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Constraining the Magnetic Field in the TeV Halo of Geminga with X-Ray Observations
Liu, Ruo-Yu; Ge, Chong; Wang, Xiang-Yu +1 more
Recently, the High Altitude Water Cherenkov (HAWC) collaboration reported the discovery of a TeV halo around the Geminga pulsar. The TeV emission is believed to originate from the inverse Compton scattering of pulsar-injected electrons/positrons off cosmic microwave background photons. During this time, these electrons should inevitably radiate X-…
Chemical and Kinematic Properties of the Galactic Disk from the LAMOST and Gaia Sample Stars
Shi, Jianrong; Chen, Yuqin; Ma, Jun +5 more
We determined the chemical and kinematic properties of the Galactic thin and thick disk using a sample of 307,246 A/F/G/K-type giant stars from the LAMOST spectroscopic survey and Gaia DR2 survey. Our study found that the thick disk globally exhibits no metallicity radial gradient, but the inner disk (R ≤ 8 kpc) and the outer disk (R > 8 kpc) h…
Investigating the X-ray enhancements of highly radio-loud quasars at z > 4
Brandt, W. N.; Garmire, G. P.; Miller, B. P. +2 more
We have investigated the jet-linked X-ray emission from highly radio-loud quasars (HRLQs; log R > 2.5) at high redshift. We studied the X-ray properties of 15 HRLQs at z > 4, using new Chandra observations for six objects and archival XMM-Newton and Swift observations for the other nine. We focused on testing the apparent enhancement of jet-…
Testing the Evolutionary Link between Type 1 and Type 2 Quasars with Measurements of the Interstellar Medium
Ho, Luis C.; Shangguan, Jinyi
In a popular scenario for the coevolution of massive black holes and galaxies, major mergers of gas-rich galaxies fuel vigorous star formation and obscured (type 2) quasar activity until energy feedback from the active galactic nucleus (AGN) clears away the gas and dust to reveal an unobscured (type 1) quasar. Under this scenario, the precursor ty…
Constraints on the Occurrence and Distribution of 1-20 M Jup Companions to Stars at Separations of 5-5000 au from a Compilation of Direct Imaging Surveys
Gagné, Jonathan; Delorme, Philippe; Lafrenière, David +4 more
We present the first statistical analysis of exoplanet direct imaging surveys combining adaptive optics (AO) imaging at small separations with deep seeing-limited observations at large separations allowing us to study the entire orbital separation domain from 5 to 5000 au simultaneously. Our sample of 344 stars includes only confirmed members of n…
Anisotropic winds in a Wolf-Rayet binary identify a potential gamma-ray burst progenitor
Callingham, J. R.; Crowther, P. A.; Tuthill, P. G. +5 more
The massive evolved Wolf-Rayet stars sometimes occur in colliding-wind binary systems in which dust plumes are formed as a result of the collision of stellar winds1. These structures are known to encode the parameters of the binary orbit and winds2-4. Here we report observations of a previously undiscovered Wolf-Rayet system,…
First stellar spectroscopy in Leo P
Lennon, D. J.; Bastian, N.; Cioni, M. -R. L. +11 more
We present the first stellar spectroscopy in the low-luminosity (MV ∼ -9.3 mag), dwarf galaxy Leo P. Its significantly low oxygen abundance (3% solar) and relative proximity (∼1.6 Mpc) make it a unique galaxy in which to investigate the properties of massive stars with near-primordial compositions akin to those in the early Universe. Fr…
Multi-epoch Direct Imaging and Time-variable Scattered Light Morphology of the HD 163296 Protoplanetary Disk
Henning, Thomas; Nakagawa, Takao; Terada, Hiroshi +58 more
We present H-band polarized scattered light imagery and JHK high-contrast spectroscopy of the protoplanetary disk around HD 163296 observed with the High-Contrast Coronographic Imager for Adaptive Optics (HiCIAO) and Subaru Coronagraphic Extreme Adaptive Optics (SCExAO)/Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) instrument…
Astrometric and photometric study of NGC 6067, NGC 2506, and IC 4651 open clusters based on wide-field ground and Gaia DR2 data
Bisht, D.; Rangwal, Geeta; Yadav, R. K. S. +2 more
We present an analysis of three southern open star clusters NGC 6067, NGC 2506, and IC 4651 using wide-field photometric and Gaia DR2 astrometric data. They are poorly studied clusters. We took advantage of the synergy between Gaia DR2 high precision astrometric measurements and ground-based wide-field photometry to isolate cluster members and fur…
X-Ray Observations of a z ∼ 6.2 Quasar/Galaxy Merger
Fan, Xiaohui; Mulchaey, John S.; Walter, Fabian +7 more
Quasars at early redshifts (z > 6) with companion galaxies offer unique insights into the growth and evolution of the first supermassive black holes. Here, we report on a 150 ks Chandra observation of PSO J308.0416-21.2339, a z = 6.23 quasar with a merging companion galaxy identified in [C II] and rest-frame UV emission. With {72.3}-8.6