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Anabel Arrieta

Universidad Iberoamericana - Mexico, Physics and Mathematics, Faculty Member

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Profesora e investigadora de la Universidad Iberoamericana desde 2003. Estudios de Física en la Facultad de Ciencias de la UNAM, Maestría y Doctorado en Astronomía en el Instituto de Astronomía de la Universidad Nacional. Estancia posdoctoral en el Space Telescope Science Institute en Baltimore, Maryland. Áreas de investigación: las nebulosas planetarias y las atmósferas de estrellas usando diferentes técnicas observacionales. Desde 2004, miembro del Sistema Nacional de Investigadores, Nivel 1.

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Papers by Anabel Arrieta

An Echelle Catalog of OB Stars

The B[e] Phenomenon: Forty Years of Studies, Feb 1, 2017

NGC 6153: Reality is complicated

Cornell University - arXiv, Oct 10, 2022

We study the kinematics of emission lines that arise from many physical processes in NGC 6153 bas... more We study the kinematics of emission lines that arise from many physical processes in NGC 6153 based upon deep, spatially-resolved, high resolution spectra acquired with the UVES spectrograph at the ESO VLT. Our most basic finding is that the plasma in NGC 6153 is complex, especially its temperature structure. The kinematics of most emission lines defines a classic expansion law, with the outer part expanding fastest (normal nebular plasma). However, the permitted lines of O I, C II, N II, O II, and Ne II present a constant expansion velocity that defines a second kinematic component (additional plasma component). The physical conditions imply two plasma components, with the additional plasma component having lower temperature and higher density. The [O II] density and the [N II] temperature are anomalous, but may be understood considering the contribution of recombination to these forbidden lines. The two plasma components have very different temperatures. The normal nebular plasma appears to be have temperature fluctuations in part of its volume (main shell), but only small fluctuations elsewhere. The additional plasma component contains about half of the mass of the N 2+ and O 2+ ions, but only 3 − 5% of the mass of H + ions, so the two plasma components have very different chemical abundances. We estimate abundances of 12 + log(O 2+ /H +) ∼ 9.2 dex and He/H ∼ 0.13. Although they are all complications, multiple plasma components, temperature fluctuations, and the contributions of multiple physical processes to a given emission line are all part of the reality in NGC 6153, and should generally be taken into account.

Creating and using large grids of precalculated model atmospheres for a rapid analysis of stellar spectra

Astronomy & Astrophysics, 2020

Aims. We present a database of 43 340 atmospheric models (∼80 000 models at the conclusion of the... more Aims. We present a database of 43 340 atmospheric models (∼80 000 models at the conclusion of the project) for stars with stellar masses between 9 and 120 M⊙, covering the region of the OB main-sequence and Wolf-Rayet stars in the Hertzsprung-Russell diagram. Methods. The models were calculated using the ABACUS I supercomputer and the stellar atmosphere code CMFGEN. Results. The parameter space has six dimensions: the effective temperature Teff, the luminosity L, the metallicity Z, and three stellar wind parameters: the exponent β, the terminal velocity V∞, and the volume filling factor Fcl. For each model, we also calculate synthetic spectra in the UV (900−2000 Å), optical (3500−7000 Å), and near-IR (10 000−40 000 Å) regions. To facilitate comparison with observations, the synthetic spectra can be rotationally broadened using ROTIN3, by covering v sin i velocities between 10 and 350 km s−1 with steps of 10 km s−1. Conclusions. We also present the results of the reanalysis of ϵ Ori ...

A Mega-Grid of CMFGEN Model Atmospheres for Rapid Analysis of Stellar Spectra

The B[e] Phenomenon: Forty Years of Studies, Feb 1, 2017

High resolution spectroscopy of NGC 7009

Asymmetric Planetary Nebulae 5 Conference, 2011

The typical expansion velocity of a planetary nebula is about 20 km s −1. Thus the frequently-use... more 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 the sky and along the line of sight. We present analysis of the physical condition of the gas inside the nebula and its relation to the abundance discrepancy factor.

