Pub Date : 2021-03-15DOI: 10.1051/0004-6361/202040148
J. Krtička, A. Feldmeier
Line-driven wind instability is expected to cause small-scale wind inhomogeneities, X-ray emission, and wind line profile variability. The instability can already develop around the sonic point if it is initiated close to the photosphere due to stochastic turbulent motions. In such cases, it may leave its imprint on the light curve as a result of wind blanketing. We study the photometric signatures of the line-driven wind instability. We used line-driven wind instability simulations to determine the wind variability close to the star. We applied two types of boundary perturbations: a sinusoidal one that enables us to study in detail the development of the instability and a stochastic one given by a Langevin process that provides a more realistic boundary perturbation. We estimated the photometric variability from the resulting mass-flux variations. The variability was simulated assuming that the wind consists of a large number of independent conical wind sectors. We compared the simulated light curves with TESS light curves of OB stars that show stochastic variability. We find two typical signatures of line-driven wind instability in photometric data: a knee in the power spectrum of magnitude fluctuations, which appears due to engulfment of small-scale structure by larger structures, and a negative skewness of the distribution of fluctuations, which is the result of spatial dominance of rarefied regions. These features endure even when combining the light curves from independent wind sectors. The stochastic photometric variability of OB stars bears certain signatures of the line-driven wind instability. The distribution function of observed photometric data shows negative skewness and the power spectra of a fraction of light curves exhibit a knee. This can be explained as a result of the line-driven wind instability triggered by stochastic base perturbations.
{"title":"Stochastic light variations in hot stars from wind instability: finding photometric signatures and testing against the TESS data","authors":"J. Krtička, A. Feldmeier","doi":"10.1051/0004-6361/202040148","DOIUrl":"https://doi.org/10.1051/0004-6361/202040148","url":null,"abstract":"Line-driven wind instability is expected to cause small-scale wind inhomogeneities, X-ray emission, and wind line profile variability. The instability can already develop around the sonic point if it is initiated close to the photosphere due to stochastic turbulent motions. In such cases, it may leave its imprint on the light curve as a result of wind blanketing. We study the photometric signatures of the line-driven wind instability. We used line-driven wind instability simulations to determine the wind variability close to the star. We applied two types of boundary perturbations: a sinusoidal one that enables us to study in detail the development of the instability and a stochastic one given by a Langevin process that provides a more realistic boundary perturbation. We estimated the photometric variability from the resulting mass-flux variations. The variability was simulated assuming that the wind consists of a large number of independent conical wind sectors. We compared the simulated light curves with TESS light curves of OB stars that show stochastic variability. We find two typical signatures of line-driven wind instability in photometric data: a knee in the power spectrum of magnitude fluctuations, which appears due to engulfment of small-scale structure by larger structures, and a negative skewness of the distribution of fluctuations, which is the result of spatial dominance of rarefied regions. These features endure even when combining the light curves from independent wind sectors. The stochastic photometric variability of OB stars bears certain signatures of the line-driven wind instability. The distribution function of observed photometric data shows negative skewness and the power spectra of a fraction of light curves exhibit a knee. This can be explained as a result of the line-driven wind instability triggered by stochastic base perturbations.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"159 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74300278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-03-15DOI: 10.1051/0004-6361/202039604
I. Cava, M. G'omez-Garrido, V. Bujarrabal, A. Castro-Carrizo, J. Alcolea, H. Winckel
There is a class of binary post-AGB stars with a remarkable near-infrared excess that are surrounded by Keplerian or quasi-Keplerian disks and extended outflows composed of gas escaping from the disk. The Keplerian dynamics had been well identified in four cases, namely the Red Rectangle, AC Her, IW Car, and IRAS 08544-4431. In these objects, the mass of the outflow represents ~ 10 % of the nebular mass, the disk being the dominant component of the nebula. We present interferometric NOEMA maps of 12CO and 13CO J=2-1 in 89 Her and 12CO J=2-1 in AC Her, IRAS 19125+0343, and R Sct. Several properties of the nebula are obtained from the data and model fitting, including the structure, density, and temperature distributions, as well as the dynamics. We also discuss the uncertainties on the derived values. The presence of an expanding component in AC Her is doubtful, but thanks to new maps and models, we estimate an upper limit to the mass of this outflow of < 3 10^-5 Mo, that is, the mass of the outflow is < 5 % of the total nebular mass. For 89 Her, we find a total nebular mass of 1.4 10^-2 Mo, of which ~ 50 % comes from an hourglass-shaped extended outflow. In the case of IRAS 19125+0343, the nebular mass is 1.1 10^-2 Mo, where the outflow contributes ~ 70 % of the total mass. The nebular mass of R Sct is 3.2 10^-2 Mo, of which ~ 75 % corresponds to a very extended outflow that surrounds the disk. Our results for IRAS 19125+0343 and R Sct lead us to introduce a new subclass of binary post-AGB stars, for which the outflow is the dominant component of the nebula. Moreover, the outflow mass fraction found in AC Her is smaller than those found in other disk-dominated binary post-AGB stars. 89 Her would represent an intermediate case between both subclasses.
