Proyecto de Investigación: ENTRE NACIMIENTO Y MUERTE: UN ESTUDIO EMPIRICO DE LA EVOLUCION DE LAS ESTRELLAS LUMINOSAS AZULES
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PGC2018-093741-B-C22
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Spectroscopic characterization of the known O-star population in Cygnus OB2: Evidence of multiple star-forming bursts
(EDP Sciences, 2020-10-15) Berlanas, S. R.; Herrero, A.; Comerón, F.; Simón Díaz, S.; Lennon, D. J.; Pasquali, A.; Maíz Apellániz, J.; Sota, A.; Pellerín, A.; Agencia Estatal de Investigación (AEI); Ministerio de Economía y Competitividad (MINECO); Pasquali, L. [0000-0003-2423-1826]; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFÍSICA DE CANARIAS (IAC), SEV-2015-0548; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. Cygnus OB2 provides a unique insight into the high-mass stellar content in one of the largest groups of young massive stars in our Galaxy. Although several studies of its massive population have been carried out over the last decades, an extensive spectroscopic study of the whole known O-star population in the association is still lacking.
Aims. We aim to carry out a spectroscopic characterization of all the currently known O stars in Cygnus OB2, determining the distribution of rotational velocities and accurate stellar parameters to obtain an improved view of the evolutionary status of the region.
Methods. Based on existing and new optical spectroscopy, we performed a detailed quantitative spectroscopic analysis of all the known O-type stars identified in the association. For this purpose, we used the user-friendly iacob-broad and iacob-gbat automatized tools, FASTWIND stellar models, and astrometry provided by the Gaia second data release.
Results. We created the most complete spectroscopic census of O stars carried out so far in Cygnus OB2 using already existing and new spectroscopy. We present the spectra for 78 O-type stars, from which we identify new binary systems, obtain the distribution of rotational velocities, and determine the main stellar parameters for all the stars in the region that have not been detected as double-line spectroscopic binaries. We also derive radii, luminosities, and masses for those stars with reliable Gaia astrometry, in addition to creating the Hertzsprung-Russell Diagram to interpret the evolutionary status of the association. Finally, we inspect the dynamical state of the population and identify runaway candidates.
Conclusions. Our spectroscopic analysis of the O-star population in Cygnus OB2 has led to the discovery of two new binary systems and the determination of the main stellar parameters, including rotational velocities, luminosities, masses, and radii for all identified stars. This work has shown the improvement reached when using accurate spectroscopic parameters and astrometry for the interpretation of the evolutionary status of a population, revealing, in the case of Cygnus OB2, at least two star-forming bursts at ~3 and ~5 Myr. We find an apparent deficit of very fast rotators in the distribution of rotational velocities. The inspection of the dynamical distribution of the sample has allowed us to identify nine O stars with peculiar proper motions and discuss a possible dynamical ejection scenario or past supernova explosions in the region.
Lucky spectroscopy, an equivalent technique to lucky imaging II. Spatially resolved intermediate-resolution blue-violet spectroscopy of 19 close massive binaries using the William Herschel Telescope
(EDP Sciences, 2021-06-29) Maíz Apellániz, J.; Barbá, R. H.; Fariña, C.; Sota, A.; Pantaleoni González, M.; Holgado, G.; Negueruela, I.; Simón Díaz, S.; European Commission (EC); Agencia Estatal de Investigación (AEI); Canary Islands Government; Agencia Canaria de Investigación, Innovación y Sociedad de la Información (ACIIS); Ministerio de Economía y Competitividad (MINECO); Maíz Apellániz, J. [0000-0003-0825-3443]; Barbá, R. H. [0000-0003-1086-1579]; Fariña, C. [0000-0003-4940-3751]; Sota, A. [0000-0002-9404-6952]; Pantaleoni González, M. [0000-0001-9933-1229]; Holgado, G. [0000-0002-9296-8259]; Negueruela, I. [0000-0003-1952-3680]; Centro de Excelencia Científica Severo Ochoa Instituto de Astrofísica de Andalucía CSIC, SEV-2015-0548
Context. Many massive stars have nearby companions. These hamper a characterization of massive stars through spectroscopy.
Aims. We continue to obtain spatially resolved spectroscopy of close massive visual binaries to derive their spectral types.
Methods. We used the lucky spectroscopy technique to obtain a large number of short long-slit spectroscopic exposures of 19 close visual binaries under good seeing conditions. We selected those with the best characteristics, extracted the spectra using multiple-profile fitting, and combined the results to derive spatially separated spectra. The results were analyzed in combination with data from lucky imaging, regular intermediate-resolution single-order spectroscopy, and échelle high-resolution spectroscopy.