Creating and Using Large Grids of Pre-calculated Model Atmospheres for Rapid Analysis of Stellar Spectra

Communications in Computer and Information Science, 2019

We present a database of 45,000 atmospheric models (which will become 80,000 models by the end of... more We present a database of 45,000 atmospheric models (which will become 80,000 models by the end of the project) with stellar masses between 9 and 120 M ⊙ , covering the region of the OB main sequence and W-R stars in the H-R diagram. The models were calculated using the ABACUS I supercomputer and the stellar atmosphere code CMFGEN. The parameter space has 6 dimensions: the effective temperature T eff , the luminosity L, the metallicity Z, and three stellar wind parameters, namely the exponent β , the terminal velocity V ∞ , and the volume filling factor F cl. For each model, we also calculate synthetic spectra in the UV (900-2000Å), optical (3500-7000Å), and near IR (10000-30000Å) regions. To facilitate comparison with observations, the synthetic spectra were rotationally broaden using ROTIN3, by covering v sin i velocities between 10 and 350 km/s with steps of 10 km/s, resulting in a library of 1 575 000 synthetic spectra. In order to demonstrate the benefits of employing the databases of pre-calculated models, we also present the results of the re-analysis of ε Ori by using our grid.

Database of CMFGEN Models in a 6-Dimensional Space

We present a database of 25,000 atmospheric models (which is to grow to a grand total of 75000 mo... more We present a database of 25,000 atmospheric models (which is to grow to a grand total of 75000 models by the conclusion of the project) with stellar masses between 9 and 120 M\(_{\odot }\), covering the region of the OB main sequence and W-R stars in the H–R diagram. The models were calculated using the ABACUS I supercomputer and the stellar atmosphere code CMFGEN. The parameter space has 6 dimensions: surface temperature of the star, also called the effective temperature (\(T_\mathrm{eff}\)), luminosity (L), metallicity (Z), and three stellar wind parameters, the exponent (\(\beta \)) of the wind velocity law, the terminal velocity (\(V_{\infty }\)), and the volume filling factor (\(F_{cl}\)). For each model, we also calculate synthetic spectra in the UV (900–2,000 A), optical (3,500–7,000 A), and near IR (10,000–30,000 A) ranges. For comparison with observations, the synthetic spectra were rotationally broaden using ROTIN3, by covering the range between 10 and 350 km s\(^{-1}\) wi...

Kinematics of recombination and collisionally excited lines in PNe

For some time there has been the concern that the abundances derived from recombination lines do ... more 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. 2013), by comparing the behavior of the position - velocity diagrams of the emission lines. We plan to continue these studies by analyzing the most signiﬁcant cases of discrepancy to try to ascertain its origin.

The Temperature and Density from Permitted O ii Lines in the Planetary Nebula NGC 7009

The Astrophysical Journal, 2019

We present spatial-and velocity-resolved spectroscopy of NGC 7009 acquired with the UVES spectrog... more We present spatial-and velocity-resolved spectroscopy of NGC 7009 acquired with the UVES spectrograph at the VLT UT2/Kueyen. We use these data to determine the structure of the electron temperature and electron density based upon O II permitted (recombination) lines. We find a strong gradient in the O II-based electron temperature. It agrees with the electron temperature determined by forbidden (collisionally excited) lines in part of the nebular volume, but also differs by more than 6000 K in other parts of the nebular volume. This result supports the hypothesis that NGC 7009 contains two plasma components, one of which emits both forbidden and permitted lines and the other that emits only permitted lines. For the component that emits only permitted lines, we find a lower limit to the electron density of 10 4 cm −3 from the O II permitted lines, which is higher than derived from forbidden lines. We are unable to determine whether the two plasma components are in pressure equilibrium from our data, but there exist temperature and density combinations that allow this equilibrium for temperatures between 600 and 6000 K. For most of the temperature and density conditions allowed for the component that emits only permitted lines, its mass of O 2+ is less than that of the plasma component that emits forbidden lines.

