); Revista del Museo de La Plata; vol. 8, no. 1, suplemento resúmenes El presente trabajo se centra en el estudio de la interacción mecánica entre las aguas superficiales y subterráneas en el extremo noreste de la Cuenca Matanza Riachuelo, en la localidad de Avellaneda, Provincia de Buenos Aires, Argentina. El objetivo del trabajo es caracterizar hidráulicamente los acuíferos semiconfinados Puelche y Paraná empleando una novedosa técnica hidrogeofísica basada en el fenómeno de marea inducida utilizando una nueva solución analítica derivada recientemente.

2023-01-01T00:00:00Z El presente trabajo se centra en el estudio de la interacción mecánica entre las aguas superficiales y subterráneas en el extremo noreste de la Cuenca Matanza Riachuelo, en la localidad de Avellaneda, Provincia de Buenos Aires, Argentina. El objetivo del trabajo es caracterizar hidráulicamente los acuíferos semiconfinados Puelche y Paraná empleando una novedosa técnica hidrogeofísica basada en el fenómeno de marea inducida utilizando una nueva solución analítica derivada recientemente. Jaque Arancibia, M. Barbá, Rodolfo Héctor Morrell, Nidia Irene Roman Lopes, A. Torres Robledo, S. Gunthardt, G. Soto, M. Ferrero Sosa, Gabriel Antonio Arias, Julia Inés Gamen, Roberto Claudio Fernández Lajús, Eduardo Eusebio http://sedici.unlp.edu.ar:80/handle/10915/199766 2026-10-07T04:25:02Z 2013-01-01T00:00:00Z

Objeto de conferencia IV Latin American Regional IAU Meeting (Florianópolis/SC, Brazil, 25-30 November 2013) We have performed a near-infrared photometric monitoring of 39 galactic youngstar clusters and star-forming regions, known as NIP of Stars, between the years 2009--2011, using the Swope telescope at Las Campanas Observatory (Chile) and the RetroCam camera, in H- and Y-bands. This monitoring program is complementary to the Vista Variables in the Vía Láctea (VVV), as the brightest sources observed in NIP of Stars are saturated in VVV. The objective of this campaign is to perform a census of photometric variability of such clusters and star-forming regions, with the main goal of discovering massive eclipsing binary stars.In this work, we present a preliminary analysis of this photometric monitoring program with the discovery of tens of candidates for variable stars, among which include candidates for massive eclipsing binaries. We included also to the analysis of variability, a small set of images obtained in the Ks with the VISTA telescope in the framework of VVV survey (Minniti et al. 2010). In special, we announce the infrared discovering of four massive eclipsing binaries in the massive young cluster NGC 3603. The stars have been classified spectroscopically as O-type stars, and one of them, MTT 58, has a rare star with a spectral type of O2 If*/WN6, as one of its components. We present a preliminary analysis of the light-curves of these binaries.

2013-01-01T00:00:00Z We have performed a near-infrared photometric monitoring of 39 galactic youngstar clusters and star-forming regions, known as NIP of Stars, between the years 2009--2011, using the Swope telescope at Las Campanas Observatory (Chile) and the RetroCam camera, in H- and Y-bands. This monitoring program is complementary to the Vista Variables in the Vía Láctea (VVV), as the brightest sources observed in NIP of Stars are saturated in VVV. The objective of this campaign is to perform a census of photometric variability of such clusters and star-forming regions, with the main goal of discovering massive eclipsing binary stars.In this work, we present a preliminary analysis of this photometric monitoring program with the discovery of tens of candidates for variable stars, among which include candidates for massive eclipsing binaries. We included also to the analysis of variability, a small set of images obtained in the Ks with the VISTA telescope in the framework of VVV survey (Minniti et al. 2010). In special, we announce the infrared discovering of four massive eclipsing binaries in the massive young cluster NGC 3603. The stars have been classified spectroscopically as O-type stars, and one of them, MTT 58, has a rare star with a spectral type of O2 If*/WN6, as one of its components. We present a preliminary analysis of the light-curves of these binaries. Moreno, Jonathan Alejandro Ferrero Sosa, Gabriel Antonio http://sedici.unlp.edu.ar:80/handle/10915/199765 2026-10-07T04:25:03Z 2023-01-01T00:00:00Z

Objeto de conferencia 3,2,1: Massive Triples, Binaries and Mergers 2023 (Leuven, Belgium, 17-21 July 2023) Our primary objective was to derive a new orbital solution for the HD 152590 binary system by employing both photometry and spectroscopy. To accomplish this, we identified the necessity to enhance the quality of the photometric data due to the typical uncertainties associated with ASAS observations, which are approximately 0.043 magnitudes. Consequently, our focus centered on obtaining photometric measurements with significantly higher precision, aiming for an error margin below 0.01 magnitudes.

2023-01-01T00:00:00Z Our primary objective was to derive a new orbital solution for the HD 152590 binary system by employing both photometry and spectroscopy. To accomplish this, we identified the necessity to enhance the quality of the photometric data due to the typical uncertainties associated with ASAS observations, which are approximately 0.043 magnitudes. Consequently, our focus centered on obtaining photometric measurements with significantly higher precision, aiming for an error margin below 0.01 magnitudes. Ferrero Sosa, Gabriel Antonio Henríquez C., Gustavo Percy Paz, R. Tumialán L., Juan Ayarza C., Ida http://sedici.unlp.edu.ar:80/handle/10915/199764 2026-10-07T04:25:03Z 2005-01-01T00:00:00Z

