Search Publications
The Spread of Metals into the Low-redshift Intergalactic Medium
Danforth, Charles W.; Stocke, John T.; Keeney, Brian A. +1 more
We investigate the association between galaxies and metal-enriched and metal-deficient absorbers in the local universe (z < 0.16) using a large compilation of far-ultraviolet spectra of bright active galactic nuclei targets observed with the Cosmic Origins Spectrograph aboard the Hubble Space Telescope. In this homogeneous sample of 18 O VI det…
A Cavity of Large Grains in the Disk around the Group II Herbig Ae/Be Star HD 142666
Rubinstein, A. E.; Calvet, N.; Zhang, K. +3 more
Herbig Ae/Be (HAeBe) stars have been classified into Group I or Group II, and were initially thought to be flared and flat disks, respectively. Several Group I sources have been shown to have large gaps, suggesting ongoing planet formation, while no large gaps have been found in the disks of Group II sources. We analyzed the disk around the Group …
Reconciling Optical and Radio Observations of the Binary Millisecond Pulsar PSR J1640+2224
Deller, Adam T.; Kaplan, David L.; Istrate, Alina G. +3 more
Previous optical and radio observations of the binary millisecond pulsar PSR J1640+2224 have come to inconsistent conclusions about the identity of its companion, with some observations suggesting that the companion is a low-mass helium-core (He-core) white dwarf (WD), while others indicate that it is most likely a high-mass carbon-oxygen (CO) WD.…
Actions Are Weak Stellar Age Indicators in the Milky Way Disk
Bedell, Megan; Ness, Melissa K.; Beane, Angus
The orbital properties of stars in the Milky Way disk are signatures of their formation, but they are also expected to change over time due to the dynamical evolution of the Galaxy. Stellar orbits can be quantified by the three dynamical actions, J r , L z , and J z , which provide measures of the orbital eccent…
Herschel Spectroscopy of the Taffy Galaxies (UGC 12914/12915 = VV 254): Enhanced [C II] Emission in the Collisionally Formed Bridge
Boulanger, F.; Falgarone, E.; Helou, G. +17 more
Using the PACS and SPIRE spectrometers on board Herschel, we obtained observations of the Taffy galaxies (UGC 12914/12915) and bridge. The Taffy system is believed to be the result of a face-on collision between two gas-rich galaxies, in which the stellar disks passed through each other, but the gas was dispersed into a massive H I and molecular b…
A Wide and Deep Exploration of Radio Galaxies with Subaru HSC (WERGS). I. The Optical Counterparts of FIRST Radio Sources
Lee, Chien-Hsiu; Kajisawa, Masaru; Toba, Yoshiki +12 more
We report the result of optical identifications of FIRST radio sources with the Hyper Suprime-Cam Subaru Strategic Program survey (HSC-SSP). The positional cross-match within 1″ between the FIRST and HSC-SSP catalogs (i ≲ 26) produced more than 3600 optical counterparts in the 156 deg2 of the HSC-SSP field. The matched counterparts acco…
Observations of Electron-driven Evaporation in a Flare Precursor
Li, Dong; Ning, Zongjun; Li, Ying +2 more
We investigate the relationship between the blueshifts of a hot emission line and the nonthermal emissions in microwave and hard X-ray (HXR) wavelengths in the precursor of a solar flare on 2014 October 27. The flare precursor is identified as a small but well-developed peak in the soft X-ray and extreme-ultraviolet passbands before the GOES flare…
Collective Study of Polar Crown Filaments in the Past Four Solar Cycles
Xu, Yan; Jing, Ju; Wang, Haimin +3 more
Polar crown filaments (PCFs) form above the magnetic polarity inversion line, which separates the unipolar polar fields and the nearest dispersed fields from the trailing part of active regions with opposite polarity. The statistical properties of PCFs are correlated with the solar cycle. Therefore, the study of PCFs plays an important role in und…
Eta Carinae’s Declining Outflow Seen in the UV, 2002-2015
Humphreys, Roberta M.; Davidson, Kris; Martin, John C. +1 more
Existing Hubble Space Telescope UV data offer many previously neglected clues to η Car’s behavior since 2000. Here we examine a subset of observations with diverse results. (1) The star’s rapid change of state is confirmed by major changes in UV absorption lines, circumstellar extinction, and other features. (2) N III] λ1750 is one of the two most…
A Candidate Tidal Disruption Event in a Quasar at z = 2.359 from Abundance Ratio Variability
Shen, Yue; Jiang, Linhua; Liu, Xin +1 more
A small fraction of quasars show an unusually high nitrogen-to-carbon ratio (N/C) in their spectra. These “nitrogen-rich” (N-rich) quasars are a long-standing puzzle because their interstellar medium implies stellar populations with abnormally high metallicities. It has recently been proposed that N-rich quasars may result from tidal disruption ev…