A5050496687- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Adaptive optics and wavefront sensing
- Spectroscopy and Laser Applications
- Atmospheric Ozone and Climate
- Scientific Research and Discoveries
- Astrophysical Phenomena and Observations
- Geophysics and Gravity Measurements
- History and Developments in Astronomy
- Calibration and Measurement Techniques
- Solar and Space Plasma Dynamics
- Astronomical and nuclear sciences
- Galaxies: Formation, Evolution, Phenomena
- Advanced Fiber Optic Sensors
- Spacecraft and Cryogenic Technologies
- Intellectual Property Law
- Optical Network Technologies
- Migration and Labor Dynamics
- Photonic Crystal and Fiber Optics
- Historical Astronomy and Related Studies
- Statistical and numerical algorithms
University of Hertfordshire
2016-2025
University of Groningen
2024
Goddard Space Flight Center
2024
St George Hospital
2022
Natural History Museum
2004-2020
University of Chile
2009-2010
Université de Montréal
2010
Liverpool John Moores University
1996-2009
University College London
2009
University of St Andrews
2009
We present a catalog of nearby exoplanets, available at http://exoplanets.org and ApJ 646, 505 (published version the link above). It contains 172 known low mass companions with orbits established through radial velocity transit measurements around stars within 200 pc. include 5 previously unpublished exoplanets orbiting HD 11964, 66428, 99109, 107148, 164922. update for 90 additional including many whose have not been revised since their announcement, time series from Lick, Keck,...
We review the observed properties of exoplanets found by Doppler technique that has revealed 152 planets to date. focus on ongoing 18-year survey 1330 FGKM type stars at Lick, Keck, and Anglo-Australian Telescopes offers both uniform precision (3 m s-1) long duration. The 104 detected in this have minimum masses (M sin i) as low 6 MEarth, orbiting between 0.02 AU. core-accretion model planet formation is supported four observations: 1) mass distribution rises toward lowest detectable masses,...
Since low-mass stars have low luminosities, orbits at which liquid water can exist on Earth-sized planets are relatively close-in, produces Doppler signals that detectable using state-of-the-art spectroscopy. GJ 667C is already known to be orbited by two super-Earth candidates. We investigate whether the data supports presence of additional companions. obtain new measurements from HARPS extracted spectra and combined them with those obtained PFS HIRES spectrographs. used Bayesian...
We present spectroscopic rotation velocities (v sin i) for 56 M dwarf stars using high resolution HET HRS red spectroscopy. In addition we have also determined photometric effective temperatures, masses and metallicities ([Fe/H]) some observed here in the literature where could acquire accurate parallax measurements relevant photometry. increased number of known v is mid by around 80% can confirm a weakly increasing velocity with decreasing temperature. Our sample peak at low (~3 km/s). find...
We re-analyze 4 years of HARPS spectra the nearby M1.5 dwarf GJ 667C available through European Southern Observatory public archive. The new radial velocity (RV) measurements were obtained using a data analysis technique that derives Doppler measurement and other instrumental effects least-squares approach. Combining these 143 with 41 additional RVs from Magellan/Planet Finder Spectrograph Keck/High Resolution Echelle Spectrometer spectrometers reveals three signals beyond previously...
We build an accurate database of 5200 HCN and HNC rotation-vibration energy levels, determined from existing laboratory data. 20~000 levels in the Harris et al. (2002) linelist are assigned approximate quantum numbers. These assignments, lab al incorporated to a new level list. A is presented, which frequencies computed using where available, ab initio otherwise. The then used compute model atmospheres synthetic spectra for carbon star WZ Cas. This results better fit spectrum Cas absorption...
Due to their higher planet–star mass ratios, M dwarfs are the easiest targets for detection of low-mass planets orbiting nearby stars using Doppler spectroscopy. Furthermore, because low masses and luminosities, measurements enable in habitable zones that correspond closer orbits than solar-type stars. We re-analyse literature Ultraviolet Visual Echelle Spectrograph (UVES) radial velocities 41 a combination with new obtained from publicly available spectra HARPS-ESO spectrograph these an...
The K2.5 dwarf HD 40307 has been reported to host three super-Earths. system lacks massive planets and is therefore a potential candidate for having additional low-mass planetary companions. We re-derive Doppler measurements from public HARPS spectra of confirm the significance signals using independent data analysis methods. also investigate these low-amplitude signals. used Bayesian our radial velocities estimate probability densities different model parameters. estimated relative...
We report the discovery of 76 new T dwarfs from UKIDSS Large Area Survey (LAS). Near-infrared broad and narrow-band photometry spectroscopy are presented for objects, along with WISE warm-Spitzer photometry. Proper motions 128 a two epoch LAS proper motion catalogue. use these to identify benchmark systems: LHS 6176AB, T8+M4 pair HD118865AB, T5.5+F8 pair. Using age constraints primaries evolutionary models constrain radii we have estimated their physical properties bolometric luminosity....
