497 research outputs found
Photometric quality of Dome C for the winter 2008 from ASTEP South
ASTEP South is an Antarctic Search for Transiting Exo- Planets in the South
pole field, from the Concordia station, Dome C, Antarctica. The instrument
consists of a thermalized 10 cm refractor observing a fixed 3.88\degree x
3.88\degree field of view to perform photometry of several thousand stars at
visible wavelengths (700-900 nm). The first winter campaign in 2008 led to the
retrieval of nearly 1600 hours of data. We derive the fraction of photometric
nights by measuring the number of detectable stars in the field. The method is
sensitive to the presence of small cirrus clouds which are invisible to the
naked eye. The fraction of night-time for which at least 50% of the stars are
detected is 74% from June to September 2008. Most of the lost time (18.5% out
of 26%) is due to periods of bad weather conditions lasting for a few days
("white outs"). Extended periods of clear weather exist. For example, between
July 10 and August 10, 2008, the total fraction of time (day+night) for which
photometric observations were possible was 60%. This confirms the very high
quality of Dome C for nearly continuous photometric observations during the
Antarctic winter
ASTEP South: An Antarctic Search for Transiting ExoPlanets around the celestial South pole
ASTEP South is the first phase of the ASTEP project (Antarctic Search for
Transiting ExoPlanets). The instrument is a fixed 10 cm refractor with a 4kx4k
CCD camera in a thermalized box, pointing continuously a 3.88 degree x 3.88
degree field of view centered on the celestial South pole. ASTEP South became
fully functional in June 2008 and obtained 1592 hours of data during the 2008
Antarctic winter. The data are of good quality but the analysis has to account
for changes in the point spread function due to rapid ground seeing variations
and instrumental effects. The pointing direction is stable within 10 arcseconds
on a daily timescale and drifts by only 34 arcseconds in 50 days. A truly
continuous photometry of bright stars is possible in June (the noon sky
background peaks at a magnitude R=15 arcsec-2 on June 22), but becomes
challenging in July (the noon sky background magnitude is R=12.5 arcsec?2 on
July 20). The weather conditions are estimated from the number of stars
detected in the field. For the 2008 winter, the statistics are between 56.3 %
and 68.4 % of excellent weather, 17.9 % to 30 % of veiled weather and 13.7 % of
bad weather. Using these results in a probabilistic analysis of transit
detection, we show that the detection efficiency of transiting exoplanets in
one given field is improved at Dome C compared to a temperate site such as La
Silla. For example we estimate that a year-long campaign of 10 cm refractor
could reach an efficiency of 69 % at Dome C versus 45 % at La Silla for
detecting 2-day period giant planets around target stars from magnitude 10 to
15. This shows the high potential of Dome C for photometry and future planet
discoveries. [Short abstract
The GTC exoplanet transit spectroscopy survey IX. Detection of haze, Na, K, and Li in the super-Neptune WASP-127b
Exoplanets with relatively clear atmospheres are prime targets for detailed
studies of chemical compositions and abundances in their atmospheres. Alkali
metals have long been suggested to exhibit broad wings due to pressure
broadening, but most of the alkali detections only show very narrow absorption
cores, probably because of the presence of clouds. We report the strong
detection of the pressure-broadened spectral profiles of Na, K, and Li
absorption in the atmosphere of the super-Neptune WASP-127b, at 4.1,
5.0, and 3.4, respectively. We performed a spectral retrieval
modeling on the high-quality optical transmission spectrum newly acquired with
the 10.4 m Gran Telescopio Canarias (GTC), in combination with the re-analyzed
optical transmission spectrum obtained with the 2.5 m Nordic Optical Telescope
(NOT). By assuming a patchy cloudy model, we retrieved the abundances of Na, K,
and Li, which are super-solar at 3.7 for K and 5.1 for Li (and
only 1.8 for Na). We constrained the presence of haze coverage to be
around 52%. We also found a hint of water absorption, but cannot constrain it
with the global retrieval owing to larger uncertainties in the probed
wavelengths. WASP-127b will be extremely valuable for atmospheric
characterization in the era of James Webb Space Telescope
The secondary eclipses of WASP-19b as seen by the ASTEP 400 telescope from Antarctica
The ASTEP (Antarctica Search for Transiting ExoPlanets) program was
originally aimed at probing the quality of the Dome C, Antarctica for the
discovery and characterization of exoplanets by photometry. In the first year
of operation of the 40 cm ASTEP 400 telescope (austral winter 2010), we
targeted the known transiting planet WASP-19b in order to try to detect its
secondary transits in the visible. This is made possible by the excellent
sub-millimagnitude precision of the binned data. The WASP-19 system was
observed during 24 nights in May 2010. The photometric variability level due to
starspots is about 1.8% (peak-to-peak), in line with the SuperWASP data from
2007 (1.4%) and larger than in 2008 (0.07%). We find a rotation period of
WASP-19 of 10.7 +/- 0.5 days, in agreement with the SuperWASP determination of
10.5 +/- 0.2 days. Theoretical models show that this can only be explained if
