Marcos Diaz - Academia.edu (original) (raw)
Papers by Marcos Diaz
When classifying by eye more than 22 000 spectra selected as possible white dwarf stars from the ... more When classifying by eye more than 22 000 spectra selected as possible white dwarf stars from the Sloan Digital Sky Survey Data Release 7, we detected Zeeman splittings in more than 800 stars, increasing by a factor of five the number of known magnetic white dwarfs. Our field estimations range from 90 MG to less than 1 MG, complementing the detections by Külebi et al. [1]. These magnetic white dwarf stars cover the whole range of temperature and spectral classes observed. As the Zeeman splittings broadens the lines, we cannot use the line profiles to estimate surface gravity directly. We therefore excluded the magnetic white dwarfs from our average mass estimate of normal DAs and DBs. Analysis of the remaining 1505 bright and hot DA white dwarfs, i.e., those with S/N>=20 and Teff = 12000 K, results in a mean mass DA = 0.604+/-0.003 Msolar, while that of our 82 bright DBs with Teff = 16000 K is DB = 0.646+/-0.006 Msolar.
Astrophysics and Space Science, 2006
Cataclysmic Variables (CVs) are close binary systems where mass is transferred from a red dwarf s... more Cataclysmic Variables (CVs) are close binary systems where mass is transferred from a red dwarf star to a white dwarf star via an accretion disk. The flickering is observed as stochastic variations in the emitted radiation both in the continuum and in the emission line profiles. The main goal of our simulations is to compare synthetic Doppler maps with observed ones, aiming to constrain the flickering properties and wind parameters. A code was developed which generates synthetic emission line profiles of a geometrically thin and optically thick accretion disk. The simulation allows us to include flares in a particular disk region. The emission line flares may be integrated over arbitrary "exposure" times, producing the synthetic line profiles. Flickering Doppler maps are created using such synthetic time series. The presence of a wind inside the Roche lobe was also implemented. Radiative transfer effects in the lines where taken into account in order to reproduce the single peaked line profiles frequently seen in nova-like CVs.
When classifying by eye more than 22 000 spectra selected as possible white dwarf stars from the ... more When classifying by eye more than 22 000 spectra selected as possible white dwarf stars from the Sloan Digital Sky Survey Data Release 7, we detected Zeeman splittings in more than 800 stars, increasing by a factor of five the number of known magnetic white dwarfs. Our field estimations range from 90 MG to less than 1 MG, complementing the detections by Külebi et al. [1]. These magnetic white dwarf stars cover the whole range of temperature and spectral classes observed. As the Zeeman splittings broadens the lines, we cannot use the line profiles to estimate surface gravity directly. We therefore excluded the magnetic white dwarfs from our average mass estimate of normal DAs and DBs. Analysis of the remaining 1505 bright and hot DA white dwarfs, i.e., those with S/N>=20 and Teff = 12000 K, results in a mean mass DA = 0.604+/-0.003 Msolar, while that of our 82 bright DBs with Teff = 16000 K is DB = 0.646+/-0.006 Msolar.
Astrophysics and Space Science, 2006
Cataclysmic Variables (CVs) are close binary systems where mass is transferred from a red dwarf s... more Cataclysmic Variables (CVs) are close binary systems where mass is transferred from a red dwarf star to a white dwarf star via an accretion disk. The flickering is observed as stochastic variations in the emitted radiation both in the continuum and in the emission line profiles. The main goal of our simulations is to compare synthetic Doppler maps with observed ones, aiming to constrain the flickering properties and wind parameters. A code was developed which generates synthetic emission line profiles of a geometrically thin and optically thick accretion disk. The simulation allows us to include flares in a particular disk region. The emission line flares may be integrated over arbitrary "exposure" times, producing the synthetic line profiles. Flickering Doppler maps are created using such synthetic time series. The presence of a wind inside the Roche lobe was also implemented. Radiative transfer effects in the lines where taken into account in order to reproduce the single peaked line profiles frequently seen in nova-like CVs.
The Astronomical Journal, 2007
Spectrophotometric observations of Hα and He I 6678 emission lines of the nova-like Cataclysmic V... more Spectrophotometric observations of Hα and He I 6678 emission lines of the nova-like Cataclysmic Variable V3885 Sgr are presented and analyzed. The binary orbital period was determined as P = 0.20716071(22) days. Doppler Tomography was performed with both Hα and He I lines. Disc radial emissivity profiles were also computed. The tomography mapping of flickering sources was performed using the Hα line, from which we concluded that the flickering is not uniformly distributed on the disc. The observed tomogram of the flickering was compared with simulations, suggesting that the most intense flickering source in the Hα is not located in the accretion disc. It is proposed that the main line flickering source may be associated with the illuminated secondary star.
