J. S. Jenkins
A5040864770- 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
- Space Exploration and Technology
- Adaptive optics and wavefront sensing
- Calibration and Measurement Techniques
- Astrophysical Phenomena and Observations
- Scientific Research and Discoveries
- Solar and Space Plasma Dynamics
- History and Developments in Astronomy
- Spectroscopy and Laser Applications
- Geophysics and Gravity Measurements
- High-pressure geophysics and materials
- Suicide and Self-Harm Studies
- Spacecraft Design and Technology
- Psychosomatic Disorders and Their Treatments
- Astronomical and nuclear sciences
- Spacecraft and Cryogenic Technologies
- Atmospheric Ozone and Climate
- Planetary Science and Exploration
- Space Science and Extraterrestrial Life
- Geology and Paleoclimatology Research
Diego Portales University
2021-2025
Millennium Institute of Astrophysics
2017-2025
Centro de Astrofísica y Tecnologías Afines
2017-2025
University of California, Merced
2024
Ames Research Center
2022-2023
Instituto de Astrofísica de Andalucía
2023
University of Chile
2013-2022
Universidad Bernardo O'Higgins
2016-2022
HRL Laboratories (United States)
2022
Purdue University West Lafayette
2022
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 describe the Next Generation Transit Survey (NGTS), which is a ground-based project searching for transiting exoplanets orbiting bright stars. NGTS builds on legacy of previous surveys, most notably WASP, and designed to achieve higher photometric precision hence find smaller planets than have previously been detected from ground. It also operates in red light, maximizing sensitivity late K early M dwarf The survey specifications call 0.1 per cent light over an instantaneous field view...
Determining the architecture of multi-planetary systems is one cornerstones understanding planet formation and evolution. Resonant are especially important as fragility their orbital configuration ensures that no significant scattering or collisional event has taken place since earliest phase when parent protoplanetary disc was still present. In this context, TOI-178 been subject particular attention first TESS observations hinted at a 2:3:3 resonant chain. Here we report results from...
Suicide is underreported for a number of reasons and the reliability official rates subject to error from variation in defining reporting cases--the kind inaccuracies encountered when ascertaining cases studies mortality any cause. Nevertheless, evidence designed see whether these sources invalidate differences reported between cultural social groups indicate that they are randomised, at least an extent allows epidemiologists compare countries districts within them, demographic groups, over time.
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...
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...
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...
We present the discovery of NGTS-1b, a hot-Jupiter transiting an early M-dwarf host ($T_{eff}=3916^{+71}_{-63}~K$) in P=2.674d orbit discovered as part Next Generation Transit Survey (NGTS). The planet has mass $0.812^{+0.066}_{-0.075}~M_{J}$, making it most massive ever M-dwarf. radius is $1.33^{+0.61}_{-0.33}~R_{J}$. Since transit grazing, we determine this by modelling data and placing prior on density from population known gas giant planets. NGTS-1b third found around M-dwarf,...
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.
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...
Proxima could host a planet on ∼5-year orbit, which Gaia can confirm in the near future providing its exact mass.
Accurately measuring stellar parameters is a key goal to increase our understanding of the observable universe. However, current methods are limited by many factors, in particular, biases and physical assumptions that basis for underlying evolutionary or atmospheric models, those these rely upon. Here we introduce code spectrAl eneRgy dIstribution bAyesian moDel averagiNg fittEr (ARIADNE), which tackles this problem using Bayesian Model Averaging incorporate information from all models...
We have acquired high-resolution echelle spectra of 225 F6-M5 type stars in the southern hemisphere. The are targets or candidates to be for Anglo-Australian Planet Search. CaII HK line cores were used derive activity indices all these objects. converted Mt. Wilson system measurements and logR'HK values determined. A number had no previously derived indices. In addition we also included from Tinney et al. (2002) using our calibration. radial-velocity instability (also known as jitter) level...
We present the results from high-resolution spectroscopic measurements to determine metallicities and activities of bright stars in southern hemisphere. have measured iron abundances ([Fe/H]) chromospheric emission indices (logR'HK) 353 solar-type with V=7.5-9.5. [Fe/H] are determined using a custom chi^2 fitting procedure within large grid Kurucz model atmospheres. The were by measuring amount cores strong CaII HK lines. sample has been compared other determinations was found agree these at...
We report the detection of GJ 832c, a super-Earth orbiting near inner edge habitable zone 832, an M dwarf previously known to host Jupiter analog in nearly-circular 9.4-year orbit. The combination precise radial-velocity measurements from three telescopes reveals presence planet with period 35.68+/-0.03 days and minimum mass (m sin i) 5.4+/-1.0 Earth masses. 832c moves on low-eccentricity orbit (e=0.18+/-0.13) towards zone. However, given large planet, it seems likely that would possess...
Context: More than 50 exoplanets have been found around giant stars, revealing different properties when compared to planets orbiting solar-type stars. In particular, they are Super-Jupiters and not interior $\sim$ 0.5 AU. Aims: We conducting a radial velocity study of sample 166 stars aimed at studying the population close-in how their orbital physical influenced by post-MS evolution host star. Methods: collected multi epochs spectra for all targets in our sample. computed precision...
We report the discovery of eight new giant planets, and updated orbits for four known orbiting dwarf subgiant stars using CORALIE, HARPS, MIKE instruments as part Calan-Hertfordshire Extrasolar Planet Search. The planets have masses in range 1.1-5.4MJs, orbital periods from 40-2900 days, eccentricities 0.0-0.6. They include a double-planet system most massive star our sample (HD147873), two eccentric (HD128356b HD154672b), rare 14 Herculis analogue (HD224538b). highlight some population...
We report the discovery of NGTS-4b, a sub-Neptune-sized planet transiting 13th magnitude K-dwarf in 1.34d orbit. NGTS-4b has mass M=$20.6\pm3.0$M_E and radius R=$3.18\pm0.26$R_E, which places it well within so-called "Neptunian Desert". The mean density ($3.45\pm0.95$g/cm^3) is consistent with composition 100% H$_2$O or rocky core volatile envelope. likely to suffer significant loss due relatively strong EUV/X-ray irradiation. Its survival Neptunian desert may be an unusually high mass, have...
We present radial velocity measurements of a sample M5V-M9V stars from our Red-Optical Planet Survey, ROPS, operating at 0.65-1.025 micron. Radial velocities for 15 stars, with r.m.s. precision down to 2.5 m/s over week long time scale are achieved using Thorium-Argon reference spectra. sensitive planets m_psin(i) >= 1.5 MEarth (3 2-sigma) in the classical habitable zone and observations currently rule out > 0.5 MJup 0.03 AU all targets. A total 9 targets exhibit < 16 m/s, which enables us...