{"title":"Keplerian disks and outflows in post-AGB stars: AC Herculis, 89 Herculis, IRAS 19125+0343, and R Scuti","authors":"I. Cava, M. G'omez-Garrido, V. Bujarrabal, A. Castro-Carrizo, J. Alcolea, H. Winckel","doi":"10.1051/0004-6361/202039604","DOIUrl":"https://doi.org/10.1051/0004-6361/202039604","url":null,"abstract":"There is a class of binary post-AGB stars with a remarkable near-infrared excess that are surrounded by Keplerian or quasi-Keplerian disks and extended outflows composed of gas escaping from the disk. The Keplerian dynamics had been well identified in four cases, namely the Red Rectangle, AC Her, IW Car, and IRAS 08544-4431. In these objects, the mass of the outflow represents ~ 10 % of the nebular mass, the disk being the dominant component of the nebula. We present interferometric NOEMA maps of 12CO and 13CO J=2-1 in 89 Her and 12CO J=2-1 in AC Her, IRAS 19125+0343, and R Sct. Several properties of the nebula are obtained from the data and model fitting, including the structure, density, and temperature distributions, as well as the dynamics. We also discuss the uncertainties on the derived values. The presence of an expanding component in AC Her is doubtful, but thanks to new maps and models, we estimate an upper limit to the mass of this outflow of < 3 10^-5 Mo, that is, the mass of the outflow is < 5 % of the total nebular mass. For 89 Her, we find a total nebular mass of 1.4 10^-2 Mo, of which ~ 50 % comes from an hourglass-shaped extended outflow. In the case of IRAS 19125+0343, the nebular mass is 1.1 10^-2 Mo, where the outflow contributes ~ 70 % of the total mass. The nebular mass of R Sct is 3.2 10^-2 Mo, of which ~ 75 % corresponds to a very extended outflow that surrounds the disk. Our results for IRAS 19125+0343 and R Sct lead us to introduce a new subclass of binary post-AGB stars, for which the outflow is the dominant component of the nebula. Moreover, the outflow mass fraction found in AC Her is smaller than those found in other disk-dominated binary post-AGB stars. 89 Her would represent an intermediate case between both subclasses.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"68 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79606879","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-03-11DOI: 10.1051/0004-6361/202039642
M. Villar-Martin, B. Emonts, A. C. Lavers, E. Bellocchi, A. Herrero, A. Humphrey, B. D. D. Oliveira, T. Storchi-Bergmann
Context. The role of radio mode feedback in non radio-loud quasars needs to be explored in depth to determine its true importance. Its effects can be identified based on the evidence of interactions between the radio structures and the ambient ionised gas. Aims. We investigate this in a sample of 13 optically selected type-2 quasars (QSO2) at z <0.2 with Very Large Array (VLA) FIRST Survey radio detections. None are radio loud. The ranges of [OIII]λ5007 and monochromatic radio luminosities are log(L[OIII]/erg s−1)∼42.08-42.79 and log(P1.4 GHz/erg s−1 Hz−1) ∼30.08-31.76. All show complex optical morphologies, with signs of distortion across tens of kpc due to mergers/interactions. Methods. We have searched for evidence of interactions between the radio structures and the ionised gas by characterising and comparing their morphologies. The first is traced by narrow band Hα images obtained with the GTC 10.4m Spanish telescope and the Osiris instrument. The second is traced by VLA radio maps obtained with A and B configurations to achieve both high resolution and brightness sensitivity. Results. The radio luminosity has an active galatic nucleus (AGN) component in 11/13 QSO2, which is spatially extended in our radio data in 9 of them (jets/lobes/other). The relative contribution of the extended radio emission to the total P1.4 GHz is in most cases in the range 30% to 90%. The maximum sizes are in the range dmax ∼few-500 kpc. QSO2 undergoing interaction/merger events appear to be invariably associated with ionised gas spread over large spatial scales with maximum distances from the AGN in the range rmax ∼12-90 kpc. The morphology of the ionised gas at <30 kpc is strongly influenced by AGN related processes. Evidence for radio-gas interactions exist in 10/13 QSO2; that is, all but one with confirmed AGN radio components. The interactions are identified across different spatial scales, from the nuclear narrow line region up to tens of kpc. Conclusions. Although this sample cannot be considered representative of the general population of QSO2, it supports the idea that large scale low/modest power radio sources can exist in radio-quiet QSO2, which can provide a source of feedback on scales of the spheroidal component of galaxies and well into the circumgalactic medium, in systems where radiative mode feedback is expected to dominate.
