The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
Gustavo E. Romero - One of the best experts on this subject based on the ideXlab platform.
-
Runaway massive stars as variable Gamma-Ray Sources
Astronomy & Astrophysics, 2014Co-Authors: M. V. Del Valle, Gustavo E. RomeroAbstract:Runaway stars are ejected from their formation sites well within molecular cores in giant dark clouds. Eventually, these stars can travel through the molecular clouds, which are highly inhomogeneous. The powerful winds of massive runaway stars interact with the medium forming bowshocks. Recent observations and theoretical modelling suggest that these bowshocks emit non-thermal radiation. As the massive stars move through the inhomogeneous ambient gas the physical properties of the bowshocks are modified, producing changes in the non-thermal emission. We aim to compute the non-thermal radiation produced in the bowshocks of runaway massive stars when travelling through a molecular cloud. We calculate the non-thermal emission and absorption for two types of massive runaway stars, an O9I and an O4I, as they move through a density gradient. We present the spectral energy distributions for the runaway stars modelled. Additionally, we obtain light curves at different energy ranges. We find significant variations in the emission over timescales of $\sim$ 1 yr. We conclude that bowshocks of massive runaway stars, under some assumptions, might be variable Gamma-Ray Sources, with variability timescales that depend on the medium density profile. These objects might constitute a population of galactic Gamma-Ray Sources turning on and off within years.
-
A microquasar model applied to unidentified Gamma-Ray Sources
Astronomy & Astrophysics, 2006Co-Authors: Valentí Bosch-ramon, Gustavo E. Romero, Josep M. Paredes, Diego F. TorresAbstract:the date of receipt and acceptance should be inserted later Abstract. Among unidentified Gamma-Ray Sources in the galactic plane, there are some that present significant variability and have been proposed to be high-mass microquasars. To deepen the study of the possible associa- tion between variable low galactic latitude Gamma-Ray Sources and microquasars, we have applied a leptonic jet model based on the microquasar scenario that reproduces the Gamma-Ray spectrum of three unidentified gamma- ray Sources, 3EG J1735 1500, 3EG J1828+0142 and GRO J1411 64, and is consistent with the observational constraints at lower energies. We conclude that if these Sources were generated by microquasars, the particle acceleration processes could not be as efficient as in other objects of this type that present harder Gamma-Ray spectra. Moreover, the dominant mechanism of high-energy emission should be synchrotron self-Compton (SSC) scattering, and the radio jets may only be observed at low frequencies. For each particular case, further predictions of jet physical conditions and variability generation mechanisms have been made in the context of the model. Although there might be other candidates able to explain the emission coming from these Sources, microquasars cannot be excluded as counterparts. Observations performed by the next generation of Gamma-Ray instruments, like GLAST, are required to test the proposed model.
-
Microquasars and Gamma-Ray Sources
Chinese Journal of Astronomy and Astrophysics, 2005Co-Authors: Gustavo E. RomeroAbstract:Microquasars are X-ray binary systems with non-thermal radio emission originated in jet-like features. They are attractive sites for Gamma-Ray production, since relativistic particles in the jet should traverse locally strong both photon and matter fields. In this review we discuss whether some of the unidentified Gamma-Ray Sources detected by the EGRET instrument of the Compton Gamma-Ray Observatory might be associated with microquasars. Relevant models for Gamma-Ray emission in such binaries are described and prospects for the detection of microquasars with instruments of new generation are briefly evaluated.
-
Multiwavelength Approach to Unidentified Gamma-Ray Sources - Multiwavelength approach to unidentified Gamma-Ray Sources : a second workshop on the nature of the high-energy unidentified Sources
2005Co-Authors: Kwong-sang Cheng, Gustavo E. RomeroAbstract:Nearly one half of the point-like Gamma-Ray Sources detected by EGRET instrument of the late Compton satellite are still defeating our attempts at identifying them. To establish the origin and nature of these enigmatic Sources has become a major problem of current high-energy astrophysics. The second workshop on Multiwavelength Approach to Unidentified Gamma-Ray Sources intends to shed new and fresh light on the problem of the nature of these mysterious Sources and the objects behind them. The proceedings contain 46 contributed papers in this subject, which cover theoretical models on Gamma-Ray Sources as well as the best multiwavelength strategies for the identification of the promising candidates. The topics of this conference also include energetic phenomena ocurring both in galactic and extragalactic scenarios, phenomena that might lead to the appearance of what we have called high-energy unidentified Sources. The book will be of interest for all active researchers in the high-energy astrophysics and related research areas as well as for scientists and graduate students interested in understanding the recent progress in this field.link_to_subscribed_fulltex
-
Unidentified Gamma-Ray Sources and Microquasars
2004Co-Authors: Gustavo E. Romero, I.a. Grenier, M. M. Kaufman Bernado, I. F. Mirabel, Diego F. TorresAbstract:Some phenomenological properties of the unidentified EGRET detections suggest that there are two distinct groups of galactic Gamma-Ray Sources that might be associated with compact objects endowed with relativistic jets. We discuss different models for Gamma-Ray production in both microquasars with low- and high-mass stellar companions. We conclude that the parent population of low-latitude and halo variable Sources might be formed by yet undetected microquasars and microblazars.
