In this paper we present the first comprehensive results extracted from the spectroscopic campaigns carried out by the EXPORT (EXoPlanetary Observational Research Team) consortium. During 1998-1999, ...EXPORT carried out an intensive observational effort in the framework of the origin and evolution of protoplanetary systems in order to obtain clues on the evolutionary path from the early stages of the pre-main sequence to stars with planets already formed. The spectral types of 70 stars, and the projected rotational velocities, $v \sin i$, of 45 stars, mainly Vega-type and pre-main sequence, have been determined from intermediate- and high-resolution spectroscopy, respectively. The first part of the work is of fundamental importance in order to accurately place the stars in the HR diagram and determine the evolutionary sequences; the second part provides information on the kinematics and dynamics of the stars and the evolution of their angular momentum. The advantage of using the same observational configuration and methodology for all the stars is the homogeneity of the set of parameters obtained. Results from previous work are revised, leading in some cases to completely new determinations of spectral types and projected rotational velocities; for some stars no previous studies were available.
We present narrow-band red light curves and surface maps of the short-period RS CVn binary system XY UMa, obtained between 1997 January and 2000 March. The light-curve morphology of this system is ...known to vary on time-scales of a few days. We have used eclipse-mapping techniques to map the distribution of cool starspots on the surface of the primary star. The resulting maps show the continued evolution of spot features on time-scales of a few days to a week. By comparison with the images of Collier Cameron & Hilditch, we also find evidence for longer term trends, including a decline to an activity minimum during 1997 and a rise in activity during 1998–2000. We also find marginal evidence from the O–C ephemeris curves for a periodicity and a peak corresponding to the time of activity minimum.
It is well accepted that 'hot Jupiters' did not form in situ, as the temperature in the protoplanetary disc at the radius at which they now orbit would have been too high for planet formation to have ...occurred. These planets, instead, form at larger radii and then move into the region in which they now orbit. The exact process that leads to the formation of these close-in planets is, however, unclear and it seems that there may be more than one mechanism that can produce these short-period systems. Dynamical interactions in multiple-planet systems can scatter planets into highly eccentric orbits which, if the pericentre is sufficiently close to the parent star, can be tidally circularised by tidal interactions between the planet and star. Furthermore, systems with distant planetary or stellar companions can undergo Kozai cycles which can result in a planet orbiting very close to its parent star. However, the most developed model for the origin of short period planets is one in which the planet exchanges angular momentum with the surrounding protoplanetary disc and spirals in towards the central star. In the case of 'hot Jupiters', the planet is expected to open a gap in the disc and migrate through Type II .migration. If this is the dominant mechanism for producing `hot Jupiters' then we would expect the currect properties of observed close-in giant planets to be consistent with an initial population resulting from Type II migration followed by evolution due to tidal interactions with the central star. We consider initial distributions that are consistent with Type II migration and find that after tidal evolution, the final distributions can be consistent with that observed. Our results suggest that a modest initial pile-up at a ~ 0.05 au is required and that the initial eccentricity distribution must peak at e \sim 0.
We report the results of an extended spectropolarimetric and photometric monitoring of the weak-line T Tauri star TAP 26, carried out within the MaTYSSE programme with the ESPaDOnS spectropolarimeter ...at the 3.6 m Canada-France-Hawaii Telescope. Applying Zeeman-Doppler Imaging to our observations, concentrating in 2015 November and 2016 January and spanning 72 d in total, 16 d in 2015 November and 13 d in 2016 January, we reconstruct surface brightness and magnetic field maps for both epochs and demonstrate that both distributions exhibit temporal evolution not explained by differential rotation alone. We report the detection of a hot Jupiter (hJ) around TAP 26 using three different methods, two using Zeeman-Doppler Imaging (ZDI) and one Gaussian-Process Regression (GPR), with a false-alarm probability smaller than 6.10^-4. However, as a result of the aliasing related to the observing window, the orbital period cannot be uniquely determined; the orbital period with highest likelihood is 10.79 +/- 0.14 d followed by 8.99 +/- 0.09 d. Assuming the most likely period, and that the planet orbits in the stellar equatorial plane, we obtain that the planet has a minimum mass M.sin(i) of 1.66 +/- 0.31 M_Jup and orbits at 0.0968 +/- 0.0032 au from its host star. This new detection suggests that disc type II migration is efficient at generating newborn hJs, and that hJs may be more frequent around young T Tauri stars than around mature stars (or that the MaTYSSE sample is biased towards hJ-hosting stars).