{"title":"Interactions between large-scale radio structures and gas in a sample of optically selected type 2 quasars","authors":"M. Villar-Martin, B. Emonts, A. C. Lavers, E. Bellocchi, A. Herrero, A. Humphrey, B. D. D. Oliveira, T. Storchi-Bergmann","doi":"10.1051/0004-6361/202039642","DOIUrl":"https://doi.org/10.1051/0004-6361/202039642","url":null,"abstract":"Context. The role of radio mode feedback in non radio-loud quasars needs to be explored in depth to determine its true importance. Its effects can be identified based on the evidence of interactions between the radio structures and the ambient ionised gas. Aims. We investigate this in a sample of 13 optically selected type-2 quasars (QSO2) at z <0.2 with Very Large Array (VLA) FIRST Survey radio detections. None are radio loud. The ranges of [OIII]λ5007 and monochromatic radio luminosities are log(L[OIII]/erg s−1)∼42.08-42.79 and log(P1.4 GHz/erg s−1 Hz−1) ∼30.08-31.76. All show complex optical morphologies, with signs of distortion across tens of kpc due to mergers/interactions. Methods. We have searched for evidence of interactions between the radio structures and the ionised gas by characterising and comparing their morphologies. The first is traced by narrow band Hα images obtained with the GTC 10.4m Spanish telescope and the Osiris instrument. The second is traced by VLA radio maps obtained with A and B configurations to achieve both high resolution and brightness sensitivity. Results. The radio luminosity has an active galatic nucleus (AGN) component in 11/13 QSO2, which is spatially extended in our radio data in 9 of them (jets/lobes/other). The relative contribution of the extended radio emission to the total P1.4 GHz is in most cases in the range 30% to 90%. The maximum sizes are in the range dmax ∼few-500 kpc. QSO2 undergoing interaction/merger events appear to be invariably associated with ionised gas spread over large spatial scales with maximum distances from the AGN in the range rmax ∼12-90 kpc. The morphology of the ionised gas at <30 kpc is strongly influenced by AGN related processes. Evidence for radio-gas interactions exist in 10/13 QSO2; that is, all but one with confirmed AGN radio components. The interactions are identified across different spatial scales, from the nuclear narrow line region up to tens of kpc. Conclusions. Although this sample cannot be considered representative of the general population of QSO2, it supports the idea that large scale low/modest power radio sources can exist in radio-quiet QSO2, which can provide a source of feedback on scales of the spheroidal component of galaxies and well into the circumgalactic medium, in systems where radiative mode feedback is expected to dominate.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"53 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80648041","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-03-11DOI: 10.1051/0004-6361/202039169
M. Muru, E. Tempel
Aims. This work provides an analysis of how the galaxy number density of the input data affects the filaments detected with the Bisous filament finder and gives estimates of the reliability of the method itself to assess the robustness of the results. Methods. We applied the Bisous filament finder to MultiDark-Galaxies data, using various magnitude cuts from the catalogue to study the effects of different galaxy number densities on the results and different parameters of the model. We compared the structures by the fraction of galaxies in filaments and the volume filled by filaments, and we analysed the similarities between the results from different cuts based on the overlap between detected filamentary structures. The filament finder was also applied to the exact same data 200 times with the same parameters to study the stochasticity of the results and the correlation between different runs was calculated. Results. Multiple samples show that galaxies in filaments have preferentially higher luminosity. We found that when a galaxy is in a filament there is a 97% chance that the same galaxy would be in a filament with even more complete input data and about 85% of filaments are persistent when detecting the filamentary network with higher-density input data. Lower galaxy number density inputs mean the Bisous model finds fewer filaments, but the filaments found are persistent even if we use more complete input data for the detection. We calculated the correlation coefficient between 200 Bisous runs on the exact same input, which is 0.98. Conclusions. This study confirms that increased number density of galaxies is important to obtain a more complete picture of the cosmic web. To overcome the limitation of the spectroscopic surveys, we will develop the Bisous model further to apply this tool to combined spectroscopic and narrow-band photometric redshift surveys, such as the J-PAS.
{"title":"Assessing the reliability of the Bisous filament finder","authors":"M. Muru, E. Tempel","doi":"10.1051/0004-6361/202039169","DOIUrl":"https://doi.org/10.1051/0004-6361/202039169","url":null,"abstract":"Aims. This work provides an analysis of how the galaxy number density of the input data affects the filaments detected with the Bisous filament finder and gives estimates of the reliability of the method itself to assess the robustness of the results. \u0000Methods. We applied the Bisous filament finder to MultiDark-Galaxies data, using various magnitude cuts from the catalogue to study the effects of different galaxy number densities on the results and different parameters of the model. We compared the structures by the fraction of galaxies in filaments and the volume filled by filaments, and we analysed the similarities between the results from different cuts based on the overlap between detected filamentary structures. The filament finder was also applied to the exact same data 200 times with the same parameters to study the stochasticity of the results and the correlation between different runs was calculated. \u0000Results. Multiple samples show that galaxies in filaments have preferentially higher luminosity. We found that when a galaxy is in a filament there is a 97% chance that the same galaxy would be in a filament with even more complete input data and about 85% of filaments are persistent when detecting the filamentary network with higher-density input data. Lower galaxy number density inputs mean the Bisous model finds fewer filaments, but the filaments found are persistent even if we use more complete input data for the detection. We calculated the correlation coefficient between 200 Bisous runs on the exact same input, which is 0.98. \u0000Conclusions. This study confirms that increased number density of galaxies is important to obtain a more complete picture of the cosmic web. To overcome the limitation of the spectroscopic surveys, we will develop the Bisous model further to apply this tool to combined spectroscopic and narrow-band photometric redshift surveys, such as the J-PAS.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"90 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77070046","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-03-10DOI: 10.1051/0004-6361/202040065