Articulo Revista de Investigación de Física; vol. 8, no. 1 Se ha desarrollado un procedimiento experimental capaz de aumentar en un factor de 50 la permeabilidad magnética de barras de mumetal (NÍ77Fe14Cu5Mo4). El procedimiento consiste en un tratamiento térmico bajo atmósfera inerte, para el cual se diseñó y construyó un control automático de temperatura programable de alta precisión. En el curso de los tratamientos se ha verificado que el sistema es capaz de mantener una temperatura estable de más de 1000 °C con un error menor que 2 °C y con gradientes lineales menores del 1%. Además se diseñó y construyó un permeámetro con fluxómetro electrónico con el cual se verificó la permeabilidad magnética alcanzada. La barra tratada se utilizó para construir un magnetopar (magnetic torquer) para satélite. El instrumento producido desarrolla un momento dipolar magnético máximo de 25 Am2 en su zona lineal con un consumo de menos de 0.3 W de potencia y una masa de 2.1 kg. Aprovechando la interacción de los magnetopares con el campo magnético terrestre, es posible introducir un torque en un satélite en órbita y de esta manera controlar su orientación en el espacio.; An experimental procedure has been developed to increase in a factor of 50 the magnetic permeability of mumetal bars (Ni77Fel4Cu5Mo4). The procedure consists of a heat treatment under inert atmosphere, for which a programmable automatic temperature regulator of high precision was designed and constructed. It has been verified that during the treatments the system is able to maintain a stable temperature of more than 1000 °C with an error smaller than 2 °C and with smaller linear gradients of 1%. In addition permeameter with electronic airflow meter was designed and constructed for monitoring the magnetic permeability. The treated bar was used to construct a magnetic pair (magnetic torquex) for satellite. The produced instrument develops a maximun magnetic dipole of 25 Am1 2 in its linear zone with a consumption of less than 0,3 W of power and one mass of 2,1 kg. Taking advantage of the interaction between the magnetic pairs and the Earth's magnetic field is possible to introduce torque in a satellite in orbit for controlling its direction in the space.

2005-01-01T00:00:00Z Se ha desarrollado un procedimiento experimental capaz de aumentar en un factor de 50 la permeabilidad magnética de barras de mumetal (NÍ77Fe14Cu5Mo4). El procedimiento consiste en un tratamiento térmico bajo atmósfera inerte, para el cual se diseñó y construyó un control automático de temperatura programable de alta precisión. En el curso de los tratamientos se ha verificado que el sistema es capaz de mantener una temperatura estable de más de 1000 °C con un error menor que 2 °C y con gradientes lineales menores del 1%. Además se diseñó y construyó un permeámetro con fluxómetro electrónico con el cual se verificó la permeabilidad magnética alcanzada. La barra tratada se utilizó para construir un magnetopar (magnetic torquer) para satélite. El instrumento producido desarrolla un momento dipolar magnético máximo de 25 Am2 en su zona lineal con un consumo de menos de 0.3 W de potencia y una masa de 2.1 kg. Aprovechando la interacción de los magnetopares con el campo magnético terrestre, es posible introducir un torque en un satélite en órbita y de esta manera controlar su orientación en el espacio. An experimental procedure has been developed to increase in a factor of 50 the magnetic permeability of mumetal bars (Ni77Fel4Cu5Mo4). The procedure consists of a heat treatment under inert atmosphere, for which a programmable automatic temperature regulator of high precision was designed and constructed. It has been verified that during the treatments the system is able to maintain a stable temperature of more than 1000 °C with an error smaller than 2 °C and with smaller linear gradients of 1%. In addition permeameter with electronic airflow meter was designed and constructed for monitoring the magnetic permeability. The treated bar was used to construct a magnetic pair (magnetic torquex) for satellite. The produced instrument develops a maximun magnetic dipole of 25 Am1 2 in its linear zone with a consumption of less than 0,3 W of power and one mass of 2,1 kg. Taking advantage of the interaction between the magnetic pairs and the Earth's magnetic field is possible to introduce torque in a satellite in orbit for controlling its direction in the space. Clocchiatti García, Alejandro http://sedici.unlp.edu.ar:80/handle/10915/198386 2026-09-08T20:22:49Z 1995-01-01T00:00:00Z

Tesis de doctorado Doctor en Filosofía; The University of Texas at Austin Five studies concerning mainly the hybrid type SN 1993J, the Type lb SN 1983N, and the Type Ic SNe 1983V, 19941 and 1987M are presented, together with less profound analyses of the Type Ic SNe 1962L, 19831, 1988L, 1990B, 1990U. We study the very early spectrophotometric evolution of SN 1993J, measure its intrinsic flux, color temperature and foreground extinction in a self consistent manner, and obtain constraints on the size of the progenitor star, and early temperature and velocity evolution. We present spectra of SN 19941 and analyze the evidence for He in the optical wavelength region finding that, contrary to earlier interpretation, Type Ic SNe contain small amounts of He expanding at high velocity. We present the late time light curve of the Type lb SN 1983N and show that, both from the photometric and photospheric velocity evolution, this SN was very similar to SN 1993J. We present a detailed study of the Type Ic SN 1983V, thoroughly discuss its photometric and spectroscopic characteristics and find that it followed a light curve very similar to that of SN 1993J, as well. We finally present a comparative analysis of seven Type Ic SNe and find that, in spite of their very similar spectra and spectroscopic evolution, the light curves of some of them are probably faster than that of a Type la SNe while those of some others are similar to the light curve of SN 1993J. The objects of Type Ib/c whose light curves are similar to those of SN 1993J, together with the the spectroscopic links connecting them, lead us to the concept of Transition Type SNe, a group of SNe which do not share the spectroscopic class but have very similar inner structure as revealed by the similar photometric behavior. This group poses a controversy: They have similar light curves but different mass to energy ratio. We conclude that, in this group of SNe at least, the late time light curves are not determined by the total mass of the ejecta but by the deposition function in substructures (or inclusions) which do not follow a homologous spherical expansion. Material digitalizado en SEDICI en colaboración con la Biblioteca de la Facultad de Ciencias Astronómicas y Geofísicas (UNLP).

1995-01-01T00:00:00Z Five studies concerning mainly the hybrid type SN 1993J, the Type lb SN 1983N, and the Type Ic SNe 1983V, 19941 and 1987M are presented, together with less profound analyses of the Type Ic SNe 1962L, 19831, 1988L, 1990B, 1990U. We study the very early spectrophotometric evolution of SN 1993J, measure its intrinsic flux, color temperature and foreground extinction in a self consistent manner, and obtain constraints on the size of the progenitor star, and early temperature and velocity evolution. We present spectra of SN 19941 and analyze the evidence for He in the optical wavelength region finding that, contrary to earlier interpretation, Type Ic SNe contain small amounts of He expanding at high velocity. We present the late time light curve of the Type lb SN 1983N and show that, both from the photometric and photospheric velocity evolution, this SN was very similar to SN 1993J. We present a detailed study of the Type Ic SN 1983V, thoroughly discuss its photometric and spectroscopic characteristics and find that it followed a light curve very similar to that of SN 1993J, as well. We finally present a comparative analysis of seven Type Ic SNe and find that, in spite of their very similar spectra and spectroscopic evolution, the light curves of some of them are probably faster than that of a Type la SNe while those of some others are similar to the light curve of SN 1993J. The objects of Type Ib/c whose light curves are similar to those of SN 1993J, together with the the spectroscopic links connecting them, lead us to the concept of Transition Type SNe, a group of SNe which do not share the spectroscopic class but have very similar inner structure as revealed by the similar photometric behavior. This group poses a controversy: They have similar light curves but different mass to energy ratio. We conclude that, in this group of SNe at least, the late time light curves are not determined by the total mass of the ejecta but by the deposition function in substructures (or inclusions) which do not follow a homologous spherical expansion. Cesanelli, Andrés Ricetti, Lorenzo Sarochar, Rubén Horacio http://sedici.unlp.edu.ar:80/handle/10915/197152 2026-08-04T20:20:38Z 2025-01-01T00:00:00Z

