Maja Vuckovic
Universidad de Valparaiso, Instituto de Fisica y Astronomia, Faculty Member
L3 mass loss can potentially affect the formation and properties of long- and short-period sdB-MS binaries. It takes place when the red giant progenitor of the sdB star overfills its Roche lobe sufficiently much to start losing parts of... more
L3 mass loss can potentially affect the formation and properties of long- and short-period sdB-MS binaries. It takes place when the red giant progenitor of the sdB star overfills its Roche lobe sufficiently much to start losing parts of its atmosphere through the L3 point behind it. The material lost through the L3 point carries away a significant amount of specific angular momentum and this way may have a strong impact on the binary orbit. We report on the results of our ongoing detailed study of this process. We have constructed an analytical expression for L3 mass loss rates as a function of the radius of the donor, have implemented it in binary stellar evolution code MESA and also have verified the framework with hydrodynamic SPH simulations. I shall present the physics behind L3 mass loss, show examples of how it affects the formation of long- and short-period systems and discuss the effect in a broader context of common-envelope evolution.
NNaPS is a python package to simplify the use of machine learning when preforming population synthesis studies. NNaPS is designed to be used in combination with the MESA stellar evolution code, bu could be used with different 1D stellar... more
NNaPS is a python package to simplify the use of machine learning when preforming population synthesis studies. NNaPS is designed to be used in combination with the MESA stellar evolution code, bu could be used with different 1D stellar evolution codes as well. It contains methods to easily compress a MESA run and extract (aggregate) parameters of interest from a large grid of MESA runs. These parameters can then be used to train a XG boosted random forest or a neural network to learn a connection between the input features and the parameters of interest. This model then acts as a fast population synthesis code.
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Context. We present the discovery of J22564-5910, a new type of hot subdwarf (sdB) which shows evidence of gas present in the system and has shallow, multi-peaked hydrogen and helium lines which vary in shape over time. All observational... more
Context. We present the discovery of J22564-5910, a new type of hot subdwarf (sdB) which shows evidence of gas present in the system and has shallow, multi-peaked hydrogen and helium lines which vary in shape over time. All observational evidence points towards J22564-5910 being observed very shortly after the merger phase that formed it. Aims. Using high-resolution, high signal-to-noise spectroscopy, combined with multi-band photometry, Gaia astrometry, and TESS light curves, we aim to interpret these unusual spectral features. Methods. The photometry, spectra and light curves are all analysed, and their results are combined in order to support our interpretation of the observations: the likely presence of a magnetic field combined with gas features around the sdB. Based on the triple-peaked H lines, the magnetic field strength is estimated and, by using the shellspec code, qualitative models of gas configurations are fitted to the observations. Results. All observations can either...
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Context. The Transiting Exoplanet Survey Satellite (TESS) mission is revolutionizing the blossoming area of asteroseismology, particularly of pulsating white dwarfs and pre-white dwarfs, thus continuing the impulse of its predecessor, the... more
Context. The Transiting Exoplanet Survey Satellite (TESS) mission is revolutionizing the blossoming area of asteroseismology, particularly of pulsating white dwarfs and pre-white dwarfs, thus continuing the impulse of its predecessor, the Kepler mission. Aims. In this paper, we present the observations from the extended TESS mission in both 120 s short-cadence and 20 s ultra-short-cadence mode of two pre-white dwarf stars showing hydrogen deficiency. We identify them as two new GW Vir stars, TIC 333432673 and TIC 095332541. We apply the tools of asteroseismology with the aim of deriving their structural parameters and seismological distances. Methods. We carried out a spectroscopic analysis and a spectral fitting of TIC 333432673 and TIC 095332541. We also processed and analyzed the high-precision TESS photometric light curves of the two target stars, and derived their oscillation frequencies. We performed an asteroseismological analysis of these stars on the basis of PG 1159 evolut...
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Context. We present photometric and spectroscopic analyses of gravity (g-mode) long-period pulsating hot subdwarf B (sdB) stars, also called V1093 Her stars, observed by the TESS space telescope in both 120 s short-cadence and 20 s... more
Context. We present photometric and spectroscopic analyses of gravity (g-mode) long-period pulsating hot subdwarf B (sdB) stars, also called V1093 Her stars, observed by the TESS space telescope in both 120 s short-cadence and 20 s ultra-short-cadence mode during the survey observation and the extended mission of the southern ecliptic hemisphere. Aims. We performed a detailed asteroseismic and spectroscopic analysis of five pulsating sdB stars observed with TESS in order to compare the observations with model predictions based on our stellar evolution computations coupled with adiabatic pulsation computations. Methods. We processed and analyzed TESS observations of long-period pulsating hot subdwarf B stars. We used standard pre-whitening techniques on the datasets to extract the pulsation periods from the TESS light curves. We applied standard seismic tools for mode identification, including asymptotic period spacings and rotational frequency multiplets. Based on the values obtaine...
