Search Publications
Simultaneous Observations of Chromospheric Evaporation and Condensation during a C-class Flare
Li, Dong; Hong, Zhenxiang; Ning, Zongjun
We explored simultaneous observations of chromospheric evaporation and condensation during the impulsive phase of a C6.7 flare on 2019 May 9. The solar flare was simultaneously observed by multiple instruments, i.e., the New Vacuum Solar Telescope (NVST), the Interface Region Imaging Spectrograph, the Atmospheric Imaging Assembly (AIA), Fermi, the…
X-Ray Reverberation Mapping of Ark 564 Using Gaussian Process Regression
Ingram, Adam; Reynolds, Christopher S.; García, Javier A. +15 more
Ark 564 is an extreme high-Eddington narrow-line Seyfert 1 galaxy, known for being one of the brightest, most rapidly variable soft X-ray active galactic nuclei (AGN), and for having one of the lowest temperature coronae. Here, we present a 410 ks NuSTAR observation and two 115 ks XMM-Newton observations of this unique source, which reveal a very …
Rapid Bursts of Magnetically Gated Accretion in the Intermediate Polar V1025 Cen
Garnavich, Peter; Littlefield, Colin; Szkody, Paula +5 more
Magnetically gated accretion has emerged as a proposed mechanism for producing extremely short, repetitive bursts of accretion onto magnetized white dwarfs in intermediate polars (IPs), but this phenomenon has not been detected previously in a confirmed IP. We report the 27 day TESS light curve of V1025 Cen, an IP that shows a remarkable series of…
Grain Alignment in the Circumstellar Shell of IRC+10° 216
Sandin, Christer; Soam, Archana; Hoang, Thiem +7 more
Dust-induced polarization in the interstellar medium (ISM) is due to asymmetric grains aligned with an external reference direction, usually the magnetic field. For both the leading alignment theories, the alignment of the grain's angular momentum with one of its principal axes and the coupling with the magnetic field requires the grain to be para…
ALMA Uncovers Highly Filamentary Structure toward the Sgr E Region
Mills, E. A. C.; Anderson, L. D.; Battersby, C. +7 more
We report on the discovery of linear filaments observed in the CO(1-0) emission for a ~2' field of view toward the Sgr E star-forming region, centered at (l, b) = (358.°720, 0.°011). The Sgr E region is thought to be at the turbulent intersection of the "far dust lane" associated with the Galactic bar and the Central Molecular Zone (CMZ). This reg…
Constraining the CME Core Heating and Energy Budget with SOHO/UVCS
Reeves, Katharine K.; Raymond, John C.; Shen, Chengcai +4 more
We describe the energy budget of a coronal mass ejection (CME) observed on 1999 May 17 with the Ultraviolet Coronagraph Spectrometer (UVCS). We constrain the physical properties of the CME's core material as a function of height along the corona by using the spectra taken by the single-slit coronagraph spectrometer at heliocentric distances of 2.6…
Fluorine Abundances in the Galactic Nuclear Star Cluster
Cunha, Katia; Smith, Verne V.; Daflon, Simone +4 more
Abundances of fluorine (19F), as well as isotopic ratios of 16O/17O, are derived in a sample of luminous young (~107-108 yr) red giants in the Galactic center (with galactocentric distances ranging from 0.6-30 pc), using high-resolution infrared spectra and vibration-rotation lines of H19…
Hubble Space Telescope Proper Motion (HSTPROMO) Catalogs of Galactic Globular Clusters. VII. Energy Equipartition
Anderson, Jay; van der Marel, Roeland P.; Alfaro-Cuello, Mayte +3 more
We examine the degree of energy equipartition in nine Galactic globular clusters using proper motions measured with the Hubble Space Telescope. For most clusters in the sample, this is the first energy equipartition study ever performed. This study is also the largest of its kind, albeit with only nine clusters. We begin by rigorously cleaning the…
Massive Black Hole Formation in Dense Stellar Environments: Enhanced X-Ray Detection Rates in High-velocity Dispersion Nuclear Star Clusters
Stone, Nicholas C.; Ostriker, Jeremiah P.; Baldassare, Vivienne F. +2 more
We analyze Chandra X-ray Observatory imaging of 108 galaxies hosting nuclear star clusters (NSCs) to search for signatures of massive black holes (BHs). NSCs are extremely dense stellar environments with conditions that can theoretically facilitate massive BH formation. Recent work by Stone et al. finds that sufficiently dense NSCs should be unsta…
Investigating the Low-flux States in Six Intermediate Polars
Littlefield, Colin; Heinke, Craig O.; Mukai, Koji +30 more
We present optical photometry of six intermediate polars that exhibit transitions to a low-flux state. For four of these systems, DW Cnc, V515 And, V1223 Sgr, and RX J2133.7+5107, we are able to perform timing analysis in and out of the low states. We find that, for DW Cnc and V515 And, the dominant periodicities in the light curves change as the …