Anabel Arrieta

Universidad Iberoamericana Ciudad de México · Department of Physics and Mathematics

For some time there has been the concern that the abundances derived from recombination lines do not agree with those derived from collisionally excited lines. There have been many attempts to explain this discrepancy. In a previous study we analyzed the kinematics of emission lines in NGC 7009 as a function of ionization structure (Richer et al. 2...

We present spatially- and velocity-resolved echelle spectroscopy for NGC 7009 obtained with the UVES spectrograph at the ESO VLT. We construct position-velocity maps for recombination, fluorescence, charge transfer, and collisionally excited lines. We find a plasma component emitting in the C II, N II, O II, and Ne II recombination lines whose kine...

We present spatially- and velocity-resolved echelle spectroscopy for NGC 7009 obtained with the UVES spectrograph at the European Southern Observatory's Very Large Telescope. Our objective is to analyze the kinematics of emission lines excited by recombination and collisions with electrons to determine whether similarities or differences could be u...

We developed a self-consistent stellar-nebular model for NGC 7009. This model reproduces the available observations ranging from optical to UV. The combined approach to the modeling process produces more constraints and thus more trustworty results. After obtaining the model, we perform a comparative study of the chemical composition of He, N, O, N...

We present a unified model of the central star and the ionized gas of the planetary nebula He2-131. Preliminary values of the nebular and stellar parameters are given together with those of the chemical composition.

In order to clarify the observed relation between the expansion velocity measured from lines of different ions and their ionization potential, we present kinematical data for several objects. We have measured radial velocities on ESO UVES high dispersion spectra to compare expansion velocities for a set of planetary nebulae.

We present a methodology to obtain a stellar-nebular self-consistent model. Distance is determined using theoretical evolutive tracks of central stars of planetary nebulae. This methodology is applied to study of the galactic planetary nebula NGC 6826. A unified model requieres more work, but its uncertainties are smaller due to their larger number...

In our previous study of M2-9 we found that the radial velocities of the forbidden lines of the ionized species in the nuclear spectra show a negative gradient which correlates with density, electron temperature and electron pressure. The size of the ionized region is relatively small and the travel time with the observed velocities is of order of...

The typical expansion velocity of a planetary nebula is about 20 km s −1. Thus the frequently-used low-resolution spectroscopy does not resolve the dynamics of the nebula and the obtained information is scrambled along the line of sight. In this poster we present UVES spectra obtained along the major axis of NGC 7009. The object is resolved both on...

Stellar evolution models predict that the chemical composition in the atmosphere of stars in the post- AGB has been enhanced in C and N. The aim of this work is to use the planetary nebula NGC 7009 as a test of the stellar evolution models, by making simultaneous models of the nebula and its central star; the parameters obtained through models are...

We present echelle spectroscopy of the unresolved nuclei of the bipolar planetary nebulae M 2-9 and M 1-91. The spectrum is dominated by emission lines emitted under a wide range of physical conditions. From the observations we identify the emission lines, derive physical conditions and relative motions of the different ionized species in the circu...

In this article we classify M1-92 and M3-60 CSPN as objects with B[e] phenomenon and suggest CRL618 as a possible candidate. A parallel between the supergiant B[e] stars and the CSPN are made on model simulations based on their spectra and line profiles similarities. We conclude, that similar spectra should point to similar physical conditions, the...

One of the open problems in PN research is the abundance discrepancy factor that is obtained from O II lines and [O III] lines. There are two main ideas that have been put forward to explain this difference: (a) variations of temperature in a chemically homogeneous medium (e.g. [4], and references therein) or (b) variations of temperature due to a...

In gaseous nebulae the abundances of heavy elements derived from recombination lines are systematically higher than those derived from collisionally excited lines. The possible explanations to obtain compatible solutions are: either to attribute the difference to the presence of temperature inhomogeneities or to the presence of dense clumps of cold...

We analyze the chemical composition of the central star of the planetary nebula NGC 6543 based on a detailed NLTE model of its stellar wind. The logarithmic abundances by number are H = 12.00, He = 11.00, C = 9.03, N = 8.36, O = 9.02, Si = 8.19, P = 5.53, S = 7.57, and Fe = 7.24. Compared with the solar abundances, most of the elements have solar c...