FIT spec : A New Algorithm for the Automated Fit of Synthetic Stellar Spectra for OB Stars

The Astrophysical Journal Supplement Series, 2018

In this paper we describe the FITspec code, a data mining tool for the automatic fitting of synth... more In this paper we describe the FITspec code, a data mining tool for the automatic fitting of synthetic stellar spectra. The program uses a database of 27 000 cmfgen models of stellar atmospheres arranged in a six-dimensional (6D) space, where each dimension corresponds to one model parameter. From these models a library of 2 835 000 synthetic spectra were generated covering the ultraviolet, optical, and infrared region of the electromagnetic spectrum. Using FITspec we adjust the effective temperature and the surface gravity. From the 6D array we also get the luminosity, the metallicity, and three parameters for the stellar wind: the terminal velocity (v ∞), the β exponent of the velocity law, and the clumping filling factor (F cl). Finally, the projected rotational velocity (v • sin i) can be obtained from the library of stellar spectra. Validation of the algorithm was performed by analyzing the spectra of a sample of eight O-type stars taken from the iacob spectroscopic survey of Northern Galactic OB stars. The spectral lines used for the adjustment of the analyzed stars are reproduced with good accuracy. In particular, the effective temperatures calculated with the FITspec are in good agreement with those derived from spectral type and other calibrations for the same stars. The stellar luminosities and projected rotational velocities are also in

Analysis and fit of stellar spectra using a mega-database of CMFGEN models

Proceedings of the International Astronomical Union, 2016

We present a tool for analysis and fit of stellar spectra using a mega database of 15,000 atmosph... more We present a tool for analysis and fit of stellar spectra using a mega database of 15,000 atmosphere models for OB stars. We have developed software tools, which allow us to find the model that best fits to an observed spectrum, comparing equivalent widths and line ratios in the observed spectrum with all models of the database. We use the Hα, Hβ, Hγ, and Hδ lines as criterion of stellar gravity and ratios of He II λ4541/He I λ4471, He II λ4200/(He I+He II λ4026), He II λ4541/He I λ4387, and He II λ4200/He I λ4144 as criterion of T eff.

Evidence of Jets in the Bipolar Planetary Nebulae M 1-91 and M 1-92

Symposium - International Astronomical Union, 2003

For M1-91 we find that the ratio of the 6717/6731 [S II] narrow band images shows two symmetrical... more 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 that from the NW knot we receive scattered light from the central region that has traveled along the line of symmetry.

High dispertion spectroscopy of the young planetary nebula M2-9

Revista Mexicana De Astronomia Y Astrofisica Serie De Conferencias, 1998

Nebular kinematics of NGC 7009 and NGC 6543 as tests of possible differences of distribution of permitted and forbidden emission lines

One of the open problems in PN research is the abundance discrepancy factor that is obtained from... more 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 chemically inhomogeneous medium where there are high density hydrogen-poor condensations of low temperature responsible for most of the recombination line intensities (e.g. [1], and references therein). To try to discriminate among these possibilities, we have examined the possible difference in distribution of the O II and [O III] lines in planetary nebulae. From long slit echelle spectroscopy of NGC 7009 and NGC 6543 we have examined their velocity distribution along the slit on two different positions of each nebula.

Nebular kinematics of planetary nebulae as tests of possible differences of distribution of permitted and forbidden emission lines

En las nebulosas gaseosas la abundancias químicas de los elementos pesados que se derivan de las ... more En las nebulosas gaseosas la abundancias químicas de los elementos pesados que se derivan de las líneas de recombinación resultan sistemáticamente más altas que las que se derivan de las líneas excitadas colisionalmente. Las explicaciones que se han ofrecido para obtener soluciones compatibles han sido atribuir estas diferencias al efecto de inhomogeneidades en la temperatura, o atribuirlas a la presencia de nudos densos de material enriquecido. Nosotros hemos obtenido observaciones de rendija larga en algunas nebulosas planetarias para tratar de resolver esta controversia. Presentamos resultados preliminares para NGC 6543.