tidal dissipation in the star is weak, i.e. the tidal dissipation factor Q'star
> 3.10^7. Separately, we find evidence for a secondary eclipse of depth 390 +/-
190 ppm with a 2.0 sigma significance, a phase consistent with a circular orbit
and a 3% false positive probability. Given the wavelength range of the
observations (420 to 950 nm), the secondary transit depth translates into a day
side brightness temperature of 2690(-220/+150) K, in line with measurements in
the z' and K bands. The day side emission observed in the visible could be due
either to thermal emission of an extremely hot day side with very little
redistribution of heat to the night side, or to direct reflection of stellar
light with a maximum geometrical albedo Ag=0.27 +/- 0.13. We also report a
low-frequency oscillation well in phase at the planet orbital period, but with
a lower-limit amplitude that could not be attributed to the planet phase alone,
and possibly contaminated with residual lightcurve trends.Comment: Accepted for publication in Astronomy and Astrophysics, 13 pages, 13
figure
Multicolour photometry for exoplanet candidate validation
Context. The TESS and PLATO missions are expected to find vast numbers of new
transiting planet candidates. However, only a fraction of these candidates will
be legitimate planets, and the candidate validation will require a significant
amount of follow-up resources. Radial velocity follow-up can be carried out
only for the most promising candidates around bright, slowly rotating, stars.
Thus, before devoting RV resources to candidates, they need to be vetted using
cheaper methods, and, in the cases for which an RV confirmation is not
feasible, the candidate's true nature needs to be determined based on these
alternative methods alone.
Aims. We study the applicability of multicolour transit photometry in the
validation of transiting planet candidates when the candidate signal arises
from a real astrophysical source. We seek to answer how securely can we
estimate the true uncontaminated star-planet radius ratio when the light curve
may contain contamination from unresolved light sources inside the photometry
aperture when combining multicolour transit observations with a physics-based
contamination model.
Methods. The study is based on simulations and ground-based transit
observations. The analyses are carried out with a contamination model
integrated into the PyTransit v2 transit modelling package, and the
observations are carried out with the MuSCAT2 multicolour imager installed in
the 1.5 m TCS in the Teide Observatory.
Results. We show that multicolour transit photometry can be used to estimate
the amount of flux contamination and the true radius ratio. Combining the true
radius ratio with an estimate for the stellar radius yields the true absolute
radius of the transiting object, which is a valuable quantity in statistical
candidate validation, and enough in itself to validate a candidate whose radius
falls below the theoretical lower limit for a brown dwarf.Comment: Accepted to A&
Is the orbit of the exoplanet WASP-43b really decaying? TESS and MuSCAT2 observations confirm no detection
We thank Dr. S. Hoyer from the Laboratoire d'Astrophysique de Marseille (LAM) in France for the helpful discussions. We also thank the anonymous reviewer for the helpful comments and suggestions. This work was supported by the Erasmus+ grant number 2017-1-CZ01-KA203-035562, by the VEGA grant of the Slovak Academy of Sciences number 2/0031/18, by an ESA PRODEX grant under contracting with the ELTE University, by the GINOP number 2.3.2-15-2016-00003 of the Hungarian National Research, Development and Innovation Office, and by the City of Szombathely under agreement number 67.177-21/2016. This paper includes data collected with the TESS mission, obtained from the MAST data archive at the Space Telescope Science Institute (STScI). Funding for the TESS mission is provided by the NASA Explorer Program. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium).Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This article is based on observations made with the MuSCAT2 instrument, developed by ABC, at Telescopio Carlos Sanchez operated on the island of Tenerife by the IAC in the Spanish Observatorio del Teide. This work was partly financed by the Spanish Ministry of Economics and Competitiveness through grant number PGC2018098153-B-C31. This work was partly supported by JSPS KAKENHI grant numbers JP17H04574, JP18H01265 and JP18H05439, and JST PRESTO grant number JPMJPR1775. This work was partly supported by Grant-in-Aid for JSPS Fellows, grant number JP20J21872. TP acknowledges support from the Slovak Research and Development Agency - the contract No. APVV-20-0148. MT was supported by MEXT/JSPS KAKENHI grant numbers 18H05442, 15H02063, and 22000005. AC acknowledges financial support from the State Agency for Research of the Spanish MCIU through the `Center of Excellence Severo Ochoa' award for the Instituto de Astrophysics of Andalusia (SEV-2017-0709). We acknowledge funding from the European Research Council under the European Union's Horizon 2020 research and innovation program under grant agreement number 694513.Up to now, WASP-12b is the only hot Jupiter confirmed to have a decaying orbit. The case of WASP-43b is still under debate. Recent studies preferred or ruled out the orbital decay scenario, but further precise transit timing