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High-resolution Doppler spectroscopy provides an avenue to study the atmosphere of both transiting and non-transiting planets. This powerful method has also yielded some of the most robust atmospheric detections to date. Currently, high-resolution Doppler spectroscopy detects atmospheric signals by cross-correlating observed data with a model atmospheric spectrum. This technique has been successful in detecting various molecules such as H2O, CO, HCN, and TiO, as well as several atomic species. Here, we present an alternative method of performing high-resolution Doppler spectroscopy, using a technique known as Doppler tomography. We present an analysis of HD 179949 b using Doppler tomography and provide Doppler tomograms confirming previous detections of CO at 2.3 μ m and H2O at both 2.3 and 3.5 μ m within the atmosphere of HD 179949 b, showing significantly lower background noise levels when compared to cross-correlation methods applied to the same data. We also present a novel detection of H2O at 2.1 μ m as well as a tentative detection of CO on the night side of the planet at 2.3 μ m. This represents the first observational evidence for molecular absorption in the night-side emission spectrum of an exoplanet using Doppler spectroscopy. [ABSTRACT FROM AUTHOR]

We analyse Sector 20 TESS photometry of the ultra-hot Jupiter WASP -12b, and extract its phase curve to study the planet's atmospheric properties. We successfully recover the phase curve with an amplitude of 549 ± 62 ppm, and a secondary eclipse depth of 609 |$^{+74}_{-73}$| ppm. The peak of the phase curve is shifted by 0.049 ± 0.015 in phase, implying that the brightest spot in the atmosphere is shifted from the substellar point towards the planet's evening terminator. Assuming zero albedo, the eclipse depth infers a day-side brightness temperature of 3128 |$^{+64}_{-68}$|  K. No significant detection of flux from the night-side is found at 60 ± 97 ppm, implying a night-side brightness temperature of <2529 K (1-σ). We do not detect any significant variability in the light from the planet over the ∼27 d of the TESS observations. Finally, we note that an ephemeris model taking orbital decay into account provides a significantly better fit than a constant-period model. [ABSTRACT FROM AUTHOR]

High-resolution Doppler spectroscopy is a powerful tool for identifying molecular species in the atmospheres of both transiting and non-transiting exoplanets. Currently, such data are analysed using cross-correlation techniques to detect the Doppler shifting signal from the orbiting planet. In this paper we demonstrate that, compared to cross-correlation methods currently used, the technique of Doppler tomography has improved sensitivity in detecting the subtle signatures expected from exoplanet atmospheres. This is partly due to the use of a regularizing statistic, which acts to suppress noise, coupled to the fact that all the data is fit simultaneously. In addition, we show that the technique can also effectively suppress contaminating spectral features that may arise due to overlapping lines, repeating line patterns, or the use of incorrect linelists. These issues can confuse conventional cross-correlation approaches, primarily due to aliasing issues inherent in such techniques, whereas Doppler tomography is less susceptible to such effects. In particular, Doppler tomography shows exceptional promise for simultaneously detecting multiple line species (e.g. isotopologues), even when there are high contrasts between such species – and far outperforms current cross-correlation function (CCF) in this respect. Finally, we demonstrate that Doppler tomography is capable of recovering molecular signals from exoplanets using real data, by confirming the strong detection of CO in the atmosphere of τ Boo b. We recover a signal with a planetary radial velocity semi-amplitude K p = 109.6 ± 2.2 km s−1, in excellent agreement with the previously reported value of 110.0 ± 3.2 km s−1. [ABSTRACT FROM AUTHOR]

