Search Publications
Tracking the Evolution of a Coherent Magnetic Flux Rope Continuously from the Inner to the Outer Corona
Cheng, X.; Ding, M. D.; Zhang, J. +6 more
The magnetic flux rope (MFR) is believed to be the underlying magnetic structure of coronal mass ejections (CMEs). However, it remains unclear how an MFR evolves into and forms the multi-component structure of a CME. In this paper, we perform a comprehensive study of an extreme-ultraviolet (EUV) MFR eruption on 2013 May 22 by tracking its morpholo…
The Variable Hard X-Ray Emission of NGC 4945 as Observed by NuSTAR
Hailey, Charles J.; Brandt, William N.; Comastri, Andrea +19 more
We present a broadband (~0.5-79 keV) spectral and temporal analysis of multiple NuSTAR observations combined with archival Suzaku and Chandra data of NGC 4945, the brightest extragalactic source at 100 keV. We observe hard X-ray (>10 keV) flux and spectral variability, with flux variations of a factor of two on timescales of 20 ks. A variable p…
A Reconnaissance of the Possible Donor Stars to the Kepler Supernova
Schmidt, Brian P.; Do, Tuan; Scharwächter, Julia +2 more
The identity of Type Ia supernova progenitors remains a mystery, with various lines of evidence pointing toward either accretion from a nondegenerate companion or the rapid merger of two degenerate stars leading to the thermonuclear destruction of a white dwarf. In this paper, we spectroscopically scrutinize 24 of the brightest stars residing in t…
Faint Submillimeter Galaxies Revealed by Multifield Deep ALMA Observations: Number Counts, Spatial Clustering, and a Dark Submillimeter Line Emitter
Ono, Yoshiaki; Ouchi, Masami; Kurono, Yasutaka +1 more
We present the statistics of faint submillimeter/millimeter galaxies (SMGs) and serendipitous detections of a submillimeter/millimeter line emitter (SLE) with no multi-wavelength continuum counterpart revealed by the deep ALMA observations. We identify faint SMGs with flux densities of 0.1-1.0 mJy in the deep Band-6 and Band-7 maps of 10 independe…
Magnetohydrodynamic Simulation of the X2.2 Solar Flare on 2011 February 15. I. Comparison with the Observations
Choe, G. S.; Park, Y. D.; Inoue, S. +2 more
We performed a magnetohydrodynamic (MHD) simulation using a nonlinear force-free field (NLFFF) in solar active region 11158 to clarify the dynamics of an X2.2-class solar flare. We found that the NLFFF never shows the dramatic dynamics seen in observations, i.e., it is in a stable state against the perturbations. On the other hand, the MHD simulat…
First Evidence of Fully Spatially Mixed First and Second Generations in Globular Clusters: The Case of NGC 6362
Dalessandro, Emanuele; Salaris, Maurizio; Mucciarelli, Alessio +6 more
We present the first evidence of multiple populations in the Galactic globular cluster NGC 6362. We used optical and near-UV Hubble Space Telescope and ground-based photometry, finding that both the sub-giant and red giant branches are split in two parallel sequences in all color-magnitude diagrams where the F336W filter (or U band) is used. This …
A Hot Cocoon in the Ultralong GRB 130925A: Hints of a POPIII-like Progenitor in a Low-Density Wind Environment
Fiore, Fabrizio; Piro, Luigi; Wieringa, Mark H. +7 more
GRB 130925A is a peculiar event characterized by an extremely long gamma-ray duration (≈7 ks), as well as dramatic flaring in the X-rays for ≈20 ks. After this period, its X-ray afterglow shows an atypical soft spectrum with photon index Γ ~ 4, as observed by Swift and Chandra, until ≈107 s, when XMM-Newton observations uncover a harder…
Water Vapor in the Spectrum of the Extrasolar Planet HD 189733b. II. The Eclipse
Deming, Drake; Madhusudhan, Nikku; Crouzet, Nicolas +1 more
Spectroscopic observations of exoplanets are crucial to infer the composition and properties of their atmospheres. HD 189733b is one of the most extensively studied exoplanets and is a cornerstone for hot Jupiter models. In this paper, we report the dayside emission spectrum of HD 189733b in the wavelength range 1.1-1.7 µm obtained with the …
Young Galaxy Candidates in the Hubble Frontier Fields. I. A2744
Broadhurst, Tom; Kelson, Daniel D.; Moustakas, John +10 more
We report the discovery of 24 Lyman-break candidates at 7 <~ z <~ 10.5, in the Hubble Frontier Fields (HFF) imaging data of A2744 (z = 0.308), plus Spitzer/IRAC data and archival ACS data. The sample includes a triple image system with a photometric redshift of z ~= 7.4. This high redshift is geometrically confirmed by our lens model corresp…
MOSFIRE Absorption Line Spectroscopy of z > 2 Quiescent Galaxies: Probing a Period of Rapid Size Growth
Ellis, Richard S.; Belli, Sirio; Newman, Andrew B. +1 more
Using the MOSFIRE near-infrared multi-slit spectrograph on the Keck 1 Telescope, we have secured high signal-to-noise ratio absorption line spectra for six massive galaxies with redshift 2 < z < 2.5. Five of these galaxies lie on the red sequence and show signatures of passive stellar populations in their rest-frame optical spectra. By fitti…