On the radiative equilibrium of a stellar atmosphere. IV

In this paper the solution to the problem of line formation given in an earlier paper is obtained in its numerical form in the first three approximations. Tables for computing the residual intensity are given

Observaciones de estrellas simbióticas con el IUE. II. Variaciones en el espectro

Uno de los objetivos del programa de observación de estrellas simbióticas con el IUE consistía en la detección de posibles cambios de los espectros en función del tiempo. Diez de las estrellas del programa fueron observados en dos épocas de 1979, con un intervalo de seis meses entre las mismas. Hasta septiembre de 1981 se habían analizado las observaciones de siete de esas estrellas, a saber: R Aquarii, T Coronae Borealis, AX Persei, AG Pegasi, HD 4174, Z Andromedae y RW Hydrae. Todas estas estrellas muestran variaciones en la intensidad de varias líneas de emisión que, en los casos de Z And, R Aqr, AG Peg y RW Hya, incluyen las de resonancia del MG II. En RW Hya hemos encontrado una variación notable en el continuo. En julio de 1979 el espectro continuo se corresponde con el modelo de Kurucz para una temperatura efectiva de 20000 K y log g=4, mientras que el espectro de enero del mismo año parece provenir de una fuente más fría, pero que no se puede hacer corresponder con ningún modelo. Las líneas de emisión han sido agrupadas tentativamente en cinco grupos y se sugiere un modelo de atmósfera extendida en el que se ubican los distintos regiones donde se originarían dichas líneas. Hemos encontrado también cambios en el espectro continuo de T CrB y, posiblemente, en Z And. El trabajo será publicado in extenso en otra parte.Asociación Argentina de Astronomí

El espectro ultravioleta de la estrella simbiótica RW Hydrae

La comparación de espectros de RW Hydrae tomados con el IUE en enero y en julio de 1979, ha permitido detectar variaciones en la intensidad de varias líneas de emisión así como variaciones en el espectro continuo. El espectro continuo de julio de 1979 se corresponde con el modelo de Kurucz para una temperatura efectiva de 20000 K y log g=4, mientras que el espectro de enero de mismo año parece provenir de una fuente más fría pero sin que pueda hacerse corresponder con ningún modelo de atmósfera estelar. Las líneas de emisión han sido agrupadas tentativamente en cinco grupos y se sugiere un modelo de atmósfera extendida en que se ubican las distintas regiones donde se originarían dichas líneas.Asociación Argentina de Astronomí

WSO/UV: World Space Observatory/Ultraviolet

We summarize the capabilities of the World Space Observatory (UV) Project (WSO/UV). An example of the importance of this project (with a planned launch date of 2007/8) for the study of Classical Novae is given.Comment: 4 pages, To appear in the proceeedings of the "Classical Nova Explosions" conference, eds. M. Hernanz and J. Jose, AI

A study of the interacting binary V 393 Scorpii

We present high resolution J-band spectroscopy of V 393 Sco obtained with the CRIRES at the ESO Paranal Observatory along with a discussion of archival IUE spectra and published broad band magnitudes. The best fit to the spectral energy distribution outside eclipse gives $T_{1}$= 19000 $\pm$ 500 $K$ for the gainer, $T_{2}$= 7250 $\pm$ 300 $K$ for the donor, $E(B-V)$= 0.13 $\pm$ 0.02 mag. and a distance of $d$= 523 $\pm$ 60 pc, although circumstellar material was not considered in the fit. We argue that V 393 Sco is not a member of the open cluster M7. The shape of the He I 1083 nm line shows orbital modulations that can be interpreted in terms of an optically thick pseudo-photosphere mimicking a hot B-type star and relatively large equatorial mass loss through the Lagrangian L3 point during long cycle minimum. IUE spectra show several (usually asymmetric) absorption lines from highly ionized metals and a narrow L$\alpha$ emission core on a broad absorption profile. The overall behavior of these lines suggests the existence of a wind at intermediate latitudes. From the analysis of the radial velocities we find $M_{2}/M_{1}$= 0.24 $\pm$ 0.02 and a mass function of $f$= 4.76 $\pm$ 0.24 M$\odot$. Our observations favor equatorial mass loss rather than high latitude outflows as the cause for the long variability.Comment: 13 pages, 14 figures, 7 tables. Accepted for publication in MNRAS, main journa

Observaciones desde Tierra y desde el IUE de V923 Aquilae

En base a observaciones simultáneas desde tierra y desde satélites se elabora un modelo semi-empírico de la envoltura de V923 Aquilae que explica los perfiles de las líneas observadas en el UV y en la región fotográfica.Asociación Argentina de Astronomí