The puzzling periodicities of the X-ray binary 2S0114+650

ABSTRACT

Combined modelling of the He2-131 planetary nebula and of its central star

Proceedings of the International Astronomical Union, 2011

We present a unified model of the central star and the ionized gas of the planetary nebula He2-13... more

Temporal Evolution of the H_2 Abundance in the Interstellar Medium

We calculate the abundance of molecular hydrogen (H2) for a wide range of interstellar conditions... more 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 abundance can be followed with dnHw/dt = Rf - RPh,d - Rd, where Rf is the formation rate of H2 on interstellar grains, RPh,d is the photodissociation rate, and Rd is the collisional dissociation rate.

Magnetic field effects in the heat flow of charged fluids

Heat conduction in ionized plasmas in the presence of magnetic fields is today a fashionable prob... more 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 perpendicular to the magnetic field are shown to yield significant contributions, under certain conditions to the ordinary Fourier component of the heat flow. The thermal conductivities associated with these effects change with the strength of the magnetic field for a given temperature and density and are shown to be significant compared with the parallel conductivity for a whole range of values of \vec{B}.

Integral stellar-nebular model of NGC 7009

Proceedings of the International Astronomical Union, 2011

We developed a self-consistent stellar-nebular model for NGC 7009. This model reproduces the avai... more 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, Ne, Cl, and S in the nebula and its central star. Concluding that the stellar composition agrees with the nebular composition with t2 ≠ 0.00.

An Echelle Catalog of OB Stars

The B[e] Phenomenon: Forty Years of Studies, Feb 1, 2017

NGC 6153: Reality is complicated

Cornell University - arXiv, Oct 10, 2022

We study the kinematics of emission lines that arise from many physical processes in NGC 6153 bas... more We study the kinematics of emission lines that arise from many physical processes in NGC 6153 based upon deep, spatially-resolved, high resolution spectra acquired with the UVES spectrograph at the ESO VLT. Our most basic finding is that the plasma in NGC 6153 is complex, especially its temperature structure. The kinematics of most emission lines defines a classic expansion law, with the outer part expanding fastest (normal nebular plasma). However, the permitted lines of O I, C II, N II, O II, and Ne II present a constant expansion velocity that defines a second kinematic component (additional plasma component). The physical conditions imply two plasma components, with the additional plasma component having lower temperature and higher density. The [O II] density and the [N II] temperature are anomalous, but may be understood considering the contribution of recombination to these forbidden lines. The two plasma components have very different temperatures. The normal nebular plasma appears to be have temperature fluctuations in part of its volume (main shell), but only small fluctuations elsewhere. The additional plasma component contains about half of the mass of the N 2+ and O 2+ ions, but only 3 − 5% of the mass of H + ions, so the two plasma components have very different chemical abundances. We estimate abundances of 12 + log(O 2+ /H +) ∼ 9.2 dex and He/H ∼ 0.13. Although they are all complications, multiple plasma components, temperature fluctuations, and the contributions of multiple physical processes to a given emission line are all part of the reality in NGC 6153, and should generally be taken into account.

Creating and using large grids of precalculated model atmospheres for a rapid analysis of stellar spectra

Astronomy & Astrophysics, 2020

Aims. We present a database of 43 340 atmospheric models (∼80 000 models at the conclusion of the... more Aims. We present a database of 43 340 atmospheric models (∼80 000 models at the conclusion of the project) for stars with stellar masses between 9 and 120 M⊙, covering the region of the OB main-sequence and Wolf-Rayet stars in the Hertzsprung-Russell diagram. Methods. The models were calculated using the ABACUS I supercomputer and the stellar atmosphere code CMFGEN. Results. The parameter space has six dimensions: the effective temperature Teff, the luminosity L, the metallicity Z, and three stellar wind parameters: the exponent β, the terminal velocity V∞, and the volume filling factor Fcl. For each model, we also calculate synthetic spectra in the UV (900−2000 Å), optical (3500−7000 Å), and near-IR (10 000−40 000 Å) regions. To facilitate comparison with observations, the synthetic spectra can be rotationally broadened using ROTIN3, by covering v sin i velocities between 10 and 350 km s−1 with steps of 10 km s−1. Conclusions. We also present the results of the reanalysis of ϵ Ori ...

