A5005732621- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Adaptive optics and wavefront sensing
- Astro and Planetary Science
- Galaxies: Formation, Evolution, Phenomena
- Impact of Light on Environment and Health
- Spectroscopy and Laser Applications
- Calibration and Measurement Techniques
- Astrophysics and Cosmic Phenomena
- Dark Matter and Cosmic Phenomena
- Solar and Space Plasma Dynamics
- Historical and Architectural Studies
- Scientific Research and Discoveries
- Advanced Thermodynamic Systems and Engines
- solar cell performance optimization
- Inertial Sensor and Navigation
- Magnetic Properties and Applications
University of Cambridge
2017-2025
Institute of Astronomy
2017-2023
Bridge University
2023
University of Hertfordshire
2012-2022
University College London
2022
European Southern Observatory
2018
ABSTRACT A key event in the history of Milky Way is formation bar. This affects subsequent structural and dynamical evolution entire Galaxy. When bar formed, gas was likely rapidly funnelled to centre Galaxy settling a star-forming nuclear disc. The can then be dated by considering age distribution oldest stars formed stellar In this highly obscured crowded region, reliable tracers are limited, but bright, high-amplitude Mira variables make useful indicators as they follow period–age...
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 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....
ABSTRACT We use the continuity equation to derive a method for measuring pattern speed of Milky Way’s bar/bulge from proper motion data. The has minimal assumptions but requires complete coverage non-axisymmetric component in two three Galactic coordinates. apply our data combination Gaia DR2 and VISTA Variables Via Lactea (VVV) measure bar as $\Omega _\mathrm{p}=(41\pm 3)\, \mathrm{km\, s^{-1}\, kpc^{-1}}$ (where error is statistical). This puts corotation radius at $(5.7\pm 0.4)\,...
Abstract We have derived absolute proper motions of the entire Galactic bulge region from VVV Infrared Astrometric Catalogue (VIRAC) and Gaia. present these both as integrated on-sky maps and, after isolating standard candle red clump (RC) stars, a function distance using RC magnitude proxy. These data provide new global, 3D view Milky Way barred kinematics. find gradient in mean longitudinal motion, $\langle \mu _ l^\star \rangle $, between different sides bar, which is sensitive to bar...
Abstract The nuclear stellar disc (NSD) is a flattened high-density structure that dominates the gravitational field of Milky Way at Galactocentric radius $30\, {\rm pc}\lesssim R\lesssim 300\, pc}$. We construct axisymmetric self-consistent equilibrium dynamical models NSD in which distribution function an analytic action variables. fit to normalized kinematic distributions (line-of-sight velocities + VIRAC2 proper motions) stars survey Fritz et al., taking foreground contamination due...
ABSTRACT During the pre-main-sequence (pre-MS) evolution stage of a star, significant amounts stellar mass are accreted during episodic accretion events, such as multidecade FUor-type outbursts. Here, we present near-infrared spectroscopic follow-up study 33 high-amplitude (most with ΔKs &gt; 4 mag) variable sources discovered by Vista Variables in Via Lactea (VVV) survey. Based on spectral features, 25 classified eruptive young objects (YSOs), including 15 newly identified FUors, six...
Context. The Galactic centre is hazardous for stellar clusters because of the strong tidal force in action there. It believed that many were destroyed there and contributed stars to crowded field bulge nuclear cluster. However, development a realistic model predict long-term evolution complex inner Galaxy has proven difficult, observations surviving central region would provide crucial insights into destruction processes. Aims. Among known globular clusters, VVV CL002 closest centre, at 0.4...
We present the spectroscopic analysis of a large sample late-M, L, and T dwarfs from United Kingdom Deep Infrared Sky Survey. Using YJHK photometry Large Area Survey red-optical Sloan Digital we selected 262 brown dwarf candidates have followed-up 196 them using echelle spectrograph X-shooter on Very Telescope. The wavelength coverage (0.30–2.48 μm) moderate resolution (R ∼ 5000–9000) allowed us to identify peculiar objects including 22 blue L dwarfs, 2 low-gravity M dwarfs. spectral...
ABSTRACT Episodic accretion is one of the competing models to explain observed luminosity spread in young stellar clusters. These short-lived high events could also have a strong impact on planet formation. Observations high-amplitude variability objects (YSOs) due large changes rate provide direct observational evidence for episodic accretion. However, there are still uncertainties frequency these and if universal among YSOs. To determine outbursts Class I YSOs, we built robust sample at...
We report the discovery of a peculiar L dwarf from United Kingdom Infrared Deep Sky Survey Large Area Survey, ULAS J222711−004547. The very red infrared photometry (MKO J − K = 2.79 ± 0.06, WISE W1−W2 0.65 0.05) J222711−004547 makes it one reddest brown dwarfs discovered so far. obtained moderate resolution spectrum this target using XSHOOTER spectrograph on Very Telescope, and we classify as L7pec, confirming its nature. Comparison to theoretical models suggests that object could be...
ABSTRACT We analyse the kinematics of Galactic bar-bulge using proper motions from ESO public survey Vista Variables in Via Lactea (VVV) and second Gaia data release. has provided some first absolute within bulge near-infrared VVV multi-epoch catalogue complements highly extincted low-latitude regions. discuss relative-to-absolute calibration Gaia. Along lines sight spanning $-10\lt \ell /\, \mathrm{deg}\lt 10$ b/\, 5$, we probabilistically model density velocity distributions as a function...
In November 2019, the nearby single, isolated DQ-type white dwarf LAWD 37 (WD 1142-645) aligned closely with a distant background source and caused an astrometric microlensing event. Leveraging astrometry from \Gaia{} followup data \textit{Hubble Space Telescope} we measure deflection of obtain gravitational mass for LAWD~37. The main challenge this analysis is in extracting lensing signal faint whilst it buried wings LAWD~37's point spread function. Removal 37's function induces significant...
