86 research outputs found
Emissivity of patterned silicon wafers in rapid thermal processing
The influence of patterns on emissivity in silicon wafers in rapid thermal processing systems has been investigated. In this study, two experiments with layered and patterned silicon wafers were conducted. The main difference in the experiments is the way in which the temperature was controlled. The first experiment was performed under Open Loop Intensity Control (OLIC). For OLIC, no feedback from the wafer is returned. It is assumed that supplying a certain power level will lead to the desired temperature. The other experiment used the Closed Loop Intensity Control. In this case, a feedback, in the form of temperature deviation is used to adjust the temperature.
By using the Stefan-Boltzmann T4-law, a heat balance equation describing the incoming and outgoing heat can be derived. This heat balance equation can be used to calculate the spatial temperature differences due to different emissivities of the various thin film layers of patterned wafers. A mathematical model was developed based on the heat balance equation. The mathematical model was verified with experiments. The model showed good agreement with the experiments
A discontinuity in the -radius relation of M-dwarfs
We report on 13 new high-precision measurements of stellar diameters for
low-mass dwarfs obtained by means of near-infrared long-baseline interferometry
with PIONIER at the Very Large Telescope Interferometer. Together with accurate
parallaxes from Gaia DR2, these measurements provide precise estimates for
their linear radii, effective temperatures, masses, and luminosities. This
allows us to refine the effective temperature scale, in particular towards the
coolest M-dwarfs. We measure for late-type stars with enhanced metallicity
slightly inflated radii, whereas for stars with decreased metallicity we
measure smaller radii. We further show that Gaia DR2 effective temperatures for
M-dwarfs are underestimated by 8.2 % and give an empirical
- relation which is better suited for M-dwarfs with between 2600 and 4000 K. Most importantly, we are able to observationally
identify a discontinuity in the -radius plane, which is likely due
to the transition from partially convective M-dwarfs to the fully convective
regime. We found this transition to happen between 3200 K and 3340 K, or
equivalently for stars with masses . We find that in
this transition region the stellar radii are in the range from 0.18 to
0.42 for similar stellar effective temperatures.Comment: 11 pages, 9 figures, accepted in MNRA
K2-113b: A dense hot-Jupiter transiting a solar analogue
We present the discovery of K2-113b, a dense hot-Jupiter discovered using
photometry from Campaign 8 of the Kepler-2 (K2) mission and high-resolution
spectroscopic follow up obtained with the FEROS spectrograph. The planet orbits
a solar analogue in a day orbit,
has a radius of and a mass of
. With a density of gr/cm,
the planet is among the densest systems known having masses below 2 and
, and is just above the temperature limit at which inflation
mechanisms are believed to start being important. Based on its mass and radius,
we estimate that K2-113b should have a heavy element content on the order of
110 or greater.Comment: 8 pages, 7 figures. Accepted to MNRAS; added new photometry from
newest version of EVEREST, which allows for a constrain on the secondary
eclipse dept
EPIC247098361b: a transiting warm Saturn on an eccentric days orbit around a star
We report the discovery of EPIC247098361b using photometric data of the
Kepler K2 satellite coupled with ground-based spectroscopic observations.
EPIC247098361b has a mass of M M, a radius of
R R, and a moderately low equilibrium temperature of
K due to its relatively large star-planet separation of
AU. EPIC247098361b orbits its bright () late F-type host star
in an eccentric orbit () every 11.2 days, and is one of only
four well characterized warm Jupiters having hosts stars brighter than .
We estimate a heavy element content of 20 7 M for
EPIC247098361b, which is consistent with standard models of giant planet
formation. The bright host star of EPIC247098361b makes this system a well
suited target for detailed follow-up observations that will aid in the study of
the atmospheres and orbital evolution of giant planets at moderate separations
from their host stars.Comment: 11 pages, 10 figures, submitted to MNRA
Discovery and Validation of a High-Density sub-Neptune from the K2 Mission
We report the discovery of BD+20594b, a high density sub-Neptune exoplanet,
made using photometry from Campaign 4 of the two-wheeled Kepler (K2) mission,
ground-based radial velocity follow-up from HARPS and high resolution lucky and
adaptive optics imaging obtained using AstraLux and MagAO, respectively. The
host star is a bright (, ), slightly metal poor
([Fe/H] dex) solar analogue located at pc
from Earth, for which we find a radius of
and a mass of . A joint analysis of the
K2 photometry and HARPS radial velocities reveal that the planet is in a
day orbit around its host star, has a radius of
, and a mass of .
Although the data at hand puts the planet in the region of the mass-radius
diagram where we could expect planets with a pure rock (i.e. magnesium
silicate) composition using two-layer models (i.e., between rock/iron and
rock/ice compositions), we discuss more realistic three-layer composition
models which can explain the high density of the discovered exoplanet. The fact
that the planet lies in the boundary between "possibly rocky" and "non-rocky"
exoplanets, makes it an interesting planet for future RV follow-up.Comment: 12 pages, 11 figures. Accepted for publication in Ap
HATS-18 b: An Extreme Short--Period Massive Transiting Planet Spinning Up Its Star
We report the discovery by the HATSouth network of HATS-18 b: a 1.980 +/-
0.077 Mj, 1.337 +0.102 -0.049 Rj planet in a 0.8378 day orbit, around a solar
analog star (mass 1.037 +/- 0.047 Msun, and radius 1.020 +0.057 -0.031 Rsun)
with V=14.067 +/- 0.040 mag. The high planet mass, combined with its short
orbital period, implies strong tidal coupling between the planetary orbit and
the star. In fact, given its inferred age, HATS-18 shows evidence of
significant tidal spin up, which together with WASP-19 (a very similar system)
allows us to constrain the tidal quality factor for Sun-like stars to be in the
range 6.5 <= lg(Q*/k_2) <= 7 even after allowing for extremely pessimistic
model uncertainties. In addition, the HATS-18 system is among the best systems
(and often the best system) for testing a multitude of star--planet
interactions, be they gravitational, magnetic or radiative, as well as planet
formation and migration theories.Comment: Submitted. 12 pages, 9 figures, 5 table
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