Articulo Journal of Hydrology; vol. 654 The availability of rainfall data is of paramount importance in most hydrological studies and is directly dependent on the type of sensors used as well as the recording systems adopted. In fact, these elements have a crucial influence on the temporal resolution (ta) of stored rainfall data, which in turn affects the types of analysis that can be conducted, making knowledge of ta on a global scale of particular interest to the entire scientific community and also for engineers. For rain gauges installed more than 70–80 years ago the earliest recordings were manual with coarse temporal resolution. Instead, mechanical recordings on paper rolls began in the early decades of the last century, while digital recordings began only in the last four decades, making analyses requiring long time series of sub-hourly rainfall data impossible. This paper presents a significant update of a previous historical analysis of the time-resolution of ta (Morbidelli et al., 2020) by which 126,438 stations, located in 77 different geographical areas, were collected into a database, quintupling the number of stations of the previous database and including areas not considered before. It was found that a high percentage of rain gauge stations currently provides useful data at any time-resolution, but there is an increasing development of rainfall networks characterized by very inexpensive, volunteer-operated stations that acquire one data per day (ta = 1440 min), allowing only limited rainfall-related analyses. The invitation for all rain gauge network op­ erators to contribute additional data to the database remains open. La lista completa de autores que integran el documento puede consultarse en el archivo.

2025-01-01T00:00:00Z The availability of rainfall data is of paramount importance in most hydrological studies and is directly dependent on the type of sensors used as well as the recording systems adopted. In fact, these elements have a crucial influence on the temporal resolution (ta) of stored rainfall data, which in turn affects the types of analysis that can be conducted, making knowledge of ta on a global scale of particular interest to the entire scientific community and also for engineers. For rain gauges installed more than 70–80 years ago the earliest recordings were manual with coarse temporal resolution. Instead, mechanical recordings on paper rolls began in the early decades of the last century, while digital recordings began only in the last four decades, making analyses requiring long time series of sub-hourly rainfall data impossible. This paper presents a significant update of a previous historical analysis of the time-resolution of ta (Morbidelli et al., 2020) by which 126,438 stations, located in 77 different geographical areas, were collected into a database, quintupling the number of stations of the previous database and including areas not considered before. It was found that a high percentage of rain gauge stations currently provides useful data at any time-resolution, but there is an increasing development of rainfall networks characterized by very inexpensive, volunteer-operated stations that acquire one data per day (ta = 1440 min), allowing only limited rainfall-related analyses. The invitation for all rain gauge network op­ erators to contribute additional data to the database remains open. Tramontini, Matías Leandro Rosas Carbajal, Marina Heap, Michael J. Besson, Pascale Marteau, Jacques Garcia, Sebastian Zyserman, Fabio Iván http://sedici.unlp.edu.ar:80/handle/10915/197125 2026-08-03T20:21:34Z 2026-01-01T00:00:00Z

Articulo Journal of Volcanology and Geothermal Research; vol. 476 Copahue volcano, located at the border between Chile and Argentina, has been among the most active volcanoes in Patagonia for the last 30 years. Copahue hosts a hyperacidic lake in its active crater, and many manifestations of intense hydrothermal activity, motivating studies of the volcano’s internal structure and how alteration may affect edifice stability. In this work, we study the structure, composition, and rock strength of the upper eastern flank of Copahue volcano, which is the most common path used to access the crater by tourists. It is also where the main water springs originating from the crater lake are found, and where most of the ejected material is deposited due to topography and the prevailing wind direction. To study the field-scale edifice structures, we installed a muon detector and computed a muon density image. In addition, we analyzed rock samples from the eastern flank in the laboratory. Using a Scanning Electron Microscope combined with Energy Dispersive X-ray analysis and X-ray Powder Diffraction, we visualized the effects of alteration and identified the minerals present. Finally, we measured the bulk density, dry uniaxial compressive strength (UCS), and static Young’s modulus of the samples. The muon imaging suggests mainly low-density values in the eastern side of the volcano, that we interpret as glacial and/or ice deposits, interleaved with tephras and tuffs, and presence of large edifice fractures. Well-defined high-density anomalies correspond to lava flows that outcrop in some parts of the edifice. Most of the samples analyzed have suffered hydrothermal alteration through rock dissolution, and precipitation of silica and secondary minerals, in accordance with the hyperacidic hydrothermal environment. The laboratory measurements suggest variable rock strength values, which appear to be controlled by rock type and primary porosity. Our multidisciplinary approach indicates that the eastern flank of Copahue volcano is characterized by mainly low-cohesion, low-density and variablestrength materials. The structures mapped, together with the rock properties measured, are key for a future flank stability assessment.

2026-01-01T00:00:00Z Copahue volcano, located at the border between Chile and Argentina, has been among the most active volcanoes in Patagonia for the last 30 years. Copahue hosts a hyperacidic lake in its active crater, and many manifestations of intense hydrothermal activity, motivating studies of the volcano’s internal structure and how alteration may affect edifice stability. In this work, we study the structure, composition, and rock strength of the upper eastern flank of Copahue volcano, which is the most common path used to access the crater by tourists. It is also where the main water springs originating from the crater lake are found, and where most of the ejected material is deposited due to topography and the prevailing wind direction. To study the field-scale edifice structures, we installed a muon detector and computed a muon density image. In addition, we analyzed rock samples from the eastern flank in the laboratory. Using a Scanning Electron Microscope combined with Energy Dispersive X-ray analysis and X-ray Powder Diffraction, we visualized the effects of alteration and identified the minerals present. Finally, we measured the bulk density, dry uniaxial compressive strength (UCS), and static Young’s modulus of the samples. The muon imaging suggests mainly low-density values in the eastern side of the volcano, that we interpret as glacial and/or ice deposits, interleaved with tephras and tuffs, and presence of large edifice fractures. Well-defined high-density anomalies correspond to lava flows that outcrop in some parts of the edifice. Most of the samples analyzed have suffered hydrothermal alteration through rock dissolution, and precipitation of silica and secondary minerals, in accordance with the hyperacidic hydrothermal environment. The laboratory measurements suggest variable rock strength values, which appear to be controlled by rock type and primary porosity. Our multidisciplinary approach indicates that the eastern flank of Copahue volcano is characterized by mainly low-cohesion, low-density and variablestrength materials. The structures mapped, together with the rock properties measured, are key for a future flank stability assessment. Araujo Furlan, Susana Beatriz Romero, Gustavo Esteban Zubieta, Ezequiel Gancio, Guillermo Matías García, Federico Palacio, Santiago del Lousto, Carlos Oscar http://sedici.unlp.edu.ar:80/handle/10915/196233 2026-06-26T20:20:16Z 2026-01-01T00:00:00Z

