Context. Early observations of comet C/2016 R2 (PanSTARRS) have shown that the composition of this comet is very peculiar. Radio observations have revealed a CO-rich and HCN-poor comet and an optical ...coma dominated by strong emission bands of CO+ and, more surprisingly, N2+ $\mathrm{N_2^+}$ N2+ . Aims. The strong detection of N2+ $\mathrm{N_2^+}$N2+ in the coma of C/2016 R2 provided an ideal opportunity to measure the 14N∕15N isotopic ratio directly from N2+ $\mathrm{N_2^+}$N2+ for the first time, and to estimate the N2∕CO ratio, which is an important diagnostic to constrain formation models of planetesimals, in addition to the more general study of coma composition. Methods. We obtained high resolution spectra of the comet in February 2018 when it was at 2.8 au from the Sun. We used the UVES spectrograph of the European Southern Observatory Very Large Telescope, complemented with narrowband images obtained with the TRAPPIST telescopes. Results. We detect strong emissions from the N2+ $\mathrm{N_2^+}$N2+ and CO+ ions, but also CO2+ $\mathrm{CO_2^+}$CO2+ , emission lines from the CH radical, and much fainter emissions of the CN, C2, and C3 radicals that were not detected in previous observations of this comet. We do not detect OH or H2O+, and we derive an upper limit of the H2O+∕CO+ ratio of 0.4, implying that the comet has a low water abundance. We measure a N2+/CO+ $\mathrm{N_2^+/CO^+}$N2+/CO+ ratio of 0.06 ± 0.01. The non-detection of NH2 indicates that most of the nitrogen content of the comet is in N2. Together with the high N2+/CO+ $\mathrm{N_2^+/CO^+}$N2+/CO+ ratio, this could indicate a low formation temperature of the comet or that the comet is a fragment of a large differentiated Kuiper Belt object. The CO2+/CO+ $\mathrm{CO_2^+/CO^+}$CO2+/CO+ ratio is 1.1 ± 0.3. We do not detect 14N15N+ lines and can only put a lower limit on the 14N∕15N ratio (measured from N2+ $\mathrm{N_2^+}$N2+ ) of about 100, which is compatible with measurements of the same isotopic ratio for NH2 and CN in other comets. Finally, in addition to the OI and CI forbidden lines, we detect for the first time the forbidden nitrogen lines NI doublet at 519.79 and 520.03 nm in the coma of a comet.
We report the discovery of two hot-Jupiter planets, each orbiting one of the stars of a wide binary system. WASP-94A (2MASS 20550794–3408079) is an F8 type star hosting a transiting planet with a ...radius of 1.72 ± 0.06 RJup, a mass of 0.452 ± 0.034 MJup, and an orbital period of 3.95 days. The Rossiter-McLaughlin effect is clearly detected, and the measured projected spin-orbit angle indicates that the planet occupies a retrograde orbit. WASP-94B (2MASS 20550915–3408078) is an F9 stellar companion at an angular separation of 15′′ (projected separation 2700 au), hosting a gas giant with a minimum mass of 0.618 ± 0.028 MJup with a period of 2.008 days, detected by Doppler measurements. The orbital planes of the two planets are inclined relative to each other, indicating that at least one of them is inclined relative to the plane of the stellar binary. These hot Jupiters in a binary system bring new insights into the formation of close-in giant planets and the role of stellar multiplicity.
We report the discovery of the transiting exoplanets WASP-69b, WASP-70Ab and WASP-84b, each of which orbits a bright star (V ~ 10). WASP-69b is a bloated Saturn-mass planet (0.26 MJup, 1.06 RJup) in ...a 3.868-d period around an active, ~1-Gyr, mid-K dwarf. ROSAT detected X-rays 60 plus or minus 27 arcsec from WASP-69. If the star is the source then the planet could be undergoing mass-loss at a rate of ~10... g s-1. This is one to two orders of magnitude higher than the evaporation rate estimated for HD 209458b and HD 189733b, both of which have exhibited anomalously large Lyman ... absorption during transit. WASP-70Ab is a sub-Jupiter-mass planet (0.59 MJup, 1.16 RJup) in a 3.713-d orbit around the primary of a spatially resolved, 9-10-Gyr, G4+K3 binary, with a separation of 3.3 arcsec ( greater than or equal to 800 au). WASP-84b is a sub-Jupiter-mass planet (0.69 MJup, 0.94 RJup) in an 8.523-d orbit around an active, ~1-Gyr, early-K dwarf. Of the transiting planets discovered from the ground to date, WASP-84b has the third-longest period. For the active stars WASP-69 and WASP-84, we pre-whitened the radial velocities using a low-order harmonic series. We found that this reduced the residual scatter more than did the oft-used method of pre-whitening with a fit between residual radial velocity and bisector span. The system parameters were essentially unaffected by pre-whitening. (ProQuest: ... denotes formulae/symbols omitted.)
