For the past six years we have carried out a search for massive planets around main sequence and evolved stars in the open cluster M 67, using radial velocity (RV) measurements obtained with HARPS at ...ESO (La Silla), SOPHIE at OHP and HRS at HET. Additional RV data come from CORALIE at the Euler Swiss Telescope. We aim to perform a long-term study on giant planet formation in open clusters and determine how it depends on stellar mass and chemical composition. We report the detection of three new extrasolar planets: two in orbit around the two G dwarfs YBP1194 and YBP1514, and one around the evolved star S364. The orbital solution for YBP1194 yields a period of 6.9 days, an eccentricity of 0.24, and a minimum mass of 0.34 MJup. YBP1514 shows periodic RV variations of 5.1 days, a minimum mass of 0.40 MJup, and an eccentricity of 0.39. The best Keplerian solution for S364 yields a period of 121.7 days, an eccentricity of 0.35 and a minimum mass of 1.54 MJup. An analysis of Hα core flux measurements as well as of the line bisectors spans revealed no correlation with the RV periods, indicating that the RV variations are best explained by the presence of a planetary companion. Remarkably, YBP1194 is one of the best solar twins identified so far, and YBP1194b is the first planet found around a solar twin that belongs to a stellar cluster. In contrast with early reports and in agreement with recent findings, our results show that massive planets around stars of open clusters are as frequent as those around field stars.
In preparation to make the most of our own planned James Webb Space Telescope investigations, we take advantage of publicly available calibration and early‐science observations to independently ...derive and test a geometric‐distortion solution for NIRCam detectors. Our solution is able to correct the distortion to better than ∼$$ \sim $$0.2 mas. Current data indicate that the solution is stable and constant over the investigated filters, temporal coverage, and even over the available filter combinations. We successfully tested our geometric‐distortion solution in three cases: (i) field‐object decontamination of M 92 field; (ii) estimate of internal proper motions of M 92; and (iii) measurement of the internal proper motions of the Large Magellanic Cloud system. To our knowledge, the here‐derived geometric‐distortion solution for NIRCam is the best available and we publicly release it, as many other investigations could potentially benefit from it. Along with our geometric‐distortion solution, we also release a Python tool to convert the raw‐pixels coordinates of each detector into distortion‐free positions, and also to put all the ten detectors of NIRCam into a common reference system.
Abstract
We have constructed the most comprehensive catalog of photometry and proper motions ever assembled for a globular cluster (GC). The core of
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Cen has been imaged over 650 times through ...WFC3's UVIS and IR channels for the purpose of detector calibration. There exist from 4 to over 60 exposures through each of 26 filters stretching continuously from F225W in the UV to F160W in the infrared. Furthermore, the 11 yr baseline between these data and a 2002 ACS survey has allowed us to more than double the proper-motion accuracy and triple the number of well-measured stars compared to our previous groundbreaking effort. This totally unprecedented complete spectral coverage of over 470,000 stars within the cluster’s core, from the tip of the red giant branch down to the white dwarfs, provides the best astro-photometric observational database yet to understand the multiple-population phenomenon in any GC. In this first paper of the series, we describe in detail the data-reduction processes and deliver the astro-photometric catalog to the astronomical community.
In this paper, we combine Wide Field Camera3/UVIS F275W, F336W, and F438W data from the ‘UV Legacy Survey of Galactic Globular Clusters: Shedding Light on Their Populations and Formation’ (GO 13297) ...Hubble Space Telescope Treasury programme with F606W, F625W, F658N, and F814W Advanced Camera for Surveys archive data for a multiwavelength study of the globular cluster NGC 6352. In the colour–magnitude and two-colour diagrams obtained with appropriate combination of the photometry in the different bands, we separate two distinct stellar populations and trace them from the main sequence to the subgiant, red giant, horizontal and asymptotic giant branches. We infer that the two populations differ in He by ΔY = 0.029 ± 0.006. With a new method, we also estimate the age difference between the two sequences. Assuming no difference in Fe/H and α/Fe, and the uncertainties on ΔY, we found a difference in age between the two populations of 10 ± 120 Myr. If we assume Fe/H and α/Fe differences of 0.02 dex (well within the uncertainties of spectroscopic measurements), the total uncertainty in the relative age rises to ∼300 Myr.
Accurate photometry with HSTs ACS shows that the main sequence (MS) of the globular cluster NGC 2808 splits into three separate branches. The three MS branches may be associated with the complexities ...of the cluster's horizontal branch and of its abundance distribution. We attribute the MS branches to successive rounds of star formation, with different helium abundances; we discuss possible sources of helium enrichment. Some other massive globulars also appear to have complex populations; we compare them with NGC 2808.
