ABSTRACT
The mass and distribution of metals in the interiors of exoplanets are essential for constraining their formation and evolution processes. Never the less, with only masses and radii ...measured, the determination of exoplanet interior structures is degenerate, and so far simplified assumptions have mostly been used to derive planetary metallicities. In this work, we present a method based on a state-of-the-art interior code, recently used for Jupiter, and a Bayesian framework, to explore the possibility of retrieving the interior structure of exoplanets. We use masses, radii, equilibrium temperatures, and measured atmospheric metallicities to retrieve planetary bulk metallicities and core masses. Following results on the giant planets in the Solar system and recent development in planet formation, we implement two interior structure models: one with a homogeneous envelope and one with an inhomogeneous one. Our method is first evaluated using a test planet and then applied to a sample of 37 giant exoplanets with observed atmospheric metallicities from the pre-JWST era. Although neither internal structure model is preferred with the current data, it is possible to obtain information on the interior properties of the planets, such as the core mass, through atmospheric measurements in both cases. We present updated metal mass fractions, in agreement with recent results on giant planets in the Solar system.
ABSTRACT
Apep is the brightest and most luminous non-thermal colliding-wind binary by over an order of magnitude. It has been suggested from infrared observations that one of the Wolf–Rayet stars in ...Apep is launching an anisotropic wind. Here we present radio observations of Apep from 0.2 to 20 GHz taken over 33 yr. The spectrum reveals an extremely steep turnover in the flux density at low frequencies, where the flux density decreases by two orders of magnitude over only 325 MHz of bandwidth. This exponential decline is best described by free–free absorption, with a turnover frequency at 0.54 ± 0.01 GHz. Above the turnover, the spectrum is well described by a power-law and a high-frequency cut-off likely caused by inverse-Compton cooling. The light curve of Apep shows significant variation over the observing period, with Apep brightening by over 50 mJy in a span of 25 yr at 1.4 GHz. Models that assume spherical winds do not replicate all of the structure evident in the radio light curve. We derived a model that allows one of the winds in the system to be anisotropic. This anisotropic model recovers most of the structure of the light curve and is a significantly better statistical fit to the data than the spherical wind model. We suggest such a result is independent support that one of the Wolf–Rayet stars in Apep is launching an anisotropic wind. If the anisotropic wind model is correct, we predict a ∼25 per cent decrease of the 1.4 GHz flux density of Apep over the next 5 yr.
ABSTRACT
We predict and compare the distributions and properties of hypervelocity stars (HVSs) ejected from the centres of the Milky Way (MW) and the Large Magellanic Cloud (LMC). In our model, HVSs ...are ejected at a constant rate – equal in both galaxies – via the Hills mechanism and are propagated in a combined potential, where the LMC orbits the MW on its first infall. By selecting $m \gt 2\, \mathrm{M_\odot }$ HVSs well separated from the Magellanic Clouds and Galactic mid-plane, we identify mock HVSs which would stand out from ordinary stars in the stellar halo in future data releases from the Gaia satellite and the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST). We find that in these deep surveys, LMC HVSs will outnumber MW ones by a factor of ∼2.5, as HVSs can more easily escape from the shallower potential of the LMC. At an assumed HVS ejection rate of $10^{-4} \, \mathrm{yr^{-1}}$, HVSs detectable in the final Gaia data release and LSST from the LMC (MW) will number $125_{-12}^{+11}$ ($50_{-8}^{+7}$) and $140_{-11}^{+10}$ ($42_{-7}^{+6}$), respectively. The MW and LMC HVS populations show different kinematics and spatial distributions. While LMC HVSs have more modest total velocities and larger Galactocentric distances clustered around those of the LMC itself, HVSs from the MW show broader distributions, including a prominent high-velocity tail above $500 \, \mathrm{km \ s^{-1}}$ that contains at least half of the stars. These predictions are robust against reasonable variation of the Galactic potential and of the LMC central black hole mass.
Stellar radio emission can measure a star’s magnetic field strength and structure, plasma density, and dynamics, and the stellar wind pressure impinging on exoplanet atmospheres. However, properly ...interpreting the radio data often requires temporal baselines that cover the rotation of the stars, orbits of their planets, and any longer-term stellar activity cycles. Here we present our monitoring campaign on the young, active M dwarf AU Microscopii with the Australia Telescope Compact Array between 1.1 and 3.1 GHz. With over 250 h of observations, these data represent the longest radio monitoring campaign on a single main-sequence star to date. We find that AU Mic produces a wide variety of radio emission, for which we introduce a phenomenological classification scheme predicated on the polarisation fraction and time-frequency structure of the emission. Such a classification scheme is applicable to radio emission from other radio-bright stars. The six types of radio emission detected on AU Mic can be broadly categorised into five distinct types of bursts, and broadband quiescent emission. We find that the radio bursts are highly circularly polarised and periodic with the rotation period of the star, implying that the emission is beamed. It is therefore most likely produced by the electron cyclotron maser instability. We present a model to show that the observed pattern of emission can be explained by emission from auroral rings on the magnetic poles. The total intensity of the broadband emission is stochastic, but we show that its circular polarisation fraction is also periodic with the rotation of the star. Such a periodicity in the polarised fraction of emission has not been observed on an M dwarf before. We present a qualitative model to describe the periodicity in the polarisation fraction of the broadband emission, using low-harmonic gyromagnetic emission. Using a simple qualitative model, we infer a magnetic obliquity of at least 20° from the observed variation in polarisation fraction. Finally, we show that the radio emission might be evolving on long timescales, hinting at a potential stellar magnetic activity cycle.