The Astrophysical Journal, 2001
ABSTRACT
The Astrophysical Journal, 2004
The distribution of 12 C 16 O J = 9 → 8 (1.037 THz) emission has been mapped in OMC-1 at 35 point... more The distribution of 12 C 16 O J = 9 → 8 (1.037 THz) emission has been mapped in OMC-1 at 35 points with 84 ′′ resolution. This is the first map of this source in this transition and only the second velocityresolved ground-based observation of a line in the THz frequency band. There is emission present at all points in the map, a region roughly 4 ′ × 6 ′ in size, with peak antenna temperature dropping only near the edges. Away from the Orion KL outflow, the velocity structure suggests that most of the emission comes from the OMC-1 photon-dominated region, with a typical line width of 3-6 km s −1 . Large velocity gradient modeling of the emission in J = 9 → 8 and six lower transitions suggests that the lines originate in regions with temperatures around 120 K and densities of at least 10 3.5 cm −3 near θ 1 C Ori and at the Orion bar, and from 70 K gas at around 10 4 cm −3 southeast and west of the bar. These observations are among the first made with the 0.8 m Smithsonian Astrophysical Observatory Receiver Lab Telescope, a new instrument designed to observe at frequencies above 1 THz from an extremely high and dry site in northern Chile.
The Astrophysical Journal, 1999
... stars: individual (V347 Puppis) 1 Instituto Astronômico e Geofísico, Universidade de São Paul... more ... stars: individual (V347 Puppis) 1 Instituto Astronômico e Geofísico, Universidade de São Paulo, CP3386 São Paulo SP Brazil; marcos@binary.iagusp ... derived semiamplitude for describing the motion of the companion center, it is important to be aware that the Roche lobe filling ...
The Astrophysical Journal, 1996
... Once the temperature, density, and opacity are modeled, the radiative transfer equation is so... more ... Once the temperature, density, and opacity are modeled, the radiative transfer equation is solved for all the frequencies of interest by the general spectral synthesis program SYNSPEC (Hubeny, Stefi, & Harmanec 1985; Hubeny, Lanz, & Jeffery 1994). ...
The Astronomical Journal, 1998
... The relative strengths of the TiO and CaH bands were then used to find the best agreement at ... more ... The relative strengths of the TiO and CaH bands were then used to find the best agreement at spectral type M5 V. In Figure 5 ... of the distribution, but still a few minutes above the theoretical limit of 75 minutes (Paczy ń ski & Sienkiewicz 1981; Rappaport, Joss, & Webbink ...
The Astronomical Journal, 2009
ABSTRACT The HR Del nova remnant was observed with the IFU-GMOS at Gemini North. The spatially re... more ABSTRACT The HR Del nova remnant was observed with the IFU-GMOS at Gemini North. The spatially resolved spectral data cube was used in the kinematic, morphological, and abundance analysis of the ejecta. The line maps show a very clumpy shell with two main symmetric structures. The first one is the outer part of the shell seen in Hα, which forms two rings projected in the sky plane. These ring structures correspond to a closed hourglass shape, first proposed by Harman & O'Brien. The equatorial emission enhancement is caused by the superimposed hourglass structures in the line of sight. The second structure seen only in the [O III] and [N II] maps is located along the polar directions inside the hourglass structure. Abundance gradients between the polar caps and equatorial region were not found. However, the outer part of the shell seems to be less abundant in oxygen and nitrogen than the inner regions. Detailed 2.5-dimensional photoionization modeling of the three-dimensional shell was performed using the mass distribution inferred from the observations and the presence of mass clumps. The resulting model grids are used to constrain the physical properties of the shell as well as the central ionizing source. A sequence of three-dimensional clumpy models including a disk-shaped ionization source is able to reproduce the ionization gradients between polar and equatorial regions of the shell. Differences between shell axial ratios in different lines can also be explained by aspherical illumination. A total shell mass of 9 × 10–4 M ☉ is derived from these models. We estimate that 50%-70% of the shell mass is contained in neutral clumps with density contrast up to a factor of 30.