PDS 110 is a young disc-hosting star in the Orion OB1A association. Two dimming events of similar depth and duration were seen in 2008 (WASP) and 2011 (KELT), consistent with an object in a closed periodic orbit. In this paper, we present data from a ground-based observing campaign designed to measure the star both photometrically and spectroscopically during the time of predicted eclipse in 2017 September. Despite high-quality photometry, the predicted eclipse did not occur, although coherent structure is present suggesting variable amounts of stellar flux or dust obscuration. We also searched for radial velocity (RV) oscillations caused by any hypothetical companion and can rule out close binaries to 0.1 M s. A search of Sonneberg plate archive data also enabled us to extend the photometric baseline of this star back more than 50 yr, and similarly does not re-detect any deep eclipses. Taken together, they suggest that the eclipses seen in WASP and KELT photometry were due to aperiodic events. It would seem that PDS 110 undergoes stochastic dimmings that are shallower and of shorter duration than those of UX Ori variables, but may have a similar mechanism. [ABSTRACT FROM AUTHOR]

We have discovered a new, near-equal-mass, eclipsing M dwarf binary from the Next Generation Transit Survey. This system is only one of three field-age (>1 Gyr), late M dwarf eclipsing binaries known, and has a period of 1.74774 d, similar to that of CM Dra and KOI126. Modelling of the eclipses and radial velocities shows that the component masses are M pri= |$0.17391 ^{+0.00153}_{-0.00099}$| M⊙, M sec= |$0.17418 ^{+0.00193}_{-0.00059}$| M⊙; and the radii are R pri= |$0.2045 ^{+0.0038}_{-0.0058}$| R⊙, R sec= |$0.2168 ^{+0.0047}_{-0.0048}$| R⊙. The effective temperatures are |$T_{\rm pri}=2995\, ^{+85}_{-105}$| K and |$T_{\rm sec}=2997\, ^{+66}_{-101}$| K, consistent with M5 dwarfs and broadly consistent with main-sequence models. This pair represents a valuable addition that can be used to constrain the mass–radius relationship at the low-mass end of the stellar sequence. [ABSTRACT FROM AUTHOR]

Detailed knowledge of stellar activity is crucial for understanding stellar dynamos, as well as pushing exoplanet radial-velocity detection limits towards Earth analogue confirmation. We directly compare archival High Accuracy Radial velocity Planet Searcher spectra taken at the minimum in α Cen B's activity cycle to a high-activity state when clear rotational modulation of logR' HK is visible. Relative to the inactive spectra, we find a large number of narrow pseudo-emission features in the active spectra with strengths that are rotationally modulated. These features most likely originate from plage, spots or a combination of both. They also display radial velocity variations of ~300 m s-1 - consistent with an active region rotating across the stellar surface. Furthermore, we see evidence that some of the lines originating from the 'active immaculate' photosphere appear broader relative to the 'inactive immaculate' case. This may be due to enhanced contributions of, for example, magnetic bright points to these lines, which then causes additional line broadening. More detailed analysis may enable measurements of plage and spot coverage using single spectra in the future. [ABSTRACT FROM AUTHOR]

Context. Recently, there have been a series of detections of molecules in the atmospheres of extrasolar planets using high spectral resolution (R ~ 100 000) observations, mostly using the CRyogenic high-resolution InfraRed Echelle Spectrograph (CRIRES) on the Very Large Telescope. These measurements are able to resolve molecular bands into individual absorption lines. Observing many lines simultaneously as their Doppler shift changes with time allows the detection of specific molecules in the atmosphere of the exoplanet. Aims. We aim to identify new ways of increasing the planet signal in these kinds of high-resolution observations. First of all, we wish to determine what wavelength settings can best be used to target certain molecules. Furthermore, we want to simulate exoplanet spectra of the day-side and night-side to see whether night-side observations are feasible at high spectral resolution. Methods. We performed simulations of high-resolution CRIRES observations of a planet's thermal emission and transit between 1 and 5 µm and performed a cross-correlation analysis on these results to assess how well the planet signal can be extracted. These simulations take into account telluric absorption, sky emission, realistic noise levels, and planet-to-star contrasts. We also simulated day-side and night-side spectra at high spectral resolution for planets with and without a day-side temperature inversion, based on the cases of HD 189733b and HD 209458b. Results. Several small wavelength regions in the L-band promise to yield cross-correlation signals from the thermal emission of hot Jupiters of H2O, CH4, CO2, C2H2, and HCN that can exceed those of the current detections by up to a factor of 2-3 for the same integration time. For transit observations, the H-band is also attractive, with the H, K, and L-bands giving cross-correlation signals of similar strength. High-resolution night-side spectra of hot Jupiters can give cross-correlation signals as high as the day-side, or even higher. Conclusions. We show that there are many new possibilities for high-resolution observations of exoplanet atmospheres that have expected planet signals at least as high as those already detected. Hence, high-resolution observations at well-chosen wavelengths and at different phases can improve our knowledge about hot Jupiter atmospheres significantly, already with currently available instrumentation. [ABSTRACT FROM AUTHOR]