A Mega-Grid of CMFGEN Model Atmospheres for Rapid Analysis of Stellar Spectra

The B[e] Phenomenon: Forty Years of Studies, Feb 1, 2017

High resolution spectroscopy of NGC 7009

Asymmetric Planetary Nebulae 5 Conference, 2011

The typical expansion velocity of a planetary nebula is about 20 km s −1. Thus the frequently-use... more 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 the sky and along the line of sight. We present analysis of the physical condition of the gas inside the nebula and its relation to the abundance discrepancy factor.

Creating and Using Large Grids of Pre-calculated Model Atmospheres for Rapid Analysis of Stellar Spectra

Communications in Computer and Information Science, 2019

We present a database of 45,000 atmospheric models (which will become 80,000 models by the end of... more We present a database of 45,000 atmospheric models (which will become 80,000 models by the end of the project) with stellar masses between 9 and 120 M ⊙ , covering the region of the OB main sequence and W-R stars in the H-R diagram. The models were calculated using the ABACUS I supercomputer and the stellar atmosphere code CMFGEN. The parameter space has 6 dimensions: the effective temperature T eff , the luminosity L, the metallicity Z, and three stellar wind parameters, namely the exponent β , the terminal velocity V ∞ , and the volume filling factor F cl. For each model, we also calculate synthetic spectra in the UV (900-2000Å), optical (3500-7000Å), and near IR (10000-30000Å) regions. To facilitate comparison with observations, the synthetic spectra were rotationally broaden using ROTIN3, by covering v sin i velocities between 10 and 350 km/s with steps of 10 km/s, resulting in a library of 1 575 000 synthetic spectra. In order to demonstrate the benefits of employing the databases of pre-calculated models, we also present the results of the re-analysis of ε Ori by using our grid.

Database of CMFGEN Models in a 6-Dimensional Space

We present a database of 25,000 atmospheric models (which is to grow to a grand total of 75000 mo... more We present a database of 25,000 atmospheric models (which is to grow to a grand total of 75000 models by the conclusion of the project) with stellar masses between 9 and 120 M\(_{\odot }\), covering the region of the OB main sequence and W-R stars in the H–R diagram. The models were calculated using the ABACUS I supercomputer and the stellar atmosphere code CMFGEN. The parameter space has 6 dimensions: surface temperature of the star, also called the effective temperature (\(T_\mathrm{eff}\)), luminosity (L), metallicity (Z), and three stellar wind parameters, the exponent (\(\beta \)) of the wind velocity law, the terminal velocity (\(V_{\infty }\)), and the volume filling factor (\(F_{cl}\)). For each model, we also calculate synthetic spectra in the UV (900–2,000 A), optical (3,500–7,000 A), and near IR (10,000–30,000 A) ranges. For comparison with observations, the synthetic spectra were rotationally broaden using ROTIN3, by covering the range between 10 and 350 km s\(^{-1}\) wi...

Kinematics of recombination and collisionally excited lines in PNe

For some time there has been the concern that the abundances derived from recombination lines do ... more 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. 2013), by comparing the behavior of the position - velocity diagrams of the emission lines. We plan to continue these studies by analyzing the most signiﬁcant cases of discrepancy to try to ascertain its origin.