We use high-precision photometry of red-giant-branch (RGB) stars in 57 Galactic globular clusters (GCs), mostly from the 'Hubble Space Telescope (HST) UV Legacy Survey of Galactic GCs', to identify ...and characterize their multiple stellar populations. For each cluster the pseudo-two-colour diagram (or 'chromosome map') is presented, built with a suitable combination of stellar magnitudes in the F275W, F336W, F438W, and F814W filters that maximizes the separation between multiple populations. In the chromosome map of most GCs (type-I clusters), stars separate in two distinct groups that we identify with the first (1G) and the second generation (2G). This identification is further supported by noticing that 1G stars have primordial (oxygen-rich, sodium-poor) chemical composition, whereas 2G stars are enhanced in sodium and depleted in oxygen. This 1G-2G separation is not possible for a few GCs where the two sequences have apparently merged into an extended, continuous sequence. In some GCs (type-II clusters) the 1G and/or the 2G sequences appear to be split, hence displaying more complex chromosome maps. These clusters exhibit multiple subgiant branches (SGBs) also in purely optical colour-magnitude diagrams, with the fainter SGB joining into a red RGB which is populated by stars with enhanced heavy-element abundance. We measure the RGB width by using appropriate colours and pseudo-colours. When the metallicity dependence is removed, the RGB width correlates with the cluster mass. The fraction of 1G stars ranges from ~8 per cent to ~67 per cent and anticorrelates with the cluster mass, indicating that incidence and complexity of the multiple population phenomenon both increase with cluster mass.
In this work, we keep pushing K2 data to a high photometric precision, close to that of the Kepler main mission, using a point-spread function (PSF)-based, neighbour-subtraction technique, which also ...overcome the dilution effects in crowded environments. We analyse the open cluster M 44 (NGC 2632), observed during the K2 Campaign 5, and extract light curves of stars imaged on module 14, where most of the cluster lies. We present two candidate exoplanets hosted by cluster members and five by field stars. As a by-product of our investigation, we find 1680 eclipsing binaries and variable stars, 1071 of which are new discoveries. Among them, we report the presence of a heartbeat binary star. Together with this work, we release to the community a catalogue with the variable stars and the candidate exoplanets found, as well as all our raw and detrended light curves.
In the last few years many globular clusters (GCs) have revealed complex color-magnitude diagrams, with the presence of multiple main sequences (MSs), broad or multiple sub-giant branches (SGBs) and ...MS turnoffs, and broad or split red giant branches (RGBs). After a careful correction for differential reddening, high-accuracy photometry with the Hubble Space Telescope (HST) presented in this paper reveals a broadened or even split SGB in five additional Milky Way GCs; NGC 362, NGC 5286, NGC 6656, NGC 6715, and NGC 7089. In addition, we confirm (with new and archival HST data) the presence of a split SGB in 47 Tue, NGC 1851, and NGC 6388. The fraction of faint SGB stars with respect to the entire SGB population varies from one cluster to another and ranges from ~0.03 for NGC 362 to ~4).50 for NGC 6715. The average magnitude difference between the bright SGB and the faint SGB is almost the same at different wavelengths. This peculiarity is consistent with the presence of two groups of stars with either an age difference of about 1-2 Gyr or a significant difference in their overall C+N+O content.
Aims.In this paper we derive the structure of the Galactic stellar warp and flare. Methods.We use 2MASS red clump and red giant stars, selected at mean and fixed heliocentric distances of ...$R_{\odot}\simeq3$, 7 and 17 kpc. Results.Our results can be summarized as follows: (i) a clear stellar warp signature is derived for the 3 selected rings, proving that the warp starts already within the solar circle; (ii) the derived stellar warp is consistent (both in amplitude and phase-angle) with that for the Galactic interstellar dust and neutral atomic hydrogen; (iii) the consistency and regularity of the stellar-gaseous warp is traced out to about $R_{\rm GC}\sim20$ kpc; (iv) the Sun seems not to fall on the line of nodes. The stellar warp phase-angle orientation ($\phi\sim15^{\circ}$) is close to the orientation angle of the Galactic bar and this, most importantly, produces an asymmetric warp for the inner $R_{\odot}\simeq3$ and 7 kpc rings; (v) a Northern/Southern warp symmetry is observed only for the ring at $R_{\odot}\simeq17$ kpc, at which the dependency on ϕ is weakened; (vi) treating a mixture of thin and thick disk stellar populations, we trace the variation with RGC of the disk thickness (flaring) and derive an almost constant scale-height (~0.65 kpc) within $R_{\rm GC}\sim15$ kpc. Further out, the disk flaring increase gradually reaching a mean scale-height of ~1.5 kpc at $R_{\rm GC}\sim23$ kpc; (vii) the derived outer disk warping and flaring provide further robust evidence that there is no disk radial truncation at $R_{\rm GC}\sim14$ kpc. Conclusions.In the particular case of the Canis Major (CMa) over-density we confirm its coincidence with the Southern stellar maximum warp occurring near $l\sim240^{\circ}$ (for $R_{\odot}\simeq7$ kpc) which brings down the Milky Way mid-plane by ~$3^{\circ}$ in this direction. The regularity and consistency of the stellar, gaseous and dust warp argues strongly against a recent merger scenario for Canis Major. We present evidence to conclude that all observed parameters (e.g. number density, radial velocities, proper motion etc) of CMa are consistent with it being a normal Milky Way outer-disk population, thereby leaving no justification for more complex interpretations of its origin. The present analysis or outer disk structure does not provide a conclusive test of the structure or origin of the Monoceros Ring. Nevertheless, we show that a warped flared Milky Way contributes significantly at the locations of the Monoceros Ring. Comparison of outer Milky Way $\ion{H}{i}$ and CO properties with those of other galaxies favors the suggestion that complex structures close to planar in outer disks are common, and are a natural aspect of warped and flaring disks.
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