We investigate the atmosphere of GJ1214b, a transiting super-Earth planet with a low mean density, by measuring its transit depth as a function of wavelength in the blue optical portion of the spectrum. It is thought that this planet is either a mini-Neptune, consisting of a rocky core with a thick, hydrogen-rich atmosphere, or a planet with a composition dominated by water. Most observations favor a water-dominated atmosphere with a small scale-height, however, some observations indicate that GJ1214b could have an extended atmosphere with a cloud layer muting the molecular features. In an atmosphere with a large scale-height, Rayleigh scattering at blue wavelengths is likely to cause a measurable increase in the apparent size of the planet toward the blue. We observed the transit of GJ1214b in the B band with the FOcal Reducing Spectrograph at the Very Large Telescope and in the g band with both ACAM on the William Herschel Telescope (WHT) and the Wide Field Camera at the Isaac Newton Telescope (INT).We find a planet-to-star radius ratio in the B band of 0.1162 ± 0.0017, and in the g band 0.1180 ± 0.0009 and 0.1174 ± 0.0017 for the WHT and INT observations, respectively. These optical data do not show significant deviations from previous measurements at longer wavelengths. In fact, a flat transmission spectrum across all wavelengths best describes the combined observations. When atmospheric models are considered, a small scale-height water-dominated model fits the data best. [ABSTRACT FROM AUTHOR]

In this paper, we present ground-based high-resolution spectroscopy of 51 Pegasi using CRIRES at the Very Large Telescope. The system was observed for 3 × 5 hr at 2.3 μm at a spectral resolution of R = 100,000, targeting potential signatures from carbon monoxide, water vapor, and methane in the planet's dayside spectrum. In the first 2 × 5 hr of data, we find a combined signal from carbon monoxide and water in absorption at a formal 5.9σ confidence level, indicating a non-inverted atmosphere. We derive a planet mass of MP = (0.46 ± 0.02)MJup and an orbital inclination i between 79. ° 6 and 82. ° 2, with the upper limit set by the non-detection of the planet transit in previous photometric monitoring. However, there is no trace of the signal in the final five hours of data. A statistical analysis indicates that the signal from the first two nights is robust, but we find no compelling explanation for its absence in the final night. The latter suffers from stronger noise residuals and greater instrumental instability than the first two nights, but these cannot fully account for the missing signal. It is possible that the integrated dayside emission from 51 Peg b is instead strongly affected by weather. However, more data are required before we can claim any time variability in the planet's atmosphere. [ABSTRACT FROM AUTHOR]