We present the discovery of EPIC 228735255b, a P= 6.57 days Jupiter-mass (M\(_P\)=1.019\(\pm\)0.070 M\(_{Jup}\)) planet transiting a V=12.5 (G5-spectral type) star in an eccentric orbit ...(e=\(0.120^{+0.056}_{-0.046}\)) detected using a combination of K2 photometry and ground-based observations. With a radius of 1.095\(\pm\)0.018R\(_{Jup}\) the planet has a bulk density of 0.726\(\pm\)0.062\(\rho_{Jup}\). The host star has a Fe/H of 0.12\(\pm\)0.045, and from the K2 light curve we find a rotation period for the star of 16.3\(\pm\)0.1 days. This discovery is the 9th hot Jupiter from K2 and highlights K2's ability to detect transiting giant planets at periods slightly longer than traditional, ground-based surveys. This planet is slightly inflated, but much less than others with similar incident fluxes. These are of interest for investigating the inflation mechanism of hot Jupiters.
Using the WASP transit survey, we report the discovery of Jupiters, new hot Jupiters, WASP-68 b, WASP-73 b and WASP-88 b. The planet WASP-68 bhas a mass of 0.95 + or - 0.03 M sub(Jup), a radius of ...1.24 sub(-0.06) super(+0.10) R sub(Jup), and orbits a V = 10.7 G0-type star (1.24+ or - 0.03 M sub(middot in circle) 1.69 sub(-0.06) super(+0.11) R sub(middot in circle), T sub(eff) = 5911 + or - 60 K) with a period of 5.084298 + or - 0.000015 days. Its size is typical of hot Jupiters with similar masses. The planet WASP-73 bis significantly more massive (1.88 sub(-0.06) super(+0.07) M sub(Jup)) and slightly larger (1.16 sub(-0.08) super(+0.12) R sub(Jup)) than Jupiter. It orbits a V = 10.5 F9-type star (1.34 sub(-0.04) super(+0.05) M sub(middot in circle) 2.07 sub(-0.08) super(+0.19) R sub(middot in circle),T sub(eff) = 6036 + or - 120 K) every 4.08722 + or - 0.00022 days. Despite its high irradiation (~2.3 x 10 super(9) ergs super(-1) cm super(-2)), WASP-73 b has a high mean density (1.20 sub(-0.30) super(+0.26) rho sub(Jup)) that suggests an enrichment of the planet in heavy elements. The planet WASP-88 bis a 0.56 + or - 0.08 M sub(Jup)hot Jupiter orbiting a V = 11.4 F6-type star (1.45 + or - 0.05 M sub(middot in circle), 2.08 sub(-0.06) super(+0.12) R sub(middot in circle), T sub(eff) = 6431 + or - 130 K) with a period of 4.954000 + or - 0.000019 days. With a radius of 1.70 sub(-0.07) super(+0.13) R sub(Jup), it joins the handful of planets with super-inflated radii. The ranges of ages we determine through stellar evolution modeling are 4.5-7.0 Gyr for WASP-68, 2.8-5.7 Gyr for WASP-73 and 1.8-4.3 Gyr for WASP-88. The star WASP-73 appears to be significantly evolved, close to or already in the subgiant phase. The stars WASP-68 and WASP-88 are less evolved, although in an advanced stage of core H-burning.
