TOI-1055 b: Neptunian planet characterised with HARPS, TESS, and CHEOPS

CONTEXT: TOI-1055 is a Sun-like star known to host a transiting Neptune-sized planet on a 17.5-day orbit (TOI-1055 b). Radial velocity (RV) analyses carried out by two independent groups using nearly the same set of HARPS spectra have provided measurements of planetary masses that differ by ∼2σ. AIMS: Our aim in this work is to solve the inconsistency in the published planetary masses by significantly extending the set of HARPS RV measurements and employing a new analysis tool that is able to account and correct for stellar activity. Our further aim was to improve the precision on measurements of the planetary radius by observing two transits of the planet with the CHEOPS space telescope. METHODS: We fit a skew normal function to each cross correlation function extracted from the HARPS spectra to obtain RV measurements and hyperparameters to be used for the detrending. We evaluated the correlation changes of the hyperparameters along the RV time series using the breakpoint technique. We performed a joint photometric and RV analysis using a Markov chain Monte Carlo scheme to simultaneously detrend the light curves and the RV time series. RESULTS: We firmly detected the Keplerian signal of TOI-1055 b, deriving a planetary mass of Mb = 20.4−2.5+2.6 M⊕ (∼12%). This value is in agreement with one of the two estimates in the literature, but it is significantly more precise. Thanks to the TESS transit light curves combined with exquisite CHEOPS photometry, we also derived a planetary radius of Rb = 3.490−0.064+0.070 R⊕ (∼1.9%). Our mass and radius measurements imply a mean density of ρb = 2.65−0.35+0.37 g cm−3 (∼14%). We further inferred the planetary structure and found that TOI-1055 b is very likely to host a substantial gas envelope with a mass of 0.41−0.20+0.34 M⊕ and a thickness of 1.05−0.29+0.30 R⊕. CONCLUSIONS: Our RV extraction combined with the breakpoint technique has played a key role in the optimal removal of stellar activity from the HARPS time series, enabling us to solve the tension in the planetary mass values published so far for TOI-1055 b

The planetary system around HD 190622 (TOI-1054): Measuring the gas content of low-mass planets orbiting F-stars

Context. Giant planets are known to dominate the long-term stability of planetary systems due to their prevailing gravitational interactions, but they are also thought to play an important role in planet formation. Observational constraints improve our understanding of planetary formation processes such as the delivery of volatile-rich planetesimals from beyond the ice line into the inner planetary system. Additional constraints may come from studies of the atmosphere, but almost all such studies of the atmosphere investigate the detection of certain species, and abundances are not routinely quantitatively measured. Aims. Accurate measurements of planetary bulk parameters-that is, mass and density-provide constraints on the inner structure and chemical composition of transiting planets. This information provides insight into properties such as the amounts of volatile species, which in turn can be related to formation and evolution processes. Methods. The Transiting Exoplanet Survey Satellite (TESS) reported a planetary candidate around HD 190622 (TOI-1054), which was subsequently validated and found to merit further characterization with photometric and spectroscopic facilities. The KESPRINT collaboration used data from the High Accuracy Radial Velocity Planet Searcher (HARPS) to independently confirm the planetary candidate, securing its mass, and revealing the presence of an outer giant planet in the system. The CHEOPS consortium invested telescope time in the transiting target in order to reduce the uncertainty on the radius, improving the characterization of the planet. Results. We present the discovery and characterization of the planetary system around HD 190622 (TOI-1054). This system hosts one transiting planet, which is smaller than Neptune (3.087-0.053+0.058REarth, 7.7 ± 1.0 MEarth) but has a similar bulk density (1.43 ± 0.21 g cm-3) and an orbital period of 16 days; and a giant planet, not known to be transiting, with a minimum mass of 227.0 ± 6.7 MEarth in an orbit with a period of 315 days. Conclusions. Our measurements constrain the structure and composition of the transiting planet. HD 190622b has singular properties among the known population of transiting planets, which we discuss in detail. Among the sub-Neptune-sized planets known today, this planet stands out because of its large gas content

