RevMexAA: Abstracts of Accepted Papers for Volume 46 Number 2


July 29, 2010

2010: December November October September August July June May April March February January


July 2010


The Absolute Parameters for NSVS 11868841 and the Oversized Stars in the Low-Mass Eclipsing Binaries

Ö. Çakirli,1,2 C. İbanoǧlu,1 and A. Dervişoǧlu1

Ege University, Science Faculty, Astronomy and Space Sciences Dept., İzmir, Turkey
Tübi  tak National Observatory, Akdeniz University Campus, Turkey

omur.cakirli@ege.edu.tr

Received: 2010 April 12

Accepted: 2010 July 29 (

)

Abstract: Spectroscopic observations of the low-mass eclipsing binary NSVS 11868841 have been obtained and the radial velocities were derived for both components. The masses and radii determined for the components are M1 = 0.870 ± 0.074 M, M2 = 0.607 ± 0.053 M and R1 = 0.983 ± 0.030 R, R2 = 0.901 ± 0.026 R. Both the primary and secondary stars’ radii are 10% and 57% larger than those of zero-age-main-sequence stars with the same masses. This discrepancy may be arisen from the large spot coverage of both stars. We collected absolute parameters of 21 low mass double-lined eclipsing binaries and compared their positions in the mass-radius and mass-effective temperature panels. The large radii and lower effective temperatures are solved neither with difference in metallicity nor in mixing length parameters. These discrepancies in the low mass stars may be originated by magnetic fields causing inhibition convective energy transport which leads to large magnetic spot coverage on the surface of a low mass star.


On the Nature of the Non-Thermal Radio Source at the Center of the Orion Streamers

Alfonso Trejo and Luis F. Rodríguez

Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Mexico

l.rodriguez@crya.unam.mx

Received: 2010 June 28

Accepted: 2010 July 27 (

)

Abstract: We present VLA continuum observations at 20 and 6 cm toward a non-thermal radio source located at the Streamers region in Orion. We compare 1991 archive observations with new ones taken by us in 2008. The radio source could be a young stellar source or an evolved object like a microquasar or even a jet from a radio galaxy. Our analysis shows that there is no evidence of changes in the flux densities between both epochs at a level higher than 10%. Also, we set an upper limit at a 3σ level of 23 mas year-1 for the proper motions. At the distance of Orion this implies an upper limit to the velocity in the plane of the sky of 45 km s-1. At 6-cm, we detect linearly polarized emission at a level of ~ 5%, while at 20-cm we do not detect it above a level of ~ 2%. We conclude that the non-thermal radio source most probably is a radio galaxy aligned by chance with the line of sight to the Streamers in Orion.


Compact Radio Sources Apparently Associated
with Extended Galactic Sources

Alfonso Trejo and Luis F. Rodríguez

Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Mexico

l.rodriguez@crya.unam.mx

Received: 2010 January 12

Accepted: 2010 July 26 (

)

Abstract: We report VLA radio observations of the 21 cm HI line toward two compact radio sources that could be associated with extended Galactic sources. In the case of the planetary nebula PHR 1735-333 we observed HI absorption against a non-thermal radio source recently discovered in the region, that was proposed to be physically associated with the planetary nebula. However, from the analysis of the HI absorption spectrum, we suggest a larger distance for this non-thermal source. In the case of the supernova remnant candidate SNR G3.8+0.3 we obtained HI absorption spectra toward it and toward a compact radio source located at its center. We conclude that SNR G3.8+0.3 is more distant than the compact radio source and that they are not physically associated.


