Search Publications
Walkaway Star Candidates in IC 348 and Their Possible Birthplaces
Fang, Min; Herczeg, Gregory J.; Ren, Bin B. +2 more
Observations and theories reveal that star-forming regions eject their members during the early evolution of the cluster. We present an initial search for stars ejected from the young cluster IC 348 based on an analysis of Gaia EDR3 astrometry of previously identified members. We identify six candidate walkaway stars with projected velocities of 5…
Nonthermal Motions and Atmospheric Heating of Cool Stars
Airapetian, V. S.; Ayres, T.; Testa, P. +6 more
The magnetic processes associated with the nonthermal broadening of optically thin emission lines appear to carry enough energy to heat the corona and accelerate the solar wind. We investigate whether nonthermal motions in cool stars exhibit the same behavior as on the Sun by analyzing archival stellar spectra taken by the Hubble Space Telescope, …
The Magnetic Sensitivity of the (250-278 nm) Fe II Polarization Spectrum
Afonso Delgado, David; del Pino Alemán, Tanausú; Trujillo Bueno, Javier
This paper presents a theoretical investigation of the polarization and magnetic sensitivity of the near-ultraviolet (near-UV) solar spectral lines of Fe II between 250 and 278 nm. In recent years, UV spectropolarimetry has become key to uncovering the magnetism of the upper layers of the solar chromosphere. The unprecedented data obtained by the …
The Nature of LoBAL QSOs. II. HST/WFC3 Observations Reveal Host Galaxies Dominated by Mergers
Lacy, Mark; Canalizo, Gabriela; Farrah, Duncan +4 more
Low-ionization broad absorption line QSOs (LoBALs) are suspected to be merging systems in which extreme, active galactic nucleus-driven outflows have been triggered. Whether or not LoBALs are uniquely associated with mergers, however, has yet to be established. To characterize the morphologies of LoBALs, we present the first high-resolution morpho…
Weighing the Darkness. III. How Gaia Could, but Probably Will Not, Astrometrically Detect Free-floating Black Holes
Andrews, Jeff J.
The gravitational pull of an unseen companion to a luminous star is well known to cause deviations to the parallax and proper motion of a star. In a previous paper in this series, we argue that the astrometric mission Gaia can identify long-period binaries by precisely measuring these arcs. An arc in a star's path can also be caused by a flyby: a …
Are the Heliosphere, Very Local Interstellar Medium, and Local Cavity in Pressure Balance with Galactic Gravity?
Linsky, Jeffrey L.; Moebius, Eberhard
The Voyager spacecraft are providing the first in situ measurements of physical properties in the outer heliosphere beyond the heliopause. These data, together with data from the IBEX and Hubble Space Telescope and physical models consistent with these data, now provide critical measurements of pressures in the heliosphere and surrounding interste…
Modeling the Spectral Energy Distribution of the Active Galactic Nucleus inside NGC 4395
Greene, Jenny E.; Goulding, Andy D.; Cruz, Hector Afonso G.
We study the broadband spectral energy distribution (SED) of the prototypical low-mass active galactic nucleus (AGN) in NGC 4395. We jointly model the optical through mid-IR SED with a combination of galaxy and AGN light, and find that on arcsecond scales the AGN dominates at most wavelengths. However, there is still some ambiguity about emission …
Surveying Flux Density in Galaxies with Apparent Large Black Holes at Millimeter/Submillimeter Wavelengths
Matsushita, Satoki; Bower, Geoffrey C.; Nakamura, Masanori +5 more
We present millimeter and submillimeter continuum observations for 36 sources with potentially large black hole shadows at 230 and 345 GHz using the Submillimeter Array. The sources are selected based on the criterion of the large diameter of the black hole shadows. Our motivation is to explore the nature of the accretion flow of the potential can…
Numerical Simulation on the Leading Edge of Coronal Mass Ejection in the Near-Sun Region
Ye, Jing; Li, Yan; Mei, Zhixing +3 more
The coronal mass ejections (CMEs) observed by white-light coronagraphs, such as the Large Angle and Spectrometric Coronagraph (LASCO) C2/C3, commonly exhibit the three-part structure, with the bright leading edge as the outermost part. In this work, we extend previous work on the leading edge by performing a large-scale 3D magnetohydrodynamic nume…
Sudden Extreme Obscuration of a Sun-like Main-sequence Star: Evolution of the Circumstellar Dust around ASASSN-21qj
Kemper, Francisca; Ertel, Steve; Scicluna, Peter +6 more
ASASSN-21qj is a distant Sun-like star that recently began an episode of deep dimming events after no prior recorded variability. Here we examine archival and newly obtained optical and near-infrared data of this star. The deep aperiodic dimming and absence of previous infrared excess are reminiscent of KIC 8462852 ("Boyajian's Star"). The observe…