Search Publications
Prevalence of Thermal Nonequilibrium over an Active Region
Antolin, Patrick; Şahin, Seray
Recent observations have shown that besides the characteristic multimillion degree component, the corona also contains a large amount of cool material called coronal rain, whose clumps are 10-100 times cooler and denser than the surroundings and are often organized in larger events, termed showers. Thermal instability (TI) within a coronal loop in…
Warm Absorbers in the Radiation-driven Fountain Model of Low-mass Active Galactic Nuclei
Wada, Keiichi; Ueda, Yoshihiro; Mizumoto, Misaki +1 more
To investigate the origins of the warm absorbers in active galactic nuclei (AGNs), we study the ionization-state structure of the radiation-driven fountain model in a low-mass AGN and calculate the predicted X-ray spectra utilizing the spectral synthesis code Cloudy. The spectra show many absorption and emission line features originating in the ou…
Hubble Space Telescope Detection of the Nucleus of Comet C/2014 UN271 (Bernardinelli-Bernstein)
Jewitt, David; Mutchler, Max J.; Hui, Man-To +1 more
We present a high-resolution observation of the distant comet C/2014 UN271 (Bernardinelli-Bernstein) using the Hubble Space Telescope on 2022 January 8. The signal of the nucleus was successfully isolated by means of a nucleus extraction technique, with an apparent V-band magnitude measured to be 21.65 ± 0.11, corresponding to an absolu…
Detectability of Rotational Modulation in Kepler Sun-like Stars as a Function of Age
Masuda, Kento
We examine how the fraction f of stars for which rotational modulation has been detected in Kepler light curves depends on the stellar mass M ⋆ and age t ⋆. Our sample consists of ≈850 FGK stars hosting transiting planet candidates detected from the prime Kepler mission. For these stars, atmospheric parameters have been deriv…
Measuring the Orbits of the Arches and Quintuplet Clusters Using HST and Gaia: Exploring Scenarios for Star Formation near the Galactic Center
Lu, Jessica R.; Anderson, Jay; Morris, Mark R. +4 more
We present new absolute proper-motion measurements for the Arches and Quintuplet clusters, two young massive star clusters near the Galactic center. Using multiepoch HST observations, we construct proper-motion catalogs for the Arches (~35,000 stars) and Quintuplet (~40,000 stars) fields in ICRF coordinates established using stars in common with t…
COLDz: Probing Cosmic Star Formation With Radio Free-Free Emission
Dickinson, Mark; Smail, Ian; Daddi, Emanuele +17 more
Radio free-free emission is considered to be one of the most reliable tracers of star formation in galaxies. However, as it constitutes the faintest part of the radio spectrum-being roughly an order of magnitude less luminous than radio synchrotron emission at the GHz frequencies typically targeted in radio surveys-the usage of free-free emission …
Panchromatic HST/WFC3 Imaging Studies of Young, Rapidly Evolving Planetary Nebulae. I. NGC 6302
Montez, Rodolfo; Frank, Adam; Balick, Bruce +4 more
We present the results of a comprehensive, near-UV-to-near-IR Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) imaging study of the young planetary nebula (PN) NGC 6302, the archetype of the class of extreme bilobed, pinched-waist PNe that are rich in dust and molecular gas. The new WFC3 emission-line image suite clearly defines the dusty t…
An Elusive Population of Massive Disk Galaxies Hosting Double-lobed Radio-loud Active Galactic Nuclei
Ho, Luis C.; Zhuang, Ming-Yang; Wu, Zihao
It is commonly accepted that radio-loud active galactic nuclei are hosted exclusively by giant elliptical galaxies. We analyze high-resolution optical Hubble Space Telescope images of a sample of radio galaxies with extended double-lobed structures associated with disk-like optical counterparts. After systematically evaluating the probability of c…
The Extended Field-aligned Suprathermal Proton Beam and Long-lasting Trapped Energetic Particle Population Observed Upstream of a Transient Interplanetary Shock
Lario, D.; Jian, L. K.; Wilson, L. B., III +3 more
The properties of the suprathermal particle distributions observed upstream of interplanetary shocks depend not only on the properties of the shocks but also on the transport conditions encountered by the particles as they propagate away from the shocks. The confinement of particles in close proximity to the shocks, as well as particle scattering …
Manifestation of Gravitational Settling in Coronal Mass Ejections Measured in the Heliosphere
Reeves, Katharine K.; Landi, Enrico; Raymond, John C. +4 more
Elemental composition in the solar wind reflects the fractionation processes at the Sun. In coronal mass ejections (CMEs) measured in the heliosphere, the elemental composition can vary between plasma of high and low ionization states as indicated by the average Fe charge state, <QFe>. It is found that CMEs with higher ionized pla…