Articulo Astronomy & Astrophysics; vol. 710 Context. XTE J1810−197 is one of the six magnetars that exhibit radio emission, sometimes visible only during periods of increased activity or outbursts. XTE J1810−197 underwent its latest outburst in December 2018. Aims. We analyzed the population of single pulses of XTE J1810−197 in radio, characterized its timing properties, and explored the potential connection between magnetars and fast radio bursts (FRBs). Methods. We observed XTE J1810−197 between 29 September 2022 and 14 July 2023 with the radio telescopes at the Argentine Institute of Radioastronomy (IAR). We searched for single pulses in time series at a dispersion measure (DM) range of 100–400 pc cm −3 , with a signal-to-noise ratio (S/N) threshold of 8. We folded each observation to obtain an integrated pulse profile. We also analyzed archival X-ray observations of the MAXI instrument from the same period, and studied the flux evolution and the magnetar’s activity. Results. We found 249 giant pulses (GPs) at a DM mean value of 178.8 ± 0.1 pc cm −3 . We measured peak flux densities up to 119 Jy, and fluences up to 58 Jy ms. We fitted a power-law distribution to the flux density, obtaining an index of −4.0 ± 0.3. We observed a maximum rate of approximately 15 pulses per hour on 20 February 2023, followed by an abrupt disappearance of transient radio emission, indicating a transition to a less active state. The brightest single pulses are limited to ∼2% of the rotational phase and have similar fluence values to the reported intermediate FRB-like bursts of SGR 1935+2154. No significant X-ray activity in the MAXI data was detected during the radio observing period. Conclusions. This is the first study of single radio pulses of a magnetar using IAR data, showing the potential of the upgraded telescopes for investigating the transient radio sky. The properties of the single pulses detected here show the magnetar transient nature and capability to emit high-luminosity pulses. We compared the detected emission to FRB-like bursts and single pulses emitted by SGR 1935+2154. Even though the mechanism producing all the events should be coherent, the luminosity of the events, features on the dynamic spectra, and the difference between being phase confined or not, indicate that XTE J1810−197 presents GP emission, while SGR 1935+2154 only shows normal single pulses or FRB bursts. This could indicate that the conditions for producing each type of event differ.

2026-01-01T00:00:00Z Context. XTE J1810−197 is one of the six magnetars that exhibit radio emission, sometimes visible only during periods of increased activity or outbursts. XTE J1810−197 underwent its latest outburst in December 2018. Aims. We analyzed the population of single pulses of XTE J1810−197 in radio, characterized its timing properties, and explored the potential connection between magnetars and fast radio bursts (FRBs). Methods. We observed XTE J1810−197 between 29 September 2022 and 14 July 2023 with the radio telescopes at the Argentine Institute of Radioastronomy (IAR). We searched for single pulses in time series at a dispersion measure (DM) range of 100–400 pc cm −3 , with a signal-to-noise ratio (S/N) threshold of 8. We folded each observation to obtain an integrated pulse profile. We also analyzed archival X-ray observations of the MAXI instrument from the same period, and studied the flux evolution and the magnetar’s activity. Results. We found 249 giant pulses (GPs) at a DM mean value of 178.8 ± 0.1 pc cm −3 . We measured peak flux densities up to 119 Jy, and fluences up to 58 Jy ms. We fitted a power-law distribution to the flux density, obtaining an index of −4.0 ± 0.3. We observed a maximum rate of approximately 15 pulses per hour on 20 February 2023, followed by an abrupt disappearance of transient radio emission, indicating a transition to a less active state. The brightest single pulses are limited to ∼2% of the rotational phase and have similar fluence values to the reported intermediate FRB-like bursts of SGR 1935+2154. No significant X-ray activity in the MAXI data was detected during the radio observing period. Conclusions. This is the first study of single radio pulses of a magnetar using IAR data, showing the potential of the upgraded telescopes for investigating the transient radio sky. The properties of the single pulses detected here show the magnetar transient nature and capability to emit high-luminosity pulses. We compared the detected emission to FRB-like bursts and single pulses emitted by SGR 1935+2154. Even though the mechanism producing all the events should be coherent, the luminosity of the events, features on the dynamic spectra, and the difference between being phase confined or not, indicate that XTE J1810−197 presents GP emission, while SGR 1935+2154 only shows normal single pulses or FRB bursts. This could indicate that the conditions for producing each type of event differ. Romero, Gustavo Esteban http://sedici.unlp.edu.ar:80/handle/10915/196226 2026-06-25T20:23:51Z 2024-01-01T00:00:00Z

Articulo Philosophies; vol. 9, no. 4 The ontology behind quantum mechanics has been the subject of endless debate since the theory was formulated some 100 years ago. It has been suggested, at one time or another, that the objects described by the theory may be individual particles, waves, fields, ensembles of particles, observers, and minds, among many other possibilities. I maintain that these disagreements are due in part to a lack of precision in the use of the theory’s various semantic designators. In particular, there is some confusion about the role of representation, reference, and denotation in the theory. In this article, I first analyze the role of the semantic apparatus in physical theories in general and then discuss the corresponding ontological implications for quantum mechanics. Subsequently, I consider the extension of the theory to quantum fields and then analyze the semantic changes of the designators with their ontological consequences. In addition to the classical arguments to rule out a particle ontology in the case of non-relativistic quantum field theory, I show how the existence of black holes makes the proposal of a particle ontology in general spacetimes unfeasible. I conclude by proposing a provisional pluralistic ontology of fields and spacetime and discussing some prospects for possible future ontological economies.

