Search Publications
The X-Ray Outburst of PG 1553+113: A Precession Effect of Two Jets in the Supermassive Black Hole Binary System
Chen, Xu; Huang, Shifeng; Yin, Hongxing +4 more
Blazar PG 1553+113 is thought to be a host of supermassive black hole binary system. A 2.2 yr quasi-periodicity in the γ-ray light curve was detected, possibly a result of jet precession. Motivated by the previous studies based on the γ-ray data, we analyzed the X-ray light curve and spectra observed during 2012-2020. The 2.2 yr quasi-periodicity …
Magnetic Fields and Star Formation around H II Regions: The S235 Complex
Ray, T. P.; Dewangan, L. K.; Luna, A. +3 more
Magnetic fields are ubiquitous and essential in star formation. In particular, their role in regulating formation of stars across diverse environments like H II regions needs to be well understood. In this study, we present magnetic field properties toward the S235 complex using near-infrared (NIR) H-band polarimetric observations, obtained with t…
Predictions of Astrometric Jitter for Sun-like Stars. I. The Model and Its Application to the Sun as Seen from the Ecliptic
Solanki, Sami K.; Shapiro, Alexander I.; Krivova, Natalie A.
The advent of Gaia, capable of measuring stellar wobbles caused by orbiting planets, raised interest in the astrometric detection of exoplanets. Another source of such wobbles (often also called jitter) is stellar magnetic activity. A quantitative assessment of the stellar astrometric jitter is important for a more reliable astrometric detection a…
Strong Correlation between Fe II/Mg II Ratio and Eddington Ratio of Type 1 Active Galactic Nuclei
Kim, Minjin; Nagao, Tohru; Woo, Jong-Hak +2 more
The Fe II/Mg II line flux ratio has been used as an indicator of the Fe/Mg abundance ratio in the broad-line region (BLR) of active galactic nuclei (AGNs). On the basis of archival rest-frame UV spectra obtained via the Hubble Space Telescope and the Sloan Digital Sky Survey, we investigate the Fe II/Mg II ratios of type 1 AGNs at z < 2. Over w…
The Challenge to MOND from Ultra-faint Dwarf Galaxies
Loeb, Abraham; Safarzadeh, Mohammadtaher
Modified Newtonian dynamics (MOND) at low acceleration has been astonishingly powerful at explaining the rotation curve of galaxies and the relation between the baryonic content of the galaxies and their observed circular velocity, known as the baryonic TullyFisher relationship. It is known that MOND fails at explaining the observed velocity dispe…
The Transition from Diffuse Molecular Gas to Molecular Cloud Material in Taurus
Kim, Hwihyun; Federman, S. R.; Lambert, David L. +6 more
We study four lines of sight that probe the transition from diffuse molecular gas to molecular cloud material in Taurus. Measurements of atomic and molecular absorption are used to infer the distribution of species and the physical conditions toward stars behind the Taurus Molecular Cloud (TMC). New high-resolution spectra at visible and near-IR w…
Filament Eruption Driving EUV Loop Contraction and Then Expansion above a Stable Filament
Schmieder, Brigitte; Joshi, Reetika; Chandra, Ramesh +2 more
We analyze the observations of EUV loop evolution associated with the filament eruption located at the border of an active region (AR). The event SOL2013-03-16T14:00 was observed with a large difference in view point by the Solar Dynamics Observatory and Solar Terrestrial Relations Observatory. The filament height is fitted with the sum of a linea…
DIISC-I: The Discovery of Kinematically Anomalous H I Clouds in M 100
Heckman, Timothy M.; Nelson, Dylan; Thilker, David +10 more
We report the discovery of two kinematically anomalous atomic hydrogen (H I) clouds in M 100 (NGC 4321), which was observed as part of the Deciphering the Interplay between the Interstellar medium, Stars, and the Circumgalactic medium (DIISC) survey in H I 21 cm at 3.3 km s-1 spectroscopic and 44″ × 30″ spatial resolution using the Karl…
The Effect of the Morphological Quenching Mechanism on Star Formation Activity at 0.5 < z < 1.5 in 3D-HST/CANDELS
Fang, Guanwen; Kong, Xu; Gu, Yizhou +3 more
Several mechanisms for the transformation of blue star-forming to red quiescent galaxies have been proposed, and the green valley (GV) galaxies amid them are widely accepted in a transitional phase. Thus, comparing the morphological and environmental differences of the GV galaxies with early-type disks (ETDs; bulge dominated and having a disk) and…
Possible Evidence of Hydrogen Emission in the First-overtone and Multimode RR Lyrae Variables
Deng, Li-Cai; Liu, Chao; Zhang, Hua-Wei +4 more
The nature of shock waves in nonfundamental mode RR Lyrae stars remains a mystery because of limited spectroscopic observations. We apply a pattern recognition algorithm on spectroscopic data from SDSS and LAMOST and report the first evidence of hydrogen emission in first-overtone (RRc) and multimode (RRd) RR Lyrae stars showing the "first apparit…