Search Publications
Revisiting the Spectral and Timing Properties of NGC 4151
Miller, J. M.; Zoghbi, A.; Cackett, E.
NGC 4151 is the brightest Seyfert 1 nucleus in X-rays. It was the first object to show short time delays in the Fe K band, which were attributed to relativistic reverberation, providing a new tool for probing regions at the black hole scale. Here we report the results of a large XMM-Newton campaign in 2015 to study these short delays further. Anal…
Self-lensing Discovery of a 0.2 M ⊙ White Dwarf in an Unusually Wide Orbit around a Sun-like Star
Bieryla, Allyson; Latham, David W.; Aoki, Wako +4 more
We report the discovery of the fifth self-lensing binary in which a low-mass white dwarf (WD) gravitationally magnifies its 15th magnitude G-star companion, KIC 8145411, during eclipses. The system was identified from a pair of such self-lensing events in the Kepler photometry, and was followed up with the Tillinghast Reflector Echelle Spectrograp…
Comparison of Gaia DR2 Parallaxes of Stars with VLBI Astrometry
Reid, Mark J.; Zhang, Bo; Xu, Shuangjing +2 more
We compare the parallaxes of stars from VLBI astrometry in the literature to those in the Gaia DR2 catalog. Our full sample contains young stellar objects, evolved AGB stars, pulsars, and other radio stars. Excluding AGB stars, which show significant discrepancies between Gaia and VLBI parallaxes, and stars in binary systems, we obtain an average,…
On the Use of Field RR Lyrae as Galactic Probes. I. The Oosterhoff Dichotomy Based on Fundamental Variables
Valenti, E.; Marinoni, S.; Thévenin, F. +21 more
We collected a large data set of field RR Lyrae stars (RRLs) by using catalogs already available in the literature and Gaia DR2. We estimated the iron abundances for a subsample of 2382 fundamental RRLs (ΔS method: Ca II K, Hβ, Hγ, and Hδ lines) for which there are publicly available medium-resolution SDSS-SEGUE spectra. We also included similar e…
GROWTH on S190426c: Real-time Search for a Counterpart to the Probable Neutron Star-Black Hole Merger using an Automated Difference Imaging Pipeline for DECam
Duev, Dmitry A.; Andreoni, Igor; De, Kishalay +17 more
The discovery of a transient kilonova following the gravitational-wave (GW) event GW170817 highlighted the critical need for coordinated rapid and wide-field observations, inference, and follow-up across the electromagnetic spectrum. In the southern hemisphere, the Dark Energy Camera (DECam) on the Blanco 4 m telescope is well suited to this task,…
Expanding the Sample of Radio Minihalos in Galaxy Clusters
Clarke, Tracy E.; Giacintucci, Simona; Venturi, Tiziana +4 more
Radio minihalos are diffuse synchrotron sources of unknown origin found in the cool cores of some galaxy clusters. We use GMRT and VLA data to expand the sample of minihalos by reporting three new minihalo detections (A2667, A907, and PSZ1 G139.61+24.20) and confirming minihalos in five clusters (MACS J0159.8-0849, MACS J0329.6-0211, RXC J2129.6+0…
The Molecular Gas Reservoirs of z ∼ 2 Galaxies: A Comparison of CO(1-0) and Dust-based Molecular Gas Masses
Walter, F.; Scoville, N.; Riechers, D. A. +7 more
We test the use of long-wavelength dust continuum emission as a molecular gas tracer at high redshift, via a unique sample of a dozen z ∼ 2 galaxies with observations of both the dust continuum and CO(1-0) line emission (obtained with the Atacama Large Millimeter Array and Karl G. Jansky Very Large Array, respectively). Our work is motivated by re…
Why Do Torus-unstable Solar Filaments Experience Failed Eruptions?
Wang, Yuming; Zhuang, Bin; Liu, Lijuan +5 more
We study the magnetic field and 3D configuration of 16 filament eruptions during 2010 July-2013 February in order to investigate the factors that control the success and/or failure of solar eruptions. All of these events, i.e., eruptions that failed to be ejected and become coronal mass ejections, have filament maximum heights exceeding 100 Mm. Th…
A Family Picture: Tracing the Dynamical Path of the Structural Properties of Multiple Populations in Globular Clusters
Dalessandro, Emanuele; Martocchia, S.; Bastian, N. +6 more
We studied the spatial distributions of multiple stellar populations (MPs) in a sample of 20 globular clusters (GCs) spanning a broad range of dynamical ages. The differences between first-population (FP) and second-population (SP) stars were measured by means of the parameter A +, defined as the area enclosed between their cumulative r…
First Detection of Plasmoids from Breakout Reconnection on the Sun
Antiochos, Spiro K.; Kumar, Pankaj; DeVore, C. Richard +2 more
Transient collimated plasma ejections (jets) occur frequently throughout the solar corona, in active regions, quiet Sun, and coronal holes. Although magnetic reconnection is generally agreed to be the mechanism of energy release in jets, the factors that dictate the location and rate of reconnection remain unclear. Our previous studies demonstrate…