Search Publications
Low-frequency GMRT observations of ultra-cool dwarfs
Chandra, Poonam; Kaplan, David L.; Murphy, Tara +2 more
Observations of radio emission in about 10 per cent of ultra-cool dwarfs (UCDs) indicate the presence of strong, persistent magnetic fields in these stars. These results are in contrast to early theoretical expectations on fully convective dynamos, and to other tracers of magnetic activity, such as H α and X-ray luminosity. Radio-frequency observa…
Cosmology with extragalactic proper motions: harmonic formalism, estimators, and forecasts
Hall, Alex
We conduct a thorough study into the feasibility of measuring large-scale correlated proper motions of galaxies with astrometric surveys. We introduce a harmonic formalism for analysing proper motions and their correlation functions on the sphere based on spin-weighted spherical harmonics, and study the statistics of the transverse velocity field …
Praesepe white dwarfs in Gaia DR2
Salaris, M.; Bedin, L. R.
We have exploited Gaia Data Release 2 to study white dwarf members of the Praesepe star cluster. We recovered 11 known white dwarf members (all DA spectral type) plus a new cluster WD never identified before. 2 of the 11 known DA objects did not satisfy all quality indicators available in the data release. The remaining nine objects of known spect…
Using HARPS-N to characterize the long-period planets in the PH-2 and Kepler-103 systems
Vanderburg, Andrew; López-Morales, Mercedes; Buchhave, Lars A. +26 more
We present confirmation of the planetary nature of PH-2b, as well as the first mass estimates for the two planets in the Kepler-103 system. PH-2b and Kepler-103c are both long-period and transiting, a sparsely populated category of exoplanets. We use Kepler light-curve data to estimate a radius, and then use HARPS-N radial velocities to determine …
Spectroscopic study of the extremely young O-type triple system Herschel 36 A in the Hourglass nebula - I. Orbital properties
Morrell, Nidia I.; Barbá, Rodolfo H.; Maíz Apellániz, Jesús +3 more
We present a detailed spectroscopic study of Herschel 36 A (H36A), the main stellar component of the massive multiple system Herschel 36 in the Hourglass nebula, based on high-resolution optical spectra obtained along an 11 yr span. The three stellar components present in the spectrum of H36A are separated by means of a spectral disentangling tech…
Nearly coeval intermediate-age Milky Way star clusters at very different dynamics evolutionary stages
Piatti, Andrés E.; Dias, Wilton S.; Angelo, Mateus S.
We report astrophysical properties of 12 Milky Way open clusters located beyond a 2 kpc circle around the Sun by using deep optical photometry. We estimated their age and metallicities on the basis of a maximum likelihood approach using astrometric members determined from Gaia DR2 data. The studied clusters turned out to be of intermediate-age (0.…
Optical and X-ray correlations during the 2015 outburst of the black hole V404 Cyg
Dhillon, V. S.; Gandhi, P.; Marsh, T. R. +6 more
We present a serendipitous multiwavelength campaign of optical photometry simultaneous with Integral X-ray monitoring of the 2015 outburst of the black hole V404 Cyg. Large-amplitude optical variability is generally correlated with X-rays, with lags of order a minute or less compatible with binary light travel time-scales or jet ejections. Rapid o…
Investigating the origin of the spectral line profiles of the Hot Wolf-Rayet Star WR 2
Crowther, P. A.; Wade, G. A.; Chené, A. -N. +12 more
The hot WN star WR 2 (HD 6327) has been claimed to have many singular characteristics. To explain its unusually rounded and relatively weak emission line profiles, it has been proposed that WR 2 is rotating close to break-up with a magnetically confined wind. Alternatively, the line profiles could be explained by the dilution of WR 2's spectrum by…
The 3D shape of Type IIb SN 2011hs
Spyromilio, J.; Wang, L.; Wheeler, J. C. +10 more
We observed seven epochs of spectropolarimetry in optical wavelengths for the Type IIb SN 2011hs, ranging from -3 to +40 d with respect to V-band maximum. A high degree of interstellar polarization was detected (up to ∼3 per cent), with a peak lying blueward of 4500 Å. Similar behaviours have been seen in some Type Ia supernovae (SNe), but had nev…
Transit analysis of the CoRoT-5, CoRoT-8, CoRoT-12, CoRoT-18, CoRoT-20, and CoRoT-27 systems with combined ground- and space-based photometry
Heras, A. M.; Casanova, V.; Fernández, M. +2 more
We have initiated a dedicated project to follow-up with ground-based photometry the transiting planets discovered by CoRoT in order to refine the orbital elements, constrain their physical parameters, and search for additional bodies in the system. From 2012 September to 2016 December we carried out 16 transit observations of six CoRoT planets (Co…