D. de la Fuente, C. Rom'an-Z'uniga, E. Jim'enez-Bail'on, J. Alves, Miriam García, Sean Venus
Context. Disentangling line-of-sight alignments of young stellar populations is crucial for observational studies of star-forming complexes. This task is particularly problematic in a Cygnus-X subregion where several components, located at different distances, are overlapped: the Berkeley 87 young massive cluster, the poorly-known [DB2001] Cl05 embedded cluster, and the ON2 star-forming complex, in turn composed of several Hii regions. Aims. To provide a methodology for building an exhaustive census of young objects that can consistently deal with large differences in both extinction and distance. Methods. OMEGA2000 near-infrared observations of the Berkeley 87 / ON2 field are merged with archival data from Gaia, Chandra, Spitzer, and Herschel, as well as cross-identifications from the literature. To address the incompleteness effects and selection biases that arise from the line-of-sight overlap, we adapt existing methods for extinction estimation and young object classification, and we define the intrinsic reddening index, Rint, a new tool to separate intrinsically red sources from those whose infrared color excess is caused by extinction. We also introduce a new method to find young stellar objects based on Rint. Results. We find 571 objects whose classification is related to recent or ongoing star formation. Together with other point sources with individual estimates of distance or extinction, we compile a catalog of 3005 objects to be used for further membership work. A new distance for Berkeley 87, (1673 ± 17) pc, is estimated as a median of 13 spectroscopic members with accurate Gaia EDR3 parallaxes. Conclusions. The flexibility of our approach, especially regarding the Rint definition, allows to overcome photometric biases caused by large extinction and distance variations, in order to obtain homogeneous catalogs of young sources. The multi-wavelength census that results from applying our methods to the Berkeley 87 / ON2 field will serve as a basis for disentangling the overlapped populations.
{"title":"Clustered star formation toward Berkeley 87/ON2","authors":"D. de la Fuente, C. Rom'an-Z'uniga, E. Jim'enez-Bail'on, J. Alves, Miriam García, Sean Venus","doi":"10.1051/0004-6361/202040065","DOIUrl":"https://doi.org/10.1051/0004-6361/202040065","url":null,"abstract":"Context. Disentangling line-of-sight alignments of young stellar populations is crucial for observational studies of star-forming complexes. This task is particularly problematic in a Cygnus-X subregion where several components, located at different distances, are overlapped: the Berkeley 87 young massive cluster, the poorly-known [DB2001] Cl05 embedded cluster, and the ON2 star-forming complex, in turn composed of several Hii regions. Aims. To provide a methodology for building an exhaustive census of young objects that can consistently deal with large differences in both extinction and distance. Methods. OMEGA2000 near-infrared observations of the Berkeley 87 / ON2 field are merged with archival data from Gaia, Chandra, Spitzer, and Herschel, as well as cross-identifications from the literature. To address the incompleteness effects and selection biases that arise from the line-of-sight overlap, we adapt existing methods for extinction estimation and young object classification, and we define the intrinsic reddening index, Rint, a new tool to separate intrinsically red sources from those whose infrared color excess is caused by extinction. We also introduce a new method to find young stellar objects based on Rint. Results. We find 571 objects whose classification is related to recent or ongoing star formation. Together with other point sources with individual estimates of distance or extinction, we compile a catalog of 3005 objects to be used for further membership work. A new distance for Berkeley 87, (1673 ± 17) pc, is estimated as a median of 13 spectroscopic members with accurate Gaia EDR3 parallaxes. Conclusions. The flexibility of our approach, especially regarding the Rint definition, allows to overcome photometric biases caused by large extinction and distance variations, in order to obtain homogeneous catalogs of young sources. The multi-wavelength census that results from applying our methods to the Berkeley 87 / ON2 field will serve as a basis for disentangling the overlapped populations.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"16 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79119914","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-03-09DOI: 10.1051/0004-6361/202039200
L. Trapman, A. Bosman, G. Rosotti, M. Hogerheijde, E. V. van Dishoeck
Context. Protoplanetary disks are thought to evolve viscously, where the disk mass the reservoir available for planet formation decreases over time as material is accreted onto the central star over a viscous timescale. Observations have shown a correlation between disk mass and the stellar mass accretion rate, as expected from viscous theory. However, this happens only when using the dust mass as a proxy of the disk mass; the gas mass inferred from CO isotopolog line fluxes, which should be a more direct measurement, shows no correlation with the stellar mass accretion rate. Aims. We investigate how 13CO and C18O J = 3 − 2 line fluxes, commonly used as gas mass tracers, change over time in a viscously evolving disk and use them together with gas disk sizes to provide diagnostics of viscous evolution. In addition, we aim to determine if the chemical conversion of CO through grain-surface chemistry combined with viscous evolution can explain the CO isotopolog observations of disks in Lupus. Methods. We ran a series of thermochemical DALI models of viscously evolving disks, where the initial disk mass is derived from observed stellar mass accretion rates. Results. While the disk mass, Mdisk, decreases over time, the 13CO and C18O J = 3 − 2 line fluxes instead increase over time due to their optically thick emitting regions growing in size as the disk expands viscously. The C18O 3-2 emission is optically thin throughout the disk for only for a subset of our models (M∗ ≤ 0.2 M and αvisc ≥ 10−3 , corresponding to Mdisk(t = 1 Myr) ≤ 10−3 M ) . For these disks the integrated C18O flux decreases with time, similar to the disk mass. Observed 13CO and C18O 3-2 fluxes of the most massive disks (Mdisk & 5 × 10−3 M ) in Lupus can be reproduced to within a factor of ∼ 2 with viscously evolving disks in which CO is converted into other species through grain-surface chemistry with a moderate cosmic-ray ionization rate of ζcr ∼ 10−17 s−1. The C18O 3-2 fluxes for the bulk of the disks in Lupus (with Mdisk . 