FIES: The high‐resolution Fiber‐fed Echelle Spectrograph at the Nordic Optical Telescope

FIES is a cross‐dispersed high‐resolution echelle spectrograph at the 2.56 m Nordic Optical Telescope (NOT), and was optimised for throughput and stability in 2006. The major 2006 upgrade involved the relocation of FIES to a stable environment and development of a fiber bundle that offers 3 different resolution modes, and made FIES an attractive tool for the user community of the NOT. Radial‐velocity stability is achieved through double‐chamber active temperature control. A dedicated data reduction tool, FIEStool, was developed. As a result of these upgrades, FIES is now one of the work‐horse instruments at the NOT. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Automatic Normalization and Equivalent-Width Measurement of High-Resolution Stellar Spectra

It is well known that normalization, radial velocity correction and equivalent-width measurement of high-resolution stellar spectra are time-consuming work. In order to improve the efficiency we present an automatic method for these routines. The continuum is determined by fitting the 'high points' in the spectrum. After continuum normalization, the program automatically searches for the position of the Ha line and obtains a rough radial velocity, then computes an accurate radial velocity by cross-correlation between the given spectrum and the solar spectrum. In this method, the equivalent-width is automatically measured using Gaussian fitting. A comparison between our results and those from traditional analysis shows that the typical error for equivalent width is around 3.8% in our method. Developing such automatic routines does not mean to replace the interactive reduction method: it is just for a quick extraction of information from the spectra, especially those obtained in large sky surveys.     

WASP-10b: a 3MJ, gas-giant planet transiting a late-type K star

We report the discovery of WASP-10b, a new transiting extrasolar planet (ESP) discovered by the Wide Angle Search for Planets (WASP) Consortium and confirmed using Nordic Optical Telescope FIbre-fed Echelle Spectrograph and SOPHIE radial velocity data. A 3.09-d period, 29 mmag transit depth and 2.36 h duration are derived for WASP-10b using WASP and high-precision photometric observations. Simultaneous fitting to the photometric and radial velocity data using a Markov Chain Monte Carlo procedure leads to a planet radius of  1.28 R _J   , a mass of  2.96 M _J   and eccentricity of ≈0.06. WASP-10b is one of the more massive transiting ESPs, and we compare its characteristics to the current sample of transiting ESP, where there is currently little information for masses greater than ≈  2 M _J   and non-zero eccentricities. WASP-10's host star, GSC 2752−00114 (USNO-B1.0 1214−0586164) is among the fainter stars in the WASP sample, with   V = 12.7  and a spectral type of K5. This result shows promise for future late-type dwarf star surveys.     

Can variable meridional flows lead to false exoplanet detections?

The search for habitable exoplanets centers on planets with Earth-like conditions around late type stars. Radial velocity searches for these planets require precisions of 1 m/s and better. That is now being achieved. At these precisions stellar surface motions might lead to false detections. Of particular interest are variable meridional flows on stellar surfaces. I review the available observations of solar surface meridional flows using both Doppler shift and local helioseismology techniques. Interpretation in terms of Doppler shifts in integrated starlight leads to estimates of the likelihood of false detections. It is unlikely that these false detections occur in the habitability zones of exoplanets. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Composite spectra: XX. 45 Cancri

From accurate radial‐velocity measurements covering 11 circuits of the orbit of the composite‐spectrum binary 45 Cnc, together with high‐resolution spectroscopy spanning nearly 3 circuits, we have (i) isolated cleanly the spectrum of the early‐type secondary, (ii) classified the component spectra as G8 III and A3 III, (iii) derived the first double‐lined orbit for the system and a mass ratio (M₁/M₂) of 1.035 ± 0.01, and (iv) extracted physical parameters for the component stars, deriving the masses and (log) luminosities of the G star and A star as 3.11 and 3.00 M_⊙, and 2.34 and 2.28 L_⊙, respectively, with corresponding uncertainties of ±0.10 M_⊙ and ±0.09 L_⊙. Since the mass ratio is close to unity, we argue that the more evolved component is unlikely to have been a red giant long enough to have made multiple ascents of the RGB, an argument that is supported somewhat by the rather high eccentricity of the orbit (e = 0.46) and the evolutionary time‐scales of the two components, but chiefly by the presence of significant Li I in the spectrum of the cool giant. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

High resolution spectroscopy of two young active late type stars within 20 parsecs of the Sun

We present high-resolution optical echell spectroscopy of HIP 544 and HIP 46843, two nearby solar like stars. The discovery of these young stars at such a close distance to the Sun is really a surprising phenomenon. It will help us to have a better understanding of the structure and evolutionary history of the Milky Way. The radial ve-locities (RV) of HIP 544 and HIP 46843 are measured to be -6.88±0.13km s-1 and 8.30±0.16km s-1, respectively, which are more accurate than before. The equivalent widths (EW) of the Li I 6707.8 A absorption line of HIP 544 and HIP 46843 are mea-sured to be 110±5mA and 195±5mA respectively. Based on these properties, HIP 544 is estimated to be 100-800Myr old and HIP 46843 30-100Myr old using three relatively creditable methods.     