The Temperature and Density from Permitted O ii Lines in the Planetary Nebula NGC 7009

The Astrophysical Journal, 2019

We present spatial-and velocity-resolved spectroscopy of NGC 7009 acquired with the UVES spectrog... more We present spatial-and velocity-resolved spectroscopy of NGC 7009 acquired with the UVES spectrograph at the VLT UT2/Kueyen. We use these data to determine the structure of the electron temperature and electron density based upon O II permitted (recombination) lines. We find a strong gradient in the O II-based electron temperature. It agrees with the electron temperature determined by forbidden (collisionally excited) lines in part of the nebular volume, but also differs by more than 6000 K in other parts of the nebular volume. This result supports the hypothesis that NGC 7009 contains two plasma components, one of which emits both forbidden and permitted lines and the other that emits only permitted lines. For the component that emits only permitted lines, we find a lower limit to the electron density of 10 4 cm −3 from the O II permitted lines, which is higher than derived from forbidden lines. We are unable to determine whether the two plasma components are in pressure equilibrium from our data, but there exist temperature and density combinations that allow this equilibrium for temperatures between 600 and 6000 K. For most of the temperature and density conditions allowed for the component that emits only permitted lines, its mass of O 2+ is less than that of the plasma component that emits forbidden lines.

FIT spec : A New Algorithm for the Automated Fit of Synthetic Stellar Spectra for OB Stars

The Astrophysical Journal Supplement Series, 2018

In this paper we describe the FITspec code, a data mining tool for the automatic fitting of synth... more In this paper we describe the FITspec code, a data mining tool for the automatic fitting of synthetic stellar spectra. The program uses a database of 27 000 cmfgen models of stellar atmospheres arranged in a six-dimensional (6D) space, where each dimension corresponds to one model parameter. From these models a library of 2 835 000 synthetic spectra were generated covering the ultraviolet, optical, and infrared region of the electromagnetic spectrum. Using FITspec we adjust the effective temperature and the surface gravity. From the 6D array we also get the luminosity, the metallicity, and three parameters for the stellar wind: the terminal velocity (v ∞), the β exponent of the velocity law, and the clumping filling factor (F cl). Finally, the projected rotational velocity (v • sin i) can be obtained from the library of stellar spectra. Validation of the algorithm was performed by analyzing the spectra of a sample of eight O-type stars taken from the iacob spectroscopic survey of Northern Galactic OB stars. The spectral lines used for the adjustment of the analyzed stars are reproduced with good accuracy. In particular, the effective temperatures calculated with the FITspec are in good agreement with those derived from spectral type and other calibrations for the same stars. The stellar luminosities and projected rotational velocities are also in

Analysis and fit of stellar spectra using a mega-database of CMFGEN models

Proceedings of the International Astronomical Union, 2016

We present a tool for analysis and fit of stellar spectra using a mega database of 15,000 atmosph... more We present a tool for analysis and fit of stellar spectra using a mega database of 15,000 atmosphere models for OB stars. We have developed software tools, which allow us to find the model that best fits to an observed spectrum, comparing equivalent widths and line ratios in the observed spectrum with all models of the database. We use the Hα, Hβ, Hγ, and Hδ lines as criterion of stellar gravity and ratios of He II λ4541/He I λ4471, He II λ4200/(He I+He II λ4026), He II λ4541/He I λ4387, and He II λ4200/He I λ4144 as criterion of T eff.

Evidence of Jets in the Bipolar Planetary Nebulae M 1-91 and M 1-92

Symposium - International Astronomical Union, 2003

For M1-91 we find that the ratio of the 6717/6731 [S II] narrow band images shows two symmetrical... more 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 that from the NW knot we receive scattered light from the central region that has traveled along the line of symmetry.

High dispertion spectroscopy of the young planetary nebula M2-9

Revista Mexicana De Astronomia Y Astrofisica Serie De Conferencias, 1998

Nebular kinematics of NGC 7009 and NGC 6543 as tests of possible differences of distribution of permitted and forbidden emission lines

One of the open problems in PN research is the abundance discrepancy factor that is obtained from... more 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 chemically inhomogeneous medium where there are high density hydrogen-poor condensations of low temperature responsible for most of the recombination line intensities (e.g. [1], and references therein). To try to discriminate among these possibilities, we have examined the possible difference in distribution of the O II and [O III] lines in planetary nebulae. From long slit echelle spectroscopy of NGC 7009 and NGC 6543 we have examined their velocity distribution along the slit on two different positions of each nebula.