5 × 10−3 M ) can be reproduced to within a factor of ∼ 2 by increasing ζcr to ∼ 5 × 10−17 − 10−16 s−1, although explaining the stacked upper limits requires a lower average abundance than our models can produce. In addition, increasing ζcr cannot explain the observed 13CO fluxes for lower mass disks, which are more than an order of magnitude fainter than what is predicted. In our models the optically thick 13CO emission originates from a layer higher up in the disk (z/r ∼ 0.25 − 0.4) where photodissociation stops the conversion of CO into other species. Reconciling the 13CO fluxes of viscously evolving disks with the observations requires either efficient vertical mixing or low mass disks (Mdust . 3× 10−5 M ) being much thinner and/or smaller than their more massive counterparts. Conclusions. The 13CO model flux predominantly traces the disk size, but the C18O model flux traces the disk mass of our viscously evolving disk models if chemical conversion of CO is
{"title":"CO isotopolog line fluxes of viscously evolving disks","authors":"L. Trapman, A. Bosman, G. Rosotti, M. Hogerheijde, E. V. van Dishoeck","doi":"10.1051/0004-6361/202039200","DOIUrl":"https://doi.org/10.1051/0004-6361/202039200","url":null,"abstract":"Context. Protoplanetary disks are thought to evolve viscously, where the disk mass the reservoir available for planet formation decreases over time as material is accreted onto the central star over a viscous timescale. Observations have shown a correlation between disk mass and the stellar mass accretion rate, as expected from viscous theory. However, this happens only when using the dust mass as a proxy of the disk mass; the gas mass inferred from CO isotopolog line fluxes, which should be a more direct measurement, shows no correlation with the stellar mass accretion rate. Aims. We investigate how 13CO and C18O J = 3 − 2 line fluxes, commonly used as gas mass tracers, change over time in a viscously evolving disk and use them together with gas disk sizes to provide diagnostics of viscous evolution. In addition, we aim to determine if the chemical conversion of CO through grain-surface chemistry combined with viscous evolution can explain the CO isotopolog observations of disks in Lupus. Methods. We ran a series of thermochemical DALI models of viscously evolving disks, where the initial disk mass is derived from observed stellar mass accretion rates. Results. While the disk mass, Mdisk, decreases over time, the 13CO and C18O J = 3 − 2 line fluxes instead increase over time due to their optically thick emitting regions growing in size as the disk expands viscously. The C18O 3-2 emission is optically thin throughout the disk for only for a subset of our models (M∗ ≤ 0.2 M and αvisc ≥ 10−3 , corresponding to Mdisk(t = 1 Myr) ≤ 10−3 M ) . For these disks the integrated C18O flux decreases with time, similar to the disk mass. Observed 13CO and C18O 3-2 fluxes of the most massive disks (Mdisk & 5 × 10−3 M ) in Lupus can be reproduced to within a factor of ∼ 2 with viscously evolving disks in which CO is converted into other species through grain-surface chemistry with a moderate cosmic-ray ionization rate of ζcr ∼ 10−17 s−1. The C18O 3-2 fluxes for the bulk of the disks in Lupus (with Mdisk . 5 × 10−3 M ) can be reproduced to within a factor of ∼ 2 by increasing ζcr to ∼ 5 × 10−17 − 10−16 s−1, although explaining the stacked upper limits requires a lower average abundance than our models can produce. In addition, increasing ζcr cannot explain the observed 13CO fluxes for lower mass disks, which are more than an order of magnitude fainter than what is predicted. In our models the optically thick 13CO emission originates from a layer higher up in the disk (z/r ∼ 0.25 − 0.4) where photodissociation stops the conversion of CO into other species. Reconciling the 13CO fluxes of viscously evolving disks with the observations requires either efficient vertical mixing or low mass disks (Mdust . 3× 10−5 M ) being much thinner and/or smaller than their more massive counterparts. Conclusions. The 13CO model flux predominantly traces the disk size, but the C18O model flux traces the disk mass of our viscously evolving disk models if chemical conversion of CO is ","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"25 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-03-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76227791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-03-08DOI: 10.1051/0004-6361/202039703
P. Sarmento, B. Rojas-Ayala, E. D. Mena, S. Blanco-Cuaresma
Context. The scientific community’s interest on the stellar parameters of M dwarfs has been increasing over the last few years, with potential applications ranging from galactic characterization to exoplanet detection. Aims. The main motivation for this work is to develop an alternative and objective method to derive stellar parameters for M dwarfs using the H-band spectra provided by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). Methods. Synthetic spectra generated with iSpec, Turbospectrum, MARCS models atmospheres and a custom made line list including over 1 000 000 water lines, are compared to APOGEE observations, and parameters are determined through χ2 minimization. Results. Spectroscopic parameters (Teff , [M/H], log g, vmic) are presented for a sample of 313 M dwarfs, obtained from their APOGEE H-band spectra. The generated synthetic spectra reproduce observed spectra to a high accuracy level. The impact of the spectra normalization on the results are analyzed as well. Conclusions. Our output parameters are compared with the ones obtained with APOGEE Stellar Parameter and Chemical Abundances Pipeline (ASPCAP) for the same stellar spectrum, and we find that the values agree within the expected uncertainties. Comparisons with other previous near-infrared and optical literature are also available, with median differences within our estimated uncertainties found in most cases. Possible reasons for these differences are explored. The full H-band line list, the line selection for the synthesis, and the synthesized spectra are available for download, as are the calculated stellar parameters.