2024-01-01T00:00:00Z The ontology behind quantum mechanics has been the subject of endless debate since the theory was formulated some 100 years ago. It has been suggested, at one time or another, that the objects described by the theory may be individual particles, waves, fields, ensembles of particles, observers, and minds, among many other possibilities. I maintain that these disagreements are due in part to a lack of precision in the use of the theory’s various semantic designators. In particular, there is some confusion about the role of representation, reference, and denotation in the theory. In this article, I first analyze the role of the semantic apparatus in physical theories in general and then discuss the corresponding ontological implications for quantum mechanics. Subsequently, I consider the extension of the theory to quantum fields and then analyze the semantic changes of the designators with their ontological consequences. In addition to the classical arguments to rule out a particle ontology in the case of non-relativistic quantum field theory, I show how the existence of black holes makes the proposal of a particle ontology in general spacetimes unfeasible. I conclude by proposing a provisional pluralistic ontology of fields and spacetime and discussing some prospects for possible future ontological economies. Abaroa, Leandro Romero, Gustavo Esteban Mancuso, Giulio Cesare Rizzo, Florencia Nadine http://sedici.unlp.edu.ar:80/handle/10915/196223 2026-06-25T20:23:52Z 2024-01-01T00:00:00Z

Articulo Astronomy & Astrophysics; vol. 691 Context. S26 is an extragalactic microquasar with the most powerful jets ever discovered. They have a kinetic luminosity of Lj ∼ 5 × 10⁴⁰ erg s⁻¹. This implies that the accretion power to the black hole should be super-Eddington, of the order of Lacc ∼ Lj. However, the observed X-ray flux of this system indicates an apparent very sub-Eddington accretion luminosity of LX ≈ 10³⁷ erg s⁻¹. Aims. We aim to characterize the nature of S26, explain the system emission, and study the feasibility of super-Eddington microquasars as potential PeVatron sources. Methods. We first analyze multi-epoch X-ray observations of S26 obtained with XMM-Newton and model the super-Eddington disk and its wind. We then develop a jet model and study the particle acceleration and radiative processes that occur in shocks generated near the base of the jet and in its terminal region. Results. We find that the discrepancy between the jet and the apparent disk luminosities in S26 is caused by the complete absorption of the disk radiation by the wind ejected from the super-Eddington disk. The nonthermal X-rays are produced near the base of the jet, and the thermal X-rays are emitted in the terminal regions. The radio emission observed with the Australia Telescope Compact Array can be explained as synchrotron radiation produced at the reverse shock in the lobes. We also find that S26 can accelerate protons to PeV energies in both the inner jet and the lobes. The ultra-high energy protons accelerated in the lobes of S26 are injected into the interstellar medium with a total power of ∼10³⁶ erg s⁻¹. Conclusions. We conclude that S26 is a super-Eddington microquasar with a dense disk-driven wind that obscures the X-ray emission from the inner disk, and that the supercritical nature of the system allows the acceleration of cosmic rays to PeV energies.

2024-01-01T00:00:00Z Context. S26 is an extragalactic microquasar with the most powerful jets ever discovered. They have a kinetic luminosity of Lj ∼ 5 × 10⁴⁰ erg s⁻¹. This implies that the accretion power to the black hole should be super-Eddington, of the order of Lacc ∼ Lj. However, the observed X-ray flux of this system indicates an apparent very sub-Eddington accretion luminosity of LX ≈ 10³⁷ erg s⁻¹. Aims. We aim to characterize the nature of S26, explain the system emission, and study the feasibility of super-Eddington microquasars as potential PeVatron sources. Methods. We first analyze multi-epoch X-ray observations of S26 obtained with XMM-Newton and model the super-Eddington disk and its wind. We then develop a jet model and study the particle acceleration and radiative processes that occur in shocks generated near the base of the jet and in its terminal region. Results. We find that the discrepancy between the jet and the apparent disk luminosities in S26 is caused by the complete absorption of the disk radiation by the wind ejected from the super-Eddington disk. The nonthermal X-rays are produced near the base of the jet, and the thermal X-rays are emitted in the terminal regions. The radio emission observed with the Australia Telescope Compact Array can be explained as synchrotron radiation produced at the reverse shock in the lobes. We also find that S26 can accelerate protons to PeV energies in both the inner jet and the lobes. The ultra-high energy protons accelerated in the lobes of S26 are injected into the interstellar medium with a total power of ∼10³⁶ erg s⁻¹. Conclusions. We conclude that S26 is a super-Eddington microquasar with a dense disk-driven wind that obscures the X-ray emission from the inner disk, and that the supercritical nature of the system allows the acceleration of cosmic rays to PeV energies. Panuco Liñan, Alan Alejandro Pérez, Daniela Luna, Carlos Romero, Gustavo Esteban http://sedici.unlp.edu.ar:80/handle/10915/196220 2026-06-25T20:23:52Z 2025-01-01T00:00:00Z

Articulo The European Physical Journal C; vol. 85, no. 4 There are several reasons to support the idea that entropy might be associated to gravity itself. In the absence of a quantum theory of gravity, classical estimators for the gravitational entropy have been proposed. Any viable description of the gravitational entropy should reproduce the Hawking–Bekenstein entropy at the event horizon of black holes. Furthermore, in any black hole transformation, these estimators must satisfy the second law of black hole thermodynamics. In this work, we analyze whether two entropy estimators, one based on the Weyl tensor and the other on the Bel–Robinson tensor, satisfy the second law in the transformation process from a Schwarzschild to a Reissner–Nordström black hole by the absorption of a charge test particle. We also address the inverse process. We show that depending whether the process is reversible or not, both estimators fulfill the second law.