Heat conduction in ionized plasmas in the presence of magnetic fields is today a fashionable problem. The kinetic theory of plasmas, in the context of non-equilibrium thermodynamics, predicts a Hall-effect-like heat flow due to the presence of a magnetic field in ionized gases. This cross effect, the Righi-Leduc effect together with a heat flow per...

The X-ray source 2S0114+650=LSI+65 010 is a binary system containing a B-type primary and a low mass companion believed to be a neutron star. The system has three reported periodicities: the orbital period, P{orb}~11.6 d, X-ray flaring with P{flare}~2.7 hr, and a "superorbital" X-ray periodicity P{super}~30.7 d. The objective of this paper is to sh...

The X-ray source 2S0114+650 is a binary system containing a B-type primary and a low mass companion believed to be a neutron star. Its variability has at least three characteristic timescales: the orbital period, Porb ˜11.6 days, derived from the radial velocity variations of optical photospheric lines; X-ray flaring with Pflare ˜2.8 hrs; and an X-...

We have studied the emission from the core of the Butterfly Nebula. We have tried to interpret the Balmer line profiles, double lines in emission. These profiles are not only observed in M2-9, but are also present in other objects of similar morphology.

In this work we investigate the relation between wind momentum Pi and the luminosity of the CSPNs in the LMC taking advantage of the less uncertain distances to these objects. We show that these winds obey the same relation as the Galactic O stars and therefore have the same physics.

We present non-LTE models of the wind for the central star in NGC 6543. The models suggest that the star is hydrogen-rich. The iron composition is solar, which, in turn, suggests that the hot X-ray emitting gas is of nebular origin.

The radiation driven wind theory states that the modified momentum Π = MV∞R0.5 is proportional to the stellar luminosity. If this relation is confirmed, it can be used as a distance indicator for the central stars (CSs) of the Galactic planetary nebulae. This relation for the massive O stars was established in [3] and [4]. An attempt to extend the...

Important similarities between the objects M1-92, a proto-planetary nebula of bipolar morphology, and MWC 560, a symbiotic star with a jet, have been found. A brief review of the previous studies for both objects is presented for the purpose of proposing mechanisms that best explain these similarities, since up to now both objects have been studied...

The central source of M2‐9 shows an exceptionally intense and wide Hα line, and anomalous Balmer profiles. We attempt to fit the complex line profiles of the Balmer series by solving the line transfer in a very dense medium surrounding the central star. © 2005 American Institute of Physics

We have searched for the emission from \fex and \fexiv that is expected from the gas emitting in diffuse X-rays in \bd, NGC 6543, NGC 7009, and NGC 7027. Neither line was detected in any object. Models that fit the X-ray spectra of these objects indicate that the \fex emission should be below our detection thresholds, but the predicted \fexiv emiss...

Se deduce la ecuación para la inestabilidad de Jeans en el caso de un plasma diluido completamente ionizado bajo la presencia de un campo gravitacional y otro campo magnético constante. Se obtiene un nuevo número de Jeans substancial- mente modificado por la presencia del campo magnético bajo el supuesto de una simetría apropiada. No obstante, nues...

In the quest to understand the origin of Planetary Nebula (PN) morphology, correlations have been sought between the nebular shapes and the evolutionary status of the central stars. Several of the mechanisms proposed to explain asymmetric shapes have a direct link with the central star's evolutionary status. Among the possible mechanisms invoked to...

Eleven objects that have been reported as proto-planetary nebula or as young planetary nebulae that show very extended Hα wings are presented. The exten-sion of these wings is larger than 800 km s −1 . Data for two symbiotic stars that show this same characteristic is also presented. Raman scattering is the mecha-nism that best explains the wings i...

Great similarities between the objects M 1-92, a proto planetary nebula of bipolar morphology, and MWC 560, a symbiotic star with a jet, have been found. A brief review of the previous studies for both objects is presented for the purpose of proposing mechanisms that best explain this similarity, since up to now, both objects have been studied inde...