Atomic species in the spectrum of the Hg-Mn star HD 53244

N. L. Maza,1,2 H. Levato,1,3 and Z. López-García1,3

Instituto de Ciencias Astronómicas, de la Tierra y del Espacio, San Juan, Argentina
Visiting astronomer Complejo Astronómico El Leoncito, Argentina
Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina

hlevato@icate-conicet.gob.ar

Received: 2009 December 29

Accepted: 2010 July 15 (

)

Abstract: Line identifications are presented for the Hg-Mn Bp star HD 53244 (γCMa), in the spectral region λλ3750-6700 Å. This object is a member of the southern open cluster Cr 121. Comparison of the spectrum of HD 53244 with other field Hg-Mn stars shows that it shares many of their spectral anomalies but also some differences exist.


Functional relationships for Teff and log g in F-G supergiants from uvby - β photometry

A. Arellano Ferro

Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico

armando@astros.unam.mx

Received: 2010 May 25

Accepted: 2010 July 2 (

)

Abstract: From photoelectric uvby - β data and recent accurate synthetic and spectroscopic values of Teff and log g for 50 F-G supergiants, we have calculated functional relationships that lead to initial estimates of effective temperature and gravities for these types of stars. It is shown that while the Teff relationships are calculated using the data on young massive supergiants, they are also valid for evolved stars of similar temperatures like post-AGB and RV Tau stars. The gravity can also be predicted from the Δ[c1] index with an uncertainty of about 0.26 dex. Although a clear and significant trend between MV and Δ[c1] is seen, no calibration is found that predicts accurate values of MV .



June 2010


The importance of nucleus rotation in determining
the largest grains ejected from comets

A. Molina1,2

Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Granada, Granada, Spain
Instituto de Astrofísica de Andalucía, CSIC, Granada, Spain

amolina@iaa.es

Received: 2010 February 18

Accepted: 2010 June 16 (

)

Abstract: The maximum diameter of large boulders ejected from the cometary nuclei is investigated using the classical model of dust grain as dragged out by radially expanding cometary gases. The importance of the inertial forces, and particularly those due to the rotation of the comet is shown. Although a larger dust grain can be lifted from the nucleus surface if the rotation is faster, the rotation period has to be larger than a certain value. A simple expression for this critical value of rotation period is given. Our results are applied to different comets and a comparison with the maximum radius values obtained by radar measurements is made. Finally, comet Churyumov-Gerasimenko, the target of the ROSETTA mission to arrive on 2014, is going to be analyzed and a range for the maximum diameter of the dust grains that can be lifted is proposed.


Hypercritical accretion onto a magnetized neutron star surface: a numerical approach

C. G. Bernal, W. H. Lee, and Dany Page

Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico

wlee@astroscu.unam.mx

Received: 2010 January 19

Accepted: 2010 June 14 (

)

Abstract: The properties of a new-born neutron star, produced in a core-collapse supernova, can be strongly affected by the possible late fallback which occurs several hours after the explosion. This accretion occurs in the regime dominated by neutrino cooling, explored initially in this context by (Chevalier 1989). Here we revisit this approach in a 1D spherically symmetric model and carry out numerical simulations in 2D in an accretion column onto a neutron star considering detailed microphysics, neutrino cooling and the presence of magnetic fields in ideal MHD. We compare our numerical results to the analytic solutions and explore how the purely hydrodynamical as well as the MHD solutions differ from them, and begin to explore how this may affect the appearance of the remnant as a typical radio pulsar.


uvby - β photoelectric photometry of Cepheid stars

J. H. Peña,2 A. Arellano Ferro,2 R. Peña-Miller,3 M. Alvarez,4 Y. Rosas,5 H. García,6 G. Muñoz,7 B. Vargas,8 J. P. Sareyan,9 C. A. Guerrero,2 and A. Rentería2

Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico
Department of Mathematics, Imperial College London, UK
Observatorio Astronomico Nacional, Universidad Nacional Autónoma de México, Mexico
Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Mexico Facultad de Ciencia, UNAN-Managua, Nicaragua
ESIME, IPN, Mexico
Instituto de Geofísica, Universidad Nacional Autónoma de México, Mexico
Lesia, Observatoire de Paris-Meudon and Observatoire de la Cote d’Azur, France

jhpena@astroscu.unam.mx

Received: 2010 May 4

Accepted: 2010 June 10 (

)

Abstract: We present time-series uvby -β photometry of 41 classical Cepheid stars. A brief discussion of a comparison between the present data and previous photometric observations is included.


