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Discovery of a Disrupting Open Cluster Far into the Milky Way Halo: A Recent Star Formation Event in the Leading Arm of the Magellanic Stream?
Choi, Yumi; Nidever, David L.; Price-Whelan, Adrian M. +4 more
We report the discovery of a young (τ ∼ 117 {{Myr}}), low-mass (M∼ 1200 {M}⊙ ), metal-poor ([{{Fe}}/{{H}}]∼ -1.14) stellar association at a heliocentric distance D≈ 28.7 {{kpc}}, placing it far into the Milky Way (MW) halo. At its present Galactocentric position (R,z)∼ (23,15) {{kpc}}, the association is (on the sky) near the leading ar…
Photoionized emission and absorption features in the high-resolution X-ray spectra of NGC 3783
Kaastra, J. S.; Kriss, G. A.; Arav, N. +14 more
Our Swift monitoring program triggered two joint XMM-Newton, NuSTAR, and HST observations on 11 and 21 December 2016 targeting NGC 3783 because its soft X-ray continuum was heavily obscured. Consequently, emission features, including the O VII radiative recombination continuum, stand out above the diminished continuum. We focus on the photoionized…
Direct T e Metallicity Calibration of R23 in Strong Line Emitters
Malhotra, Sangeeta; Yang, Huan; Rhoads, James E. +1 more
The gas metallicity of galaxies is often estimated using strong emission lines such as the optical lines of [O III] and [O II]. The most common measure is “R23,” defined as ([O II]λλ3726, 3729 + [O III]λλ4959,5007)/Hβ. Most calibrations for these strong-line metallicity indicators are for continuum selected galaxies. We report a new empirical cali…
The Third Data Release of the Beijing-Arizona Sky Survey
Myers, Adam D.; Fan, Xiaohui; Jiang, Linhua +45 more
The Beijing-Arizona Sky Survey (BASS) is a wide and deep imaging survey that covers a 5400 deg2 area in the northern Galactic cap with the 2.3 m Bok telescope using two filters (g and r bands). The Mosaic z-band Legacy Survey (MzLS) covers the same area in the z band with the 4 m Mayall telescope. These two surveys will be used for spec…
A 3 Gyr White Dwarf with Warm Dust Discovered via the Backyard Worlds: Planet 9 Citizen Science Project
Debes, John H.; Wisniewski, John; Meisner, Aaron M. +13 more
Infrared excesses due to dusty disks have been observed orbiting white dwarfs with effective temperatures between 7200 and 25,000 K, suggesting that the rate of tidal disruption of minor bodies massive enough to create a coherent disk declines sharply beyond 1 Gyr after white dwarf formation. We report the discovery that the candidate white dwarf …
Combined Scattering of Radiation Belt Electrons Caused by Landau and Bounce Resonant Interactions With Magnetosonic Waves
Fu, Song; Ni, Binbin; Gu, Xudong +2 more
We develop a full relativistic test particle code to model the combined electron scattering effect of Landau and bounce resonances with magnetosonic waves. Test particle simulations of magnetosonic wave-electron interactions indicate that the two resonances coexist to affect radiation belt electrons at different energies and pitch angles, and the …
Reverberation Mapping of the Narrow-line Seyfert 1 Galaxy I Zwicky 1: Black Hole Mass
Ho, Luis C.; Bian, Wei-Hao; Zhang, Zhi-Xiang +11 more
We report results of the first reverberation mapping campaign of I Zwicky 1 during 2014-2016, which showed unambiguous reverberations of the broad Hβ line emission in the varying optical continuum. From analysis using several methods, we obtain a reverberation lag of {τ }{{H}β }={37.2}-4.9+4.5 {days}. Taking a viri…
CO Detected in CI Tau b: Hot Start Implied by Planet Mass and M K
Johns-Krull, Christopher M.; Prato, L.; Flagg, Laura +5 more
We acquired high-resolution infrared spectra of CI Tau, the host star of one of the few young planet candidates amenable to direct spectroscopic detection. We confirm the planet’s existence with a direct detection of CO in the planet’s atmosphere. We also calculate a mass of 11.6 M J based on the amplitude of its radial velocity variati…
Direct evidence of nonstationary collisionless shocks in space plasmas
Pulkkinen, Tuija I.; Russell, Christopher T.; Dandouras, Iannis +11 more
Distances and ages from isochrone fits of 150 open clusters using Gaia DR2 data
Dias, W. S.; Monteiro, H.
We investigate a sample of open cluster candidates with no previous age determination using astrometric and photometric data from the Gaia DR2 catalogue. Using proper motions and parallaxes and the full co-variance matrix we determined the astrometric membership probability of the stars in the field of each candidate. The memberships were used as …