We present high-resolution spectroscopic observations of the massive X-ray binary system LS I +65 010 (2S 0114+650) in the optical wavelength region. A correlation between equivalent width and radial velocity of photospheric absorption lines is found. The systemic velocity, inferred from the weaker lines, is Vhelio _31 _ 5kms_1, which, if attribute...

For M1-91 we find that the ratio of the 6717/6731 [S II] narrow band images shows two symmetrical very collimated high density regions, or jets, along the major axis. We infer many properties of M 1-92 from the similarity of the spectral features with the symbiotic star MWC 560. We show that M 1-92 could also have a jet along the major axis and tha...

In a sample of 30 young planetary nebulae, proto-PNe and other emission line objects we have found 11 young PNe and 2 symbiotic stars that show very broad wings of the emission H alpha line (from 800 km s-1 and up to 5100 km s-1). For 7 objects it is the first time that these wide lines are reported.

De una muestra de 30 nebulosas planetarias j ovenes, proto-NPs y otros objetos con l neas de emisi on hemos encontrado 11 NPs j ovenes y dos estrellas simbi oticas que muestran la l nea de emisi on H extremadamente ancha (desde 800 km s

We have analyzed high resolution echelle spectra of the nuclei of the young planetary nebulae M2-9 and M1-91. In M2-9 there is a well defined negative gradient of ionization potential, electron density, electron temperature and gas pressure with radial velocity. This behavior can be interpreted as a negative gradient in these parameters with distan...

We report on optical imaging and spectroscopic observations of the Wolf-Rayet candidate star MLA 1159 and the surrounding ionization nebula BA 1-642 in the Andromeda Galaxy. Though both objects have been known for many years, our observations (1) confirm the Wolf-Rayet nature of MLA 1159, (2) allow one to determine the nebula as an ionization nebul...

Aimed at identifying supersoft X-ray sources in ionization nebulae, we have searched for extended optical emission within the X-ray error boxes of the 15 supersoft sources in M31 (Greiner et al. 1996). One optical nebula was found, of which we obtained spectroscopy, narrow-band imaging and FP-interferometry, to determine its relation to the positio...

An atlas of high dispersion profiles of Balmer lines of 50 objects which are in the transition from AGB to PNe. The origin of these profiles is discussed in terms of the dynamics of the gas ejected by the star in the different phases of mass loss. The possible effects of electron scattering are discussed as a mechanism for line broadening.

We have carried out 3600 - 6800 Angstroms \ long slit echelle spectroscopy of this bipolar nebula at the 2.1-m telescope of Observatorio Astronomico Nacional in San Pedro Martir, Baja California, Mexico. The emission in the lobes is dominated by the Balmer lines; they also show emission in He I, [N II], [N I], [O III], [O II], [O I], [S III], and [...

We present spectroscopy of Nova Scorpii 1997 obtained within a week of its discovery. The classical nova displayed strong and broad Balmer emission as well as [Ca II] and [Fe II] emission. Echelle spectroscopy revealed a significant increase in Ha emission in 24 hours while HB remained the same.

IR OBSERVATIONS. We have extended previous infrared imaging studies (cf. Hora & Latter 1994 ApJ 437, 281; Kastner et al. 1996 ApJ 462, 777) through wide and narrow band filters. In these images: (a) JHK ′ morphology is similar to the optical structure. The knots are brighter at the shorter wavelengths, while the core is brighter at K ′. (b) [He I]...

We calculate the abundance of molecular hydrogen (H2) for a wide range of interstellar conditions including the following cases: i) constant density and temperature. ii) constant density and variable temperature (isochoric case), and iii) constant pressure (isobaric case). Starting with a diffuse atomic medium, the time evolution of the H2 abundanc...

Context. The X-ray source 2S0114+650=LSI+65 010 is a binary system containing a B-type primary and a low mass companion believed to be a neutron star. The system has three reported periodiciti es: the orbital period, P orb ∼11.6 days, X-ray flaring with P f lare ∼2.7 hours and a "superorbital" X-ray periodicity P super =30.7 days. Aims. The objecti...