2025-01-01T00:00:00Z There are several reasons to support the idea that entropy might be associated to gravity itself. In the absence of a quantum theory of gravity, classical estimators for the gravitational entropy have been proposed. Any viable description of the gravitational entropy should reproduce the Hawking–Bekenstein entropy at the event horizon of black holes. Furthermore, in any black hole transformation, these estimators must satisfy the second law of black hole thermodynamics. In this work, we analyze whether two entropy estimators, one based on the Weyl tensor and the other on the Bel–Robinson tensor, satisfy the second law in the transformation process from a Schwarzschild to a Reissner–Nordström black hole by the absorption of a charge test particle. We also address the inverse process. We show that depending whether the process is reversible or not, both estimators fulfill the second law. Palacio, Santiago del Gancio, Guillermo Matías García, Federico Romero, Gustavo Esteban Zubieta, Ezequiel http://sedici.unlp.edu.ar:80/handle/10915/196218 2026-06-25T20:23:54Z 2026-01-01T00:00:00Z

Articulo The Astrophysical Journal; vol. 1005, no. 1 Among known neutron stars, the Vela pulsar is one of the best targets for gravitational-wave searches. It is also one of the most prolific in terms of glitches, which are sudden frequency changes in a pulsar’s rotation. Such glitches could cause a variety of transient gravitational-wave signals. Here, we search for signals associated with a Vela glitch on 2024 April 29 in data of the two LIGO detectors from the fourth LIGO–Virgo–KAGRA observing run. We search both for seconds-scale burst-like emission, primarily from fundamental ( f -)mode oscillations, and for longer quasi-monochromatic transients up to 4 months in duration, primarily from quasi-static quadrupolar deformations. We find no significant detection candidates, but for the first time we set direct observational upper limits on gravitational strain amplitude that are stricter than what can be indirectly inferred from the overall glitch energy scale. We discuss the short- and long-duration observational constraints in the context of specific emission models. These results demonstrate the potential of gravitational-wave probes of glitching pulsars as detector sensitivity continues to improve. La lista completa de autores que integran el documento puede consultarse en el archivo.

2026-01-01T00:00:00Z Among known neutron stars, the Vela pulsar is one of the best targets for gravitational-wave searches. It is also one of the most prolific in terms of glitches, which are sudden frequency changes in a pulsar’s rotation. Such glitches could cause a variety of transient gravitational-wave signals. Here, we search for signals associated with a Vela glitch on 2024 April 29 in data of the two LIGO detectors from the fourth LIGO–Virgo–KAGRA observing run. We search both for seconds-scale burst-like emission, primarily from fundamental ( f -)mode oscillations, and for longer quasi-monochromatic transients up to 4 months in duration, primarily from quasi-static quadrupolar deformations. We find no significant detection candidates, but for the first time we set direct observational upper limits on gravitational strain amplitude that are stricter than what can be indirectly inferred from the overall glitch energy scale. We discuss the short- and long-duration observational constraints in the context of specific emission models. These results demonstrate the potential of gravitational-wave probes of glitching pulsars as detector sensitivity continues to improve. Regnier, M. Manzan, E. Hamilton, J. Ch. Mennella, A. Errard, J. Zapelli, L. Torchinsky, S. Paradiso, S. Battistelli, E. De Bernardis, P. Colombo, L. De Petris, M. D'Alessandro, G. García, Beatriz Gervasi, M. Masi, S. Mousset, L. Mirón Granese, Nahuel Omar O’Sullivan, C. Piat, M. Rasztocky, Emiliano Romero, Gustavo Esteban Scóccola, Claudia Graciela Zannoni, M. http://sedici.unlp.edu.ar:80/handle/10915/196212 2026-06-25T20:23:55Z 2024-01-01T00:00:00Z

Articulo Astronomy & Astrophysics; vol. 686 Context. Astrophysical polarized foregrounds represent the most critical challenge in cosmic microwave background (CMB) B-mode experiments, requiring multifrequency observations to constrain astrophysical foregrounds and isolate the CMB signal. However, recent observations indicate that foreground emission may be more complex than anticipated. Not properly accounting for these complexities during component separation can lead to a bias in the recovered tensor-to-scalar ratio. Aims. In this paper we investigate how the increased spectral resolution provided by band-splitting in bolometric interferometry (BI) through a technique called spectral imaging can help control the foreground contamination in the case of an unaccounted-for Galactic dust frequency de-correlation along the line of sight (LOS). Methods. We focused on the next-generation ground-based CMB experiment CMB-S4 and compared its anticipated sensitivity, frequency, and sky coverage with a hypothetical version of the same experiment based on BI (CMB-S4/BI). We performed a Monte Carlo analysis based on parametric component separation methods (FGBuster and Commander) and computed the likelihood of the recovered tensor-to-scalar ratio, r. Results. The main result is that spectral imaging allows us to detect systematic uncertainties on r from frequency de-correlation when this effect is not accounted for in the component separation. Conversely, an imager such as CMB-S4 would detect a biased value of r and would be unable to spot the presence of a systematic effect. We find a similar result in the reconstruction of the dust spectral index, and we show that with BI we can more precisely measure the dust spectral index when frequency de-correlation is present and not accounted for in the component separation. Conclusions. The in-band frequency resolution provided by BI allows us to identify dust LOS frequency de-correlation residuals where an imager with a similar level of performance would fail. This creates the possibility of exploiting this potential in the context of future CMB polarization experiments that will be challenged by complex foregrounds in their quest for B-mode detection.

2024-01-01T00:00:00Z Context. Astrophysical polarized foregrounds represent the most critical challenge in cosmic microwave background (CMB) B-mode experiments, requiring multifrequency observations to constrain astrophysical foregrounds and isolate the CMB signal. However, recent observations indicate that foreground emission may be more complex than anticipated. Not properly accounting for these complexities during component separation can lead to a bias in the recovered tensor-to-scalar ratio. Aims. In this paper we investigate how the increased spectral resolution provided by band-splitting in bolometric interferometry (BI) through a technique called spectral imaging can help control the foreground contamination in the case of an unaccounted-for Galactic dust frequency de-correlation along the line of sight (LOS). Methods. We focused on the next-generation ground-based CMB experiment CMB-S4 and compared its anticipated sensitivity, frequency, and sky coverage with a hypothetical version of the same experiment based on BI (CMB-S4/BI). We performed a Monte Carlo analysis based on parametric component separation methods (FGBuster and Commander) and computed the likelihood of the recovered tensor-to-scalar ratio, r. Results. The main result is that spectral imaging allows us to detect systematic uncertainties on r from frequency de-correlation when this effect is not accounted for in the component separation. Conversely, an imager such as CMB-S4 would detect a biased value of r and would be unable to spot the presence of a systematic effect. We find a similar result in the reconstruction of the dust spectral index, and we show that with BI we can more precisely measure the dust spectral index when frequency de-correlation is present and not accounted for in the component separation. Conclusions. The in-band frequency resolution provided by BI allows us to identify dust LOS frequency de-correlation residuals where an imager with a similar level of performance would fail. This creates the possibility of exploiting this potential in the context of future CMB polarization experiments that will be challenged by complex foregrounds in their quest for B-mode detection. Araujo Furlan, Susana Beatriz Palacio, Santiago del Gancio, Guillermo Matías García, Federico Romero, Gustavo Esteban Zubieta, Ezequiel http://sedici.unlp.edu.ar:80/handle/10915/196207 2026-06-25T20:23:56Z 2025-01-01T00:00:00Z