Publications of the Astronomical Society of the Pacific, 1999
... Laboratório Nacional de Astrofísica/CNPq, 37500‐000, MG, Itajubá, Brazil; marcos@lna.br. ABST... more ... Laboratório Nacional de Astrofísica/CNPq, 37500‐000, MG, Itajubá, Brazil; marcos@lna.br. ABSTRACT. ... Successful light‐curve models were obtained in which the primary is a hot subdwarf filling its Roche lobe while the companion is well contained within its Roche surface. ...
Publications of the Astronomical Society of the Pacific, 2006
We present the results of spectrophotometric observations of the old nova RR Pictoris performed i... more We present the results of spectrophotometric observations of the old nova RR Pictoris performed in two spectral ranges, one centered in the Halpha line, and other covering Hbeta and Hgamma spectral lines. From the Hbeta radial velocity study, we found a primary radial semiamplitude of K1=37(1) km s-1 and a systemic velocity of gamma = 1.8(2) km s-1. With these
Publications of the Astronomical Society of the Pacific, 2004
We report the results of a search in the MACHO light-curve database aiming to find new cataclysmi... more We report the results of a search in the MACHO light-curve database aiming to find new cataclysmic variables. The targets were selected from variables toward the Magellanic Clouds and Galactic bulge using as main criteria the amplitude of photometric variability and color indices. ...
Publications of the Astronomical Society of the Pacific, 2011
ABSTRACT Classical nova remnants are important scenarios for improving the photoionization modeli... more ABSTRACT Classical nova remnants are important scenarios for improving the photoionization modeling. This work describes the pseudo-three-dimensional code RAINY3D, which drives the photoionization code Cloudy as a subroutine. Photoionization simulations of old nova remnants are also presented and discussed. In these simulations we analyze the effect of condensation in the remnant spectra. The condensed mass fraction affects the Balmer lines by a factor of greater than 4 when compared with homogeneous models, and this directly impacts the shell mass determination. The He II 4686/Hβ ratio decreases by a factor of 10 in clumpy shells. These lines are also affected by the clump size and density distributions. The behavior of the strongest nebular line observed in nova remnants is also analyzed for heterogeneous shells. The gas diagnoses in novae ejecta are thought to be more accurate during the nebular phase, but we have determined that at this phase the matter distribution can strongly affect the derived shell physical properties and chemical abundances.
The Astrophysical Journal Supplement Series, 1993
When classifying by eye more than 22 000 spectra selected as possible white dwarf stars from the ... more When classifying by eye more than 22 000 spectra selected as possible white dwarf stars from the Sloan Digital Sky Survey Data Release 7, we detected Zeeman splittings in more than 800 stars, increasing by a factor of five the number of known magnetic white dwarfs. Our field estimations range from 90 MG to less than 1 MG, complementing the detections by Külebi et al. [1]. These magnetic white dwarf stars cover the whole range of temperature and spectral classes observed. As the Zeeman splittings broadens the lines, we cannot use the line profiles to estimate surface gravity directly. We therefore excluded the magnetic white dwarfs from our average mass estimate of normal DAs and DBs. Analysis of the remaining 1505 bright and hot DA white dwarfs, i.e., those with S/N>=20 and Teff = 12000 K, results in a mean mass DA = 0.604+/-0.003 Msolar, while that of our 82 bright DBs with Teff = 16000 K is DB = 0.646+/-0.006 Msolar.
Astrophysics and Space Science, 2006
Cataclysmic Variables (CVs) are close binary systems where mass is transferred from a red dwarf s... more Cataclysmic Variables (CVs) are close binary systems where mass is transferred from a red dwarf star to a white dwarf star via an accretion disk. The flickering is observed as stochastic variations in the emitted radiation both in the continuum and in the emission line profiles. The main goal of our simulations is to compare synthetic Doppler maps with observed ones, aiming to constrain the flickering properties and wind parameters. A code was developed which generates synthetic emission line profiles of a geometrically thin and optically thick accretion disk. The simulation allows us to include flares in a particular disk region. The emission line flares may be integrated over arbitrary "exposure" times, producing the synthetic line profiles. Flickering Doppler maps are created using such synthetic time series. The presence of a wind inside the Roche lobe was also implemented. Radiative transfer effects in the lines where taken into account in order to reproduce the single peaked line profiles frequently seen in nova-like CVs.