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Wide hot subdwarf B (sdB) binaries with main-sequence companions are outcomes of stable mass transfer from evolved red giants. The orbits of these binaries show a strong correlation between their orbital periods and mass ratios. The... more
Wide hot subdwarf B (sdB) binaries with main-sequence companions are outcomes of stable mass transfer from evolved red giants. The orbits of these binaries show a strong correlation between their orbital periods and mass ratios. The origins of this correlation have, so far, been lacking a conclusive explanation. We aim to find a binary evolution model which can explain the observed correlation. Radii of evolved red giants, and hence the resulting orbital periods, strongly depend on their metallicity. We have performed a small but statistically significant binary population synthesis study with the binary stellar evolution code MESA. We have used a standard model for binary mass loss and a standard Galactic metallicity history. The resulting sdBs were selected based on the same criteria as used in observations and then compared with the observed population. We have achieved an excellent match to the observed period - mass ratio correlation without explicitly fine-tuning any parameter...
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We present an analysis of about 400 high-resolution time-resolved VLT/UVES spectra of the eclipsing subdwarf binary system PG 1336 -018 - a rapidly pulsating subdwarf B primary in a short orbit with an M5 companion. We analysed the... more
We present an analysis of about 400 high-resolution time-resolved VLT/UVES spectra of the eclipsing subdwarf binary system PG 1336 -018 - a rapidly pulsating subdwarf B primary in a short orbit with an M5 companion. We analysed the spectra of PG 1336 -018 with the aim to detect the pulsational signal of the primary in line-profile variations. After removing the domi- nant radial-velocity component inherent to the orbital motion, we computed cross-correlation functions for each individual spectrum and assumed these to approximate the average line profile. The dominant pulsation mode is detected in the cross-correlation functions and may lead to the first spectroscopic mode identification for this star.
We present the fresh XSHOOTER1 phase-resolved spectra of HW Vir. In the light of the recent reports of planets detected in many post common envelope binary systems and in particular in short sdB + dM systems, we have started dedicated... more
We present the fresh XSHOOTER1 phase-resolved spectra of HW Vir. In the light of the recent reports of planets detected in many post common envelope binary systems and in particular in short sdB + dM systems, we have started dedicated monitoring of HW Vir system, a prototype of eclipsing short-period sdB + dM binaries where 2 circumbinary planets have been claimed. Aiming to unveil HW Vir as a double lined eclipsing binary and hence determine the absolute masses of both components of this system, we are also investigating the effects of irradiation through the analysis of various irradiated spectral features in order to map the temperature distribution of the irradiated M dwarf.
PG 0014+067 is one of the most promising pulsating subdwarf B (sdB) stars for seismic analysis as it is a `typical' pulsating sdB star with a rich pulsation spectrum. The richness of its pulsations, however, poses a fundamental... more
PG 0014+067 is one of the most promising pulsating subdwarf B (sdB) stars for seismic analysis as it is a `typical' pulsating sdB star with a rich pulsation spectrum. The richness of its pulsations, however, poses a fundamental challenge to understanding the pulsations of these stars. The mode density is too rich to be explained only with radial and nonradial low degree l ( l<3 ) p-modes without rotational splittings. One proposed solution requires invoking modes with high degree ( l=3 ). An alternative interpretation explains this rich mode density via rapid internal rotation. With these models, this rich pulsation spectrum results from the presence of a few triplet ( l=1 ), quintuplet ( l=2 ) and radial ( l=0 ) p-modes. To critically examine competing theoretical models for these stars we need better frequency resolution and denser longitude coverage. Therefore, we observed this star with the Whole Earth Telescope network from eighteen sites for two weeks in October 2004. ...
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We present constraints on the formation of the sdBV+dM eclipsing binary PG 1336-018 derived from a detailed evolutionary study. These are confronted with the orbital solutions permitted by our high-resolution time series VLT/UVES spectra... more
We present constraints on the formation of the sdBV+dM eclipsing binary PG 1336-018 derived from a detailed evolutionary study. These are confronted with the orbital solutions permitted by our high-resolution time series VLT/UVES spectra and high-speed multicolour VLT/ULTRACAM photometric observations. We found two orbital solutions (MsdB=0.466 M&sun; and 0.389 M&sun;) which are consistent with the sdB primary having gone through a core-He flash and a common-envelope phase described by the alpha-formalism.
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We present the first-look analysis of the high-speed multicolour photometry of the bright V361 Hya-type star EO Ceti ( m V=12.3). The observations were gathered with the three-channel ULTRACAM instrument attached to the 4.2-m William... more
We present the first-look analysis of the high-speed multicolour photometry of the bright V361 Hya-type star EO Ceti ( m V=12.3). The observations were gathered with the three-channel ULTRACAM instrument attached to the 4.2-m William Herschel Telescope. The data set has a total time span of 6.2 d and consists of 31 h simultaneous three colour photometry. The main power
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We report on the current performances and measurements done with X-shooter during its first year of operations at Paranal. We present the current instrumental problems, recent and future improvements, and give advice for the observations.