One aim of modern astronomy is to detect temperate, Earth-like exoplanets that are well suited for atmospheric characterization. Recently, three Earth-sized planets were detected that transit (that ...is, pass in front of) a star with a mass just eight per cent that of the Sun, located 12 parsecs away. The transiting configuration of these planets, combined with the Jupiter-like size of their host star-named TRAPPIST-1-makes possible in-depth studies of their atmospheric properties with present-day and future astronomical facilities. Here we report the results of a photometric monitoring campaign of that star from the ground and space. Our observations reveal that at least seven planets with sizes and masses similar to those of Earth revolve around TRAPPIST-1. The six inner planets form a near-resonant chain, such that their orbital periods (1.51, 2.42, 4.04, 6.06, 9.1 and 12.35 days) are near-ratios of small integers. This architecture suggests that the planets formed farther from the star and migrated inwards. Moreover, the seven planets have equilibrium temperatures low enough to make possible the presence of liquid water on their surfaces.
We present preliminary results from our investigation into using an 'inside-out' velocity space for creating a Doppler tomogram. The aim is to transpose the inverted appearance of the Cartesian ...velocity space used in normal Doppler tomography. In a comparison between normal and inside-out Doppler tomograms of cataclysmic variables, we show that the inside-out velocity space has the potential to produce new insights into the accretion dynamics in these systems.
We present the results of applying our inside-out velocity projection and flux modulation mapping techniques to the Doppler tomography of magnetic cataclysmic variables. The inside-out tomogram is ...constructed by directly projecting phase-resolved spectra onto the inside-out framework. In addition, our flux modulation mapping technique extracts any information related to the modulation of the line flux by utilising consecutive half-phase tomograms. We apply this to both the standard and the inside-out techniques. Our test cases, the polars HU Aqr and V834 Cen, and the intermediate polar PQ Gem, were chosen because of their known accretion characteristics, namely ballistic, magnetic and curtain dominated accretion, respectively. In all three cases the inside-out tomogram better exposes low-velocity emission details which are overly compacted in the standard tomogram. This is especially apparent for the mid-inclination V834 Cen where the almost blob-like blended lower velocity emission in the standard tomogram is more exposed in the inside-out tomogram, making it easier to distinguish between the ballistic and magnetically confined accretion flows that are evident in the trailed spectra. Similarly, the inside-out tomogram enhances high velocity emission details which are washed out in the standard tomogram. This is particularly effective in revealing the high velocity magnetic accretion flows in the polars HU Aqr and V834 Cen. The addition of our flux modulation technique gives a significant improvement in reproducing the trailed input spectra adding more confidence to the interpretation of the Doppler maps. Furthermore, amplitude and phase maps are constructed that further reveal amplitude and phasing characteristics of the emission components in the three test cases.
We present phase-resolved spectroscopy, photometry and circular spectropolarimetry of the eclipsing polar UZ Fornacis. Doppler tomography of the strongest emission lines using the inside-out ...projection revealed the presence of three emission regions: from the irradiated face of the secondary star, the ballistic stream and the threading region, and the magnetically confined accretion stream. The total intensity spectrum shows broad emission features and a continuum that rises in the blue. The circularly polarized spectrum shows the presence of three cyclotron emission harmonics at \(\sim\)4500 \AA{}, 6000 \AA{} and 7700 \AA{}, corresponding to harmonic numbers 4, 3, and 2, respectively. These features are dominant before the eclipse and disappear after the eclipse. The harmonics are consistent with a magnetic field strength of \(\sim\)57 MG. We also present phase-resolved circular and linear photopolarimetry to complement the spectropolarimetry around the times of eclipse. MeerKAT radio observations show a faint source which has a peak flux density of 30.7 \(\pm\) 5.4 \(\mu\)Jy/beam at 1.28 GHz at the position of UZ For.
An automated control system was developed for the bench-scale evaluation of continuous catalytic regeneration (CCR) naphtha reforming catalysts. Deactivation of these catalysts is too rapid for fixed ...bed operation, and regenerating the catalyst continually is not feasible on bench scale. To emulate the commercial process, a solution was required which would allow catalyst evaluation at a constant research octane number (iso-RON). Because changes are too fast for manual adjustment (especially when using Fischer–Tropsch naphtha), automated adjustment of process conditions was required. This was achieved through the use of simple matrix algebra, semiautomated gas chromatography and on-line near-infrared (NIR) analyses. Commercial catalysts with very small activity and reformate yield differences, could be compared and their RON versus yield correlations determined. Product samples large enough for engine research octane number (RON) analyses could also be collected at steady state. Through the use of multidisciplinary analytical and advanced process control techniques, substantial improvement of bench-scale piloting methodology in naphtha reforming was obtained.
We report on the first multi-color precision light curve of the bright
Wolf-Rayet binary $\gamma^2$ Velorum, obtained over six months with the
nanosatellites in the BRITE- Constellation fleet. In ...parallel, we obtained 488
high-resolution optical spectra of the system. In this first report on the
datasets, we revise the spectroscopic orbit and report on the bulk properties
of the colliding winds. We find a dependence of both the light curve and excess
emission properties that scales with the inverse of the binary separation. When
analyzing the spectroscopic properties in combination with the photometry, we
find that the phase dependence is caused only by excess emission in the lines,
and not from a changing continuum. We also detect a narrow, high-velocity
absorption component from the He I $\lambda$5876 transition, which appears
twice in the orbit. We calculate smoothed-particle hydrodynamical simulations
of the colliding winds and can accurately associate the absorption from He I to
the leading and trailing arms of the wind shock cone passing tangentially
through our line of sight. The simulations also explain the general strength
and kinematics of the emission excess observed in wind lines such as C III
$\lambda$5696 of the system. These results represent the first in a series of
investigations into the winds and properties of $\gamma^2$ Velorum through
multi-technique and multi-wavelength observational campaigns.
From $5.5$ months of dual-band optical photometric monitoring at the $1$ mmag
level, BRITE-Constellation has revealed two simultaneous types of variability
in the O4I(n)fp star $\zeta$ Puppis: one ...single periodic non-sinusoidal
component superimposed on a stochastic component. The monoperiodic component is
the $1.78$ d signal previously detected by Coriolis/SMEI, but this time along
with a prominent first harmonic. The shape of this signal changes over time, a
behaviour that is incompatible with stellar oscillations but consistent with
rotational modulation arising from evolving bright surface inhomogeneities. By
means of a constrained non-linear light curve inversion algorithm we mapped the
locations of the bright surface spots and traced their evolution. Our
simultaneous ground-based multi-site spectroscopic monitoring of the star
unveiled cyclical modulation of its He II $\lambda4686$ wind emission line with
the $1.78$-day rotation period, showing signatures of Corotating Interaction
Regions (CIRs) that turn out to be driven by the bright photospheric spots
observed by BRITE. Traces of wind clumps are also observed in the He II
$\lambda4686$ line and are correlated with the amplitudes of the stochastic
component of the light variations probed by BRITE at the photosphere,
suggesting that the BRITE observations additionally unveiled the photospheric
drivers of wind clumps in $\zeta$ Pup and that the clumping phenomenon starts
at the very base of the wind. The origins of both the bright surface
inhomogeneities and the stochastic light variations remain unknown, but a
subsurface convective zone might play an important role in the generation of
these two types of photospheric variability.
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