- ID:
- ivo://CDS.VizieR/J/A+A/646/A132
- Title:
- beta Pictoris debris disk image
- Short Name:
- J/A+A/646/A132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The nearby young star beta Pictoris hosts a rich and complex planetary system, with at least two giant planets and a nearly edge-on debris disk that contains several dynamical subpopulations of planetesimals. While the inner ranges of the debris disk have been studied extensively, less information is known about the outer, fainter parts of the disk. Here we present an analysis of archival FORS V-band imaging data from 2003-2004, which have previously not been explored scientifically because the halo substructure of the bright stellar point spread function is complex. Here we present the deepest imaging yet for the outer range of the beta Pic disk.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/642/A179
- Title:
- beta Pictoris moving group RV of 81 stars
- Short Name:
- J/A+A/642/A179
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The {beta} Pictoris moving group is one of the most well-known young associations in the solar neighbourhood and several members are known to host circumstellar discs, planets, and comets. Measuring its age with precision is basic to study several astrophysical processes such as planet formation and disc evolution which are strongly age dependent. We aim to determine a precise and accurate dynamical traceback age for the {beta} Pictoris moving group. Our sample combines the extremely precise Gaia DR2 astrometry with ground-based radial velocities measured in an homogeneous manner. We use an updated version of our algorithm to determine dynamical ages. The new approach takes into account a robust estimate of the spatial and kinematic covariance matrices of the association to improve the sample selection process and to perform the traceback analysis. We estimate a dynamical age of 18.5_-2.4_^+2.0^Myr for the {beta} Pictoris moving group. We investigated the spatial substructure of the association at birth time and we propose the existence of a core of stars more concentrated. We also provide precise radial velocity measurements for 81 members of {beta} Pic, including ten stars with the first determination of their radial velocities. Our dynamical traceback age is three times more precise than previous traceback age estimates and, more important, for the first time, reconciles the traceback age with the most recent estimates of other dynamical, lithium depletion boundary, and isochronal ages. This has been possible thanks to the excellent astrometric and spectroscopic precisions, the homogeneity of our sample, and the detailed analysis of binaries and membership.
1793. beta Pictoris photometry
- ID:
- ivo://CDS.VizieR/J/A+A/648/A15
- Title:
- beta Pictoris photometry
- Short Name:
- J/A+A/648/A15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric monitoring of beta Pictoris in 1981 showed anomalous fluctuations of up to 4% over several days, consistent with foreground material transiting the stellar disk. The subsequent discovery of the gas giant planet beta Pictoris b and the predicted transit of its Hill sphere to within 0.1 au projected distance of the planet provided an opportunity to search for the transit of a circumplanetary disk in this 21+/-4Myr-old planetary system. Continuous broadband photometric monitoring of beta Pictoris requires ground- based observatories at multiple longitudes to provide redundancy and to provide triggers for rapid spectroscopic followup. These observatories include the dedicated beta Pictoris monitoring observatory bRing at Sutherland and Siding Springs, the ASTEP400 telescope at Concordia, and observations from the space observatories BRITE and Hubble Space Telescope. We search the combined light curves for evidence of short period transient events caused by rings and for longer term photometric variability due to diffuse circumplanetary material. We find no photometric event that matches with the event seen in November 1981, and there is no systematic photometric dimming of the star as a function of the Hill sphere radius. We conclude that the 1981 event was not caused by the transit of a circumplanetary disk around beta Pictoris b. The upper limit on the long term variability of beta Pictoris places an upper limit of 1.8x10^22^g of dust within the Hill sphere. Circumplanetary material is either condensed into a non-transiting disk, is condensed into a disk with moons that has a small obliquity, or is below our detection threshold. This is the first time that a dedicated international campaign has mapped the Hill sphere transit of a gas giant extrasolar planet at 10 au.
- ID:
- ivo://CDS.VizieR/J/MNRAS/457/4160
- Title:
- BETA pilot multi-epoch continuum survey
- Short Name:
- J/MNRAS/457/4160
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Boolardy Engineering Test Array is a 6x12m dish interferometer and the prototype of the Australian Square Kilometre Array Pathfinder (ASKAP), equipped with the first generation of ASKAP's phased array feed (PAF) receivers. These facilitate rapid wide-area imaging via the deployment of simultaneous multiple beams within an ~30deg^2^ field of view. By cycling the array through 12 interleaved pointing positions and using nine digitally formed beams, we effectively mimic a traditional 1hx108 pointing survey, covering ~150deg^2^ over 711-1015MHz in 12h of observing time. Three such observations were executed over the course of a week. We verify the full bandwidth continuum imaging performance and stability of the system via self-consistency checks and comparisons to existing radio data. The combined three epoch image has arcminute resolution and a 1{sigma} thermal noise level of 375{mu}Jy/beam, although the effective noise is a factor of ~3 higher due to residual sidelobe confusion. From this we derive a catalogue of 3722 discrete radio components, using the 35 per cent fractional bandwidth to measure in-band spectral indices for 1037 of them. A search for transient events reveals one significantly variable source within the survey area. The survey covers approximately two-thirds of the Spitzer South Pole Telescope Deep Field. This pilot project demonstrates the viability and potential of using PAFs to rapidly and accurately survey the sky at radio wavelengths.
