Multiwavelength study of RCW 108 as a massive star forming region

NGC 6193 is an open cluster embedded in an HII region (RCW 108, Rodgers et al. 1960) located 15^´ eastwards of NGC 6188. The later is a bright rimmed cloud that stretches over 30^´ in the north-south direction, and marks the interface between RCW 108 and nearby dark clouds. RCW 108 is being powered by the multiple O-type star systems, namely HD 150135-HD 150136 (Niemela & Gamen 2005) in the core of NGC 6193. The UV photons emitted by these stars may drive photoinization-induced shocks into the nearby molecular clouds, possibly originating the well studied infrared cluster RCW 108-IR (Comerón et al. 2005, and references therein). In this work we describe the morphology of the distribution of the photoionized and shock-excited gas based on Hα, [O III] and [S II] images, ^{13}CO observations, and infrared data (2MASS, MSX).Fil: Romero, Gisela Andrea. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomia; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Barba, Rodolfo Hector. Universidad de la Serena; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Arnal, Edmundo Marcelo. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomia; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentin

A new massive double-lined spectroscopic binary system: The Wolf-Rayet star WR68a

Double-lined spectroscopic binary systems, containing a Wolf-Rayet and a massive O-type star, are key objects for the study of massive star evolution because these kinds of systems allow the determination of fundamental astrophysical parameters of their components. We have performed spectroscopic observations of the star WR 68a as part of a dedicated monitoring program of WR stars to discover new binary systems. We identified spectral lines of the two components of the system and disentangled the spectra. We measured the radial velocities in the separated spectra and determined the orbital solution. We discovered that WR 68a is a double-lined spectroscopic binary with an orbital period of 5.2207 days, very small or null eccentricity, and inclination ranging between 75 and 85 deg. We classified the binary components as WN6 and O5.5-6. The WN star is less massive than the O-type star with minimum masses of 15 ± 5 M⊙ and 30 ± 4 M⊙, respectively. The equivalent width of the He ii λ4686 emission line shows variations with the orbital phase, presenting a minimum when the WN star is in front of the system. The light curve constructed from available photometric data presents minima in both conjunctions of the system.Fil: Collado, Ana Elisa. Consejo Nacional de Investigaciones Cienti­ficas y Tecnicas. Centro Cientifico Tecnologico San Juan. Instituto de Ciencias Astronomicas de la Tierra y del Espacio; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Fisicas y Naturales; ArgentinaFil: Gamen, Roberto Claudio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Instituto de Astrofísica de La Plata; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Barba, Rodolfo Hector. Universidad de la Serena; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Morrell, Nidia Irene. Carnegie Observatories; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Resolving the clumpy circumstellar environment of the B[e] supergiant LHA 120-S 35

Context. B[e] supergiants are massive post-main-sequence stars, surrounded by a complex circumstellar environment where moleculesand dust can survive. The shape in which the material is distributed around these objects and its dynamics as well as the mechanismsthat give rise to these structures are not well understood.Aims. The aim of this work is to deepen our knowledge of the structure and kinematics of the circumstellar disc of the B[e] supergiantLHA 120-S 35.Methods. High-resolution optical spectra were obtained in three different years. Forbidden emission lines, that contribute to trace thedisc at different distances from the star, are modelled in order to determine the kinematical properties of their line-forming regions,assuming Keplerian rotation. In addition, we used low-resolution near-infrared spectra to explore the variability of molecular emission.Results. LHA 120-S 35 displays an evident spectral variability in both optical and infrared regions. The P-Cygni line profiles of H i,as well as those of Fe ii and O i, suggest the presence of a strong bipolar clumped wind. We distinguish density enhancements in theP-Cygni absorption component of the first Balmer lines, which show variations in both velocity and strength. The P-Cygni profileemission component is double-peaked, indicating the presence of a rotating circumstellar disc surrounding the star. We also observeline-profile variations in the permitted and forbidden features of Fe ii and O i. In the infrared, we detect variations in the intensity ofthe H i emission lines as well as in the emission of the CO band-heads. Moreover, we find that the profiles of each [Ca ii] and [O i]emission lines contain contributions from spatially different (complete or partial) rings. Globally, we find evidence of detached multi-ring structures, revealing density variations along the disc. We identify an inner ring, with sharp edge, where [Ca ii] and [O i] linesshare their forming region with the CO molecular bands. The outermost regions show a complex structure, outlined by fragmentedclumps or partial-ring features of Ca ii and O i. Additionally, we observe variations in the profiles of the only visible absorptionfeatures, the He i lines.Conclusions. We suggest that LHA 120-S 35 has passed through the red-supergiant (RSG) phase and evolves back bluewards in theHertzsprung-Russell diagram. In this scenario, the formation of the complex circumstellar structure could be the result of the wind-wind interactions of the post-RSG wind with the previously ejected material from the RSG. The accumulation of material in thecircumstellar environment could be attributed to enhanced mass-loss, probably triggered by stellar pulsations. However, the presenceof a binary companion can not be excluded. Finally, we find that LHA 120-S 35 is the third B[e] supergiant belonging to a youngstellar cluster.Fil: Torres, Andrea Fabiana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Cidale, Lydia Sonia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Kraus, M.. Tartu Observatory, Estonia; Estonia. Astronomický Ústav, Akademie Ved Ceské Republiky; República ChecaFil: Arias, María Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Barba, Rodolfo Hector. Universidad de La Serena; ChileFil: Maravelias, G.. Universidad de Valparaiso; Chile. Astronomický Ústav, Akademie Ved Ceské Republiky; República ChecaFil: Borges Fernandes, M.. Ministério de Ciencia, Tecnologia e Innovacao. Observatorio Nacional; Brasi