The chemical composition of the Small Magellanic Cloud

The Small Magellanic Cloud is a close, irregular galaxy that has experienced a complex star formation history due to the strong interactions occurred both with the Large Magellanic Cloud and the Galaxy. Despite its importance, the chemical composition of its stellar populations older than ∼ 1–2 Gyr is still poorly investigated. I present the first results of a spectroscopic survey of ∼ 200 Small Magellanic Cloud giant stars performed with FLAMES@VLT. The derived metallicity distribution peaks at [Fe/H] ∼ –0.9/–1.0 dex, with a secondary peak at [Fe/H] ∼ –0.6 dex. All these stars show [α /Fe] abundance ratios that are solar or mildly enhanced (∼+0.1 dex). Also, three metal‐poor stars (with [Fe/H] ∼ –2.5 dex and enhanced [α /Fe] ratios compatible with those of the Galactic Halo) have been detected in the outskirts of the SMC: These giants are the most metal‐poor stars discovered so far in the Magellanic Clouds. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Simulations for multi-object spectrograph planet surveys

Radial velocity surveys for extrasolar planets generally require substantial amounts of large telescope time in order to monitor a sufficient number of stars. Two of the aspects which can limit such surveys are the single-object capabilities of the spectrograph, and an inefficient observing strategy for a given observing window. In addition, the detection rate of extrasolar planets using the radial velocity method has thus far been relatively linear with time. With the development of various multi-object Doppler survey instruments, there is growing potential to dramatically increase the detection rate using the Doppler method. Several of these instruments have already begun usage in large-scale surveys for extrasolar planets, such as Fibre Large Array Multi Element Spectrograph (FLAMES) on the Very Large Telescope (VLT) and Keck Exoplanet Tracker (ET) on the Sloan 2.5-m wide-field telescope.
In order to plan an effective observing strategy for such a program, one must examine the expected results based on a given observing window and target selection. We present simulations of the expected results from a generic multi-object survey based on calculated noise models and sensitivity for the instrument and the known distribution of exoplanetary system parameters. We have developed code for automatically sifting and fitting the planet candidates produced by the survey to allow for fast follow-up observations to be conducted. The techniques presented here may be applied to a wide range of multi-object planet surveys.     

The fraction of double degenerates among DA white dwarfs

We present the results of a radial velocity survey designed to measure the fraction of double degenerates among DA white dwarfs. The narrow core of the H line was observed twice or more for 46 white dwarfs yielding radial velocities accurate to a few km s¹. This makes our survey the most sensitive to the detection of double degenerates undertaken to date. We found no new double degenerates in our sample, though H emission from distant companions is seen in two systems. Two stars known to be double degenerates prior to our observations are included in the analysis. We find a 95 per cent probability that the fraction of double degenerates among DA white dwarfs lies in the range [0.017, 0.19].     

A Bayesian Kepler periodogram detects a second planet in HD 208487

An automatic Bayesian Kepler periodogram has been developed for identifying and characterizing multiple planetary orbits in precision radial velocity data. The periodogram is powered by a parallel tempering Markov chain Monte Carlo (MCMC) algorithm which is capable of efficiently exploring a multiplanet model parameter space. The periodogram employs an alternative method for converting the time of an observation to true anomaly that enables it to handle much larger data sets without a significant increase in computation time. Improvements in the periodogram and further tests using data from HD 208487 have resulted in the detection of a second planet with a period of 909⁸²₋₉₂ d, an eccentricity of 0.37^0.26_−0.20, a semimajor axis of 1.87^0.13_−0.14 au and an M sin  i = 0.45^+0.11_−0.13 M _J. The revised parameters of the first planet are period = 129.8 ± 0.4 d, eccentricity = 0.20 ± 0.09, semimajor axis = 0.51 ± 0.02 au and M sin  i = 0.41 ± 0.05  M _J. Particular attention is paid to several methods for calculating the model marginal likelihood which is used to compare the probabilities of models with different numbers of planets.     

A search for starlight reflected from HD 75289b

We have used a Doppler tomographic analysis to conduct a deep search for the starlight reflected from the planetary companion to HD 75289. In four nights on VLT(UT2)/UVES in 2003 January, we obtained 684 high-resolution echelle spectra with a total integration time of 26 h. We establish an upper limit on the geometric albedo of the planet   p < 0.12  (to the 99.9 per cent significance level) at the most probable orbital inclination   i ≃ 60°  , assuming a grey albedo, a Venus-like phase function and a planetary radius   R _p= 1.6 R_Jup  . We are able to rule out some combinations of the predicted planetary radius and atmospheric albedo models with high, reflective cloud decks.     