- ID:
- ivo://nasa.heasarc/askapbeta
- Title:
- BETA Pilot Multi-Epoch Continuum Survey of Spitzer SPT Deep Field
- Short Name:
- ASKAPBETA
- Date:
- 14 Feb 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The Boolardy Engineering Test Array (BETA) is a 6 x 12m-dish interferometer and the prototype of the Australian Square Kilometre Array Pathfinder (ASKAP), equipped with the first generation of ASKAP's phased array feed (PAF) receivers. These facilitate rapid wide-area imaging via the deployment of simultaneous multiple beams within an ~30 deg<sup>2</sup> field of view. By cycling the array through 12 interleaved pointing positions and using nine digitally formed beams, the authors have effectively mimicked a traditional 1 hours x 108 pointing survey, covering ~150 deg<sup>2</sup> over 711-1015 MHz in just 12 hours of observing time. Three such observations were executed over the course of a week. The authors verified the full bandwidth continuum imaging performance and stability of the system via self-consistency checks and comparisons to existing radio data. The combined three epoch image has arcminute resolution and a 1-sigma thermal noise level of 375 µJy/beam, although the effective noise is a factor of ~3 higher due to residual sidelobe confusion. From this, the authors have derived a catalog of 3,722 discrete radio components, using the 35% fractional bandwidth to measure in-band spectral indices for 1037 of them. A search for transient events reveals one significantly variable source within the survey area. The survey covers approximately two-thirds of the Spitzer South Pole Telescope (SPT) Deep Field. This pilot project demonstrates the viability and potential of using PAFs to rapidly and accurately survey the sky at radio wavelengths. The target field was observed with BETA on three separate occasions as part of the commissioning and verification of the instrument. The telescope delivers 304 MHz of instantaneous bandwidth and for these observations the sky frequency range was 711-1015 MHz, corresponding to a fractional bandwidth of 35%. The data were captured with a frequency resolution of 18.5 kHz, using 16,416 frequency channels across the band. The PYBDSM source finder was used to extract a component catalog from the deep mosaic image formed from a combination of all epochs and sub-bands. Components were fit to islands of emission that had a peak brightness of >5 sigma and an island boundary threshold of >3 sigma, where sigma is the local estimate of the background noise level. Component spectral indices were assigned by matching positions at which spectral indices were successfully fit (Section 4.5 of the reference paper). Following the excision of some spurious detections at the noisy edge of the mosaic, the final catalog contains 3,722 components, 1,037 of which have in-band spectral index measurements. This table was created by the HEASARC in March 2017 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/457/4160">CDS Catalog J/MNRAS/457/4160</a> file table3.dat, the list of source components found in the ASKAP-BETA Survey covering two-thirds of the Spitzer SPT Deep Field. This is a service provided by NASA HEASARC .
1796. Bet Aur light curves
- ID:
- ivo://CDS.VizieR/J/A+A/467/1215
- Title:
- Bet Aur light curves
- Short Name:
- J/A+A/467/1215
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the most precise light curve ever obtained of a detached eclipsing binary star and use it investigate the inclusion of non-linear limb darkening laws in light curve models of eclipsing binaries. This light curve, of the bright eclipsing system beta Aurigae, was obtained using the star tracker aboard the WIRE satellite and contains 30000 datapoints with a point-to-point scatter of 0.3mmag. We analyse the WIRE light curve using a version of the EBOP code modified to include non-linear limb darkening laws and to directly incorporate observed times of minimum light and spectroscopic light ratios into the photometric solution as individual observations. We also analyse the dataset with the Wilson-Devinney code to ensure that the two models give consistent results. EBOP is able to provide an excellent fit to the high-precision WIRE data. Whilst the fractional radii of the stars are only defined to a precision of 5% by this light curve, including an accurate published spectroscopic light ratio improves this dramatically to 0.5%. Using non-linear limb darkening improves the quality of the fit significantly compared to the linear law and causes the measured radii to increase by 0.4%. It is possible to derive all of the limb darkening coefficients from the light curve, although they are strongly correlated with each other. The fitted coefficients agree with theoretical predictions to within their fairly large error estimates. We were able to obtain a reasonably good fit to the data using the Wilson- Devinney code, but only using the highest available integration accuracy and by iterating for a long time. Bolometric albedos of 0.6 were found, which are appropriate to convective rather than radiative envelopes. The radii and masses of the components of beta Aurigae are R_A_=2.762+/-0.017R_{sun}_, R_B_=2.568+/-0.017R_{sun}_, M_A_=2.376+/-0.027M_{sun}_ and M_B_=2.291+/-0.027M_{sun}_, where A and B denote the primary and secondary star, respectively. Theoretical stellar evolutionary models can match these parameters for a solar metal abundance and an age of 450 to 500Myr. The Hipparcos trigonometric parallax and an interferometrically-derived orbital parallax give distances to beta Aurigae which are in excellent agreement with each other and with distances derived using surface brightness relations and several sets of empirical and theoretical bolometric corrections.