{"title":"Determination of spectroscopic parameters for 313 M dwarf stars from their APOGEE Data Release 16 H-band spectra","authors":"P. Sarmento, B. Rojas-Ayala, E. D. Mena, S. Blanco-Cuaresma","doi":"10.1051/0004-6361/202039703","DOIUrl":"https://doi.org/10.1051/0004-6361/202039703","url":null,"abstract":"Context. The scientific community’s interest on the stellar parameters of M dwarfs has been increasing over the last few years, with potential applications ranging from galactic characterization to exoplanet detection. Aims. The main motivation for this work is to develop an alternative and objective method to derive stellar parameters for M dwarfs using the H-band spectra provided by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). Methods. Synthetic spectra generated with iSpec, Turbospectrum, MARCS models atmospheres and a custom made line list including over 1 000 000 water lines, are compared to APOGEE observations, and parameters are determined through χ2 minimization. Results. Spectroscopic parameters (Teff , [M/H], log g, vmic) are presented for a sample of 313 M dwarfs, obtained from their APOGEE H-band spectra. The generated synthetic spectra reproduce observed spectra to a high accuracy level. The impact of the spectra normalization on the results are analyzed as well. Conclusions. Our output parameters are compared with the ones obtained with APOGEE Stellar Parameter and Chemical Abundances Pipeline (ASPCAP) for the same stellar spectrum, and we find that the values agree within the expected uncertainties. Comparisons with other previous near-infrared and optical literature are also available, with median differences within our estimated uncertainties found in most cases. Possible reasons for these differences are explored. The full H-band line list, the line selection for the synthesis, and the synthesized spectra are available for download, as are the calculated stellar parameters.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"21 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76532366","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-03-07DOI: 10.1051/0004-6361/202039742
A. Dobrotka, M. Orio, D. Benka, A. Vanderburg
AIMS: A few well studied cataclysmic variables (CVs) have shown discrete characteristic frequencies of fast variability; the most prominent ones are around log(f/Hz) $simeq$ -3. Because we still have only small number statistics, we obtained a new observation to test whether this is a general characteristic of CVs, especially if mass transfer occurs at a high rate typical for dwarf nova in outbursts, in the so called "high state". METHODS: We analyzed optical Kepler data of the quiescent nova and intermediate polar V4743 Sgr. This system hosts a white dwarf accreting through a disk in the high state. We calculated the power density spectra, and searched for break or characteristic frequencies. Our goal is to assess whether the mHz frequency of the flickering is a general characteristic. RESULTS: V4743 Sgr has a clear break frequency at log(f/Hz) $simeq$ -3. This detection increases the probability that the mHz characteristic frequency is a general feature of CVs in the high state, from 69% to 91%. Furthermore, we propose the possibility that the variability is generated by similar mechanism as in the nova-like system MV Lyr, which would make V4743 Sgr unique.
目的:一些被充分研究的突变变量(cv)显示出快速变化的离散特征频率;最突出的是log(f/Hz) $simeq$ -3。因为我们仍然只有少量的统计数据，所以我们获得了一个新的观察结果来测试这是否是CVs的一般特征，特别是如果质量传递以矮新星爆发时典型的高速率发生，即所谓的“高状态”。方法:我们分析了静止新星和中极V4743 Sgr的光学开普勒数据。这个系统的宿主是一颗白矮星，它通过一个处于高状态的圆盘吸积。我们计算了功率密度谱，并搜索了中断或特征频率。我们的目标是评估闪烁的兆赫频率是否为一般特征。结果:V4743 Sgr的断裂频率为log(f/Hz) $simeq$ -3。这种检测增加了mHz特征频率是高状态下CVs的一般特征的可能性，从69% to 91%. Furthermore, we propose the possibility that the variability is generated by similar mechanism as in the nova-like system MV Lyr, which would make V4743 Sgr unique.
