Search Publications
Detection of a Multiphase Intragroup Medium: Results from the COS-IGrM Survey
Heckman, Timothy; Tumlinson, Jason; Borthakur, Sanchayeeta +3 more
We present the results of the Cosmic Origins Spectrograph-Intragroup Medium (COS-IGrM) Survey that used the COS on the Hubble Space Telescope to observe a sample of 18 UV bright quasars, each probing the IGrM of a galaxy group. We detect Lyα, C II, N V, Si II, Si III, and O VI in multiple sightlines. The highest ionization species detected in our …
In the Trenches of the Solar-stellar Connection. IV. Solar Full-disk Scans of C II, Si IV, and Mg II by the Interface Region Imaging Spectrograph
Testa, Paola; De Pontieu, Bart; Ayres, Thomas
About once a month, the Interface Region Imaging Spectrograph conducts day-long raster scans of the full Sun in three ultraviolet spectral channels. These full-disk mosaics are valuable in the solar context, but provide a unique connection to the distant, unresolved stars. Here, 10 deep-exposure scans (4-8 s per slit step), collected during the pe…
In the Trenches of the Solar-Stellar Connection. III. The HST/COS Ecliptic-poles Stellar Survey (EclipSS)
Ayres, Thomas R.
The Ecliptic-poles Stellar Survey (EclipSS) collected far-ultraviolet (FUV: 1160-1420 Å) spectra of 49 nearby (d ≲ 100 pc) F3-K3 main-sequence stars, located at high ecliptic latitudes (north and south), using the Cosmic Origins Spectrograph of the Hubble Space Telescope. The ecliptic poles receive higher exposures from scanning missions like the …
A Hard Look at Relativistic Reverberation in MCG-5-23-16 and SWIFT J2127.4+5654: Testing the Lamppost Model
Miller, J. M.; Zoghbi, A.; Cackett, E.
X-ray reverberation mapping has emerged as a new tool to probe accretion in active galactic nuclei (AGN), providing a potentially powerful probe of accretion at the black hole scale. The lags, along with relativistic spectral signatures are often interpreted in light of the lamppost model. Focusing specifically on testing the prediction of the rel…
The Merger Dynamics of the Galaxy Cluster A1775: New Insights from Chandra and XMM-Newton for a Cluster Simultaneously Hosting a Wide-angle Tail and a Narrow-angle Tail Radio Source
Hu, Dan; Xu, Haiguang; Zhu, Zhenghao +13 more
We present a new study of the merger dynamics of A1775 by analyzing the high-quality Chandra and XMM-Newton archival data. We confirm/identify an arc-shaped edge (i.e., the head) at ∼48 kpc west of the X-ray peak, a split cold gas tail that extends eastward to ∼163 kpc, and a plume of spiral-like X-ray excess (within about 81-324 kpc northeast of …
Multiple Populations in Low-mass Globular Clusters: Palomar 13
Carballo-Bello, Julio A.; Li, Chengyuan; Cabrera-Lavers, Antonio +7 more
Since the discovery of chemically peculiar stars in globular clusters in the last century, the study of multiple populations has become increasingly important, given that chemical inhomogeneity is found in almost all globular clusters. Despite various proposed theories attempting to explain this phenomenon, fitting all the observational evidence i…
Chemical Analysis of Two Extremely Metal-poor Stars HE 2148-2039 and HE 2155-2043
Goswami, Aruna; Purandardas, Meenakshi
We present elemental abundance results for HE 2148-2039 and HE 2155-2043 based on a detailed high-resolution spectroscopic analysis. The high-resolution Subaru/High Dispersion Spectrograph (HDS) spectra used for our analysis have a resolution of R ∼ 60,000. Although limited information based on photometry and low-resolution spectroscopy is availab…
Cooling Models for the Most Massive White Dwarfs
Schwab, Josiah
We present a set of ultramassive white dwarf models, focused on masses above 1.3 M⊙. Given the uncertainties about the formation and compositions of such objects, we construct parameterized model sequences, guided by evolutionary calculations including both single star and double white dwarf merger formation channels. We demonstrate tha…
The ACTIONFINDER: An Unsupervised Deep Learning Algorithm for Calculating Actions and the Acceleration Field from a Set of Orbit Segments
Famaey, Benoit; Ibata, Rodrigo; Monari, Giacomo +1 more
We introduce the ACTIONFINDER, a deep learning algorithm designed to transform a sample of phase-space measurements along orbits in a static potential into action and angle coordinates. The algorithm finds the mapping from positions and velocities to actions and angles in an unsupervised way, by using the fact that points along the same orbit have…
The Mass and Age Distribution of Halo White Dwarfs in the Canada-France Imaging Survey
Gwyn, Stephen D. J.; McConnachie, Alan W.; Cuillandre, Jean-Charles +6 more
We present optical spectroscopy for 18 halo white dwarfs identified using photometry from the Canada-France Imaging Survey and Pan-STARRS1 DR1 3π survey combined with astrometry from Gaia DR2. The sample contains 13 DA, 1 DZ, 2 DC, and 2 potentially exotic types of white dwarf. We fit both the spectrum and the spectral energy distribution in order…