Search Publications
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…
Comparison of Observed Galaxy Properties with Semianalytic Model Predictions Using Machine Learning
Mobasher, Bahram; Chartab, Nima; Lu, Yu +1 more
With current and upcoming experiments such as the Wide Field Infrared Survey Telescope, Euclid, and Large Synoptic Survey Telescope, we can observe up to billions of galaxies. While such surveys cannot obtain spectra for all observed galaxies, they produce galaxy magnitudes in color filters. This data set behaves like a high-dimensional nonlinear …
Emergence of Internetwork Magnetic Fields through the Solar Atmosphere
Gošić, M.; De Pontieu, B.; Bellot Rubio, L. R. +2 more
Internetwork (IN) magnetic fields are highly dynamic, short-lived magnetic structures that populate the interior of supergranular cells. Since they emerge all over the Sun, these small-scale fields bring a substantial amount of flux, and therefore energy, to the solar surface. Because of this, IN fields are crucial for understanding the quiet Sun …
The Effects of Biconical Outflows on Lyα Escape from Green Peas
Scarlata, Claudia; Henry, Alaina; Carr, Cody +1 more
We analyze the spectra of 10 Green Pea galaxies, previously studied by Henry et al., using a semi-analytical line transfer model to interpret emission and absorption features observed in UV galactic spectra. We focus our analysis on various ionization states of silicon, associated with the cool (∼104 K) and warm (∼105 K) gas.…
Galaxy Properties at the Faint End of the H I Mass Function
McQuinn, Kristen B. W.; Cannon, John M.; Dolphin, Andrew E. +9 more
The Survey of H I in Extremely Low-mass Dwarfs (SHIELD) includes a volumetrically complete sample of 82 gas-rich dwarfs with ${M}_{{\rm{H}}\,{\rm\small{I}}}\lesssim {10}^{7.2}$ ${M}_{\odot }$ selected from the ALFALFA survey. We are obtaining extensive follow-up observations of the SHIELD galaxies to study their gas, stellar, and chemical content,…
The Blue Supergiant Progenitor of the Supernova Imposter AT 2019krl
Van Dyk, Schuyler D.; Filippenko, Alexei V.; Kochanek, C. S. +20 more
Extensive archival Hubble Space Telescope, Spitzer Space Telescope, and Large Binocular Telescope imaging of the recent intermediate-luminosity transient, AT 2019krl in M74, reveal a bright optical and mid-infrared progenitor star. While the optical peak of the event was missed, a peak was detected in the infrared with an absolute magnitude of M
Far-ultraviolet Spectra of Main-sequence O Stars at Extremely Low Metallicity
McQuinn, Kristen B. W.; Chisholm, John; Berg, Danielle A. +1 more
Metal-poor massive stars dominate the light we observe from star-forming dwarf galaxies and may have produced the bulk of energetic photons that reionized the universe at high redshift. Yet, the rarity of observations of individual O stars below the 20% solar metallicity (Z ⊙) of the Small Magellanic Cloud (SMC) hampers our ability to m…