B. I. Luchkov - One of the best experts on this subject based on the ideXlab platform.
-
Spatial correlation of unidentified Gamma-Ray Sources with flaring and Wolf-Rayet stars
Astronomy Letters, 2004Co-Authors: A. M. Galper, B. I. LuchkovAbstract:The spatial positions of unidentified Gamma-Ray Sources ( E>100 MeV) were analyzed. This analysis shows that Gamma-Ray Sources with fluxes >5×10−7 cm−2 s−1 correlate with Wolf-Rayet stars, while Gamma-Ray Sources with fluxes
-
Identification of Gamma-Ray Sources with Wolf-Rayet stars
Astronomy Reports, 2004Co-Authors: A. M. Gal’per, B. I. LuchkovAbstract:An analysis of unidentified discrete Sources of Gamma-Rays with energies E>100 MeV demonstrates that the spatial characteristics of this group of Gamma-Ray Sources coincides with those of Wolf-Rayet stars. It is concluded that Wolf-Rayet stars are potential steady Sources of high-energy gamma rays with mean luminosities L(>100 MeV)≈1035 erg/s.
Diego F. Torres - One of the best experts on this subject based on the ideXlab platform.
-
A microquasar model applied to unidentified Gamma-Ray Sources
Astronomy & Astrophysics, 2006Co-Authors: Valentí Bosch-ramon, Gustavo E. Romero, Josep M. Paredes, Diego F. TorresAbstract:the date of receipt and acceptance should be inserted later Abstract. Among unidentified Gamma-Ray Sources in the galactic plane, there are some that present significant variability and have been proposed to be high-mass microquasars. To deepen the study of the possible associa- tion between variable low galactic latitude Gamma-Ray Sources and microquasars, we have applied a leptonic jet model based on the microquasar scenario that reproduces the Gamma-Ray spectrum of three unidentified gamma- ray Sources, 3EG J1735 1500, 3EG J1828+0142 and GRO J1411 64, and is consistent with the observational constraints at lower energies. We conclude that if these Sources were generated by microquasars, the particle acceleration processes could not be as efficient as in other objects of this type that present harder Gamma-Ray spectra. Moreover, the dominant mechanism of high-energy emission should be synchrotron self-Compton (SSC) scattering, and the radio jets may only be observed at low frequencies. For each particular case, further predictions of jet physical conditions and variability generation mechanisms have been made in the context of the model. Although there might be other candidates able to explain the emission coming from these Sources, microquasars cannot be excluded as counterparts. Observations performed by the next generation of Gamma-Ray instruments, like GLAST, are required to test the proposed model.
-
Unidentified Gamma-Ray Sources and Microquasars
2004Co-Authors: Gustavo E. Romero, I.a. Grenier, M. M. Kaufman Bernado, I. F. Mirabel, Diego F. TorresAbstract:Some phenomenological properties of the unidentified EGRET detections suggest that there are two distinct groups of galactic Gamma-Ray Sources that might be associated with compact objects endowed with relativistic jets. We discuss different models for Gamma-Ray production in both microquasars with low- and high-mass stellar companions. We conclude that the parent population of low-latitude and halo variable Sources might be formed by yet undetected microquasars and microblazars.
-
Luminous infrared galaxies as plausible Gamma-Ray Sources for GLAST and IACTs
The Astrophysical Journal, 2004Co-Authors: Diego F. Torres, Olaf Reimer, E. Domingo-santamaría, Seth DigelAbstract:We argue that luminous infrared galaxies (LIGs) may constitute a newly detectable population of Gamma-Ray Sources for the next generation of ground and space-based high energy telescopes. Additionally, we report for the first time upper limits on their fluxes using data obtained with the EGRET telescope.
-
Gamma-Ray Sources at high latitudes (Extragalactic Gamma-Ray Sources)
arXiv: Astrophysics, 2003Co-Authors: Diego F. TorresAbstract:This Chapter provides a review of $\gamma$-ray Sources lying at high Galactic latitudes. Their statistical properties and variability status, as well as studies involving cross correlations with lower frequency catalogs and multiwavelength observations, are summarized. The case for active galactic nuclei is analyzed with special emphasis, since they represent the largest population of high energy Sources known to date. Other potential $\gamma$-ray emitters (including nearby starburst galaxies, normal galaxies, molecular clouds in the Galactic halo, galaxy clusters, and radio galaxies) that may appear in the next generation of $\gamma$-ray catalogs and, perhaps, that might have been already observed by EGRET as unidentified detections, are discussed.