Articulo The Astrophysical Journal; vol. 983, no. 2 Continuous gravitational waves (CWs) emission from neutron stars carries information about their internal structure and equation of state, and it can provide tests of general relativity. We present a search for CWs from a set of 45 known pulsars in the first part of the fourth LIGO–Virgo–KAGRA observing run, known as O4a. We conducted a targeted search for each pulsar using three independent analysis methods considering single-harmonic and dual-harmonic emission models. We find no evidence of a CW signal in O4a data for both models and set upper limits on the signal amplitude and on the ellipticity, which quantifies the asymmetry in the neutron star mass distribution. For the single-harmonic emission model, 29 targets have the upper limit on the amplitude below the theoretical spin-down limit. The lowest upper limit on the amplitude is 6.4 × 10 −27 for the young energetic pulsar J0537−6910, while the lowest constraint on the ellipticity is 8.8 × 10 −9 for the bright nearby millisecond pulsar J0437−4715. Additionally, for a subset of 16 targets, we performed a narrowband search that is more robust regarding the emission model, with no evidence of a signal. We also found no evidence of nonstandard polarizations as predicted by the Brans–Dicke theory. La lista completa de autores que integran el documento puede consultarse en el archivo.

2025-01-01T00:00:00Z Continuous gravitational waves (CWs) emission from neutron stars carries information about their internal structure and equation of state, and it can provide tests of general relativity. We present a search for CWs from a set of 45 known pulsars in the first part of the fourth LIGO–Virgo–KAGRA observing run, known as O4a. We conducted a targeted search for each pulsar using three independent analysis methods considering single-harmonic and dual-harmonic emission models. We find no evidence of a CW signal in O4a data for both models and set upper limits on the signal amplitude and on the ellipticity, which quantifies the asymmetry in the neutron star mass distribution. For the single-harmonic emission model, 29 targets have the upper limit on the amplitude below the theoretical spin-down limit. The lowest upper limit on the amplitude is 6.4 × 10 −27 for the young energetic pulsar J0537−6910, while the lowest constraint on the ellipticity is 8.8 × 10 −9 for the bright nearby millisecond pulsar J0437−4715. Additionally, for a subset of 16 targets, we performed a narrowband search that is more robust regarding the emission model, with no evidence of a signal. We also found no evidence of nonstandard polarizations as predicted by the Brans–Dicke theory. Martínez, Javier Rodrigo Palacio, Santiago del Bosch Ramon, Valenti Romero, Gustavo Esteban http://sedici.unlp.edu.ar:80/handle/10915/196199 2026-06-25T20:23:57Z 2022-01-01T00:00:00Z

Articulo Astronomy & Astrophysics; vol. 661 Context.There is a population of runaway stars that move at extremely high speeds with respect to their surroundings. The fast motion and the stellar wind of these stars, plus the wind-medium interaction, can lead to particle acceleration and non-thermal radiation.Aims.We characterise the interaction between the winds of fast runaway stars and their environment, in particular to establish their potential as cosmic-ray accelerators and non-thermal emitters.Methods.We model the hydrodynamics of the interaction between the stellar wind and the surrounding material. We self-consistently calculate the injection and transport of relativistic particles in the bow shock using a multi-zone code, and compute their broadband emission from radio toγ-rays.Results.Both the forward and reverse shocks are favourable sites for particle acceleration, although the radiative efficiency of particles is low and therefore the expected fluxes are in general rather faint.Conclusions.We show that high-sensitivity observations in the radio band can be used to detect the non-thermal radiation associated with bow shocks from hyper-velocity and semi-relativistic stars. Hyper-velocity stars are expected to be modest sources of sub-TeV cosmic rays, accounting perhaps for ∼0.1% of that of galactic cosmic rays.

2022-01-01T00:00:00Z Context.There is a population of runaway stars that move at extremely high speeds with respect to their surroundings. The fast motion and the stellar wind of these stars, plus the wind-medium interaction, can lead to particle acceleration and non-thermal radiation.Aims.We characterise the interaction between the winds of fast runaway stars and their environment, in particular to establish their potential as cosmic-ray accelerators and non-thermal emitters.Methods.We model the hydrodynamics of the interaction between the stellar wind and the surrounding material. We self-consistently calculate the injection and transport of relativistic particles in the bow shock using a multi-zone code, and compute their broadband emission from radio toγ-rays.Results.Both the forward and reverse shocks are favourable sites for particle acceleration, although the radiative efficiency of particles is low and therefore the expected fluxes are in general rather faint.Conclusions.We show that high-sensitivity observations in the radio band can be used to detect the non-thermal radiation associated with bow shocks from hyper-velocity and semi-relativistic stars. Hyper-velocity stars are expected to be modest sources of sub-TeV cosmic rays, accounting perhaps for ∼0.1% of that of galactic cosmic rays. Abaroa, Leandro Romero, Gustavo Esteban Bosch Ramon, Valentí http://sedici.unlp.edu.ar:80/handle/10915/196198 2026-06-25T20:23:58Z 2026-01-01T00:00:00Z

Articulo Astronomy & Astrophysics; vol. 705 The Large High Altitude Air Shower Observatory (LHAASO) has revealed numerous ultrahigh-energy gamma-ray sources of unknown origin. We propose that a fraction of them can be explained by microquasar remnants, i.e., binary systems where mass transfer has ceased and the central engine is quenched. Cosmic rays injected during the active phase of a microquasar may remain confined within its cocoon and subsequently interact with nearby molecular clouds, producing bright gamma-ray emission through pp collisions. Remnants of former super-Eddington systems can act as dark PeVatrons, releasing particles up to ∼10 PeV that illuminate surrounding clouds producing gamma rays reaching hundreds of tera-electron volts. This scenario provides a natural explanation for several unidentified Galactic LHAASO sources.