We present the detection of 68 sources from the most sensitive radio survey in circular polarisation conducted to date. We used the second data release of the 144 MHz LOFAR Two-metre Sky Survey to ...produce circularly polarised maps with a median noise of 140 µJy beam
−1
and resolution of 20″ for ≈27% of the northern sky (5634 deg
2
). The leakage of total intensity into circular polarisation is measured to be ≈0.06%, and our survey is complete at flux densities ≥1 mJy. A detection is considered reliable when the circularly polarised fraction exceeds 1%. We find the population of circularly polarised sources is composed of four distinct classes: stellar systems, pulsars, active galactic nuclei, and sources unidentified in the literature. The stellar systems can be further separated into chromospherically active stars, M dwarfs, and brown dwarfs. Based on the circularly polarised fraction and lack of an optical counterpart, we show it is possible to infer whether the unidentified sources are likely unknown pulsars or brown dwarfs. By the completion of this survey of the northern sky, we expect to detect 300±100 circularly polarised sources.
Apep is the brightest and most luminous non-thermal colliding-wind binary by over an order of magnitude. It has been suggested from infrared observations that one of the Wolf-Rayet stars in Apep is ...launching an anisotropic wind. Here we present radio observations of Apep from 0.2 to 20 GHz taken over 33 years. The spectrum reveals an extremely steep turnover in the flux density at low frequencies, where the flux density decreases by two orders of magnitude over only 325 MHz of bandwidth. This exponential decline is best described by free-free absorption, with a turnover frequency at 0.54 \(\pm\) 0.01 GHz. Above the turnover, the spectrum is well described by a power-law and a high-frequency cut-off likely caused by inverse-Compton cooling. The lightcurve of Apep shows significant variation over the observing period, with Apep brightening by over 50 mJy in a span of 25 years at 1.4 GHz. Models that assume spherical winds do not replicate all of the structure evident in the radio lightcurve. We derived a model that allows one of the winds in the system to be anisotropic. This anisotropic model recovers most of the structure of the lightcurve and is a significantly better statistical fit to the data than the spherical wind model. We suggest such a result is independent support that one of the Wolf-Rayet stars in Apep is launching an anisotropic wind. If the anisotropic wind model is correct, we predict a ~25% decrease of the 1.4 GHz flux density of Apep over the next five years.
We present the detection of 68 sources from the most sensitive radio survey in circular polarisation conducted to date. We use the second data release of the 144 MHz LOFAR Two-metre Sky Survey to ...produce circularly-polarised maps with median 140 \(\mu\)Jy beam\(^{-1}\) noise and resolution of 20\(''\) for \(\approx\)27% of the northern sky (5634 deg\(^{2}\)). The leakage of total intensity into circular polarisation is measured to be \(\approx\)0.06%, and our survey is complete at flux densities \(\geq1\) mJy. A detection is considered reliable when the circularly-polarised fraction exceeds 1%. We find the population of circularly-polarised sources is composed of four distinct classes: stellar systems, pulsars, active galactic nuclei, and sources unidentified in the literature. The stellar systems can be further separated into chromospherically-active stars, M dwarfs, and brown dwarfs. Based on the circularly-polarised fraction and lack of an optical counterpart, we show it is possible to infer whether the unidentified sources are likely unknown pulsars or brown dwarfs. By the completion of this survey of the northern sky, we expect to detect 300\(\pm\)100 circularly-polarised sources.
Improved cleaning module after tungsten etch Bloot, A.S.; Leene, J.; Sinnott, T. ...
1999 IEEE International Symposium on Semiconductor Manufacturing Conference Proceedings (Cat No.99CH36314),
1999
Conference Proceeding
Integrated dry photoresist and residue removal is increasingly being implemented over traditional dry resist strip and wet residue removal process flows. The primary motivation is to improve the ...wafer surface cleanliness after a cleaning module in order to improve device performance. A case study will be reviewed for the post tungsten etch cleaning module. Using the traditional cleaning sequence of dry/wet strip caused unacceptable titanium undercut and electrical leakage. The improved cleaning module for integrated dry resist and residue removal increased device performance, controlled the titanium undercut and reduced the time in the wet strip solvent bath by over six times. Additional benefits such as decreased defects and improved SACVD coverage were also results of the integrated cleaning module. A study of the original problem, the replacement process and optimization are provided with defect data, cross sections and electrical measurements.
Damage-free plasma treatment before SACVD deposition Bloot, A.S.; Peters, W.; Luchies, J.-M.
2000 5th International Symposium on Plasma Process-Induced Damage (IEEE Cat. No.00TH8479),
2000
Conference Proceeding
Charging impact of various plasma treatments before intermetal dielectric SACVD deposition has been investigated. Dry strip using CF/sub 4//O/sub 2/ or CF/sub 4//H/sub 2/O plasma as well as SACVD ...pre-treatments with O/sub 2/, N/sub 2/ are compared with no plasma treatment. Furthermore, O/sub 2/, pre-treatment is investigated for a lamp-heated and a D/spl times/Z SACVD deposition tool. The evaluation methods in-line Plasma Damage Monitor (PDM) wafers, end-of-line electrically tested antenna structures, Q/sub bd/ measurements and product yield data show consistent results. The studied dry strip recipes using CF/sub 4//O/sub 2/ or CF/sub 4//H/sub 2/O plasma introduce some charging. A N/sub 2/ plasma pre-treatment results in high PDM values (40 V), no failing antenna structures, no Q/sub bd/ fails and some yield loss (0.9%). This work showed for O/sub 2/ pre-treatment on a lamp-heated deposition tool excessive PDM values (-31 V), failing antenna structures (6.9%), Q/sub bd/ fails (4.2%) and yield loss (1.8%). However, the use of a O/sub 2/ plasma in a D/spl times/Z tool is found to be the best pre-treatment.
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