The Astronomy and Astrophysics Review最新文献

{"title":"Gravitational instability of solar prominence threads","authors":"A. Adrover-Gonz'alez, J. Terradas, R. Oliver, M. Carbonell","doi":"10.1051/0004-6361/202039677","DOIUrl":"https://doi.org/10.1051/0004-6361/202039677","url":null,"abstract":"Prominence threads are dense and cold structures lying on curved magnetic fields that can be suspended in the solar atmosphere against gravity. The gravitational stability of threads, in the absence of non-ideal effects, is comprehensively investigated in the present work by means of an elementary but effective model. Based on purely hydrodynamic equations in one spatial dimension and applying line-tying conditions at the footpoints of the magnetic field lines, we derive analytical expressions for the different feasible equilibria and the corresponding frequencies of oscillation. We find that the system allows for stable and unstable equilibrium solutions subject to the initial position of the thread, its density contrast and length, and the total length of the magnetic field lines. The transition between the two types of solutions is produced at specific bifurcation points that have been determined analytically in some particular cases. When the thread is initially at the top of the concave magnetic field, that is at the apex, we find a supercritical pitchfork bifurcation, while for a shifted initial thread position with respect to this point the symmetry is broken and the system is characterised by an S-shaped bifurcation. The plain results presented in this paper shed new light on the behaviour of threads in curved magnetic fields under the presence of gravity and help to interpret more complex numerical magnetohydrodynamics (MHD) simulations about similar structures.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"19 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77840931","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}

{"title":"The Hubble PanCET program: long-term chromospheric evolution and flaring activity of the M dwarf host GJ 3470","authors":"V. Bourrier, L. D. Santos, J. Sanz-Forcada, A. G. Muñoz, G. Henry, P. Lavvas, A. Lecavelier, M. López-Morales, T. Mikal-Evans, D. Sing, H. Wakeford, D. Ehrenreich","doi":"10.1051/0004-6361/202140487","DOIUrl":"https://doi.org/10.1051/0004-6361/202140487","url":null,"abstract":"Neptune-size exoplanets seem particularly sensitive to atmospheric evaporation, making it essential to characterize the stellar high-energy radiation that drives this mechanism. This is particularly important with M dwarfs, which emit a large and variable fraction of their luminosity in the ultraviolet and can display strong flaring behavior. The warm Neptune GJ 3470b, hosted by an M2 dwarf, was found to harbor a giant exosphere of neutral hydrogen thanks to three transits observed with the Hubble Space Telescope Imaging Spectrograph (HST/STIS). Here we report on three additional transit observations from the Panchromatic Comparative Exoplanet Treasury (PanCET) program, obtained with the HST Cosmic Origin Spectrograph (COS). These data confirm the absorption signature from GJ 3470b’s exosphere in the stellar Lyman-α line and demonstrate its stability over time. No planetary signatures are detected in other stellar lines, setting a 3σ limit on GJ 3470b’s far-ultraviolet (FUV) radius at 1.3 times its Roche lobe radius. We detect three flares from GJ3470. They show different spectral energy distributions but peak consistently in the Si iii line, which traces intermediate-temperature layers in the transition region. These layers appear to play a particular role in GJ 3470’s activity as emission lines that form at lower or higher temperatures than Si iii evolved differently over the long term. Based on the measured emission lines, we derive synthetic X-ray and extreme-ultraviolet (X+EUV, or XUV) spectra for the six observed quiescent phases, covering one year, as well as for the three flaring episodes. Our results suggest that most of GJ 3470’s quiescent high-energy emission comes from the EUV domain, with flares amplifying the FUV emission more strongly. The neutral hydrogen photoionization lifetimes and mass loss derived for GJ 3470b show little variation over the epochs, in agreement with the stability of the exosphere. Simulations informed by our XUV spectra are required to understand the atmospheric structure and evolution of GJ 3470b and the role played by evaporation in the formation of the hot-Neptune desert.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"2 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91367017","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}

{"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}

{"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}

{"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}

{"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}

{"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}

{"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}

{"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}

{"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}