Search Publications
Rotation and spots in normal A and Am/Fm stars
Joshi, Santosh; De Cat, Peter; Trust, Otto +1 more
Frequency analysis of long-term ultraprecise photometry can lead to precise values of rotation frequencies of rotating stars with `hump and spike' features in their periodograms. Using these features, we computed the rotation frequencies and amplitudes. The corresponding equatorial rotational velocity (V_{{rot}}) and spot size were estimated. On f…
The ancient main-sequence solar proxy HIP 102152 unveils the activity and rotational fate of our Sun
Meléndez, Jorge; Lorenzo-Oliveira, Diego; Ponte, Geisa +1 more
We present a detailed analysis of the possible future Sun's rotational evolution scenario based on the 8-Gyr-old solar twin HIP 102152. Using HARPS high-cadence observations (and TESS light curves), we analysed the modulation of a variety of activity proxies (Ca II, H I Balmer, and Na I lines), finding a strong rotational signal of 35.7 ± 1.4 d (l…
The contribution of quasar absorption outflows to AGN feedback
Xu, Xinfeng; Kriss, Gerard A.; Arav, Nahum +1 more
Determining the distance of quasar absorption outflows from the central source (R) and their kinetic luminosity ($\dot{E}_\mathrm{\scriptstyle k}$) is crucial for understanding their contribution to active galactic nucleus (AGN) feedback. Here, we summarize the results for a sample of nine luminous quasars that were observed with the Hubble Space …
Extended main sequence turnoffs in open clusters as seen by Gaia - II. The enigma of NGC 2509
Cabrera-Ziri, I.; Usher, C.; Bastian, N. +6 more
We investigate the morphology of the colour-magnitude diagram (CMD) of the open cluster NGC 2509 in comparison with other Galactic open clusters of similar age using Gaia photometry. At ∼900 {Myr} Galactic open clusters in our sample all show an extended main sequence turnoff (eMSTO) with the exception of NGC 2509, which presents an exceptionally …
Constraints on the spin-pole orientation, jet morphology, and rotation of interstellar comet 2I/Borisov with deep HST imaging
Lisse, Carey M.; Bolin, Bryce T.
We present high resolution, deep imaging of interstellar comet 2I/Borisov taken with the Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3) on 2019 December 8 UTC and 2020 January 27 UTC (HST GO 16040, PI: Bolin) before and after its perihelion passage in combination with HST/WFC3 images taken on 2019 October 12 UTC and 2019 November 16 UTC (HS…
The auroral radio emission of the magnetic B-type star ρ-=OphC
Umana, G.; Fossati, L.; Loru, S. +19 more
The non-thermal radio emission of main-sequence early-type stars is a signature of stellar magnetism. We present multiwavelength (1.6-16.7 GHz) ATCA measurements of the early-type magnetic star ρ-=OphC, which is a flat-spectrum non-thermal radio source. The ρ-=OphC radio emission is partially circularly polarized with a steep spectral dependence: …
The power of coordinate transformations in dynamical interpretations of Galactic structure
Hogg, David W.; Kawata, Daisuke; Johnston, Kathryn V. +3 more
Gaia DR2 has provided an unprecedented wealth of information about the positions and motions of stars in our Galaxy and has highlighted the degree of disequilibria in the disc. As we collect data over a wider area of the disc, it becomes increasingly appealing to start analysing stellar actions and angles, which specifically label orbit space, ins…
The M31/M33 tidal interaction: a hydrodynamic simulation of the extended gas distribution
Li, Di; Bland-Hawthorn, Joss; Tepper-García, Thor
We revisit the orbital history of the Triangulum galaxy (M33) around the Andromeda galaxy (M31) in view of the recent Gaia Data Release 2 proper motion measurements for both Local Group galaxies. Earlier studies consider highly idealized dynamical friction, but neglect the effects of dynamical mass loss. We show the latter process to be important …
The WAGGS project-III. Discrepant mass-to-light ratios of Galactic globular clusters at high metallicity
Martocchia, S.; Da Costa, G. S.; Usher, C. +10 more
Observed mass-to-light ratios (M/L) of metal-rich globular clusters (GCs) disagree with theoretical predictions. This discrepancy is of fundamental importance since stellar population models provide the stellar masses that underpin most of extragalactic astronomy, near and far. We have derived radial velocities for 1622 stars located in the centre…
Chromosome maps of young LMC clusters: an additional case of coeval multiple populations
Martocchia, S.; Dalessandro, E.; Salaris, M. +9 more
Recent studies have revealed that the multiple populations (MPs) phenomenon does not occur only in ancient and massive Galactic globular clusters (GCs), but it is also observed in external galaxies, where GCs sample a wide age range with respect to the Milky Way. However, for a long time, it was unclear whether we were looking at the same phenomen…