Results. The new application of lucky spectroscopy has allowed us (among other results) to [a] spatially disentangle two O stars (FN CMa B and 6 Cas B) with brighter BA supergiant companions for the first time; [b] determine that two B stars (α Sco B and HD 164 492 B) with close and more massive companions are fast rotators (in the second case, solving a case of mistaken identity); [c] extend the technique to cases with extreme magnitude differences (the previous two cases plus CS Cam A,B), shorter separations (HD 193 443 A,B), and fainter primary magnitudes down to B = 11 (HD 219 460 A,B); [d] spatially disentangle the spectra of stars with companions as diverse as an A supergiant (6 Cas A), a Wolf-Rayet star (HD 219 460 B = WR 157), and an M supergiant (α Sco A); [e] discover the unexpected identity of some targets such as two previously unknown bright O stars (HD 51 756 B and BD +60 544) and a new member of the rare OC category (HD 8768 A); and [f] identify and classify (in some cases for the first time) which of the components of four visual binaries (σ Ori, HD 219 460, HD 194 649, and HD 191 201) is a double-lined spectroscopic binary. For another seven systems (FN CMa, σ Sco, HD 51 756, HD 218 195, HD 17 520, HD 24 431, and HD 164 492), we detect signs of spectroscopic binarity using high-spectral-resolution spectroscopy. We also determine the limits of the technique.
Advances in Understanding High-Mass X-ray Binaries with INTEGRALand Future Directions
(Elsevier BV, 2019-12-13) Kretschmar, P.; Fürst, F.; Sidoli, L.; Bozzo, E.; Alfonso Garzón, J.; Bodaghee, A.; Chaty, S.; Chernyakova, M.; Ferrigno, C.; Manousakis, A.; Negueruela, I.; Postnov, K.; Paizis, A.; Reig, P.; Rodes Roca, J. J.; Coe, M. J.; Domingo, A.; Doroshenko, V.; Ducci, L.; Falanga, M.; Grebenev, S. A.; Grinberg, V.; Hemphill, P.; Kreykenbohm, I.; Fritz, S. K.; Li, J.; Lutovinov, A. A.; Martínez Nuñez, S.; Mas Hesse, J. M.; Masetti, N.; McBride, V. A.; Neronov, A.; Pottschmidt, K.; Rodríguez, J.; Romano, P.; Rothschild, R. E.; Santangelo, A.; Sguera, V.; Staubert, R.; Tomsick, J. A.; Torrejón, José Miguel; Torres, D. F.; Walter, R.; Wilms, J.; Wilson Hodge, C. A.; Zhang, S.; Agenzia Spaziale Italiana (ASI); Istituto Nazionale Astrofisica (INAF); Russian Foundation for Basic Research (RFBR); Agencia Estatal de Investigación (AEI); Wilms, J. [0000-0003-2065-5410]; Santangelo, A. [0000-0003-4187-9560]; Grinberg, V. [0000-0003-2538-0188]; Sguera, V. [0000-0001-8202-9381]; Martínez Núñez, S. [0000-0002-5134-4191]; Rodes Roca, J. J. [0000-0003-4363-8138]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
High mass X-ray binaries are among the brightest X-ray sources in the Milky Way, as well as in nearby Galaxies. Thanks to their highly variable emissions and complex phenomenology, they have attracted the interest of the high energy astrophysical community since the dawn of X-ray Astronomy. In more recent years, they have challenged our comprehension of physical processes in many more energy bands, ranging from the infrared to very high energies.
In this review, we provide a broad but concise summary of the physical processes dominating the emission from high mass X-ray binaries across virtually the whole electromagnetic spectrum. These comprise the interaction of stellar winds with the high gravitational and magnetic fields of compact objects, the behaviour of matter under extreme magnetic and gravity conditions, and the perturbation of the massive star evolutionary processes by presence in a binary system.
We highlight the role of the INTEGRAL mission in the discovery of many of the most interesting objects in the high mass X-ray binary class and its contribution in reviving the interest for these sources over the past two decades. We show how the INTEGRAL discoveries have not only contributed to significantly increase the number of high mass X-ray binaries known, thus advancing our understanding of the population as a whole, but also have opened new windows of investigation that stimulated the multi-wavelength approach nowadays common in most astrophysical research fields.
We conclude the review by providing an overview of future facilities being planned from the X-ray to the very high energy domain that will hopefully help us in finding an answer to the many questions left open after more than 18 years of INTEGRAL scientific observations.