Spectral Variability of Romano’s Star

O. Maryeva,1, 2 and P. Abolmasov3

Stavropol State University, Russia
Special Astrophysical Observatory, Russia
Sternberg Astronomical Institute, Russia

olga.maryeva@gmail.com

Received: 2010 February 3

Accepted: 2010 June 10 (

)

Abstract: We combine archival spectral observations of the LBV star V532 (Romano’s star) together with the existing photometric data in the B band. Spectroscopic data cover 15 years of observations (from 1992 to 2007). We show that the object in maximum of brightness behaves as an emission line supergiant while in minimum V532 moves along the sequence of late WN stars. In this sence, the object behaves similarly to the well-known Luminous Blue Variable (LBV) stars AG Car and R127, but is somewhat hotter in the minima. We identify about 100 spectral lines in the 3700 - 7300 Å wavelength range. For today, our spectroscopy is the most comprehensive for this object. The velocity of the wind is derived using HeI triplet lines (360 ± 30 km s-1). Physical parameters of the nebula around V532 are estimated.


Orbital elements for eight binaries. Study of the nature of wide components. I

F. M. Rica Romero1,2

Agrupación Astronómica de Mérida, Spain
Liga Iberoamericana de Astronomía (LIADA), Argentina

frica0@gmail.com

Received: 2010 March 25

Accepted: 2010 June 5 (

)

Abstract: ew orbital parameters and masses for eight binaries were determined. Most of these were noted as being in need of correction due to large residuals to the previous best orbit. A modified Thiele-van den Bos method was used to obtain initial orbits which were improved using the differential correction method of Heintz. The Thiele-van den Bos method was modified so that an approximate value of the areal constant allows good results to be obtained. The nature of wide components were studied using BV IJHK photometry, historical astrometry and kinematical data. A search for new unreported companions around the binaries was carried out.


Compact radio sources in the vicinity of the ultracompact HII region G78.4+2.6

Citlali Neria, Yolanda Gómez, and Luis F. Rodríguez

Centro de Radioastronomía y Astrofísica
Universidad Nacional Autónoma de México, Morelia, Mexico

c.neria@crya.unam.mx

Received: 2010 January 26

Accepted: 2010 June 4 (

)

Abstract: Using the Very Large Array (VLA) at 3.6 cm we identify four new compact radio sources in the vicinity of the cometary HII region G78.4+2.6 (VLA 1). The four compact radio sources (named VLA 2 to VLA 5), have near-infrared counterparts, as seen in the 3.6 μm Spitzer image. One of them (VLA 5) clearly shows evidence of radio variability in a timescale of hours. We explore the possibility that these radio sources are associated with pre-main sequence (PMS) stars in the vicinity of the UC HII region G78.4+2.6. Our results favor the smaller distance value of 1.7 kpc for G78.4+2.6. In addition to the detection of the radio sources in the vicinity of G78.4+2.6, we detected another group of five sources which appear located about 3to the northwest of the HII region. Some of them exhibit extended emission.



May 2010


Speckle Interferometry at the Observatorio Astronómico Nacional. II

V. G. Orlov, V. V. Voitsekhovich, J. L. Rivera, C. A. Guerrero, and F. Ortiz

Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico

orlov@astro.unam.mx

Received: 2010 March 27

Accepted: 2010 May 27 (

)

Abstract: We present speckle interferometric measurements of binary stars made during the June of 2009 with the 1.5 m telescope of the Observatorio Astronómico Nacional at SPM (Mexico). The data contain 189 position angle and separation measures of 144 systems. The measured angular separations range from 0.′′16 to 3.′′64. The maximum magnitude of the brighter component was 10.96. The mean error in separation is 0.02′′ and on the position angles is 1.5. Some of the position angles were determined with the usual 180 ambiguity.


