Search Publications
Extensive Globular Cluster Systems Associated with Ultra Diffuse Galaxies in the Coma Cluster
Mowla, Lamiya; van Dokkum, Pieter; Romanowsky, Aaron J. +7 more
We present Hubble Space Telescope (HST) imaging of two ultra diffuse galaxies (UDGs) with measured stellar velocity dispersions in the Coma cluster. The galaxies, Dragonfly 44 and DFX1, have effective radii of 4.7 kpc and 3.5 kpc and velocity dispersions of {47}-6+8 km s-1 and {30}-7+7 km s
Statistical Studies of Solar White-light Flares and Comparisons with Superflares on Solar-type Stars
Notsu, Yuta; Maehara, Hiroyuki; Namekata, Kosuke +9 more
Recently, many superflares on solar-type stars have been discovered as white-light flares (WLFs). The statistical study found a correlation between their energies (E) and durations (τ): τ \propto {E}0.39, similar to those of solar hard/soft X-ray flares, τ \propto {E}0.2{--0.33}. This indicates a universal mechanism of energy…
Simultaneous X-Ray, Gamma-Ray, and Radio Observations of the Repeating Fast Radio Burst FRB 121102
Ransom, S. M.; Chatterjee, S.; Cordes, J. M. +19 more
We undertook coordinated campaigns with the Green Bank, Effelsberg, and Arecibo radio telescopes during Chandra X-ray Observatory and XMM-Newton observations of the repeating fast radio burst FRB 121102 to search for simultaneous radio and X-ray bursts. We find 12 radio bursts from FRB 121102 during 70 ks total of X-ray observations. We detect no …
The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. VII. Properties of the Host Galaxy and Constraints on the Merger Timescale
Berger, E.; Rest, A.; Annis, J. +21 more
We present the properties of NGC 4993, the host galaxy of GW170817, the first gravitational-wave (GW) event from the merger of a binary neutron star (BNS) system and the first with an electromagnetic (EM) counterpart. We use both archival photometry and new optical/near-IR imaging and spectroscopy, together with stellar population synthesis models…
Hitomi Constraints on the 3.5 keV Line in the Perseus Galaxy Cluster
Mukai, K.; Yamaguchi, H.; Koyama, K. +215 more
High-resolution X-ray spectroscopy with Hitomi was expected to resolve the origin of the faint unidentified E≈ 3.5 {keV} emission line reported in several low-resolution studies of various massive systems, such as galaxies and clusters, including the Perseus cluster. We have analyzed the Hitomi first-light observation of the Perseus cluster. The e…
Global Energetics of Solar Flares. V. Energy Closure in Flares and Coronal Mass Ejections
Xu, Yan; Jing, Ju; Warren, Harry P. +11 more
In this study we synthesize the results of four previous studies on the global energetics of solar flares and associated coronal mass ejections (CMEs), which include magnetic, thermal, nonthermal, and CME energies in 399 solar M- and X-class flare events observed during the first 3.5 yr of the Solar Dynamics Observatory (SDO) mission. Our findings…
The Distance to NGC 4993: The Host Galaxy of the Gravitational-wave Event GW170817
Gall, Christa; Hjorth, Jens; Tanvir, Nial R. +6 more
The historic detection of gravitational waves from a binary neutron star merger (GW170817) and its electromagnetic counterpart led to the first accurate (sub-arcsecond) localization of a gravitational-wave event. The transient was found to be ∼10″ from the nucleus of the S0 galaxy NGC 4993. We report here the luminosity distance to this galaxy usi…
Placing the Spotted T Tauri Star LkCa 4 on an HR Diagram
Herczeg, Gregory J.; Jose, Jessy; Liu, Chun-Fan +12 more
Ages and masses of young stars are often estimated by comparing their luminosities and effective temperatures to pre-main-sequence stellar evolution tracks, but magnetic fields and starspots complicate both the observations and evolution. To understand their influence, we study the heavily spotted weak-lined T-Tauri star LkCa 4 by searching for sp…
Calibrating Star Formation in WISE Using Total Infrared Luminosity
Dale, D. A.; Smith, J. -D. T.; Brown, M. J. I. +3 more
We present accurate resolved WISE photometry of galaxies in the combined SINGS and KINGFISH sample. The luminosities in the W3 12 µm and W4 23 µm bands are calibrated to star formation rates (SFRs) derived using the total infrared luminosity, avoiding UV/optical uncertainties due to dust extinction corrections. The W3 relation has a 1σ…
z ∼ 2: An Epoch of Disk Assembly
Trump, Jonathan R.; Weiner, Benjamin J.; Pacifici, Camilla +8 more
We explore the evolution of the internal gas kinematics of star-forming galaxies from the peak of cosmic star formation at z∼ 2 to today. Measurements of galaxy rotation velocity V rot, which quantify ordered motions, and gas velocity dispersion {σ }g, which quantify disordered motions, are adopted from the DEEP2 and SIGMA su…