Submillimetre observations of comets with Odin: 2001-2005

The Odin satellite, launched in February 2001, is equipped with a 1.1-m submillimetre telescope. Odin was used to observe the 557 GHz line of water with high spectral resolution in 12 comets between 2001 and 2005. Line shapes and spatial mapping provide information on the anisotropy of the outgassing and constraints on water excitation, enabling accurate measurements of the water production rate. Five comets were regularly observed over periods of more than one month to monitor the variation of their water outgassing rate with heliocentric distance. Observing campaigns have been generally coordinated with ground-based observations of molecular lines at Nançay, CSO or IRAM 30-m telescopes to obtain molecular abundances relative to water. Thanks to Odin's frequency coverage, it was also possible to detect the H 2 18O 548 GHz line, first in comet 153P/Ikeya-Zhang in April 2002 [Lecacheux, A., Biver, N., Crovisier, J. et al., 2003, Observations of water in comets with Odin. Astron. Astrophys. 402, L55-L58.] and then in comets C/2002 T7 (LINEAR), C/2001 Q4 (NEAT) and C/2004 Q2 (Machholz). The 16O/ 18O isotopic ratio (≈ 450) is consistent with the terrestrial value. Ammonia has been searched for in three comets through its J K = 1 0 - 0 0 line at 572 GHz and was tentatively detected in C/2001 Q4 and C/2002 T7. The derived abundances of NH 3 relative to water are 0.5% and 0.3%, respectively, similar to values obtained in other comets with different techniques. © 2006 Elsevier Ltd. All rights reserved.link_to_subscribed_fulltex

Radio observations of Comet 9P/Tempel 1 before and after Deep Impact

Comet 9P/Tempel 1 was the target of a multi-wavelength worldwide investigation in 2005. The NASA Deep Impact mission reached the comet on 4.24 July 2005, delivering a 370-kg impactor which hit the comet at 10.3 km s -1. Following this impact, a cloud of gas and dust was excavated from the comet nucleus. The comet was observed in 2005 prior to and after the impact, at 18-cm wavelength with the Nançay radio telescope, in the millimeter range with the IRAM and CSO radio telescopes, and at 557 GHz with the Odin satellite. OH observations at Nançay provided a 4-month monitoring of the outgassing of the comet from March to June, followed by the observation of H 2O with Odin from June to August 2005. The peak of outgassing was found to be around 1 × 10 28   molec. s -1 between May and July. Observations conducted with the IRAM 30-m radio telescope in May and July 2005 resulted in detections of HCN, CH 3OH and H 2S with classical abundances relative to water (0.12, 2.7 and 0.5%, respectively). In addition, a variation of the HCN production rate with a period of 1.73 ± 0.10 days was observed in May 2005, consistent with the 1.7-day rotation period of the nucleus. The phase of these variations, as well as those of CN seen in July by Jehin et al. [Jehin, E., Manfroid, J., Hutsemékers, D., Cochran, A.L., Arpigny, C., Jackson, W.M., Rauer, H., Schulz, R., Zucconi, J.-M., 2006. Astrophys. J. 641, L145-L148], is consistent with a rotation period of the nucleus of 1.715 days and a strong variation of the outgassing activity by a factor 3 from minimum to maximum. This also implies that the impact took place on the rising phase of the "natural" outgassing which reached its maximum ≈4 h after the impact. Post-impact observations at IRAM and CSO did not reveal a significant change of the outgassing rates and relative abundances, with the exception of CH 3OH which may have been more abundant by up to one order of magnitude in the ejecta. Most other variations are linked to the intrinsic variability of the comet. The Odin satellite monitored nearly continuously the H 2O line at 557 GHz during the 38 h following the impact on the 4th of July, in addition to weekly monitoring. Once the periodic variations related to the nucleus rotation are removed, a small increase of outgassing related to the impact is present, which corresponds to the release of ≈ 5000 ± 2000 tons of water. Two other bursts of activity, also observed at other wavelengths, were seen on 23 June and 7 July; they correspond to even larger releases of gas. © 2006 Elsevier Inc. All rights reserved.link_to_subscribed_fulltex

Observations of water in comets with Odin

The Odin satellite, which can observe the l10-l01 rotational line at 557 GHz of ortho water with a high spectral resolution (80 m s-1) and a spatial resolution of 2.1′, is well suited for cometary studies. The intensity of this line provides an estimate of the water production rate. The line width gives a direct measure of the coma expansion velocity. The line centre position and shape are affected by the anisotropy of the outgassing and by optical depth effects. Comets observed with Odin up to now are C/2001 A2 (LINEAR) during the commissioning phase of the satellite, 19P/Borrelly at the time of the Deep Space 1 flyby, C/2000 WM1 (LINEAR), and 153P/2002 C1 (Ikeya-Zhang). For this last comet, thorough observations were made at the moment of its closest approach to Earth at the end of April 2002. A deep integration resulted in the detection of the l10-l01 line of H2 18O at 548 GHz. No 16O/18O isotopic anomaly is found.link_to_subscribed_fulltex