Echelle spectroscopy of the nuclei of the highly collimated bipolar planetary nebulae M 2-9 and M 1-91

S. Torres-Peimbert,2 A. Arrieta,3 and M. Bautista4

Instituto of Astronomia, Universidad Nacional Autónoma de México, Mexico
Universidad Iberoamericana, Depto. de Física y Matemáticas, Mexico
Department of Physics, Western Michigan University, USA

silvia@astroscu.unam.mx

Received: 2010 January 21

Accepted: 2010 May 20 (

)

Abstract: 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 circumstellar region of both objects. We propose that the observed forbidden lines arise in the inner part of the extended torus that surrounds each object.


On the Size of the Non-Thermal Component in the Radio Emission from Cyg OB2 #5

Luis F. Rodríguez,1 Yolanda Gómez,1 Laurent Loinard,1 and Amy J. Mioduszewski2

Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Morelia, Michoacán, Mexico
National Radio Astronomy Observatory, USA

l.rodriguez@astrosmo.unam.mx

Received: 2010 January 11

Accepted: 2010 May 19 (

)

Abstract: Cyg OB2 #5 is a contact binary system with variable radio continuum emission. This emission has a low-flux state where it is dominated by thermal emission from the ionized stellar wind and a high-flux state where an additional non-thermal component appears. The variations are now known to have a period of 6.7 ± 0.2 yr. The non-thermal component has been attributed to different agents: an expanding envelope ejected periodically from the binary, emission from a wind-collision region, or a star with non-thermal emission in an eccentric orbit around the binary. The determination of the angular size of the non-thermal component is crucial to discriminate between these alternatives. We present the analysis of VLA archive observations made at 8.46 GHz in 1994 (low state) and 1996 (high state), that allow us to subtract the effect of the persistent thermal emission and to estimate an angular size of 0.′′02 for the non-thermal component. This compact size favors the explanation in terms of a star with non-thermal emission or of a wind-collision region.



April 2010


The San Pedro Mártir Planetary Nebula
Kinematic Catalogue: Extragalactic Planetary Nebulae

M. G. Richer,1 J. A. López,1 E. Díaz-Méndez,2 H. Riesgo,1 S.-H. Báez,3 Ma.-T. García-Díaz,1 J. Meaburn4 D. M. Clark,1 R. M. Calderón Olvera,5 G. López Soto,5 and O. Toledano Rebolo6

Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico
Texas Christian University, Fort Worth, Texas, USA
Facultad de Física e Inteligencia Artificial, Universidad Veracruzana, Mexico
Jodrell Bank Observatory, University of Manchester, UK
Universidad Nacional Autónoma de México, Mexico
Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Mexico

richer@astro.unam.mx

Received: 2009 October 14

Accepted: 2010 April 17 (

)

Abstract: We present kinematic data for 211 bright planetary nebulae in eleven Local Group galaxies: M31 (137 PNe), M32 (13), M33 (33), Fornax (1), Sagittarius (3), NGC 147 (2), NGC 185 (5), NGC 205 (9), NGC 6822 (5), Leo A (1), and Sextans A (1). The data were acquired at the Observatorio Astronómico Nacional in the Sierra de San Pedro Mártir using the 2.1m telescope and the Manchester Echelle Spectrometer in the light of [O III]λ5007 at a resolution of 11 km s-1. A few objects were observed in Hα. The internal kinematics of bright planetary nebulae do not depend strongly upon the metallicity or age of their progenitor stellar populations, though small systematic differences exist. The nebular kinematics and Hβ luminosity require that the nebular shells be accelerated during the early evolution of their central stars. Thus, kinematics provides an additional argument favoring similar stellar progenitors for bright planetary nebulae in all galaxies.