Aims.
2I/Borisov (hereafter 2I) is the first visibly active interstellar comet observed in the Solar System, allowing us for the first time to sample the composition of a building block from another ...system. We report on the monitoring of 2I with the Ultraviolet-Visual Echelle Spectrograph, the high-resolution optical spectrograph of the ESO Very Large Telescope at Paranal, for four months from November 15, 2019 to March 16, 2020. Our goal is to characterise the activity and composition of 2I with respect to Solar System comets.
Methods.
We collected high-resolution spectra at 12 different epochs from 2.1 au pre-perihelion to 2.6 au post-perihelion.
Results.
On December 24 and 26, 2019, close to perihelion, we detected several OH lines of the 309 nm (0–0) band and derived a water production rate of 2.2 ± 0.2 × 10
26
molecules s
−1
. The three OI forbidden oxygen lines were detected at different epochs and we derived a green-to-red doublet intensity ratio (G/R) of 0.31 ± 0.05 close to perihelion. The NH
2
ortho and para lines from various bands were measured and allowed us to derive an ortho-to-para abundance ratio (OPR) of 3.21 ± 0.15, corresponding to an OPR and spin temperature of ammonia of 1.11 ± 0.08 and 31
−5
+10
K, respectively. These values are consistent with the values usually measured for Solar System comets. Emission lines of the radicals NH (336 nm), CN (388 nm), CH (431 nm), and C
2
(517 nm) were also detected. Several FeI and NiI lines were identified and their intensities were measured to provide a ratio of log (NiI/FeI) = 0.21 ± 0.18, which is in agreement with the value recently found in Solar System comets.
Conclusions.
Our high spectral resolution observations of 2I/Borisov and the associated measurements of the NH
2
OPR and the Ni/Fe abundance ratio are remarkably similar to Solar System comets. Only the G/R ratio is unusually high, but it is consistent with the high abundance ratio of CO/H
2
O found by other investigators.
Abstract
The TRAPPIST-1 planetary system is a favourable target for the atmospheric characterization of temperate earth-sized exoplanets by means of transmission spectroscopy with the forthcoming ...James Webb Space Telescope (JWST). A possible obstacle to this technique could come from the photospheric heterogeneity of the host star that could affect planetary signatures in the transit transmission spectra. To constrain further this possibility, we gathered an extensive photometric data set of 25 TRAPPIST-1 transits observed in the near-IR J band (1.2 μm) with the UKIRT and the AAT, and in the NB2090 band (2.1 μm) with the VLT during the period 2015–18. In our analysis of these data, we used a special strategy aiming to ensure uniformity in our measurements and robustness in our conclusions. We reach a photometric precision of 0.003 (RMS of the residuals), and we detect no significant temporal variations of transit depths of TRAPPIST-1 b, c, e, and g over the period of 3 yr. The few transit depths measured for planets d and f hint towards some level of variability, but more measurements will be required for confirmation. Our depth measurements for planets b and c disagree with the stellar contamination spectra originating from the possible existence of bright spots of temperature 4500 K. We report updated transmission spectra for the six inner planets of the system which are globally flat for planets b and g and some structures are seen for planets c, d, e, and f.
Context. Transmission spectroscopy has proven to be a useful tool for the study of exoplanet atmospheres, because the absorption and scattering signatures of the atmosphere manifest themselves as ...variations in the planetary transit depth. Several planets have been studied with this technique, leading to the detection of a small number of elements and molecules (Na, K, H2O), but also revealing that many planets show flat transmission spectra consistent with the presence of opaque high-altitude clouds. Aims. We apply this technique to the MP = 0.40MJ, Rp = 1.20RJ, P = 2.78 d planet WASP-49b, aiming to characterize its transmission spectrum between 0.73 and 1 ¯m and search for the features of K and H2O. Owing to its density and temperature, the planet is predicted to possess an extended atmosphere and is thus a good target for transmission spectroscopy. Methods. Three transits of WASP-49b have been observed with the FORS2 instrument installed at the VLT/UT1 telescope at the ESO Paranal site. We used FORS2 in MXU mode with grism GRIS_600z, producing simultaneous multiwavelength transit light curves throughout the i′ and z′ bands. We combined these data with independent broadband photometry from the Euler and TRAPPIST telescopes to obtain a good measurement of the transit shape. Strong correlated noise structures are present in the FORS2 light curves, which are due to rotating flat-field structures that are introduced by inhomogeneities of the linear atmospheric dispersion corrector’s transparency. We accounted for these structures by constructing common noise models from the residuals of light curves bearing the same noise structures and used them together with simple parametric models to infer the transmission spectrum. Results. We present three independent transmission spectra of WASP-49b between 0.73 and 1.02 ¯m, as well as a transmission spectrum between 0.65 and 1.02 ¯m from the combined analysis of FORS2 and broadband data. The results obtained from the three individual epochs agree well. The transmission spectrum of WASP-49b is best fit by atmospheric models containing a cloud deck at pressure levels of 1 mbar or lower.