Large non-radial propagation of a coronal mass ejection on 2011 January 24

Understanding the deflection of coronal mass ejections (CMEs) is of great interest to the space weather community because of their implications for improving the prediction of CME. This paper aims to shed light into the effects of the coronal magnetic field environment on CME trajectories. We analyze the influence of the magnetic environment on the early development of a particular CME event. On 2011 January 24 an eruptive filament was ejected in association with a CME that suffered a large deflection from its source region and expected trajectory. We characterize the 3D evolution of the prominence material using the tie-pointing/triangulation reconstruction technique on EUV and white-light images. To estimate the coordinates in 3D space of the apex of the CME we use a forward-modeling technique that reproduces the large-scale structure of the flux rope-like CME, the Graduated Cylindrical Shell model. We found that the deflection amounts to 42° in latitude and 20° in longitude and that most of it occurs at altitudes below 4R⊙. Moreover, we found a non-negligible deflection at higher altitudes. Combining images of different wavelengths with the extrapolated magnetic field obtained from a potential field source surface model we confirm the presence of two magnetic structures near the erupting event. The magnetic field environment suggests that field lines from the southern coronal hole act as a magnetic wall that produces the large latitudinal deflection; while a nearby pseudostreamer and a northward extension of the southern coronal hole may be responsible for the eastward deflection of the CME.Fil: Cécere, Mariana Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Sieyra, María Valeria. Universidad Tecnológica Nacional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cremades Fernandez, Maria Hebe. Universidad Tecnológica Nacional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mierla, M.. Institute of Geodynamics of the Romanian Academy; BélgicaFil: Sahade, Abril. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Stenborg, G.. Spece Sciences División. Naval Research Laboratory; Estados UnidosFil: Costa, A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: West, M. J.. Royal Observatory Of Belgium; BélgicaFil: D'Huys, E.. Royal Observatory Of Belgium; Bélgic

CoRoT photometry and high-resolution spectroscopy of the interacting eclipsing binary AU Mon

Analyses of very accurate CoRoT space photometry, past Johnson V photoelectric photometry and high-resolution \'echelle spectra led to the determination of improved and consistent fundamental stellar properties of both components of AU Mon. We derived new, accurate ephemerides for both the orbital motion (with a period of 11.113d) and the long-term, overall brightness variation (with a period of 416.9d) of this strongly interacting Be + G semi-detached binary. It is shown that this long-term variation must be due to attenuation of the total light by some variable circumbinary material. We derived the binary mass ratio $M_{\rm G}/M_{\rm B}$ = 0.17\p0.03 based on the assumption that the G-type secondary fills its Roche lobe and rotates synchronously. Using this value of the mass ratio as well as the radial velocities of the G-star, we obtained a consistent light curve model and improved estimates of the stellar masses, radii, luminosities and effective temperatures. We demonstrate that the observed lines of the B-type primary may not be of photospheric origin. We also discover rapid and periodic light changes visible in the high-quality residual CoRoT light curves. AU Mon is put into perspective by a comparison with known binaries exhibiting long-term cyclic light changes.Comment: Accepted for publication in MNRA

A Spectroscopic Study of Mass Outflows in the Interacting Binary RY Scuti

The massive interacting binary RY Scuti is an important representative of an active mass-transferring system that is changing before our eyes and which may be an example of the formation of a Wolf-Rayet star through tidal stripping. Utilizing new and previously published spectra, we present examples of how a number of illustrative absorption and emission features vary during the binary orbit. We identify spectral features associated with each component, calculate a new, double-lined spectroscopic binary orbit, and find masses of 7.1 +/- 1.2 M_sun for the bright supergiant and 30.0 +/- 2.1 M_sun for the hidden massive companion. Through tomographic reconstruction of the component spectra from the composite spectra, we confirm the O9.7 Ibpe spectral class of the bright supergiant and discover a B0.5 I spectrum associated with the hidden massive companion; however, we suggest that the latter is actually the spectrum of the photosphere of the accretion torus immediately surrounding the massive companion. We describe the complex nature of the mass loss flows from the system in the context of recent hydrodynamical models for beta Lyr, leading us to conclude RY Scuti has matter leaving the system in two ways: 1) a bipolar outflow from winds generated by the hidden massive companion, and 2) mass from the bright O9.7 Ibpe supergiant flowing from the region near the L2 point to fill out a large, dense circumbinary disk. This circumbinary disk (radius ~ 1 AU) may feed the surrounding double-toroidal nebula (radius ~ 2000 AU).Comment: 41 pages with 7 tables and 11 figures, accepted to Ap