Search Publications
A New Generation of Cool White Dwarf Atmosphere Models. IV. Revisiting the Spectral Evolution of Cool White Dwarfs
Dufour, P.; Allard, N. F.; Blouin, S. +1 more
As a result of competing physical mechanisms, the atmospheric composition of white dwarfs changes throughout their evolution, a process known as spectral evolution. Because of the ambiguity of their atmospheric compositions and the difficulties inherent to the modeling of their dense atmospheres, no consensus exists regarding the spectral evolutio…
Extremely metal-poor galaxies with HST/COS: laboratories for models of low-metallicity massive stars and high-redshift galaxies
Charlot, Stéphane; Chevallard, Jacopo; Stark, Daniel P. +3 more
Ultraviolet (UV) observations of local star-forming galaxies have begun to establish an empirical baseline for interpreting the rest-UV spectra of reionization-era galaxies. However, existing high-ionization emission line measurements at z > 6 (W_{C riptscIV,0}{} ≳ 20 Å) are uniformly stronger than observed locally (W_{C riptscIV,0}{} ≲ 2 Å), l…
Connecting the Properties of Coronal Shock Waves with Those of Solar Energetic Particles
Vourlidas, Angelos; Kouloumvakos, Athanasios; Rouillard, Alexis P. +5 more
We develop and exploit a new catalog of coronal pressure waves modeled in 3D to study the potential role of these waves in accelerating solar energetic particles (SEPs) measured in situ. Our sample comprises modeled shocks and SEP events detected during solar cycle 24 observed over a broad range of longitudes. From the 3D reconstruction of shock w…
400 pc Imaging of a Massive Quasar Host Galaxy at a Redshift of 6.6
Hennawi, Joseph F.; Neeleman, Marcel; Rix, Hans-Walter +4 more
We report high spatial resolution (∼0.″076, 410 pc) Atacama Large Millimeter/submillimeter Array imaging of the dust continuum and the ionized carbon line [C II] in a luminous quasar host galaxy at z = 6.6, 800 million years after the big bang. Based on previous studies, this galaxy hosts a ∼1 × 109 {M}⊙ black hole and has a…
EvryFlare. I. Long-term Evryscope Monitoring of Flares from the Cool Stars across Half the Southern Sky
Law, Nicholas M.; Corbett, Hank; Fors, Octavi +5 more
We search for superflares from 4068 cool stars in 2+ yr of Evryscope photometry, focusing on those with high-cadence data from both Evryscope and the Transiting Exoplanet Survey Satellite (TESS). The Evryscope array of small telescopes observed 575 flares from 284 stars, with a median energy of 1034.0 erg. Since 2016, Evryscope has enab…
Chemical Abundances of Main-sequence, Turnoff, Subgiant, and Red Giant Stars from APOGEE Spectra. II. Atomic Diffusion in M67 Stars
Bovy, Jo; Pan, Kaike; Cunha, Katia +14 more
Chemical abundances for 15 elements (C, N, O, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, and Ni) are presented for 83 stellar members of the 4 Gyr old solar-metallicity open cluster M67. The sample contains stars spanning a wide range of evolutionary phases, from G dwarfs to red clump stars. The abundances were derived from near-IR (λ1.5-1.7 µ…
Physical Characterization of an Unlensed, Dusty Star-forming Galaxy at z = 5.85
Finkelstein, Steven L.; Casey, Caitlin M.; Kartaltepe, Jeyhan S. +23 more
We present a physical characterization of MM J100026.36+021527.9 (a.k.a. “MAMBO-9”), a dusty star-forming galaxy (DSFG) at z = 5.850 ± 0.001. This is the highest-redshift unlensed DSFG (and fourth most distant overall) found to date and is the first source identified in a new 2 mm blank-field map in the COSMOS field. Though identified in prior sam…
Signatures of resonance and phase mixing in the Galactic disc
Bovy, Jo; Kawata, Daisuke; Mackereth, J. Ted +3 more
Gaia DR2 has provided an unprecedented wealth of information about the kinematics of stars in the Solar neighbourhood, and has highlighted the degree of features in the Galactic disc. We confront the data with a range of bar and spiral models in both action-angle space, and the RG-vϕ plane. We find that the phase mixing induc…
XCLUMPY: X-Ray Spectral Model from Clumpy Torus and Its Application to the Circinus Galaxy
Fukazawa, Yasushi; Tanimoto, Atsushi; Ueda, Yoshihiro +3 more
We construct an X-ray spectral model from the clumpy torus in an active galactic nucleus, designated as “XCLUMPY,” utilizing the Monte Carlo simulation for Astrophysics and Cosmology framework. The adopted geometry of the torus is the same as that in Nenkova et al. who assume a power-law distribution of clumps in the radial direction and a normal …
Homogeneous Analysis of Hot Earths: Masses, Sizes, and Compositions
Winn, Joshua N.; Dai, Fei; Masuda, Kento +1 more
Terrestrial planets have been found orbiting Sun-like stars with extremely short periods—some as short as 4 hr. These “ultra-short-period planets” or “hot Earths” are so strongly irradiated that any initial H/He atmosphere has probably been lost to photoevaporation. As such, the sample of hot Earths may give us a glimpse at the rocky cores that ar…