2026-01-01T00:00:00Z The Large High Altitude Air Shower Observatory (LHAASO) has revealed numerous ultrahigh-energy gamma-ray sources of unknown origin. We propose that a fraction of them can be explained by microquasar remnants, i.e., binary systems where mass transfer has ceased and the central engine is quenched. Cosmic rays injected during the active phase of a microquasar may remain confined within its cocoon and subsequently interact with nearby molecular clouds, producing bright gamma-ray emission through pp collisions. Remnants of former super-Eddington systems can act as dark PeVatrons, releasing particles up to ∼10 PeV that illuminate surrounding clouds producing gamma rays reaching hundreds of tera-electron volts. This scenario provides a natural explanation for several unidentified Galactic LHAASO sources. Sotomayor, Pablo Romero, Gustavo Esteban http://sedici.unlp.edu.ar:80/handle/10915/196197 2026-06-26T11:17:06Z 2022-01-01T00:00:00Z

Articulo Astronomy & Astrophysics; vol. 664 Context.The radio emission mechanism in active galactic nuclei (AGNs) with high accretion rates is unclear. It has been suggested that low-power jets may explain the observed radiation at subparsec scales. The mechanisms for jet formation at super-Eddington rates, however, are not well understood. On the same scale, clouds from the broad-line region (BLR) propagating with supersonic velocities in the wind launched by the accretion disk may lead to the production of nonthermal radiation.Aims.We aim to characterize the nonthermal emission produced by the propagation of clouds through the wind of the accretion disk in super-accreting AGNs, and to estimate the relevance of such a contribution to the radio band of the electromagnetic spectrum.Methods.We determined the conditions under which the BLR clouds are not destroyed by shocks or hydrodynamic instabilities when immersed in the powerful wind of the accretion disk. These clouds form bowshocks which are suitable sites for particle acceleration. We developed a semianalytical model to calculate the distribution of relativistic particles in these bowshocks and the associated spectral energy distribution (SED) of the emitted radiation.Results.For typical parameters of super-accreting AGNs, we find that the cloud-wind interactions can produce nonthermal emission from radio up to a few tens of TeV, with slight absorption effects, if the processes occur outside the wind photosphere.Conclusions.Radio emission in AGNs without jets can be explained if the accretion rate is super-Eddington and if there is a BLR at subparsec scales around the central black hole. The accretion rate must not be extremely high so most of the clouds orbit outside of the wind photosphere and the radiation can escape to the observer. Instabilities in the disk wind, which have previously been reported in numerical simulations, generate clumps that increase the filling factor of the overdensities in the BLR and enhance the emitted radiation.

2022-01-01T00:00:00Z Context.The radio emission mechanism in active galactic nuclei (AGNs) with high accretion rates is unclear. It has been suggested that low-power jets may explain the observed radiation at subparsec scales. The mechanisms for jet formation at super-Eddington rates, however, are not well understood. On the same scale, clouds from the broad-line region (BLR) propagating with supersonic velocities in the wind launched by the accretion disk may lead to the production of nonthermal radiation.Aims.We aim to characterize the nonthermal emission produced by the propagation of clouds through the wind of the accretion disk in super-accreting AGNs, and to estimate the relevance of such a contribution to the radio band of the electromagnetic spectrum.Methods.We determined the conditions under which the BLR clouds are not destroyed by shocks or hydrodynamic instabilities when immersed in the powerful wind of the accretion disk. These clouds form bowshocks which are suitable sites for particle acceleration. We developed a semianalytical model to calculate the distribution of relativistic particles in these bowshocks and the associated spectral energy distribution (SED) of the emitted radiation.Results.For typical parameters of super-accreting AGNs, we find that the cloud-wind interactions can produce nonthermal emission from radio up to a few tens of TeV, with slight absorption effects, if the processes occur outside the wind photosphere.Conclusions.Radio emission in AGNs without jets can be explained if the accretion rate is super-Eddington and if there is a BLR at subparsec scales around the central black hole. The accretion rate must not be extremely high so most of the clouds orbit outside of the wind photosphere and the radiation can escape to the observer. Instabilities in the disk wind, which have previously been reported in numerical simulations, generate clumps that increase the filling factor of the overdensities in the BLR and enhance the emitted radiation. Abaroa, Leandro Romero, Gustavo Esteban http://sedici.unlp.edu.ar:80/handle/10915/196196 2026-06-26T11:18:37Z 2024-01-01T00:00:00Z

Articulo Astronomy & Astrophysics; vol. 691 Supermassive black holes (SMBHs) at the centers of active galaxies are fed by accretion disks that radiate from the infrared or optical to the X-ray bands. Several types of objects can orbit SMBHs, including massive stars, neutron stars, clouds from the broad- and narrow-line regions, and X-ray binaries. Isolated black holes with a stellar origin (BHs of ∼10 M⊙) should also be present in large numbers within the central parsec of the galaxies. These BHs are expected to form a cluster around the SMBH as a result of the enhanced star formation rate in the inner galactic region and the BH migration caused by gravitational dynamical friction. However, except for occasional microlensing effects on background stars or gravitational waves from binary BH mergers, the presence of a BH population is hard to verify. In this paper, we explore the possibility of detecting electromagnetic signatures of a central cluster of BHs when the accretion rate onto the central SMBH is greater than the Eddington rate. In these supercritical systems, the accretion disk launches powerful winds that interact with the objects orbiting the SMBH. Isolated BHs can capture matter from this dense wind, leading to the formation of small accretion disks around them. If jets are produced in these single microquasars, they could be sites of particle acceleration to relativistic energies. These particles in turn are expected to cool by various radiative processes. Therefore, the wind of the SMBH might illuminate the BHs through the production of both thermal and nonthermal radiation.

2024-01-01T00:00:00Z Supermassive black holes (SMBHs) at the centers of active galaxies are fed by accretion disks that radiate from the infrared or optical to the X-ray bands. Several types of objects can orbit SMBHs, including massive stars, neutron stars, clouds from the broad- and narrow-line regions, and X-ray binaries. Isolated black holes with a stellar origin (BHs of ∼10 M⊙) should also be present in large numbers within the central parsec of the galaxies. These BHs are expected to form a cluster around the SMBH as a result of the enhanced star formation rate in the inner galactic region and the BH migration caused by gravitational dynamical friction. However, except for occasional microlensing effects on background stars or gravitational waves from binary BH mergers, the presence of a BH population is hard to verify. In this paper, we explore the possibility of detecting electromagnetic signatures of a central cluster of BHs when the accretion rate onto the central SMBH is greater than the Eddington rate. In these supercritical systems, the accretion disk launches powerful winds that interact with the objects orbiting the SMBH. Isolated BHs can capture matter from this dense wind, leading to the formation of small accretion disks around them. If jets are produced in these single microquasars, they could be sites of particle acceleration to relativistic energies. These particles in turn are expected to cool by various radiative processes. Therefore, the wind of the SMBH might illuminate the BHs through the production of both thermal and nonthermal radiation.