Nebular kinematics of planetary nebulae as tests of possible differences of distribution of permitted and forbidden emission lines

En las nebulosas gaseosas la abundancias químicas de los elementos pesados que se derivan de las ... more En las nebulosas gaseosas la abundancias químicas de los elementos pesados que se derivan de las líneas de recombinación resultan sistemáticamente más altas que las que se derivan de las líneas excitadas colisionalmente. Las explicaciones que se han ofrecido para obtener soluciones compatibles han sido atribuir estas diferencias al efecto de inhomogeneidades en la temperatura, o atribuirlas a la presencia de nudos densos de material enriquecido. Nosotros hemos obtenido observaciones de rendija larga en algunas nebulosas planetarias para tratar de resolver esta controversia. Presentamos resultados preliminares para NGC 6543.

The puzzling periodicities of the X-ray binary 2S0114+650

ABSTRACT

Combined modelling of the He2-131 planetary nebula and of its central star

Proceedings of the International Astronomical Union, 2011

We present a unified model of the central star and the ionized gas of the planetary nebula He2-13... more

Temporal Evolution of the H_2 Abundance in the Interstellar Medium

We calculate the abundance of molecular hydrogen (H2) for a wide range of interstellar conditions... more 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 abundance can be followed with dnHw/dt = Rf - RPh,d - Rd, where Rf is the formation rate of H2 on interstellar grains, RPh,d is the photodissociation rate, and Rd is the collisional dissociation rate.

Magnetic field effects in the heat flow of charged fluids

Heat conduction in ionized plasmas in the presence of magnetic fields is today a fashionable prob... more 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 perpendicular to the magnetic field are shown to yield significant contributions, under certain conditions to the ordinary Fourier component of the heat flow. The thermal conductivities associated with these effects change with the strength of the magnetic field for a given temperature and density and are shown to be significant compared with the parallel conductivity for a whole range of values of \vec{B}.

Integral stellar-nebular model of NGC 7009

Proceedings of the International Astronomical Union, 2011

We developed a self-consistent stellar-nebular model for NGC 7009. This model reproduces the avai... more 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, Ne, Cl, and S in the nebula and its central star. Concluding that the stellar composition agrees with the nebular composition with t2 ≠ 0.00.

The planetary nebula NGC 7009 and its central star

Stellar evolution models predict that the chemical composition in the atmosphere of stars in the ... more 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
supported by the semi-analytical study of the nebula. This type of work
yields a self-consistent model of the whole object imposing more
observational constraints to models.

High resolution spectroscopy of NGC 7009

The typical expansion velocity of a planetary nebula is about 20 km s −1. Thus the frequently-use... more 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 the sky and along the line of sight. We present analysis of the physical condition of the gas inside the nebula and its relation to the abundance discrepancy factor.

Nebular kinematics of NGC 7009 and NGC 6543 as tests of possible differences of distribution of permitted and forbidden emission lines

One of the open problems in PN research is the abundance discrepancy factor that is obtained from... more 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 chemically inhomogeneous medium where there are high density hydrogen-poor condensations of low temperature responsible for most of the recombination line intensities (e.g. [1], and references therein). To try to discriminate among these possibilities, we have examined the possible difference in distribution of the O II and [O III] lines in planetary nebulae. From long slit echelle spectroscopy of NGC 7009 and NGC 6543 we have examined their velocity distribution along the slit on two different positions of each nebula.

B[e] phenomenon in bipolar planetary nebulae. Is the central star's wind symmetric?

In this article we classify M1-92 and M3-60 CSPN as objects with B[e] phenomenon and suggest CRL6... more 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, therefore the cPNB[e] objects should contain fast rotators with a slowly expanding equatorial disks. The conservation of momentum of these disks, at least in the objects where the binarity is not confirmed, favours the magnetic field + rotation scenario for the collimation of the nebula.