{"title":"Searching for the 1 mHz variability in the flickering of V4743 Sgr: A cataclysmic variable accreting at a high rate","authors":"A. Dobrotka, M. Orio, D. Benka, A. Vanderburg","doi":"10.1051/0004-6361/202039742","DOIUrl":"https://doi.org/10.1051/0004-6361/202039742","url":null,"abstract":"AIMS: A few well studied cataclysmic variables (CVs) have shown discrete characteristic frequencies of fast variability; the most prominent ones are around log(f/Hz) $simeq$ -3. Because we still have only small number statistics, we obtained a new observation to test whether this is a general characteristic of CVs, especially if mass transfer occurs at a high rate typical for dwarf nova in outbursts, in the so called \"high state\". METHODS: We analyzed optical Kepler data of the quiescent nova and intermediate polar V4743 Sgr. This system hosts a white dwarf accreting through a disk in the high state. We calculated the power density spectra, and searched for break or characteristic frequencies. Our goal is to assess whether the mHz frequency of the flickering is a general characteristic. RESULTS: V4743 Sgr has a clear break frequency at log(f/Hz) $simeq$ -3. This detection increases the probability that the mHz characteristic frequency is a general feature of CVs in the high state, from 69% to 91%. Furthermore, we propose the possibility that the variability is generated by similar mechanism as in the nova-like system MV Lyr, which would make V4743 Sgr unique.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"18 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76342085","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-03-05DOI: 10.1051/0004-6361/202039426
S. Martinet, G. Meynet, S. Ekström, S. Simón-Díaz, G. Holgado, N. Castro, C. Georgy, P. Eggenberger, G. Buldgen, S. Salmon, R. Hirschi, J. Groh, E. Farrell, L. Murphy
Spectroscopic studies of Galactic O and B stars show that many stars with masses above 8 M$_{odot}$ are observed in the HR diagram just beyond the Main-Sequence (MS) band predicted by stellar models computed with a moderate overshooting. This may be an indication that the convective core sizes in stars in the upper part of the HR diagram are larger than predicted by these models. Combining stellar evolution models and spectroscopic parameters derived for a large sample of Galactic O and B stars, including brand new information about their projected rotational velocities, we reexamine the question of the convective core size in MS massive stars. We confirm that for stars more massive than about 8 M$_{odot}$, the convective core size at the end of the MS phase increases more rapidly with the mass than in models computed with a constant step overshoot chosen to reproduce the main sequence width in the low mass range (around 2 M$_{odot}$). This conclusion is valid for both the cases of non-rotating models and rotating models either with a moderate or a strong angular momentum transport. The increase of the convective core mass with the mass obtained from the TAMS position is, however, larger than the one deduced from the surface velocity drop for masses above about 15 M$_{odot}$. Although observations available at the moment cannot decide what is the best choice between the core sizes given by the TAMS and the velocity drop, we discuss different methods to get out of this dilemma. At the moment, comparisons with eclipsing binaries seem to favor the solution given by the velocity drop. While we confirm the need for larger convective cores at higher masses, we find tensions in-between different methods for stars more massive than 15 M$_{odot}$. The use of single-aged stellar populations (non-interacting binaries or stellar clusters) would be a great asset to resolve this tension.
{"title":"Convective core sizes in rotating massive stars","authors":"S. Martinet, G. Meynet, S. Ekström, S. Simón-Díaz, G. Holgado, N. Castro, C. Georgy, P. Eggenberger, G. Buldgen, S. Salmon, R. Hirschi, J. Groh, E. Farrell, L. Murphy","doi":"10.1051/0004-6361/202039426","DOIUrl":"https://doi.org/10.1051/0004-6361/202039426","url":null,"abstract":"Spectroscopic studies of Galactic O and B stars show that many stars with masses above 8 M$_{odot}$ are observed in the HR diagram just beyond the Main-Sequence (MS) band predicted by stellar models computed with a moderate overshooting. This may be an indication that the convective core sizes in stars in the upper part of the HR diagram are larger than predicted by these models. Combining stellar evolution models and spectroscopic parameters derived for a large sample of Galactic O and B stars, including brand new information about their projected rotational velocities, we reexamine the question of the convective core size in MS massive stars. We confirm that for stars more massive than about 8 M$_{odot}$, the convective core size at the end of the MS phase increases more rapidly with the mass than in models computed with a constant step overshoot chosen to reproduce the main sequence width in the low mass range (around 2 M$_{odot}$). This conclusion is valid for both the cases of non-rotating models and rotating models either with a moderate or a strong angular momentum transport. The increase of the convective core mass with the mass obtained from the TAMS position is, however, larger than the one deduced from the surface velocity drop for masses above about 15 M$_{odot}$. Although observations available at the moment cannot decide what is the best choice between the core sizes given by the TAMS and the velocity drop, we discuss different methods to get out of this dilemma. At the moment, comparisons with eclipsing binaries seem to favor the solution given by the velocity drop. While we confirm the need for larger convective cores at higher masses, we find tensions in-between different methods for stars more massive than 15 M$_{odot}$. The use of single-aged stellar populations (non-interacting binaries or stellar clusters) would be a great asset to resolve this tension.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"65 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90418942","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-03-05DOI: 10.1051/0004-6361/202040003