-
Gamma-Ray Sources at high latitudes
2003Co-Authors: Diego F. TorresAbstract:This Chapter provides a review of $\gamma$-ray Sources lying at high Galactic latitudes. Their statistical properties and variability status, as well as studies involving cross correlations with lower frequency catalogs and multiwavelength observations, are summarized. The case for active galactic nuclei is analyzed with special emphasis, since they represent the largest population of high energy Sources known to date. Other potential $\gamma$-ray emitters (including nearby starburst galaxies, normal galaxies, molecular clouds in the Galactic halo, galaxy clusters, and radio galaxies) that may appear in the next generation of $\gamma$-ray catalogs and, perhaps, that might have been already observed by EGRET as unidentified detections, are discussed.
Yuan-gui Yang - One of the best experts on this subject based on the ideXlab platform.
-
Gamma-Ray Sources like V407 Cygni in symbiotic stars
Monthly Notices of the Royal Astronomical Society: Letters, 2011Co-Authors: Chunhua Zhu, Zhaojun Wang, Wensheng Huo, Yuan-gui YangAbstract:Using a simple accelerating model and an assumption that Gamma-Rays originate from p-p collisions for a pi(0) model, we investigate Gamma-Ray Sources like V407 Cygni in symbiotic stars. The upper limit of their occurrence rate in the Galaxy is between 0.5 and 5 yr(-1), indicating that they may be important Sources of high-energy Gamma-Rays. The maximum energies of the accelerated protons mainly distribute around 10(11) eV, and barely reach 10(15) eV. The novae occurring in D-type SSs with ONe white dwarfs and long orbital periods are good candidates for Gamma-Ray Sources. Due to a short orbital period which results in a short acceleration duration, the nova occurring in symbiotic star RS Oph cannot produce Gamma-Ray emission like that in V407 Cygni.
-
Gamma-Ray Sources like V407 Cygni in Symbiotic Stars
arXiv: Solar and Stellar Astrophysics, 2011Co-Authors: Chunhua Zhu, Zhaojun Wang, Wensheng Huo, Yuan-gui YangAbstract:Using a simple accelerating model and an assumption that $\gamma$-rays originate from $p-p$ collisions for a $\pi^0$ model, we investigate $\gamma$-ray Sources like V407 Cygni in symbiotic stars. The upper limit of their occurrence rate in the Galaxy is between 0.5 and 5 yr$^{-1}$, indicating that they may be an important source of the high-energy $\gamma$-rays. The maximum energies of the accelerated protons mainly distribute around $10^{11}$ eV, and barely reach $10^{15}$ eV. The novae occurring in D-type SSs with ONe WDs and long orbital periods are good candidates for $\gamma$-ray Sources. Due to a short orbital period which results in a short acceleration duration, the nova occurring in symbiotic star RS Oph can not produce the $\gamma$-ray emission like that in V407 Cygni.
Chunhua Zhu - One of the best experts on this subject based on the ideXlab platform.
-
Gamma-Ray Sources like V407 Cygni in symbiotic stars
Monthly Notices of the Royal Astronomical Society: Letters, 2011Co-Authors: Chunhua Zhu, Zhaojun Wang, Wensheng Huo, Yuan-gui YangAbstract:Using a simple accelerating model and an assumption that Gamma-Rays originate from p-p collisions for a pi(0) model, we investigate Gamma-Ray Sources like V407 Cygni in symbiotic stars. The upper limit of their occurrence rate in the Galaxy is between 0.5 and 5 yr(-1), indicating that they may be important Sources of high-energy Gamma-Rays. The maximum energies of the accelerated protons mainly distribute around 10(11) eV, and barely reach 10(15) eV. The novae occurring in D-type SSs with ONe white dwarfs and long orbital periods are good candidates for Gamma-Ray Sources. Due to a short orbital period which results in a short acceleration duration, the nova occurring in symbiotic star RS Oph cannot produce Gamma-Ray emission like that in V407 Cygni.
-
Gamma-Ray Sources like V407 Cygni in Symbiotic Stars
arXiv: Solar and Stellar Astrophysics, 2011Co-Authors: Chunhua Zhu, Zhaojun Wang, Wensheng Huo, Yuan-gui YangAbstract:Using a simple accelerating model and an assumption that $\gamma$-rays originate from $p-p$ collisions for a $\pi^0$ model, we investigate $\gamma$-ray Sources like V407 Cygni in symbiotic stars. The upper limit of their occurrence rate in the Galaxy is between 0.5 and 5 yr$^{-1}$, indicating that they may be an important source of the high-energy $\gamma$-rays. The maximum energies of the accelerated protons mainly distribute around $10^{11}$ eV, and barely reach $10^{15}$ eV. The novae occurring in D-type SSs with ONe WDs and long orbital periods are good candidates for $\gamma$-ray Sources. Due to a short orbital period which results in a short acceleration duration, the nova occurring in symbiotic star RS Oph can not produce the $\gamma$-ray emission like that in V407 Cygni.
