Testing the chemical tagging technique with open clusters

Context. Stars are born together from giant molecular clouds and, if we assume that the priors were chemically homogeneous and well-mixed, we expect them to share the same chemical composition. Most of the stellar aggregates are disrupted while orbiting the Galaxy and most of the dynamic information is lost, thus the only possibility of reconstructing the stellar formation history is to analyze the chemical abundances that we observe today. Aims. The chemical tagging technique aims to recover disrupted stellar clusters based merely on their chemical composition. We evaluate the viability of this technique to recover co-natal stars that are no longer gravitationally bound. Methods. Open clusters are co-natal aggregates that have managed to survive together. We compiled stellar spectra from 31 old and intermediate-age open clusters, homogeneously derived atmospheric parameters, and 17 abundance species, and applied machine learning algorithms to group the stars based on their chemical composition. This approach allows us to evaluate the viability and efficiency of the chemical tagging technique. Results. We found that stars at different evolutionary stages have distinct chemical patterns that may be due to NLTE effects, atomic diffusion, mixing, and biases. When separating stars into dwarfs and giants, we observed that a few open clusters show distinct chemical signatures while the majority show a high degree of overlap. This limits the recovery of co-natal aggregates by applying the chemical tagging technique. Nevertheless, there is room for improvement if more elements are included and models are improved.Comment: accepted for publication in Astronomy and Astrophysics. Corrected typo

Retrieval of the dayside atmosphere of WASP-43b with CRIRES+

Accurately estimating the C/O ratio of hot Jupiter atmospheres is a promising pathway towards understanding planet formation and migration, as well as the formation of clouds and the overall atmospheric composition. The atmosphere of the hot Jupiter WASP-43b has been extensively analysed using low-resolution observations with HST and Spitzer, but these previous observations did not cover the K band, which hosts prominent spectral features of major carbon-bearing species such as CO and CH$_{4}$. As a result, the ability to establish precise constraints on the C/O ratio was limited. Moreover, the planet has not been studied at high spectral resolution, which can provide insights into the atmospheric dynamics. In this study, we present the first high-resolution dayside spectra of WASP-43b with the new CRIRES$^+$ spectrograph. By observing the planet in the K band, we successfully detected the presence of CO and provide evidence for the existence of H$_2$O using the cross-correlation method. This discovery represents the first direct detection of CO in the atmosphere of WASP-43b. Furthermore, we retrieved the temperature-pressure profile, abundances of CO and H$_2$O, and a super-solar C/O ratio of 0.78 by applying a Bayesian retrieval framework to the data. Our findings also shed light on the atmospheric characteristics of WASP-43b. We found no evidence for a cloud deck on the dayside, and recovered a line broadening indicative of an equatorial super-rotation corresponding to a jet with a wind speed of $\sim$ 5 km s$^{-1}$, matching the results of previous forward models and low-resolution atmospheric retrievals for this planet.Comment: 15 pages, 14 figure

Label-free electrochemical monitoring of DNA ligase activity

This study presents a simple, label-free electrochemical technique for the monitoring of DNA ligase activity. DNA ligases are enzymes that catalyze joining of breaks in the backbone of DNA and are of significant scientific interest due to their essential nature in DNA metabolism and their importance to a range of molecular biological methodologies. The electrochemical behavior of DNA at mercury and some amalgam electrodes is strongly influenced by its backbone structure, allowing a perfect discrimination between DNA molecules containing or lacking free ends. This variation in electrochemical behavior has been utilized previously for a sensitive detection of DNA damage involving the sugar-phosphate backbone breakage. Here we show that the same principle can be utilized for monitoring of a reverse process, i.e., the repair of strand breaks by action of the DNA ligases. We demonstrate applications of the electrochemical technique for a distinction between ligatable and unligatable breaks in plasmid DNA using T4 DNA ligase, as well as for studies of the DNA backbone-joining activity in recombinant fragments of E. coli DNA ligase