We present VIRAC version 1, a near-infrared proper motion and parallax catalogue of the VISTA VVV survey for 312,587,642 unique sources averaged across all overlapping pawprint tile images covering 560 deg$^2$ bulge Milky Way southern disk. The includes 119 million high quality measurements, which 47 have statistical uncertainties below 1 mas yr$^{-1}$. In 11$<K_s<$14 magnitude range motions median uncertainty 0.67 also 6,935 with quality-controlled 5 $\sigma$ parallaxes 1.1 mas. show...
We present Spitzer IRAC photometry of twelve very late-type T dwarfs; nine have [3.6], [4.5], [5.8] and [8.0] three [3.6] [4.5] only. investigate trends with type color for the planning interpretation surveys coldest or Y dwarfs. Brown dwarfs effective temperature (T_eff) below 700K emit more than half their flux at wavelengths beyond 3um, ratio mid-infrared to near-infrared becomes sensitive T_eff. The H-[4.5] is a good indicator T_eff relatively weak dependence on metallicity gravity....
ABSTRACT We present updated simulations of the detectability Jupiter analogs by 17-year Anglo-Australian Planet Search. The occurrence rate Jupiter-like planets that have remained near their formation locations beyond ice line is a critical datum necessary to constrain details planet formation. It also vital in our quest fully understand how common (or rare) planetary systems like own are Galaxy. From sample 202 solar-type stars, and correcting for imperfect on star-by-star basis, we derive...
Abstract The removal of noise typically correlated in time and wavelength is one the main challenges for using radial-velocity (RV) method to detect Earth analogues. We analyze τ Ceti RV data find robust evidence wavelength-dependent noise. that this can be modeled by a combination moving average models so-called “differential radial velocities.” apply model various sets Ceti, four periodic signals at 20.0, 49.3, 160, 642 days, which we interpret as planets. identify two new with orbital...
In this work we present chromospheric activity indices, kinematics, radial-velocities and rotational velocities for more than 850 FGK-type dwarfs subgiant stars in the southern hemisphere test how best to calibrate measure S-indices from echelle spectra. We confirm bimodal distribution of activities such highlight role that active K-dwarfs play biasing number stars. show age-activity relationship does appear continue ages older Sun if simply compare main sequence stars, with an offset around...
Context. The abilities of radial velocity exoplanet surveys to detect the lowest-mass extra-solar planets are currently limited by a combination instrument precision, lack data, and "jitter". Jitter is general term for any unknown features in noise, reflects detailed knowledge stellar physics (asteroseismology, starspots, magnetic cycles, granulation, other surface phenomena), as well possible underestimation noise.
ABSTRACT Our understanding of planetary systems different to our own has grown dramatically in the past 30 yr. However, efforts ascertain degree which Solar system is abnormal or unique have been hindered by observational biases inherent methods that yielded greatest exoplanet hauls. On basis such surveys, one might consider highly unusual – but reality we are only now beginning uncover true picture. In this work, use full 18-yr archive data from Anglo-Australian Planet Search examine...
Exoplanets of a few Earth masses can be now detected around nearby low-mass stars using Doppler spectroscopy. In this paper, we investigate the radial velocity variations Kapteyn's star, which is both sub-dwarf M-star and nearest halo object to Sun. The observations comprise archival new HARPS, HIRES PFS measurements. Two signals are at periods 48 120 days likelihood periodograms Bayesian analysis data. Using same techniques, activity indicies ASAS-3 photometry show evidence for low-level...
Determining the orbital eccentricity of an extrasolar planet is critically important for understanding system's dynamical environment and history. However, often poorly determined or entirely mischaracterized due to poor observational sampling, low signal-to-noise, and/or degeneracies with other planetary signals. Some systems previously thought contain a single, moderate-eccentricity have been shown, after further monitoring, host two planets on nearly-circular orbits. We investigate...
Radial-velocity (RV) signals induce RV variations an order of magnitude larger than the signal created by orbit Earth-twins, thus preventing their detection. The goal this paper is to compare efficiency different methods used deal with stellar recover extremely low-mass planets despite. However, because observed at m/s precision level or below a combination induced unresolved orbiting planets, star, and instrument, performing such comparison using real data challenging. To circumvent...
Proxima could host a planet on ∼5-year orbit, which Gaia can confirm in the near future providing its exact mass.
Abstract We analyze 5108 AFGKM stars with at least five high-precision radial velocity points, as well Gaia and Hipparcos astrometric data, utilizing a novel pipeline developed in previous work. find 914 signals periods longer than 1000 days. Around these signals, 167 cold giants 68 other types of companions are identified, through combined analyses velocity, astrometry, imaging data. Without correcting for detection bias, we estimate the minimum occurrence rate wide-orbit brown dwarfs to be...
Precise Doppler measurements from the Anglo-Australian Telescope (AAT) UCLES spectrometer reveal periodic Keplerian velocity variations in stars HD 160691 and 27442. has a period of 743 days, semiamplitude 54 m s-1, high eccentricity, e = 0.62, typical extrasolar planets orbiting beyond 0.2 AU. The minimum (M sin i) mass companion is 1.97 MJ, semimajor axis 1.65 27442 415 day period, 32 an eccentricity 0.058. 1.43 1.18 This first planet AU that circular orbit similar to solar system planets....