Odin water mapping in the Orion KL region

New results from water mapping observations of the Orion KL region using the submm/mm wave satellite Odin (2.1′ beam size at 557 GHz), are presented. The ortho-H 2O J K(+)K(-) = l 1.0 → l 0.1 ground state transition was observed in a 7′ × 7′ rectangular grid with a spacing of 1′, while the same line of H 2 18O was measured in two positions, Orion KL itself and 2′ south of Orion KL. In the main water species, the KL molecular outflow is largely resolved from the ambient cloud and it is found to have an extension of 60″-110″. The H 2O outflow profile exhibits a rather striking absorption-like asymmetry at the line centre. Self-absorption in the near (or "blue") part of the outflow (and possibly in foreground quiescent halo gas) is tentatively suggested to play a role here. We argue that the dominant part of the KL H 2 18O outflow emission emanates from the compact (size ∼15″) low-velocity flow and here estimate an H 2O abundance of circa 10 -5 compared to all H 2 in the flow - an order of magnitude below earlier estimates of the H 2O abundance in the shocked gas of the high-velocity flow. The narrow ambient cloud lines show weak velocity trends, both in the N-S and E-W directions. H 2 18O is detected for the first time in the southern position at a level of ∼0.15 K and we here estimate an H 2O abundance of (1-8) × 10 -8.link_to_subscribed_fulltex

Highlights from the first year of Odin observations

Key Odin operational and instrumental features and highlights from our sub-millimetre and millimetre wave observations of H 2O, H 2 18O, NH 3, 15NH 3 and O 2 are presented, with some insights into accompanying Odin Letters in this A&A issue. We focus on new results where Odin's high angular resolution, high frequency resolution, large spectrometer bandwidths, high sensitivity or/and frequency tuning capability are crucial: H 2O mapping of the Orion KL, W3, DR 21, S 140 regions, and four comets; H 2O observations of Galactic Centre sources, of shock enhanced H 2O towards the SNR IC 443, and of the candidate infall source IRAS 16293-2422; H 2 18O detections in Orion KL and in comet Ikeya-Zhang; sub-mm detections of NH 3 in Orion KL (outflow, ambient cloud and bar) and ρ Oph, and very recently, of 15NH 3 in Orion KL. Simultaneous sensitive searches for the 119 GHz line of O 2 have resulted in very low abundance limits, which are difficult to accommodate in chemical models. We also demonstrate, by means of a quantitative comparison of Orion KL H 2O results, that the Odin and SWAS observational data sets are very consistently calibrated.link_to_subscribed_fulltex

The EBLM project-VIII. First results for M-dwarf mass, radius, and effective temperature measurements using CHEOPS light curves

The accuracy of theoretical mass, radius and effective temperature values for M-dwarf stars is an active topic of debate. Differences between observed and theoretical values have raised the possibility that current theoretical stellar structure and evolution models are inaccurate towards the low-mass end of the main sequence. To explore this issue we use the CHEOPS satellite to obtain high-precision light curves of eclipsing binaries with low mass stellar companions. We use these light curves combined with the spectroscopic orbit for the solar-type companion to measure the mass, radius and effective temperature of the M-dwarf star. Here we present the analysis of three eclipsing binaries. We use the pycheops data analysis software to fit the observed transit and eclipse events of each system. Two of our systems were also observed by the TESS satellite -- we similarly analyse these light curves for comparison. We find consistent results between CHEOPS and TESS, presenting three stellar radii and two stellar effective temperature values of low-mass stellar objects. These initial results from our on-going observing programme with CHEOPS show that we can expect to have ~24 new mass, radius and effective temperature measurements for very low mass stars within the next few years

EPOXI: Comet 103P/Hartley 2 observations from a worldwide campaign

Earth- and space-based observations provide synergistic information for space mission encounters by providing data over longer timescales, at different wavelengths and using techniques that are impossible with an in situ flyby. We report here such observations in support of the EPOXI spacecraft flyby of comet 103P/Hartley 2. The nucleus is small and dark, and exhibited a very rapidly changing rotation period. Prior to the onset of activity, the period was 16.4hr. Starting in 2010 August the period changed from 16.6hr to near 19hr in December. With respect to dust composition, most volatiles and carbon and nitrogen isotope ratios, the comet is similar to other Jupiter-family comets. What is unusual is the dominance of CO 2 -driven activity near perihelion, which likely persists out to aphelion. Near perihelion the comet nucleus was surrounded by a large halo of water-ice grains that contributed significantly to the total water production. © 2011. The American Astronomical Society. All rights reserved.