MOST discovers a multimode delta Scuti star in a triple system: HD 61199

A field star, HD 61199 (V ~ 8), simultaneously observed with Procyon by the MOST (Microvariability & Oscillations of STars) satellite in continuous runs of 34, 17, and 34 days in 2004, 2005, and 2007, was found to pulsate in 11 frequencies in the delta Scuti range with amplitudes from 1.7 down to 0.09 mmag. The photometry also showed variations with a period of about four days. To investigate the nature of the longer period, 45 days of time-resolved spectroscopy was obtained at the Thueringer Landessternwarte Tautenburg in 2004. The radial velocity measurements indicate that HD 61199 is a triple system. A delta Scuti pulsator with a rich eigenspectrum in a multiple system is promising for asteroseismology. Our objectives were to identify which of the stars in the system is the delta Scuti variable and to obtain the orbital elements of the system and the fundamental parameters of the individual components, which are constrained by the pulsation frequencies of the delta Scuti star. Classical Fourier techniques and least-squares multi-sinusoidal fits were applied to the MOST photometry to identify the pulsation frequencies. The groundbased spectroscopy was analysed with least-squares-deconvolution (LSD) techniques, and the orbital elements derived with the KOREL and ORBITX routines. Asteroseismic models were also generated. The photometric and spectroscopic data are compatible with a triple system consisting of a close binary with an orbital period of 3.57 days and a delta Scuti companion (HD 61199,A) as the most luminous component. The delta Scuti star is a rapid rotator with about vsin i = 130 km/s and an upper mass limit of about 2.1 Msun. For the close binary components, we find they are of nearly equal mass, with lower mass limits of about 0.7 Msun.Comment: 11 pages, 14 figures, accepted by A&

Improved stellar parameters of CoRoT-7

Accurate parameters of the host stars of exoplanets are important for the interpretation of the new planet systems that continue to emerge. The CoRoT satellite recently discovered a transiting rocky planet with a density similar to the inner planets in our solar system, a so-called Super Earth. This planet is orbiting a relatively faint G9V star called CoRoT-7, and we wish to refine its physical properties, which are important for the interpretation of the properties of the planet system. We used spectra from [email protected] and [email protected]. From the analysis of Fe-1 and Fe-2 lines we determine Teff, log g and microturbulence. We use the Balmer lines to constrain Teff and pressure sensitive Mg-1b and Ca lines to constrain log g. From the analysis we find Teff=5250+-60K, log g = 4.47+-0.05, [M/H]=+0.12+-0.06, and vsini = 1.1 km/s. We compared the L/M ratio with isochrones to constrain the evolutionary status. Using the age estimate of 1.2-2.3 Gyr based on stellar activity, we determine the mass and radius 0.91+-0.03 Msun and 0.82+-0.04 Rsun. With these updated constraints we fitted the CoRoT transit light curve for CoRoT-7b. We revise the planet radius to be slightly smaller, R = 1.58+-0.10 Rearth, and the density becomes higher, rho = 7.2+-1.8 g/cm3. The host star CoRoT-7 is a slowly rotating, metal rich, unevolved type G9V star. The star is relatively faint (V=11.7) and its fundamental parameters can only be determined through indirect methods. Our methods rely on detailed spectral analyses that depend on the adopted model atmospheres. From the analysis of spectra of stars with well-known parameters with similar parameters to CoRoT-7 (the Sun and alpha Cen B) we demonstrate that our methods are robust within the claimed uncertainties. Therefore our methods can be reliably used in subsequent analyses of similar exoplanet host stars.Comment: Accepted by A&A; 10 pages; abstract abridged; resolution decreased in Fig.

Concept and optical design of the cross-disperser module for CRIRES

This is the peer reviewed version of the following article: Oliva, Ernesto, A. Tozzi, D. Ferruzzi, L. Origlia, A. Hatzes, R. Follert, T. Loewinger et al. "Concept and optical design of the cross-disperser module for CRIRES+." In SPIE Astronomical Telescopes+ Instrumentation, pp. 91477R-91477R. International Society for Optics and Photonics, 2014, which has been published in final form at 10.1117/12.2054381

The Gaia-ESO Survey: the most metal-poor stars in the Galactic bulge

We present the first results of the EMBLA survey (Extremely Metal-poor BuLge stars with AAOmega), aimed at finding metal-poor stars in the Milky Way bulge, where the oldest stars should now preferentially reside. EMBLA utilises SkyMapper photometry to pre-select metal-poor candidates, which are subsequently confirmed using AAOmega spectroscopy. We describe the discovery and analysis of four bulge giants with -2.72<=[Fe/H]<=-2.48, the lowest metallicity bulge stars studied with high-resolution spectroscopy to date. Using FLAMES/UVES spectra through the Gaia-ESO Survey we have derived abundances of twelve elements. Given the uncertainties, we find a chemical similarity between these bulge stars and halo stars of the same metallicity, although the abundance scatter may be larger, with some of the stars showing unusual [{\alpha}/Fe] ratios.Comment: 7 pages, 5 figures. Accepted for publication by MNRA