The bright southern Cepheid β Doradus: the radial velocity curve, distance and size

A new high-accuracy velocity curve is presented for the bright southern Cepheid β Doradus (HR 1922), and an investigation into the long-term stability of the velocity curve is made. An upper limit of 0.57 km s⁻¹ is placed on cycle-to-cycle variations. This work is compared with a similar analysis previously applied to the long-period Cepheid ℓ Carinae (HR 3884).   Using a near-infrared variant of the Barnes–Evans method, the mean radius of and distance to β Dor are found to be R  = 67.8 ± 0.7 R⊙ and d  = 349 ± 4 pc. The systematic errors in these parameters are less than 3 per cent. If these systematics can be resolved, through the development of advanced theoretical models and/or the direct measurement of angular diameters, a calibration of the cosmic distance scale to better than 1 per cent can be achieved.     

WASP-3b: a strongly irradiated transiting gas-giant planet

We report the discovery of WASP-3b, the third transiting exoplanet to be discovered by the WASP and SOPHIE collaboration. WASP-3b transits its host star USNO-B1.0 1256−0285133 every  1.846 834 ± 0.000 002  d. Our high-precision radial velocity measurements present a variation with amplitude characteristic of a planetary-mass companion and in phase with the light curve. Adaptive optics imaging shows no evidence for nearby stellar companions, and line-bisector analysis excludes faint, unresolved binarity and stellar activity as the cause of the radial velocity variations. We make a preliminary spectroscopic analysis of the host star and find it to have   T _eff= 6400 ± 100 K  and  log   g = 4.25 ± 0.05  which suggests it is most likely an unevolved main-sequence star of spectral type F7-8V. Our simultaneous modelling of the transit photometry and reflex motion of the host leads us to derive a mass of  1.76^+0.08_−0.14 M _J  and radius  1.31^+0.07_−0.14 R _J  for WASP-3b. The proximity and relative temperature of the host star suggests that WASP-3b is one of the hottest exoplanets known, and thus has the potential to place stringent constraints on exoplanet atmospheric models.     

WASP-1b and WASP-2b: two new transiting exoplanets detected with SuperWASP and SOPHIE

We have detected low-amplitude radial-velocity variations in two stars, USNO-B1.0 1219–0005465 (GSC  02265–00107 = WASP–1  ) and USNO-B1.0 0964–0543604 (GSC  00522–01199 = WASP–2  ). Both stars were identified as being likely host stars of transiting exoplanets in the 2004 SuperWASP wide-field transit survey. Using the newly commissioned radial-velocity spectrograph SOPHIE at the Observatoire de Haute-Provence, we found that both objects exhibit reflex orbital radial-velocity variations with amplitudes characteristic of planetary-mass companions and in-phase with the photometric orbits. Line-bisector studies rule out faint blended binaries as the cause of either the radial-velocity variations or the transits. We perform preliminary spectral analyses of the host stars, which together with their radial-velocity variations and fits to the transit light curves yield estimates of the planetary masses and radii. WASP-1b and WASP-2b have orbital periods of 2.52 and 2.15 d, respectively. Given mass estimates for their F7V and K1V primaries, we derive planet masses 0.80–0.98 and 0.81–0.95 times that of Jupiter, respectively. WASP-1b appears to have an inflated radius of at least 1.33 R _Jup, whereas WASP-2b has a radius in the range 0.65–1.26 R _Jup.     

Studies of multiple stellar systems – IV. The triple-lined spectroscopic system Gliese 644

We present a radial velocity study of the triple-lined system Gliese 644 and derive spectroscopic elements for the inner and outer orbits with periods of 2.965 5 and 627 d. We also utilize old visual data, as well as modern speckle and adaptive optics observations, to derive a new astrometric solution for the outer orbit. These two orbits together allow us to derive masses for each of the three components in the system: M _A=0.410±0.028 (6.9 per cent), M _Ba=0.336±0.016 (4.7 per cent), and M _Bb=0.304±0.014 (4.7 per cent) M_⊙. We suggest that the relative inclination of the two orbits is very small. Our individual masses and spectroscopic light ratios for the three M stars in the Gliese 644 system provide three points for the mass–luminosity relation near the bottom of the main sequence, where the relation is poorly determined. These three points agree well with theoretical models for solar metallicity and an age of 5 Gyr. Our radial velocities for Gliese 643 and vB 8, two common proper motion companions of Gliese 644, support the interpretation that all five M stars are moving together in a physically bound group. We discuss possible scenarios for the formation and evolution of this configuration, such as the formation of all five stars in a sequence of fragmentation events leading directly to the hierarchical configuration now observed, versus formation in a small N cluster with subsequent dynamical evolution into the present hierarchical configuration.