We use high quality K2 light curves for hundreds of stars in the Pleiades to understand better the angular momentum evolution and magnetic dynamos of young, low mass stars. The K2 light curves ...provide not only rotational periods but also detailed information from the shape of the phased light curve not available in previous studies. A slowly rotating sequence begins at \((V-K_{\rm s})_0\sim\)1.1 (spectral type F5) and ends at \((V-K_{\rm s})_0\sim\) 3.7 (spectral type K8), with periods rising from \(\sim\)2 to \(\sim\)11 days in that interval. Fifty-two percent of the Pleiades members in that color interval have periods within 30\% of a curve defining the slow sequence; the slowly rotating fraction decreases significantly redward of \((V-K_{\rm s})_0\)=2.6. Nearly all of the slow-sequence stars show light curves that evolve significantly on timescales less than the K2 campaign duration. The majority of the FGK Pleiades members identified as photometric binaries are relatively rapidly rotating, perhaps because binarity inhibits star-disk angular momentum loss mechanisms during pre-main sequence evolution. The fully convective, late M dwarf Pleiades members (5.0 \(<(V-K_{\rm s})_0<\) 6.0) nearly always show stable light curves, with little spot evolution or evidence of differential rotation. During PMS evolution from \(\sim\)3 Myr (NGC2264 age) to \(\sim\)125 Myr (Pleiades age), stars of 0.3 \(M_{\odot}\) shed about half their angular momentum, with the fractional change in period between 3 and 125 Myr being nearly independent of mass for fully convective stars. Our data also suggest that very low mass binaries form with rotation periods more similar to each other and faster than would be true if drawn at random from the parent population of single stars.
Young (125 Myr), populous (\(>\)1000 members), and relatively nearby, the Pleiades has provided an anchor for stellar angular momentum models for both younger and older stars. We used K2 to explore ...the distribution of rotation periods in the Pleiades. With more than 500 new periods for Pleiades members, we are vastly expanding the number of Pleiads with periods, particularly at the low mass end. About 92\% of the members in our sample have at least one measured spot-modulated rotation period. For the \(\sim\)8\% of the members without periods, non-astrophysical effects often dominate (saturation, etc.), such that periodic signals might have been detectable, all other things being equal. We now have an unusually complete view of the rotation distribution in the Pleiades. The relationship between \(P\) and \((V-K_{\rm s})_0\) follows the overall trends found in other Pleiades studies. There is a slowly rotating sequence for \(1.1\lesssim(V-K_{\rm s})_0\lesssim 3.7\), and a primarily rapidly rotating population for \((V-K_{\rm s})_0\gtrsim 5.0\). There is a region in which there seems to be a disorganized relationship between \(P\) and \((V-K_{\rm s})_0\) for \(3.7 \lesssim(V-K_{\rm s})_0\lesssim 5.0\). Paper II continues the discussion, focusing on multi-period structures, and Paper III speculates about the origin and evolution of the period distribution in the Pleiades.
We use K2 to continue the exploration of the distribution of rotation periods in Pleiades that we began in Paper I. We have discovered complicated multi-period behavior in Pleiades stars using these ...K2 data, and we have grouped them into categories, which are the focal part of this paper. About 24% of the sample has multiple, real frequencies in the periodogram, sometimes manifesting as obvious beating in the light curves. Those having complex and/or structured periodogram peaks, unresolved multiple periods, and resolved close multiple periods are likely due to spot/spot group evolution and/or latitudinal differential rotation; these largely compose the slowly rotating sequence in \(P\) vs.~\((V-K_{\rm s})_0\) identified in Paper I. The fast sequence in \(P\) vs.~\((V-K_{\rm s})_0\) is dominated by single-period stars; these are likely to be rotating as solid bodies. Paper III continues the discussion, speculating about the origin and evolution of the period distribution in the Pleiades.
We report the discovery WASP-103b, WASP-103b, a new ultra-short-period planet (P = 22.2 h) transiting a 12.1 V-magnitude F8-type main-sequence star (1.22 + or - 0.04 M sub(+ in circle), 1.44 ...sub(-0.03) super(+0.05) R sub(+ in circle) T sub(eff) = 6110 + or - 160 K). WASP-103 b is significantly more massive (1.49 + or - 0.09 M sub(Jup)) and larger (1.53 sub(-0.07) super(+0.05) R sub(Jup)) than Jupiter. Its large size and extreme irradiation (~ 9 x 10 super(9) ergs super(-1) cm super(-2)) make it an exquisite target for a thorough atmospheric characterization with existing facilities. Furthermore, its orbital distance is less than 20% larger than its Roche radius, meaning that it might be significantly distorted by tides and might experience mass loss through Roche-lobe overflow. It thus represents a new key object for understanding the last stage of the tidal evolution of hot Jupiters.
PDF
