Search Publications
UOCS - VII. Blue straggler populations of open cluster NGC 7789 with UVIT/AstroSat
Subramaniam, Annapurni; Panthi, Anju; Vaidya, Kaushar +4 more
NGC 7789 is a ~1.6 Gyr old, populous open cluster located at ~2000 pc. We characterize the blue straggler stars (BSS) of this cluster using the Ultraviolet (UV) data from the UVIT/AstroSat. We present spectral energy distributions (SED) of 15 BSS candidates constructed using multiwavelength data ranging from UV to IR wavelengths. In 8 BSS candidat…
Combined APOGEE-GALAH stellar catalogues using the Cannon
Lewis, Geraint F.; Wittenmyer, Robert A.; Buder, Sven +21 more
APOGEE and GALAH are two high resolution multi-object spectroscopic surveys that provide fundamental stellar parameters and multiple elemental abundance estimates for about half a million stars in the Milky Way. Both surveys observe in different wavelength regimes and use different data reduction pipelines leading to significant offsets and trends…
A population synthesis fitting of the Gaia resolved white dwarf binary population within 100 pc
Solano, E.; Rebassa-Mansergas, A.; Torres, S. +2 more
The Gaia mission has provided an unprecedented wealth of information about the white dwarf population of our Galaxy. In particular, our studies show that the sample up to 100 pc from the Sun can be considered as practically complete. This fact allows us to estimate a precise fraction of double-degenerate (1.18 ± 0.10 per cent) and white dwarf plus…
The VISCACHA survey - IV. The SMC West Halo in 8D
Minniti, D.; Geisler, D.; Bica, E. +18 more
The structure of the Small Magellanic Cloud (SMC) is very complex, in particular in the periphery that suffers more from the interactions with the Large Magellanic Cloud (LMC). A wealth of observational evidence has been accumulated revealing tidal tails and bridges made up of gas, stars, and star clusters. Nevertheless, a full picture of the SMC …
Using AGN light curves to map accretion disc temperature fluctuations
Kochanek, C. S.; Neustadt, J. M. M.
We introduce a new model for understanding AGN continuum variability. We start from a Shakura-Sunyaev thin accretion disc with a steady-state radial temperature profile T(R) and assume that the variable flux is due to axisymmetric temperature perturbations δT(R, t). After linearizing the equations, we fit UV-optical AGN light curves to determine δ…
The vertical structure of debris discs and the impact of gas
Henning, Thomas; Boccaletti, Anthony; Kral, Quentin +10 more
The vertical structure of debris discs provides clues about their dynamical evolution and the collision rate of the unseen planetesimals. Thanks to the ever-increasing angular resolution of contemporary instruments and facilities, we are beginning to constrain the scale height of a handful of debris discs, either at near-infrared or millimeter wav…
A comprehensive analysis of WASP-17b's transmission spectrum from space-based observations
May, E. M.; Wakeford, H. R.; Sing, D. K. +9 more
Due to its 1770 K equilibrium temperature, WASP-17b, a 1.99 RJup, 0.486 MJup exoplanet, sits at the critical juncture between hot and ultra-hot Jupiters. We present its 0.3-5 $\rm{\mu m}$ transmission spectrum, newly obtained with Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) measurements, and, taking advantage of i…
Hidden cooling flows in clusters of galaxies
Fabian, A. C.; Pinto, C.; Ferland, G. J. +3 more
The radiative cooling time of the hot gas at the centres of cool cores in clusters of galaxies drops down to 10 Myr and below. The observed mass cooling rate of such gas is very low, suggesting that active galactic nucleus feedback is very tightly balanced or that the soft X-ray emission from cooling is somehow hidden from view. We use an intrinsi…
Astrometric excess noise in Gaia EDR3 and the search for X-ray binaries
Knigge, C.; Charles, P. A.; Gandhi, P. +6 more
Astrometric noise (ϵ) in excess of parallax and proper motion is a potential signature of orbital wobble (ω) of individual components in binary star systems. The combination of X-ray selection with astrometric noise could then be a powerful tool for robustly isolating accreting binaries in large surveys. Here, we mine the Gaia EDR3 catalogue for G…
The size-luminosity relation of lensed galaxies at z 6-9 in the Hubble Frontier Fields
Castellano, Marco; Fontana, Adriano; Treu, Tommaso +8 more
We measure the size-luminosity relation of photometrically selected galaxies within the redshift range z ~ 6-9, using galaxies lensed by six foreground Hubble Frontier Fields (HFF) clusters. The power afforded by strong gravitational lensing allows us to observe fainter and smaller galaxies than in blank fields. We select our sample of galaxies an…