Context. One of the biggest challenges facing large transit surveys is the elimination of false-positives from the vast number of transit candidates. A large amount of expensive follow-up time is spent on verifying the nature of these systems. Aims. We investigate to what extent information from the lightcurves can identify blend scenarios and eliminate them as planet candidates, to significantly decrease the amount of follow-up observing time required to identify the true exoplanet systems. Methods. If a lightcurve has a sufficiently high signal-to-noise ratio, a distinction can be made between the lightcurve of a stellar binary blended with a third star and the lightcurve of a transiting exoplanet system. We first simulate lightcurves of stellar blends and transiting planet systems to determine what signal-to-noise level is required to make the distinction between blended and non-blended systems as function of transit depth and impact parameter. Subsequently we test our method on real data from the first IRa01 field observed by the CoRoT satellite, concentrating on the 51 candidates already identified by the CoRoT team. Results. Our simulations show that blend scenarios can be constrained for transiting systems at low impact parameters. At high impact parameter, blended and non-blended systems are indistinguishable from each other because they both produce V-shaped transits. About 70% of the planet candidates in the CoRoT IRa01 field are best fit with an impact parameter of b > 0.85, while less than 15% are expected in this range considering random orbital inclinations. By applying a cut at b < 0.85, meaning that ∼15% of the potential planet population would be missed, the candidate sample decreases from 41 to 11. The lightcurves of 6 of those are best fit with such low host star densities that the planet-to-star size ratii imply unrealistic planet radii of R > 2 RJup. Two of the five remaining systems, CoRoT1b and CoRoT4b, have been identified as planets by the CoRoT team, for which the lightcurves alone rule out blended light at 14% (2σ) and 31% (2σ). One system possesses a M-dwarf secondary, one a candidate Neptune. Conclusions. We show that in the first CoRoT field, IRa01, 85% of the planet candidates can be rejected from the lightcurves alone, if a cut in impact parameter of b < 0.85 is applied, at the cost of a <15% loss in planet yield. We propose to use this method on the Kepler database to study the fraction of real planets and to potentially increase the efficiency of follow-up [ABSTRACT FROM AUTHOR]

Context. GJ 1214b, the 6.55 Earth-mass transiting planet recently discovered by the MEarth team, has a mean density of ∼35% of that of the Earth. It is thought that this planet is either a mini-Neptune, consisting of a rocky core with a thick, hydrogen-rich atmosphere, or a planet with a composition dominated by water. Aims. In the case of a hydrogen-rich atmosphere, molecular absorption and scattering processes may result in detectable radius variations as a function of wavelength. The aim of this paper is to measure these variations. Methods. We have obtained observations of the transit of GJ 1214b in the r- and I-band with the Isaac Newton Telescope (INT), in the g-, r-, i- and z-bands with the 2.2 m MPI/ESO telescope, in the Ks-band with the Nordic Optical Telescope (NOT), and in the Kc-band with the William Herschel Telescope (WHT). By comparing the transit depth between the the different bands, which is a measure for the planet-to-star size ratio, the atmosphere is investigated. Results. We do not detect clearly significant variations in the planet-to-star size ratio as function of wavelength. Although the ratio at the shortest measured wavelength, in g-band, is 2σ larger than in the other bands. The uncertainties in the Ks and Kc bands are large, due to systematic features in the light curves. Conclusions. The tentative increase in the planet-to-star size ratio at the shortest wavelength could be a sign of an increase in the effective planet-size due to Rayleigh scattering, which would require GJ 1214b to have a hydrogen-rich atmosphere. If true, then the atmosphere has to have both clouds, to suppress planet-size variations at red optical wavelengths, as well as a sub-solar metallicity, to suppress strong molecular features in the near- and mid-infrared. However, star spots, which are known to be present on the hoststar's surface, can (partly) cancel out the expected variations in planet-to-star size ratio, because the lower surface temperature of the spots causes the effective size of the star to vary with wavelength. A hypothetical spot-fraction of ∼10%, corresponding to an average stellar dimming of ∼5% in the i-band, would be able to raise the near- and mid-infrared points sufficiently with respect to the optical measurements to be inconsistent with a water-dominated atmosphere. Modulation of the spot fraction due to the stellar rotation would in such case cause the observed flux variations of GJ 1214 [ABSTRACT FROM AUTHOR]