The Gaia-ESO Survey: Detailed Abundances in the Metal-poor Globular Cluster NGC 4372

We present the abundance analysis for a sample of 7 red giant branch stars in the metal-poor globular cluster NGC 4372 based on UVES spectra acquired as part of the Gaia-ESO Survey. This is the first extensive study of this cluster from high resolution spectroscopy. We derive abundances of O, Na, Mg, Al, Si, Ca, Sc, Ti, Fe, Cr, Ni, Y, Ba, and La. We find a metallicity of [Fe/H] = -2.19 $\pm$ 0.03 and find no evidence for a metallicity spread. This metallicity makes NGC 4372 one of the most metal-poor galactic globular clusters. We also find an {\alpha}-enhancement typical of halo globular clusters at this metallicity. Significant spreads are observed in the abundances of light elements. In particular we find a Na-O anti-correlation. Abundances of O are relatively high compared with other globular clusters. This could indicate that NGC 4372 was formed in an environment with high O for its metallicity. A Mg-Al spread is also present which spans a range of more than 0.5 dex in Al abundances. Na is correlated with Al and Mg abundances at a lower significance level. This pattern suggests that the Mg-Al burning cycle is active. This behavior can also be seen in giant stars of other massive, metal-poor clusters. A relation between light and heavy s-process elements has been identified.Comment: 14 pages, 14 figures, accepted for publication in A&

CRIRES+ detection of CO emissions lines and temperature inversions on the dayside of WASP-18b and WASP-76b

The dayside atmospheres of ultra-hot Jupiters (UHJs) are predicted to possess temperature inversion layers with extremely high temperatures at high altitudes. We observed the dayside thermal emission spectra of WASP-18b and WASP-76b with the new CRIRES+ high-resolution spectrograph at near-infrared wavelengths. Using the cross-correlation technique, we detected strong CO emission lines in both planets, which confirms the existence of temperature inversions on their dayside hemispheres. The two planets are the first UHJs orbiting F-type stars with CO emission lines detected; previous detections were mostly for UHJs orbiting A-type stars. Evidence of weak H2O emission signals is also found for both planets. We further applied forward-model retrievals on the detected CO lines and retrieved the temperature-pressure profiles along with the CO volume mixing ratios. The retrieved logarithmic CO mixing ratio of WASP-18b (-2.2) is slightly higher than the value predicted by the self-consistent model assuming solar abundance. For WASP-76b, the retrieved CO mixing ratio (-3.6) is broadly consistent with the value of solar abundance. In addition, we included the equatorial rotation velocity (Veq ) in the retrieval when analyzing the line profile broadening. The obtained Veq is 7.0 km/s for WASP-18b and 5.2 km/s for WASP-76b, which are consistent with the tidally locked rotational velocities.Comment: 11 pages, 12 figures; accepted for publication in A&

On the Period-Luminosity-Colour-Metallicity relation and the pulsational characteristics of lambda Bootis type stars

The group of lambda Bootis type stars comprises late B- to early F-type, Population I objects which are basically metal weak, in particular the Fe group elements, but with the clear exception of C, N, O and S. The present work is a continuation of the studies by Paunzen et al. (1998, A&A, 335, 533), who presented first results on the pulsational characteristics of the lambda Bootis stars. Since then, we have observed 22 additional objects; we found eight new pulsators and confirmed another one. Furthermore, new spectroscopic data (Paunzen, 2001, A&A, 373, 633) allowed us to sort out misidentified candidates and to add true members to the group. From 67 members of this group, only two are not photometrically investigated yet which makes our analysis highly representative. We have compared our results on the pulsational behaviour of the lambda Bootis stars with those of a sample of delta Scuti type objects. We find that at least 70% of all lambda Bootis type stars inside the classical instability strip pulsate, and they do so with high overtone modes (Q < 0.020d). Only a few stars, if any, pulsate in the fundamental mode. Compared to the delta Scuti stars, the cool and hot borders of the instability strip of the lambda Bootis stars are shifted by about 25mmag, towards smaller (b-y)0. Using published abundances and the metallicity sensitive indices of the Geneva 7-colour and Stroemgren uvbybeta systems, we have derived [Z] values which describe the surface abundance of the heavier elements for the group members. We find that the Period-Luminosity-Colour relation for the group of lambda Bootis stars is within the errors identical with that of the normal delta Scuti stars. No clear evidence for a statistically significant metallicity term was detected.Comment: 14 pages, 8 figures, accepted by A&