- ID:
- ivo://CDS.VizieR/J/other/Nat/594.365
- Title:
- Betelgeuse during its Great Dimming
- Short Name:
- J/other/Nat/594.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Red supergiants represent the most common final stage of the evolution of stars with initial masses between 8 and 30-35 times the mass of the Sun. During this phase of lifetime ~10^5 yrs, they experience substantial mass loss of unknown mechanism (Arroyo-Torres et al., 2015A&A...575A..50A). This mass loss can affect their evolutionary path, collapse, future supernova light curve, and ultimate fate as a neutron star or a black hole. From November 2019 to March 2020, the second closest red supergiant (RSG, 222^+48^_-34_pc) Betelgeuse experienced a historic dimming of its visible brightness, witnessed worldwide. Usually between 0.1 and 1.0mag, it went down to 1.614+/-0.008mag around 7-13 February 2020. Here we report high angular resolution observations showing that the southern hemisphere of the star was ten times darker than usual in the visible. Observations and modeling support the scenario of a dust clump recently formed in the vicinity of the star due to a local temperature decrease in a cool patch appearing on the photosphere. The directly imaged brightness variations of Betelgeuse evolved on a timescale of weeks. This event suggests that an inhomogeneous component of red supergiant mass loss is linked to a very contrasted and rapidly changing photosphere.
- ID:
- ivo://CDS.VizieR/J/MNRAS/388/1198
- Title:
- Be/X-ray binaries in Small Magellanic Cloud
- Short Name:
- J/MNRAS/388/1198
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spectral distributions of Be/X-ray binaries in the Large Magellanic Cloud and Galaxy have been shown to differ significantly from the distribution of isolated Be stars in the Galaxy. Population synthesis models can explain this difference in spectral distributions through substantial angular momentum loss from the binary system. In this work, we explore the spectral distribution of Be/X-ray binaries in the Small Magellanic Cloud (SMC) using high signal-to-noise ratio spectroscopy of a sample of 37 optical counterparts to known X-ray pulsars. Our results show that the spectral distribution of Be/X-ray binaries in the SMC is consistent with that of the Galaxy, despite the lower metallicity environment of the SMC. This may indicate that, although the metallicity of the SMC is conducive to the formation of a large number of high-mass X-ray binaries, the spectral distribution of these systems is likely to be most strongly influenced by angular momentum losses during binary evolution, which are not particularly dependent on the local metallicity.
- ID:
- ivo://CDS.VizieR/J/A+A/630/A135
- Title:
- Beyond the exoplanet mass-radius relation
- Short Name:
- J/A+A/630/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The mass and radius are two fundamental properties to characterize exoplanets but only for a relatively small fraction of exoplanets are they both available. The mass is often derived from radial velocity measurements while the radius is almost always measured with the transit method. For a large number of exoplanets, either the radius or the mass is unknown, while the host star has been characterized. Several mass-radius relations dependent on the planet's type have been published which often allow to predict the radius, as well as a bayesian code which forecasts the radius of an exoplanet given the mass or vice versa. Our goal is to derive the radius of exoplanets using only observables extracted from spectra used primarily to determine radial velocities and spectral parameters. Our objective is to obtain a mass-radius relation that is independent of the planet's type. We work with a database of confirmed exoplanets with known radii and masses as well as the planets from our Solar System. Using random forests, a machine learning algorithm, we compute the radius of exoplanets and compare the results to the published radii. Our code, BEM, is available online. On top of this, we also explore how the radius estimates compare to previously published mass-radius relations. The estimated radii reproduces the spread in radius found for high mass planets better than previous mass-radius relations. The average error on the radius is 1.8R_Earth_ across the whole range of radii from 1 to 22R_Earth_. We found that a random forest algorithm is able to derive reliable radii especially for planets between 4 and 20R_Earth_, for which the error is smaller than 25%. The algorithm has a low bias but still a high variance, which could be reduced by limiting the growth of the forest or adding more data. The random forest algorithm is a promising method to derive exoplanet properties. We show that the exoplanet's mass and equilibrium temperature are the relevant properties which constrain the radius, and do it with higher accuracy than the previous methods.
1800. BF Aur UBV photometry
- ID:
- ivo://CDS.VizieR/J/A+A/362/673
- Title:
- BF Aur UBV photometry
- Short Name:
- J/A+A/362/673
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Because the question of the mass ratio of the early-type system BF Aur has not yet fully been clarified, we present and analyse new UBV photometry and nearly contemporaneous radial velocity observations. From a simultaneous least squares analysis of the photometric light curves and the new radial velocity curves we derive a mass ratio of q=1.048+/-0.02. With even much more accurate photometric and spectroscopic data the mass ratio remains weakly defined. The resulting stellar parameters are consistent with the line ratios derived from old and our new spectra and available Stroemgren indices. We confirm earlier conclusions that BF Aur is detached and that the more massive component is almost filling its Roche lobe. New data indicating a period change support the interpretation that mass exchange has already started or is about to start.
