Search Publications
A Hard Look at Local, Optically Selected, Obscured Seyfert Galaxies
Kaastra, J. S.; Stern, D.; Brandt, W. N. +11 more
We study the X-ray spectra of a sample of 19 obscured, optically selected Seyfert galaxies (Sy 1.8, 1.9, and 2) in the local universe (d ≤ 175 Mpc), drawn from the CfA Seyfert sample. Our analysis is driven by the high sensitivity of NuSTAR in the hard X-rays, coupled with soft X-ray spectra using XMM-Newton, Chandra, Suzaku, and Swift/XRT. We als…
Binary Stars in Upper Scorpius
Tokovinin, Andrei; Briceño, Cesar
To address the statistics of binary stars in the 8 Myr old Upper Scorpius (USco) star formation region, we conducted a speckle interferometric survey of 614 association members more massive than 0.4 {{ \mathcal M }}⊙ (spectral types earlier than M3V) based on the list of Luhman et al. (2018). We resolved 187 pairs, 55 of which are new …
Asymmetric expansion of coronal mass ejections in the low corona
Cremades, H.; Iglesias, F. A.; Merenda, L. A.
Aims: Understanding how magnetic fields are structured within coronal mass ejections (CMEs), and how they evolve from the low corona into the heliosphere, is a major challenge for space weather forecasting and for solar physics. The study of CME morphology is a particularly auspicious approach to this problem, given that it holds a close rela…
Vetting the optical transient candidates detected by the GWAC network using convolutional neural networks
Bertin, E.; Xu, Y.; Leroy, N. +11 more
The observation of the transient sky through a multitude of astrophysical messengers has led to several scientific breakthroughs in the last two decades, thanks to the fast evolution of the observational techniques and strategies employed by the astronomers. Now, it requires to be able to coordinate multiwavelength and multimessenger follow-up cam…
The ASAS-SN catalogue of variable stars - VIII. 'Dipper' stars in the Lupus star-forming region
Kochanek, C. S.; Stanek, K. Z.; Shappee, B. J. +9 more
Some young stellar objects such as T Tauri-like 'dipper' stars vary due to transient partial occultation by circumstellar dust, and observations of this phenomenon inform us of conditions in the planet-forming zones close to these stars. Although many dipper stars have been identified with space missions such as Kepler/K2, ground-based telescopes …
Tracing the anemic stellar halo of M 101
Bell, Eric F.; Holwerda, Benne W.; Monachesi, Antonela +3 more
Models of galaxy formation in a cosmological context predict that massive disk galaxies should have structured extended stellar halos. Recent studies in integrated light, however, report that a few galaxies, including the nearby disk galaxy M 101, have no measurable stellar halos to the detection limit. We aim to quantify the stellar content and s…
Direct Measurement of the Solar-wind Taylor Microscale Using MMS Turbulence Campaign Data
Strangeway, Robert J.; Russell, Christopher T.; Chasapis, Alexandros +7 more
Using the novel Magnetospheric Multiscale (MMS) mission data accumulated during the 2019 MMS Solar Wind Turbulence Campaign, we calculate the Taylor microscale (λT) of the turbulent magnetic field in the solar wind. The Taylor microscale represents the onset of dissipative processes in classical turbulence theory. However, an accurate e…
Plasma characterization at comet 67P between 2 and 4 AU from the Sun with the RPC-MIP instrument
Henri, Pierre; Vallières, Xavier; Deca, Jan +2 more
The plasma of comet 67P/Churyumov-Gerasimenko is analyzed based on the RPC-MIP mutual impedance probe data of the Rosetta mission. Numerical simulations of the RPC-MIP instrumental response considering two populations of electrons were fit on experimental responses acquired from January to September 2016 to extract the electron densities and tempe…
A multi-chord stellar occultation by the large trans-Neptunian object (174567) Varda
Berthier, J.; Carry, B.; Souami, D. +41 more
Context. We present results from the first recorded stellar occultation by the large trans-Neptunian object (174567) Varda that was observed on September 10, 2018. Varda belongs to the high-inclination dynamically excited population, and has a satellite, Ilmarë, which is half the size of Varda.
Aims: We determine the size and albedo of Varda …
Cloud Atlas: Weak Color Modulations Due to Rotation in the Planetary-mass Companion GU Psc b and 11 Other Brown Dwarfs
Schneider, Glenn; Apai, Dániel; Marley, Mark +10 more
Among the greatest challenges in understanding ultracool brown dwarf and exoplanet atmospheres is the evolution of cloud structure as a function of temperature and gravity. In this study, we present the rotational modulations of GU Psc b—a rare mid-T spectral type planetary-mass companion at the end of the L/T spectral type transition. Based on th…