Search Publications
The ACS LCID Project. X. The Star Formation History of IC 1613: Revisiting the Over-cooling Problem
Ferguson, Henry C.; Dolphin, Andrew E.; Skillman, Evan D. +13 more
We present an analysis of the star formation history (SFH) of a field near the half-light radius in the Local Group dwarf irregular galaxy IC 1613 based on deep Hubble Space Telescope Advanced Camera for Surveys imaging. Our observations reach the oldest main sequence turn-off, allowing a time resolution at the oldest ages of ~1 Gyr. Our analysis …
Herschel Finds Evidence for Stellar Wind Particles in a Protostellar Envelope: Is This What Happened to the Young Sun?
Ceccarelli, C.; Dominik, C.; Caux, E. +4 more
There is evidence that the young Sun emitted a high flux of energetic (>=10 MeV) particles. The collisions of these particles with the material at the inner edge of the Protosolar Nebula disk induced spallation reactions that formed short-lived radionuclei, like 10Be, whose trace is now visible in some meteorites. However, it is poor…
Asymmetry in the CME-CME Interaction Process for the Events from 2011 February 14-15
Temmer, M.; Veronig, A. M.; Vršnak, B. +1 more
We present a detailed study of the interaction process of two coronal mass ejections (CMEs) successively launched on 2011 February 14 (CME1) and 2011 February 15 (CME2). Reconstructing the three-dimensional shape and evolution of the flux ropes, we verify that the two CMEs interact. The frontal structure of both CMEs, measured along different posi…
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…