A close encounter of the massive kind

We have used (a) HST ACS imaging and STIS spectroscopy, (b) ground-basedPIONIER/VLT long-baseline interferometry, and (c) ground-basedspectroscopy from different instruments to study the orbit of theextreme multiple system HD 93 129 Aa,Ab, which is composed of (at least)two very massive stars in a long-period orbit with e>0.92 that willpass through periastron in 2017/2018. In several ways, the system is aneta Car precursor. Around the time of periastron passage the two verystrong winds will collide and generate an outburst of non-thermal hardX-ray emission without precedent in an O+O binary since astronomers havebeen able to observe above Earth's atmosphere. A coordinatedmultiwavelength monitoring in the next two years will enable abreakthrough understanding of the wind interactions in such extremeclose encounters. Furthermore, we have found evidence that HD 93 129 Aamay be a binary system itself. In that case, we could witness athree-body interaction that may yield a runaway star or a stellarcollision close to or shortly after the periastron passage. Either ofthose outcomes would be unprecedented, as they are predicted to below-frequency events in the Milky Way.Instituto de Astrofísica de La Plat

A close encounter of the massive kind

We have used (a) HST ACS imaging and STIS spectroscopy, (b) ground-basedPIONIER/VLT long-baseline interferometry, and (c) ground-basedspectroscopy from different instruments to study the orbit of theextreme multiple system HD 93 129 Aa,Ab, which is composed of (at least)two very massive stars in a long-period orbit with e>0.92 that willpass through periastron in 2017/2018. In several ways, the system is aneta Car precursor. Around the time of periastron passage the two verystrong winds will collide and generate an outburst of non-thermal hardX-ray emission without precedent in an O+O binary since astronomers havebeen able to observe above Earth's atmosphere. A coordinatedmultiwavelength monitoring in the next two years will enable abreakthrough understanding of the wind interactions in such extremeclose encounters. Furthermore, we have found evidence that HD 93 129 Aamay be a binary system itself. In that case, we could witness athree-body interaction that may yield a runaway star or a stellarcollision close to or shortly after the periastron passage. Either ofthose outcomes would be unprecedented, as they are predicted to below-frequency events in the Milky Way.Instituto de Astrofísica de La Plat

The eccentric short-period orbit of the supergiant fast X-ray transient HD 74194 (=LM Vel)

Aims. We present the first orbital solution for the O-type supergiantstar HD 74194, which is the optical counterpart of the supergiant fastX-ray transient IGR J08408-4503. Methods. We measured the radialvelocities in the optical spectrum of HD 74194, and we determined theorbital solution for the first time. We also analysed the complexHα profle. Results. HD 74194 is a binary system composed of anO-type supergiant and a compact object in a short-period (P=9.5436± 0.0002 d) and high-eccentricity (e=0.63 ± 0.03) orbit.The equivalent width of the Hα line is not modulated entirely withthe orbital period, but seems to vary in a superorbital period (P=285± 10 d) nearly 30 times longer than the orbital one.Fil: Gamen, Roberto Claudio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Astrofísica de la Plata; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Barba, Rodolfo Hector. Universidad de la Serena; ChileFil: Walborn, N. R.. Space Telescope Science Institute; Estados UnidosFil: Morrell, Nidia Irene. Universidad de la Serena; ChileFil: Arias, Julia Ines. Universidad de la Serena; ChileFil: Maíz Apellániz, J.. Consejo Superior de Investigaciones Cientificas; EspañaFil: Sota, A.. Consejo Superior de Investigaciones Cientificas; EspañaFil: Alfaro, E. J.. Consejo Superior de Investigaciones Cientificas; Españ

Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality

A study of the effect of rotational mixing on massive stars evolution: Surface abundances of Galactic O7-8 giant stars

Context. Massive star evolution remains only partly constrained. In particular, the exact role of rotation has been questioned by puzzling properties of OB stars in the Magellanic Clouds. Aims. Our goal is to study the relation between surface chemical composition and rotational velocity, and to test predictions of evolutionary models including rotation. Methods. We have performed a spectroscopic analysis of a sample of fifteen Galactic O7-8 giant stars. This sample is homogeneous in terms of mass, metallicity and evolutionary state. It is made of stars with a wide range of projected rotational velocities. Results. We show that the sample stars are located on the second half of the main sequence, in a relatively narrow mass range (25-40 M · ). Almost all stars with projected rotational velocities above 100 km s -1 have N/C ratios about ten times the initial value. Below 100 km s -1 a wide range of N/C values is observed. The relation between N/C and surface gravity is well reproduced by various sets of models. Some evolutionary models including rotation are also able to consistently explain slowly rotating, highly enriched stars. This is due to differential rotation which efficiently transports nucleosynthesis products and allows the surface to rotate slower than the core. In addition, angular momentum removal by winds amplifies surface braking on the main sequence. Comparison of the surface composition of O7-8 giant stars with a sample of B stars with initial masses about four times smaller reveal that chemical enrichment scales with initial mass, as expected from theory. Conclusions. Although evolutionary models that include rotation face difficulties in explaining the chemical properties of O- and B-type stars at low metallicity, some of them can consistently account for the properties of main-sequence Galactic O stars in the mass range 25-40 M · .Fil: Martins, F.. Université de Montpellier; FranciaFil: Simón Díaz, S.. Instituto de Astrofísica de Canarias; España. Universidad de La Laguna; EspañaFil: Barba, Rodolfo Hector. Universidad de La Serena; ChileFil: Gamen, Roberto Claudio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Elkstrom, S.. University of Geneva; Suiz