Search Publications
What Makes Quadruply Lensed Quasars Quadruple?
Schechter, Paul L.; Luhtaru, Richard; de Soto, Kaylee M.
Among known strongly lensed quasar systems, ~25% have gravitational potentials sufficiently flat (and sources sufficiently well aligned) to produce four images rather than two. The projected flattening of the lensing galaxy and tides from neighboring galaxies both contribute to the potential's quadrupole. Witt's hyperbola and Wynne's ellipse permi…
A Case against a Significant Detection of Precession in the Galactic Warp
López-Corredoira, M.; Chrobáková, Ž.
Recent studies of warp kinematics using Gaia DR2 data have produced detections of warp precession for the first time, which greatly exceeds theoretical predictions of models. However, this detection assumes a warp model derived for a young population (few tens of megayears) to fit velocities of an average older stellar population of the thin disk …
Strong Mg II and Fe II Absorbers at 2.2 < z < 6.0
Willott, Chris J.; Shen, Yue; Ho, Luis C. +13 more
We present a study of strong intervening absorption systems in the near-IR spectra of 31 luminous quasars at z > 5.7. The quasar spectra were obtained with Gemini GNIRS that provide continuous wavelength coverage from ∼0.9 to ∼2.5 µm. We detect 32 strong Mg II doublet absorbers with rest-frame equivalent width Wr(λ2796) > 1.…
Dynamical Masses and Stellar Evolutionary Model Predictions of M Stars
Herczeg, Gregory J.; Wilner, David J.; Andrews, Sean M. +9 more
In this era of Gaia and ALMA, dynamical stellar mass measurements, derived from spatially and spectrally resolved observations of the Keplerian rotation of circumstellar disks, provide benchmarks that are independent of observations of stellar characteristics and their uncertainties. These benchmarks can then be used to validate and improve stella…
Semiempirical Modeling of the Atmospheres of the M Dwarf Exoplanet Hosts GJ 832 and GJ 581
France, Kevin; Linsky, Jeffrey L.; Buccino, Andrea P. +2 more
Stellar ultraviolet (UV) radiation drives photochemistry, and extreme-ultraviolet (EUV) radiation drives mass loss in exoplanet atmospheres. However, the UV flux is partly unobservable due to interstellar absorption, particularly in the EUV range (100-912 Å). It is therefore necessary to reconstruct the unobservable spectra in order to characteriz…
The Atacama Cosmology Telescope: A Search for Planet 9
Hasselfield, Matthew; Sifón, Cristóbal; Aiola, Simone +37 more
We use Atacama Cosmology Telescope (ACT) observations at 98 GHz (2015-2019), 150 GHz (2013-2019), and 229 GHz (2017-2019) to perform a blind shift-and-stack search for Planet 9. The search explores distances from 300 au to 2000 au and velocities up to 6.'3 per year, depending on the distance (r). For a 5 Earth-mass Planet 9 the detection limit var…
Characteristics of Magnetic Holes in the Solar Wind Revealed by Parker Solar Probe
Zhang, J.; Huang, S. Y.; Xu, S. B. +6 more
We present a statistical analysis for the characteristics and radial evolution of linear magnetic holes (LMHs) in the solar wind from 0.166 to 0.82 au using Parker Solar Probe observations of the first two orbits. It is found that the LMHs mainly have a duration less than 25 s and the depth is in the range from 0.25 to 0.7. The durations slightly …
NICER Discovery of Millisecond X-Ray Pulsations and an Ultracompact Orbit in IGR J17494-3030
Chakrabarty, Deepto; Ray, Paul S.; Wolff, Michael T. +11 more
We report the detection of 376.05 Hz (2.66 ms) coherent X-ray pulsations in NICER observations of a transient outburst of the low-mass X-ray binary IGR J17494-3030 in 2020 October/November. The system is an accreting millisecond X-ray pulsar in a 75-minute ultracompact binary. The mass donor is most likely a ≃0.02 M⊙ finite-entropy whit…
The Remarkable Spin-down and Ultrafast Outflows of the Highly Pulsed Supersoft Source of Nova Herculis 2021
Luna, G. J. M.; Singh, K. P.; Drake, Jeremy J. +12 more
Nova Her 2021 (V1674 Her), which erupted on 2021 June 12, reached naked-eye brightness and has been detected from radio to γ-rays. An extremely fast optical decline of 2 magnitudes in 1.2 days and strong Ne lines imply a high-mass white dwarf. The optical pre-outburst detection of a 501.42 s oscillation suggests a magnetic white dwarf. This is the…
A Large Population of Luminous Active Galactic Nuclei Lacking X-Ray Detections: Evidence for Heavy Obscuration?
Stern, Daniel; Hickox, Ryan C.; Assef, Roberto J. +5 more
We present a large sample of infrared-luminous candidate active galactic nuclei (AGNs) that lack X-ray detections in Chandra, XMM-Newton, and NuSTAR fields. We selected all optically detected SDSS sources with redshift measurements, combined additional broadband photometry from WISE, UKIDSS, 2MASS, and GALEX, and modeled the spectral energy distri…