We present two separate ground-based detections of sodium in the transmission spectrum of HD 209458b. First we reanalyzed an archival data set from the HDS spectrograph on Subaru, which shows sodium at a >5σ level. Secondly, our preliminary results of a UVES/VLT data set indicate sodium absorption at a similar level, although the data cover the eclipse only partially. Both results are fully consistent with the HST results of Charbonneau et al. (2002). The Na D absorption feature seems to be resolved in the narrowest passband. [ABSTRACT FROM PUBLISHER]

High-precision photometry of transiting exoplanet systems has contributed significantly to our understanding of the properties of their atmospheres. The best targets are the bright exoplanet systems, for which the high number of photons allow very high signal-to-noise ratios. Most of the current instruments are not optimised for these high-precision measurements, either they have a large read-out overhead to reduce the readnoise and/or their field-of-view is limited, preventing simultaneous observations of both the target and a reference star. Recently we have proposed a new wide-field imager for the Observatoir de Mont-Megantic optimised for these bright systems (PI: Jayawardhana). The instruments has a dual beam design and a field-of-view of 17' by 17'. The cameras have a read-out time of 2 seconds, significantly reducing read-out overheads. Over the past years we have obtained significant experience with how to reach the high precision required for the characterisation of exoplanet atmospheres. Based on our experience we provide the following advice: Get the best calibrations possible. In the case of bad weather, characterise the instrument (e.g. non-linearity, dome flats, bias level), this is vital for better understanding of the science data. Observe the target for as long as possible, the out-of-transit baseline is as important as the transit/eclipse itself. A short baseline can lead to improperly corrected systematic and mis-estimation of the red-noise. Keep everything (e.g. position on detector, exposure time) as stable as possible. Take care that the defocus is not too strong. For a large defocus, the contribution of the total flux from the sky-background in the aperture could well exceed that of the target, resulting in very strict requirements on the precision at which the background is measured.

The Multi-site All-Sky CAmeRA, MASCARA, is an instrument currently in the design phase, that is aimed to find the brightest transiting planet systems in the sky. It will consist of several stations across the globe, each monitoring the near-entire sky using a battery of CCD-detectors plus wide-field lenses, targeting stars in the V = 4 − 8 magnitude range. MASCARA will be able to detect individual transits from Jupiter-size planets over this whole magnitude range, while smaller planets will be found by co-adding transit events. We expect to discover up to a dozen bright transit systems in this way. These will be extremely valuable for atmospheric follow-up studies.

We present a novel, to the best of our knowledge, remote gas detection and identification technique based on correlation spectroscopy with a piezoelectric tunable fiber-optic Fabry-Perot filter. We show that the spectral correlation amplitude between the filter transmission window and gas absorption features is related to the gas absorption optical depth, and that different gases can be distinguished from one another using their correlation signal phase. Using a previously captured telluric-corrected high-resolution near-infrared spectrum of Venus, we show that the radial velocity of Venus can be extracted from the phase of higher order harmonic lock-in signals. This correlation spectroscopy technique has applications in the detection and radial velocity determination of weak spectral features in astronomy and remote sensing. We experimentally demonstrate a remote C O 2 detection system using a lock-in amplifier, fiber-optic Fabry-Perot filter, and single channel avalanche photodiode.

We present a summary of the campaign of remote observations that supported the European Space Agency's Rosetta mission. Telescopes across the globe (and in space) followed comet 67P/Churyumov-Gerasimenko from before Rosetta's arrival until nearly the end of the mission in September 2016. These provided essential data for mission planning, large-scale context information for the coma and tails beyond the spacecraft and a way to directly compare 67P with other comets. The observations revealed 67P to be a relatively 'well-behaved' comet, typical of Jupiter family comets and with activity patterns that repeat from orbit to orbit. Comparison between this large collection of telescopic observations and the in situ results from Rosetta will allow us to better understand comet coma chemistry and structure. This work is just beginning as the mission ends-in this paper, we present a summary of the ground-based observations and early results, and point to many questions that will be addressed in future studies.This article is part of the themed issue 'Cometary science after Rosetta'., (© 2017 The Author(s).)