We have performed a comprehensive search of VISTA Variables in the Via Lactea (VVV) database 9.5 yr light curves for variable sources with $\Delta K_s \ge 4$ mag, aiming to provide large sample high amplitude eruptive young stellar objects (YSOs) and detect unusual or new types infrared source. find 222 transient Galactic bulge disc, most which are discoveries. The mainly comprises novae, YSOs, microlensing events, Long Period Variable stars (LPVs) few rare unclassified sources....
Context. The ESO public survey VISTA Variables in the Vía Láctea (VVV) surveyed inner Galactic bulge and adjacent southern disk from 2009–2015. Upon its conclusion, complementary VVV extended (VVVX) has expanded both temporal as well spatial coverage of original area, widening it 562 to 1700 sq. deg., providing additional epochs JHK s filters 2016–2023. Aims. With completion VVVX observations during first semester 2023, we present here observing strategy, a description data quality access,...
Context . High reddening near the Galactic plane hampers observations and proper characterization of globular clusters (GCs) located toward inner regions Milky Way. Aims The VISTA Variables in Vía Láctea (VVV) survey observed bulge adjacent disk for several years, providing multi-epoch, near-infrared images 41 GCs. Detecting RR Lyrae variable stars belonging to these GCs will aid their accurate parameterization. Methods By fully leveraging astrometric, photometric, variability VVV catalogs,...
High reddening near the Galactic plane hampers observations and proper characterization of globular clusters (GCs) located toward inner regions Milky Way. The VISTA Variables in Via Lactea (VVV) survey observed bulge adjacent disk for several years, providing multi-epoch, near-infrared images 41 GCs. Detecting RRLyrae variables belonging to these GCs will aid their accurate parameterization. By fully leveraging astrometric, photometric, variability VVV catalogs, we searched stars associated...
Abstract We present the Cambridge Exoplanet Transit Recovery Algorithm (cetra), a fast and sensitive transit detection algorithm, optimised for GPUs. cetra separates task into search signals across linear time space, followed by phase-folding of former to enable periodic signal search, using physically motivated model improve sensitivity. It outperforms traditional methods like Box Least Squares in both sensitivity speed. Tests on synthetic light curves demonstrate that can identify at least...
We have searched the WISE first data release for widely separated (<10,000AU) late T dwarf companions to Hipparcos and Gliese stars. discovered a new binary system containing K-band suppressed T8p WISEP J1423+0116 mildly metal poor ([Fe/H]=-0.38+-0.06) primary BD+01 2920 (Hip 70319), G1 at distance of 17.2pc. This benchmark has Teff=680+-55K mass 20-50 Mjup. Its spectral properties are well modelled except known discrepancies in Y K bands. Based on determined metallicity its companion, 2920B...
The properties of the Milky Way's nuclear stellar disc give crucial information on epoch bar formation. Mira variables are promising bright candidates to study disc, and through their period-age relation dissect its star formation history. We report a sample $1782$ variable across central $3\times3\,\mathrm{deg}^2$ Galaxy using multi-epoch infrared VISTA Variables in Via Lactea (VVV) survey. describe algorithms employed select candidate stars then model light curves periodogram Gaussian...
ABSTRACT We analyse 1602 microlensing events found in the VISTA Variables Via Lactea (VVV) near-infrared (NIR) survey data. obtain spatially resolved, efficiency-corrected time-scale distributions across Galactic bulge (|ℓ| &lt; 10°, |b| 5°), using a Bayesian hierarchical model. Spatially resolved peaks and means of distributions, along with their marginal strips longitude latitude, are agreement at 1σ level predictions based on Besançon model Galaxy. find that event time-scales central...
We present 27 new L subdwarfs and classify five of them as esdL 22 sdL. Our subdwarf candidates were selected with the UKIRT Infrared Deep Sky Survey Sloan Digital Survey. Spectroscopic follow-up was carried out primarily OSIRIS spectrograph on Gran Telescopio Canarias. Some these objects followed up X-shooter instrument Very Large Telescope. studied photometric properties population known using colour-spectral type diagrams colour-colour diagrams, by comparison dwarfs main-sequence stars,...
Gaia DR2 published positions, parallaxes and proper motions for an unprecedented 1,331,909,727 sources, revolutionising the field of Galactic dynamics. We complement this data with Astrometry Spread Function (ASF), expected uncertainty in measured parallax a non-accelerating point source. The ASF is Gaussian function which we construct 5D astrometric covariance matrix as position on sky apparent magnitude using scanning law demonstrate excellent agreement observed data. This can be used to...
ABSTRACT The decade-long Vista Variables in the Via Lactea (VVV) survey has detected numerous highly variable young stellar objects (YSOs). We present a study of 61 VVV YSOs (ΔKs = 1–5 mag), combining near-infrared spectra from Magellan and ESO Very Large Telescope with NEOWISE light curves to investigate physical mechanisms behind eruptive events. Most sources are spectroscopically confirmed as variables (typically Class I YSOs) but extinction is also seen. Among them, magnetically...
ABSTRACT The extinction law from 0.9 to 8 microns in the inner $3\times 3\deg ^2$ of Milky Way is measured using data VISTA Variables Via Lactea, GLIMPSE, and WISE. Absolute ratios are found by requiring that observed red clump density peaks at GRAVITY collaboration distance Galactic centre. When combined with selective bulge giant colour–colour diagrams, we find an $A_Z:A_Y:A_J:A_H:A_{K_s}:A_{W1}:A_{[3.6]}:A_{[4.5]}:A_{W2}:A_{[5.8]}:A_{[8.0]}...