Search Publications
The Nature of Ionized Gas in the Milky Way Galactic Fountain
Zheng, Y.; Prochaska, J. X.; Deason, A. J. +6 more
We address the spatial scale, ionization structure, mass, and metal content of gas at the Milky Way disk-halo interface detected as absorption in the foreground of seven closely spaced, high-latitude halo blue horizontal branch stars with heights z = 3-14 kpc. We detect transitions that trace multiple ionization states (e.g., Ca II, Fe II, Si IV, …
Constraints on Upper Cutoffs in the Mass Functions of Young Star Clusters
Fall, S. Michael; Chandar, Rupali; Mok, Angus
We test claims that the power-law mass functions of young star clusters (ages ≲ few × 108 yr) have physical upper cutoffs at {M}* ∼ {10}5 {M}⊙ . Specifically, we perform maximum likelihood fits of the Schechter function, \psi (M)={dN}/{dM}\propto {M}β \exp (-M/{M}* ), to the observe…
The Transiting Multi-planet System HD15337: Two Nearly Equal-mass Planets Straddling the Radius Gap
Torres, Guillermo; Cochran, William D.; Endl, Michael +53 more
We report the discovery of a super-Earth and a sub-Neptune transiting the star HD 15337 (TOI-402, TIC 120896927), a bright (V = 9) K1 dwarf observed by the Transiting Exoplanet Survey Satellite (TESS) in Sectors 3 and 4. We combine the TESS photometry with archival High Accuracy Radial velocity Planet Searcher spectra to confirm the planetary natu…
Clues on the Origin and Evolution of Massive Contact Binaries: Atmosphere Analysis of VFTS 352
Sana, Hugues; Tramper, Frank; Justham, Stephen +10 more
The massive O4.5 V + O5.5 V binary VFTS 352 in the Tarantula Nebula is one of the shortest-period and most massive overcontact binaries known. Recent theoretical studies indicate that some of these systems could ultimately lead to the formation of gravitational waves via black hole binary mergers through the chemically homogeneous evolution pathwa…
Can the Superposition of Evaporative Flows Explain Broad Fe XXI Profiles during Solar Flares?
Polito, Vanessa; Testa, Paola; De Pontieu, Bart
The observation of the high-temperature (≳10 MK) Fe XXI 1354.1 Å line with the Interface Region Imaging Spectrograph has provided significant insights into the chromospheric evaporation process in flares. In particular, the line is often observed to be completely blueshifted, in contrast to previous observations at lower spatial and spectral resol…
Subarcsecond Blobs in Flare-related Coronal Jets
Zhang, Q. M.; Ni, L.
In this paper, we report multiwavelength observations of subarcsecond blobs in coronal jets. In AR 12149, a C5.5 circular-ribbon flare occurred at ∼04:55 UT on 2014 August 24, which consisted of a discrete circular ribbon and a short inner ribbon inside. Two jets (jet1 and jet2) were related to the flare. Jet1 appeared first and experienced untwis…
GROWTH on S190510g: DECam Observation Planning and Follow-up of a Distant Binary Neutron Star Merger Candidate
Duev, Dmitry A.; Kong, Albert K. H.; Cook, David O. +23 more
The first two months of the third Advanced LIGO and Virgo observing run (2019 April-May) showed that distant gravitational-wave (GW) events can now be readily detected. Three candidate mergers containing neutron stars (NS) were reported in a span of 15 days, all likely located more than 100 Mpc away. However, distant events such as the three new N…
SOFIA Far-infrared Imaging Polarimetry of M82 and NGC 253: Exploring the Supergalactic Wind
Morris, Mark R.; Staguhn, Johannes; Dowell, C. Darren +23 more
We present far-infrared polarimetry observations of M82 at 53 and 154 µm and NGC 253 at 89 µm, which were taken with High-resolution Airborne Wideband Camera-plus (HAWC+) in polarimetry mode on the Stratospheric Observatory for Infrared Astronomy. The polarization of M82 at 53 µm clearly shows a magnetic field geometry perpendicu…
Current Sheets, Magnetic Islands, and Associated Particle Acceleration in the Solar Wind as Observed by Ulysses near the Ecliptic Plane
Zank, Gary P.; Bruno, Roberto; Li, Gang +16 more
Recent studies of particle acceleration in the heliosphere have revealed a new mechanism that can locally energize particles up to several MeV nucleon-1. Stream-stream interactions, as well as the heliospheric current sheet (CS)—stream interactions, lead to formation of large magnetic cavities, bordered by strong CSs, which in turn prod…
Hot Subdwarf Stars Observed in Gaia DR2 and LAMOST DR5
Han, Zhanwen; Deng, Licai; Luo, Yangping +1 more
Combing Gaia DR2 with LAMOST DR5, we spectroscopically identified 924 hot subdwarf stars, among which 32 stars exhibit strong double-lined composite spectra. We measured the effective temperature T eff, surface gravity {log} g, helium abundance y = nHe/nH, and radial velocities (RVs) of 892 non-composite spectra hot subdwarf stars by fi…