When classifying by eye more than 22 000 spectra selected as possible white dwarf stars from the ... more When classifying by eye more than 22 000 spectra selected as possible white dwarf stars from the Sloan Digital Sky Survey Data Release 7, we detected Zeeman splittings in more than 800 stars, increasing by a factor of five the number of known magnetic white dwarfs. Our field estimations range from 90 MG to less than 1 MG, complementing the detections by Külebi et al. [1]. These magnetic white dwarf stars cover the whole range of temperature and spectral classes observed. As the Zeeman splittings broadens the lines, we cannot use the line profiles to estimate surface gravity directly. We therefore excluded the magnetic white dwarfs from our average mass estimate of normal DAs and DBs. Analysis of the remaining 1505 bright and hot DA white dwarfs, i.e., those with S/N>=20 and Teff = 12000 K, results in a mean mass DA = 0.604+/-0.003 Msolar, while that of our 82 bright DBs with Teff = 16000 K is DB = 0.646+/-0.006 Msolar.
Astrophysics and Space Science, 2006
Cataclysmic Variables (CVs) are close binary systems where mass is transferred from a red dwarf s... more Cataclysmic Variables (CVs) are close binary systems where mass is transferred from a red dwarf star to a white dwarf star via an accretion disk. The flickering is observed as stochastic variations in the emitted radiation both in the continuum and in the emission line profiles. The main goal of our simulations is to compare synthetic Doppler maps with observed ones, aiming to constrain the flickering properties and wind parameters. A code was developed which generates synthetic emission line profiles of a geometrically thin and optically thick accretion disk. The simulation allows us to include flares in a particular disk region. The emission line flares may be integrated over arbitrary "exposure" times, producing the synthetic line profiles. Flickering Doppler maps are created using such synthetic time series. The presence of a wind inside the Roche lobe was also implemented. Radiative transfer effects in the lines where taken into account in order to reproduce the single peaked line profiles frequently seen in nova-like CVs.
The Astronomical Journal, 2007
Spectrophotometric observations of Hα and He I 6678 emission lines of the nova-like Cataclysmic V... more Spectrophotometric observations of Hα and He I 6678 emission lines of the nova-like Cataclysmic Variable V3885 Sgr are presented and analyzed. The binary orbital period was determined as P = 0.20716071(22) days. Doppler Tomography was performed with both Hα and He I lines. Disc radial emissivity profiles were also computed. The tomography mapping of flickering sources was performed using the Hα line, from which we concluded that the flickering is not uniformly distributed on the disc. The observed tomogram of the flickering was compared with simulations, suggesting that the most intense flickering source in the Hα is not located in the accretion disc. It is proposed that the main line flickering source may be associated with the illuminated secondary star.
The Astrophysical Journal, 2001
ABSTRACT
The Astrophysical Journal, 2004
The distribution of 12 C 16 O J = 9 → 8 (1.037 THz) emission has been mapped in OMC-1 at 35 point... more The distribution of 12 C 16 O J = 9 → 8 (1.037 THz) emission has been mapped in OMC-1 at 35 points with 84 ′′ resolution. This is the first map of this source in this transition and only the second velocityresolved ground-based observation of a line in the THz frequency band. There is emission present at all points in the map, a region roughly 4 ′ × 6 ′ in size, with peak antenna temperature dropping only near the edges. Away from the Orion KL outflow, the velocity structure suggests that most of the emission comes from the OMC-1 photon-dominated region, with a typical line width of 3-6 km s −1 . Large velocity gradient modeling of the emission in J = 9 → 8 and six lower transitions suggests that the lines originate in regions with temperatures around 120 K and densities of at least 10 3.5 cm −3 near θ 1 C Ori and at the Orion bar, and from 70 K gas at around 10 4 cm −3 southeast and west of the bar. These observations are among the first made with the 0.8 m Smithsonian Astrophysical Observatory Receiver Lab Telescope, a new instrument designed to observe at frequencies above 1 THz from an extremely high and dry site in northern Chile.
The Astrophysical Journal, 1999
... stars: individual (V347 Puppis) 1 Instituto Astronômico e Geofísico, Universidade de São Paul... more ... stars: individual (V347 Puppis) 1 Instituto Astronômico e Geofísico, Universidade de São Paulo, CP3386 São Paulo SP Brazil; marcos@binary.iagusp ... derived semiamplitude for describing the motion of the companion center, it is important to be aware that the Roche lobe filling ...
The Astrophysical Journal, 1996
... Once the temperature, density, and opacity are modeled, the radiative transfer equation is so... more ... Once the temperature, density, and opacity are modeled, the radiative transfer equation is solved for all the frequencies of interest by the general spectral synthesis program SYNSPEC (Hubeny, Stefi, & Harmanec 1985; Hubeny, Lanz, & Jeffery 1994). ...
