RevMexAA: Abstracts of Accepted Papers for Volume 47 Number 1


January 17, 2011

2011: January

2010: December November September



January 2011


UBVR polarimetry of high-galactic latitude carbon stars

J. M. López and D. Hiriart

Instituto de Astronomía
Universidad Nacional Autónoma de México, Ensenada, B.C., México

jmlopez@astrosen.unam.mx

Received: 2010 October 20
Accepted: 2011 January 17

Abstract: We present UBVR polarimetry and photometry obtained over a period of one year of eight high-galactic latitude carbon stars: V Hya, CZ Hya, R For, R Lep, Y Cvn, T Dra, RV Aqr, and RT Cap. The observed polarization is the highest in the U band and highly variable with time. Similarly, the polarization in the B band is highly variable but the values are always lower than those in U band. The origin and variability of the linear polarization in these bands may be explained as dispersion of radiation from the central star at the inner regions of the circumstellar envelope where grains and molecules are created, destroyed, and stirred by shock waves.



Planetary nebulae in the inner Milky Way II: the Bulge-Disk transition

O. Cavichia, R. D. D. Costa, and W. J. Maciel

Instituto de Astronomia, Geofísica e Ciências Atmosféricas
Universidade de São Paulo, Brazil

cavichia@astro.iag.usp.br

Received: 2010 November 29
Accepted: 2011 January 14

Abstract: In this work, a sample of planetary nebulae located in the inner-disk and bulge of the Galaxy is used in order to find the galactocentric distance which better separates these two populations, from the point of view of abundances. Statistical distance scales were used to study the distribution of abundances across the disk-bulge interface. A Kolmogorov-Smirnov test was used to find the distance in which the chemical properties of these regions better separate.

The results of the statistical analysis indicate that, on the average, the inner population has lower abundances than the outer. Additionally, for the α-elements abundances, the inner population does not follow the disk radial gradient towards the galactic center. Based on our results, we suggest a bulge-disk interface at 1.5 kpc, marking the transition between the bulge and inner-disk of the Galaxy, as defined by the intermediate mass population.



December 2010


Mid-Infrared Observations of Planetary Nebulae detected in the GLIMPSE 3D Survey

J. A. Quino-Mendoza, J. P. Phillips, and G. Ramos-Larios

Instituto de Astronomía y Meteorología, Universidad de Guadalajara, México

jpp@astro.iam.udg.mx

Received: 2010 September 23
Accepted: 2010 December 13

Abstract: We present mapping, profiles and photometry for 24 planetary nebulae (PNe) detected in the GLIMPSE 3D mid-infrared (MIR) survey of the Galactic plane. The PNe show many of the properties observed in previous studies of these sources, including evidence for longer wave emission from outside of the ionised zones, a likely consequence of emission from polycyclic aromatic hydrocarbons (PAHs) within the nebular photo-dissociation regimes (PDRs). We also note variations in 5.8μm/4.5μm and 8.0μm/4.5μm flux ratios with distance from the nuclei; present evidence for enhanced MIR emission in the halos of the sources; and note evidence for variations in colour with nebular evolution.



November 2010


The Parker instability in axisymmetric filaments: final equilibria with longitudinal magnetic field

F. J. Sánchez-Salcedo1 and A. Santillán2

1Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico
2Cómputo Aplicado-DGSCA, Universidad Nacional Autónoma de México, Mexico

jsanchez@astroscu.unam.mx

Received: 2010 August 4
Accepted: 2010 November 18

Abstract: We study the final equilibrium states of the Parker instability arising from an initially unstable cylindrical equilibrium configuration of gas in the presence of a radial gravitational field and a longitudinal magnetic field. The aim of this work is to compare the properties of the nonlinear final equilibria with those found in a system with Cartesian geometry. Maps of the density and magnetic field lines, when the strength of the gravitational field is constant, are given in both geometries. We find that the magnetic buoyancy and the drainage of gas along field lines are less efficient under axial symmetry than in a Cartesian atmosphere. As a consequence, the column density enhancement arising in gas condensations in the axially-symmetric model is smaller than in Cartesian geometry. The magnetic-to-gas pressure ratio in the final equilibrium state takes more extreme values in the Cartesian model. Models with non-uniform radial gravity are also discussed.



September 2010


FUNDPAR: A program for Deriving Fundamental Parameters from Equivalent Widths

C. Saffe

Instituto de Ciencias Astronómicas, de la Tierra y del Espacio (ICATE), San Juan, Argentina

csaffe@icate-conicet.gob.ar

Received: 2010 July 2
Accepted: 2010 September 14

Abstract: We implemented a fortran code that determine fundamental parameters of solar type stars from a list of Fe line equivalent widths. The solution should verify 3 conditions in the standard method: ionization equilibrium, excitation equilibrium and independence between metallicity and equivalent widths. We added the condition that the input metallicity of the model atmosphere should be similar to the output metallicity derived with equivalent widths. Solar-scaled Kurucz model atmospheres with NEWODF opacities are calculated with an independent program. Parameter files control different details, such as the mixing-length parameter, the overshooting, the damping of the lines and the weight factors in the definition of the χ2 function. FUNDPAR derive the uncertainties following 2 methods: the criteria of Gonzalez & Vanture (1998) and the dispersion using the χ2 function. The code use the 2009 version of the MOOG program. The results derived with FUNDPAR are in agreement with previous determinations in the literature. In particular we obtained the fundamental parameters of 58 exoplanet host stars. The program is freely available from the web http://icate-conicet.gob.ar/saffe/fundpar/.