Search Publications
X-ray and UV radiation in the planet-forming T-Tauri system PDS 70. Signs of accretion and coronal activity
Güdel, Manuel; Pye, John P.; Barrado, David +3 more
Planet formation takes place in protoplanetary discs around young T-Tauri stars. PDS 70 is one of the first confirmed examples of a system where the planets are currently forming in gaps in the disc, and can be directly imaged. One of the main early influences on planet formation is the lifetime of the protoplanetary disc, which is limited by the …
The Pristine survey - XXII. A serendipitous discovery of an extremely Li-rich very metal-poor giant and a new method of 6Li/7Li isotope measurement
Sestito, F.; González Hernández, J. I.; Sitnova, T. M. +5 more
We report the serendipitous discovery of a very metal-poor (VMP) Li-rich giant star (Teff = 4690 ± 80 K, log g = 1.34 ± 0.13, [Fe/H] = -2.43 ± 0.07). We analyse the Li I 6103 and 6707 Å lines accounting for departures from local thermodynamic equilibrium (NLTE) and correcting for 3D effects using literature data, which yields a lithium …
Origin and trends in NH4+ observed in the coma of 67P
Altwegg, K.; Goetz, C.; Rubin, M. +6 more
The European Space Agency/Rosetta mission escorted comet 67P/Churyumov-Gerasimenko and witnessed the evolution of its coma from low activity (~2.5-3.8 au) to rich ion-neutral chemistry (~1.2-2.0 au). We present an analysis of the ion composition in the coma, focusing on the presence of protonated high proton affinity (HPA) species, in particular $…
Integral Field Spectroscopy of the cometary starburst galaxy NGC 4861
Roche, Nathan; Sánchez, Sebastian F.; Vílchez, José M. +4 more
Using the PMAS Integral Field Unit on the Calar Alto 3.5 m telescope, we observed the southern component (Markarian 59) of the 'cometary' starburst galaxy NGC 4861. Mrk 59 is centred on a giant nebula and concentration of stars 1 kpc in diameter. Strong $\rm H\,\alpha$ emission points to a star-formation rate (SFR) at least 0.47 $\rm M_{\odot }\, …
Optimizing machine learning methods to discover strong gravitational lenses in the deep lens survey
Jones, Tucker; Keerthi Vasan, G. C.; Sheng, Stephen +2 more
Machine learning models can greatly improve the search for strong gravitational lenses in imaging surveys by reducing the amount of human inspection required. In this work, we test the performance of supervised, semi-supervised, and unsupervised learning algorithms trained with the ResNetV2 neural network architecture on their ability to efficient…
Big flares from small stars: detecting flares from faint low-mass stars with NGTS full-frame images
Jackman, James A. G.; Wheatley, Peter J.; Jenkins, James S. +2 more
High-cadence observations of high-energy stellar flares from cool and ultracool dwarfs are often limited by the faint nature of their host stars. Many low-mass sources cannot be detected in quiescence by photometric surveys, meaning they are not targeted for high-cadence observations. This reduces the chances of detecting the rarest high-energy fl…
Search for particle acceleration in two massive Wolf-Rayet stars using uGMRT observations
Tej, Anandmayee; del Palacio, Santiago; Saha, Anindya +4 more
Large wind kinetic power of Wolf-Rayet (WR) stars make them ideal targets in low radio frequencies to search for non-thermal emission due to relativistic particle acceleration. In this paper, we present observations of two WR stars, WR 114 and WR 142, in Band 4 (550-950 MHz) and Band 5 (1050-1450 MHz) using the upgraded Giant Meterwave Radio Teles…
New transient ULX candidate in NGC 4254: evidence of circumbinary disc?
Allak, Sinan
This paper presents the identification of a new transient ultraluminous X-ray source (ULX) candidate (ULX-3) with reaching a peak luminosity of ~4 × 1039 erg s-1 in NGC 4254 by using archival Chandra, Swift/X-Ray Telescope, Hubble Space Telescope, and JWST observations. From precise astrometric calculations, unique optical, n…
A statistical analysis of the structure of the interstellar medium in the disc of the Milky Way
Whitworth, A. P.; Bates, M. L.
We construct Convolutional Neural Networks (CNNs) trained on exponentiated fractional Brownian motion (xfBm) images, and use these CNNs to analyse Hi-GAL images of surface density in the Galactic Plane. The CNNs estimate the Hurst parameter, ${\cal H}$ (a measure of the power spectrum), and the scaling exponent, ${\cal S}$ (a measure of the range …
Debris rings from extrasolar irregular satellites
Hansen, Bradley M. S.; Hayakawa, Kevin T.
Irregular satellites are the minor bodies found orbiting all four Solar system giant planets, with large semimajor axes, eccentricities, and inclinations. Previous studies have determined that the Solar system's irregular satellites are extremely collisionally evolved populations today, having lost ~99 per cent of their initial mass over the cours…