ABSTRACT We report the discovery of three new transiting hot Jupiters by WASP-South together with the TRAPPIST photometer and the Euler/CORALIE spectrograph. WASP-74b orbits a star of V = 9.7, making ...it one of the brighter systems accessible to southern telescopes. It is a 0.95MJup planet with a moderately bloated radius of 1.5 in a 2 day orbit around a slightly evolved F9 star. WASP-83b is a Saturn-mass planet at 0.3 with a radius of 1.0 . It is in a 5 day orbit around a fainter (V = 12.9) G8 star. WASP-89b is a 6 MJup planet in a 3 day orbit with an eccentricity of e = 0.2. It is thus similar to massive, eccentric planets such as XO-3b and HAT-P-2b, except that those planets orbit F stars whereas WASP-89 is a K star. The V = 13.1 host star is magnetically active, showing a rotation period of 20.2 days, while star spots are visible in the transits. There are indications that the planet's orbit is aligned with the stellar spin. WASP-89 is a good target for an extensive study of transits of star spots.
Abstract
Simultaneously to the ESA Rosetta mission, a world-wide ground-based campaign provided measurements of the large scale activity of comet 67P/Churyumov–Gerasimenko through measurement of ...optically active gas species and imaging of the overall dust coma. We present more than 2 yr of observations performed with the FORS2 low-resolution spectrograph at the VLT, TRAPPIST and ACAM at the WHT. We focus on the evolution of the CN production as a tracer of the comet activity. We find that it is asymmetric with respect to perihelion and different from that of the dust. The CN emission is detected for the first time at 1.34 au pre-perihelion and production rates then increase steeply to peak about 2 weeks after perihelion at (1.00 ± 0.10) × 1025 molecules s−1, while the post-perihelion decrease is more shallow. The evolution of the comet activity is strongly influenced by seasonal effects with enhanced CN production when the Southern hemisphere is illuminated.
We report the discovery of the transiting exoplanets WASP-95b, WASP-96b, WASP-97b, WASP-98b, WASP-99b, WASP-100b and WASP-101b. All are hot Jupiters with orbital periods in the range 2.1-5.7 d, ...masses of 0.5-2.8 ... and radii of 1.1-1.4 ... The orbits of all the planets are compatible with zero eccentricity. WASP-99b produces the shallowest transit yet found by WASP-South, at 0.4 per cent. The host stars are of spectral type F2-G8. Five have metallicities of Fe/H from -0.03 to +0.23, while WASP-98 has a metallicity of -0.60, exceptionally low for a star with a transiting exoplanet. Five of the host stars are brighter than V = 10.8, which significantly extends the number of bright transiting systems available for follow-up studies. WASP-95 shows a possible rotational modulation at a period of 20.7 d. We discuss the completeness of WASP survey techniques by comparing to the HATnet project. (ProQuest: ... denotes formulae/symbols omitted.)
We present the results of intense photometric monitoring in the near-infrared (~0.9 μm) with the TRAPPIST robotic telescope of the newly discovered binary brown dwarf WISE J104915.57-531906.1, the ...third closest system to the Sun at a distance of only 2 pc. Our twelve nights of time-series photometry reveal a quasi-periodic (P = 4.87 ± 0.01h) variability with a maximum peak-peak amplitude of ~11% and strong night-to-night evolution. We attribute this variability to the rotational modulation of fast-evolving weather patterns in the atmosphere of the coolest component (~T1-type) of the binary. No periodic signal is detected for the hottest component (~L8-type). For both brown dwarfs, our data allow us to firmly discard any unique transit during our observations for planets ≥2 R⊕. For orbital periods smaller than ~9.5 h, transiting planets are excluded down to an Earth-size.
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