K2-138 is a moderately bright (V = 12.2, K = 10.3) main sequence K-star observed in Campaign 12 of the NASA K2 mission. It hosts five small (1.6-3.3R_Earth) transiting planets in a compact ...architecture. The periods of the five planets are 2.35 d, 3.56 d, 5.40 d, 8.26 d, and 12.76 d, forming an unbroken chain of near 3:2 resonances. Although we do not detect the predicted 2-5 minute transit timing variations with the K2 timing precision, they may be observable by higher cadence observations with, for example, Spitzer or CHEOPS. The planets are amenable to mass measurement by precision radial velocity measurements, and therefore K2-138 could represent a new benchmark systems for comparing radial velocity and TTV masses. K2-138 is the first exoplanet discovery by citizen scientists participating in the Exoplanet Explorers project on the Zooniverse platform.
We present reverberation mapping results from the first year of combined
spectroscopic and photometric observations of the Sloan Digital Sky Survey
Reverberation Mapping Project. We successfully ...recover reverberation time
delays between the $g+i$-band emission and the broad H$\beta$ emission line for
a total of 44 quasars, and for the broad H$\alpha$ emission line in 18 quasars.
Time delays are computed using the JAVELIN and CREAM software and the
traditional interpolated cross-correlation function (ICCF): Using well defined
criteria, we report measurements of 32 H$\beta$ and 13 H$\alpha$ lags with
JAVELIN, 42 H$\beta$ and 17 H$\alpha$ lags with CREAM, and 16 H$\beta$ and 8
H$\alpha$ lags with the ICCF. Lag values are generally consistent among the
three methods, though we typically measure smaller uncertainties with JAVELIN
and CREAM than with the ICCF, given the more physically motivated light curve
interpolation and more robust statistical modeling of the former two methods.
The median redshift of our H$\beta$-detected sample of quasars is 0.53,
significantly higher than that of the previous reverberation-mapping sample. We
find that in most objects, the time delay of the H$\alpha$ emission is
consistent with or slightly longer than that of H$\beta$. We measure black hole
masses using our measured time delays and line widths for these quasars. These
black hole mass measurements are mostly consistent with expectations based on
the local M-sigma relationship, and are also consistent with single-epoch black
hole mass measurements. This work increases the current sample size of
reverberation-mapped active galaxies by about two-thirds and represents the
first large sample of reverberation mapping observations beyond the local
universe (z < 0.3).
We report chemical abundances obtained by SDSS-III/APOGEE for giant stars in five globular clusters located within 2.2 kpc of the Galactic centre. We detect the presence of multiple stellar ...populations in four of those clusters (NGC 6553, NGC 6528, Terzan 5, and Palomar 6) and find strong evidence for their presence in NGC 6522. All clusters present a significant spread in the abundances of N, C, Na, and Al, with the usual correlations and anti-correlations between various abundances seen in other globular clusters. Our results provide important quantitative constraints on theoretical models for self-enrichment of globular clusters, by testing their predictions for the dependence of yields of elements such as Na, N, C, and Al on metallicity. They also confirm that, under the assumption that field N-rich stars originate from globular cluster destruction, they can be used as tracers of their parental systems in the high- metallicity regime.
This paper reports on the three seasons of excavations conducted at Eynan (Ain Mallaha) from 2003 to 2005. It is also aimed at recording the laboratory work that took place since the last report ...published (Valla et al. 2004). Following the presentation of new 14C dates, the paper describes Early Natufian burials (Locus 239), one of which includes two decorated skeletons in a plastered grave. The next sections are devoted to analyses of Final Natufian findings. Because most of the sequence inside each excavated structure is now known, special interest is devoted to the succession of the phases in their occupation. This results in a dynamic vision, which suggests that some buildings (possibly houses) were used intermittently, whereas others may have been occupied on a more continuous basis. Among new features uncovered during those last seasons, a fire pit in structure 228 and a structure that includes a deep mortar in working position are worth mentioning. New graves are described as well. The most unexpected among them is a pit where at least seven individuals from newborn to adult were successively buried. Lithic analyses include an attempt at reconstructing the way both Helwan and regular Final Natufian lunates were shaped. This demonstrates that the changes in retouch techniques are probably linked to the diminished size of the desired end product. Following a more traditional approach we examine then a sample of tools from the lower part of the Final Natufian layer. The results suggest that there is no major change in the flint assemblages during the time span represented by the layer. Obsidian study confirms that this material is coming from Cappadocia, as will be the case in the Southern Levant for most of the PPN. Faunal analyses include a note on mammal carcass treatment. New research on birds confirms that Final Natufian people mainly targeted waterfowls for food but new species of raptors are identified. A preliminary analysis of fish emphasizes the diversity in species. Two studies are devoted to crabs and land and freshwater mollusks respectively. They suggest that both crabs and terrestrial mollusks were probably used as food by the inhabitants of the site. Also of importance is the presence of Palearctic mollusks, which confirm that average temperatures were probably somewhat lower by the end of the Pleistocene than to day, as already suggested by Pichon. More bone tools confirm the trends already observed previously: this workmanship is deeply rooted in the tradition initiated during the Early Natufian phase. Hooks are relatively frequent. Of interest is the finding of a new "spoon", a tool that seems to be a Natufian invention. Due to poor preservation of vegetal remains, phytoliths are the main testimony of the use Natufian people made of flora. New samples confirm that reeds and sedges may have been used for building and matting, whereas a variety of grasses, among them small quantities of barley and wheat, were probably brought to the site for consumption. Finally, preliminary presentations of shell and stone beads are offered, followed by a description of the few incised stone items recovered lately. A discussion emphasizes the many time scales involved in the findings and the possible different readings allowed thereby.
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