C. Pinccon, T. Appourchaux, G. Buldgen
The detection of gravity modes is expected to give us unprecedented insights into the inner dynamics of the Sun. Within this framework, predicting their amplitudes is essential to guide future observational strategies and seismic studies. In this work, we predict the amplitude of low-frequency asymptotic gravity modes generated by penetrative convection at the top of the radiative zone. The result is found to depend critically on the time evolution of the plumes inside the generation region. Using a solar model, we compute the GOLF apparent surface radial velocity of low-degree gravity modes in the frequency range $10~mu H_zle nu le 100~mu H_z$. In case of a Gaussian plume time evolution, gravity modes turn out to be undetectable because of too small surface amplitudes. This holds true despite a wide range of values considered for the parameters of the model. In the other limiting case of an exponential time evolution, plumes are expected to drive gravity modes in a much more efficient way because of a much higher temporal coupling between the plumes and the modes than in the Gaussian case. Using reasonable values for the plume parameters based on semi-analytical models, the apparent surface velocities in this case turn out to be one order of magnitude smaller than the 22-years GOLF detection threshold and than the previous estimates considering turbulent pressure as the driving mechanism, with a maximum value of $0.05$ cm s${}^{-1}$ for $ell =1$ and $nuapprox 100~mu H_z$. When accounting for uncertainties on the plume parameters, the apparent surface velocities in the most favorable plausible case become comparable to those predicted with turbulent pressure, and the GOLF observation time required for a detection at $ nu approx100~mu H_z$ and $ell=1$ is reduced to about 50 yrs.
对引力模式的探测有望让我们对太阳的内部动力学有前所未有的了解。在这个框架内，预测它们的振幅对于指导未来的观测策略和地震研究至关重要。在这项工作中，我们预测了辐射区顶部穿透对流产生的低频渐近重力模态的振幅。结果发现，关键取决于羽流在产生区域内的时间演化。利用太阳模型，我们计算了频率范围$10~mu H_zle nu le 100~mu H_z$的低重力模式的GOLF视表面径向速度。在高斯羽流时间演化的情况下，由于表面振幅太小，重力模式无法被探测到。尽管模型参数的取值范围很广，但这一点仍然成立。在指数时间演化的另一种极限情况下，由于羽流和模式之间的时间耦合比高斯情况下高得多，因此预计羽流将以更有效的方式驱动重力模式。利用基于半解析模型的羽流参数的合理值，在这种情况下的地表表观速度比22年GOLF探测阈值小一个数量级，比以前考虑湍流压力作为驱动机制的估计小一个数量级，$ell =1$和$nuapprox 100~mu H_z$的最大值为$0.05$ cm s ${}^{-1}$。当考虑到羽流参数的不确定性时，在最有利的可信情况下的地表表观速度与湍流压力预测的速度相当，并且在$ nu approx100~mu H_z$和$ell=1$探测所需的GOLF观测时间减少到约50年。
{"title":"Amplitude of solar gravity modes generated by penetrative plumes","authors":"C. Pinccon, T. Appourchaux, G. Buldgen","doi":"10.1051/0004-6361/202040003","DOIUrl":"https://doi.org/10.1051/0004-6361/202040003","url":null,"abstract":"The detection of gravity modes is expected to give us unprecedented insights into the inner dynamics of the Sun. Within this framework, predicting their amplitudes is essential to guide future observational strategies and seismic studies. In this work, we predict the amplitude of low-frequency asymptotic gravity modes generated by penetrative convection at the top of the radiative zone. The result is found to depend critically on the time evolution of the plumes inside the generation region. Using a solar model, we compute the GOLF apparent surface radial velocity of low-degree gravity modes in the frequency range $10~mu H_zle nu le 100~mu H_z$. In case of a Gaussian plume time evolution, gravity modes turn out to be undetectable because of too small surface amplitudes. This holds true despite a wide range of values considered for the parameters of the model. In the other limiting case of an exponential time evolution, plumes are expected to drive gravity modes in a much more efficient way because of a much higher temporal coupling between the plumes and the modes than in the Gaussian case. Using reasonable values for the plume parameters based on semi-analytical models, the apparent surface velocities in this case turn out to be one order of magnitude smaller than the 22-years GOLF detection threshold and than the previous estimates considering turbulent pressure as the driving mechanism, with a maximum value of $0.05$ cm s${}^{-1}$ for $ell =1$ and $nuapprox 100~mu H_z$. When accounting for uncertainties on the plume parameters, the apparent surface velocities in the most favorable plausible case become comparable to those predicted with turbulent pressure, and the GOLF observation time required for a detection at $ nu approx100~mu H_z$ and $ell=1$ is reduced to about 50 yrs.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"128 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85738404","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：