observations are needed to definitively confirm or refute the period change of WASP-43b. This possibility is given by the Transiting Exoplanet Survey Satellite (TESS) space telescope. In this work, we used the available TESS data, multicolour photometry data obtained with the Multicolor Simultaneous Camera for studying Atmospheres of Transiting exoplanets 2 (MuSCAT2) and literature data to calculate the period change rate of WASP-43b and to improve its precision, and to refine the parameters of the WASP-43 planetary system. Based on the observed-minus-calculated data of 129 mid-transit times in total, covering a time baseline of about 10 yr, we obtained an improved period change rate of (P)over dot = -0.6 +/- 1.2 ms yr(-1) that is consistent with a constant period well within 1 sigma. We conclude that new TESS and MuSCAT2 observations confirm no detection of WASP-43b orbital decay.Erasmus+ grant 2017-1-CZ01-KA203-035562VEGA grant of the Slovak Academy of Sciences 2/0031/18ESA PRODEX grantELTE UniversityNational Research, Development & Innovation Office (NRDIO) - Hungary 2.3.2-15-2016-00003City of Szombathely 67.177-21/2016National Aeronautics & Space Administration (NASA)
NAS 5-26555Gaia Multilateral AgreementSpanish Ministry of Economics and Competitiveness PGC2018098153-B-C31Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT)
Japan Society for the Promotion of Science
Grants-in-Aid for Scientific Research (KAKENHI) JP17H04574
JP18H01265
JP18H05439JST PRESTO grant JPMJPR1775Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT)
Japan Society for the Promotion of Science JP20J21872Slovak Research and Development Agency APVV-20-0148Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT)
Japan Society for the Promotion of Science
Grants-in-Aid for Scientific Research (KAKENHI) 18H05442
15H02063
22000005State Agency for Research of the Spanish MCIU through the 'Center of Excellence Severo Ochoa' award for the Instituto de Astrophysics of Andalusia SEV-2017-0709European Research Council under the European Union's Horizon 2020 research and innovation program 69451
Protein crystals in adenovirus type 5-infected cells: requirements for intranuclear crystallogenesis, structural and functional analysis
Intranuclear crystalline inclusions have been observed in the nucleus of epithelial cells infected with Adenovirus serotype 5 (Ad5) at late steps of the virus life cycle. Using immuno-electron microscopy and confocal microscopy of cells infected with various Ad5 recombinants modified in their penton base or fiber domains, we found that these inclusions represented crystals of penton capsomers, the heteromeric capsid protein formed of penton base and fiber subunits. The occurrence of protein crystals within the nucleus of infected cells required the integrity of the fiber knob and part of the shaft domain. In the knob domain, the region overlapping residues 489–492 in the FG loop was found to be essential for crystal formation. In the shaft, a large deletion of repeats 4 to 16 had no detrimental effect on crystal inclusions, whereas deletion of repeats 8 to 21 abolished crystal formation without altering the level of fiber protein expression. This suggested a crucial role of the five penultimate repeats in the crystallisation process. Chimeric pentons made of Ad5 penton base and fiber domains from different serotypes were analyzed with respect to crystal formation. No crystal was found when fiber consisted of shaft (S) from Ad5 and knob (K) from Ad3 (heterotypic S5-K3 fiber), but occurred with homotypic S3K3 fiber. However, less regular crystals were observed with homotypic S35-K35 fiber. TB5, a monoclonal antibody directed against the Ad5 fiber knob was found by immunofluorescence microscopy to react with high efficiency with the intranuclear protein crystals in situ. Data obtained with Ad fiber mutants indicated that the absence of crystalline inclusions correlated with a lower infectivity and/or lower yields of virus progeny, suggesting that the protein crystals might be involved in virion assembly. Thus, we propose that TB5 staining of Ad-infected 293 cells can be used as a prognostic assay for the viability and productivity of fiber-modified Ad5 vectors
Obliquity measurement and atmospheric characterization of the WASP-74 planetary system
We present new transit observations of the hot Jupiter WASP-74 b
( 1860 K) using the high-resolution spectrograph HARPS-N
and the multi-colour simultaneous imager MuSCAT2. We refine the orbital
properties of the planet and its host star, and measure its obliquity for the
first time. The measured sky-projected angle between the stellar spin-axis and
the planet's orbital axis is compatible with an orbit well-aligned with the
equator of the host star (). We are not
able to detect any absorption feature of H, or any other atomic
spectral features, in its high-resolution transmission spectra due to low S/N
at the line cores. Despite previous claims regarding the presence of strong
optical absorbers such TiO and VO gases in the atmosphere of WASP-74 b, the new
ground-based photometry combined with a reanalysis of previously reported
observations from the literature shows a slope in the low-resolution
transmission spectrum steeper than expected from Rayleigh scattering alone.Comment: Accepted for publication in Astronomy & Astrophysics. 12 pages, 8
figures, 5 table
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