The Astronomical Journal, 1998
... The relative strengths of the TiO and CaH bands were then used to find the best agreement at ... more ... The relative strengths of the TiO and CaH bands were then used to find the best agreement at spectral type M5 V. In Figure 5 ... of the distribution, but still a few minutes above the theoretical limit of 75 minutes (Paczy ń ski & Sienkiewicz 1981; Rappaport, Joss, & Webbink ...
The Astronomical Journal, 2009
ABSTRACT The HR Del nova remnant was observed with the IFU-GMOS at Gemini North. The spatially re... more ABSTRACT The HR Del nova remnant was observed with the IFU-GMOS at Gemini North. The spatially resolved spectral data cube was used in the kinematic, morphological, and abundance analysis of the ejecta. The line maps show a very clumpy shell with two main symmetric structures. The first one is the outer part of the shell seen in Hα, which forms two rings projected in the sky plane. These ring structures correspond to a closed hourglass shape, first proposed by Harman & O'Brien. The equatorial emission enhancement is caused by the superimposed hourglass structures in the line of sight. The second structure seen only in the [O III] and [N II] maps is located along the polar directions inside the hourglass structure. Abundance gradients between the polar caps and equatorial region were not found. However, the outer part of the shell seems to be less abundant in oxygen and nitrogen than the inner regions. Detailed 2.5-dimensional photoionization modeling of the three-dimensional shell was performed using the mass distribution inferred from the observations and the presence of mass clumps. The resulting model grids are used to constrain the physical properties of the shell as well as the central ionizing source. A sequence of three-dimensional clumpy models including a disk-shaped ionization source is able to reproduce the ionization gradients between polar and equatorial regions of the shell. Differences between shell axial ratios in different lines can also be explained by aspherical illumination. A total shell mass of 9 × 10–4 M ☉ is derived from these models. We estimate that 50%-70% of the shell mass is contained in neutral clumps with density contrast up to a factor of 30.
Publications of the Astronomical Society of the Pacific, 1999
... Laboratório Nacional de Astrofísica/CNPq, 37500‐000, MG, Itajubá, Brazil; marcos@lna.br. ABST... more ... Laboratório Nacional de Astrofísica/CNPq, 37500‐000, MG, Itajubá, Brazil; marcos@lna.br. ABSTRACT. ... Successful light‐curve models were obtained in which the primary is a hot subdwarf filling its Roche lobe while the companion is well contained within its Roche surface. ...
Publications of the Astronomical Society of the Pacific, 2006
We present the results of spectrophotometric observations of the old nova RR Pictoris performed i... more We present the results of spectrophotometric observations of the old nova RR Pictoris performed in two spectral ranges, one centered in the Halpha line, and other covering Hbeta and Hgamma spectral lines. From the Hbeta radial velocity study, we found a primary radial semiamplitude of K1=37(1) km s-1 and a systemic velocity of gamma = 1.8(2) km s-1. With these
Publications of the Astronomical Society of the Pacific, 2004
We report the results of a search in the MACHO light-curve database aiming to find new cataclysmi... more We report the results of a search in the MACHO light-curve database aiming to find new cataclysmic variables. The targets were selected from variables toward the Magellanic Clouds and Galactic bulge using as main criteria the amplitude of photometric variability and color indices. ...
Publications of the Astronomical Society of the Pacific, 2011
ABSTRACT Classical nova remnants are important scenarios for improving the photoionization modeli... more ABSTRACT Classical nova remnants are important scenarios for improving the photoionization modeling. This work describes the pseudo-three-dimensional code RAINY3D, which drives the photoionization code Cloudy as a subroutine. Photoionization simulations of old nova remnants are also presented and discussed. In these simulations we analyze the effect of condensation in the remnant spectra. The condensed mass fraction affects the Balmer lines by a factor of greater than 4 when compared with homogeneous models, and this directly impacts the shell mass determination. The He II 4686/Hβ ratio decreases by a factor of 10 in clumpy shells. These lines are also affected by the clump size and density distributions. The behavior of the strongest nebular line observed in nova remnants is also analyzed for heterogeneous shells. The gas diagnoses in novae ejecta are thought to be more accurate during the nebular phase, but we have determined that at this phase the matter distribution can strongly affect the derived shell physical properties and chemical abundances.
The Astrophysical Journal Supplement Series, 1993