Search Publications
Multiwavelength Evidence for a New Flare-mode Transitional Millisecond Pulsar
Strader, Jay; Bahramian, Arash; Chomiuk, Laura +7 more
We report the discovery of a new low-mass X-ray binary near the center of the unassociated Fermi GeV γ-ray source 4FGL J0540.0-7552. The source shows the persistent presence of an optical accretion disk and exhibits extreme X-ray and optical variability. It also has an X-ray spectrum well-fit by a hard power law with Γ = 1.8 and a high ratio of X-…
Long Term Evolution of Surface Features on the Red Supergiant AZ Cyg
Gies, Douglas R.; Monnier, John D.; Schaefer, Gail H. +23 more
We present H-band interferometric observations of the red supergiant (RSG) AZ Cyg that were made with the Michigan Infra-Red Combiner (MIRC) at the six-telescope Center for High Angular Resolution Astronomy (CHARA) Array. The observations span 5 yr (2011-2016), which offers insight into the short and long-term evolution of surface features on RSGs…
On the Rigidity Spectrum of Cosmic-Ray Variations within Propagating Interplanetary Disturbances: Neutron Monitor and SOHO/EPHIN Observations at ∼1-10 GV
Vourlidas, Angelos; Heber, Bernd; Papaioannou, Athanasios +9 more
The rigidity dependence of all Forbush decreases (FDs) recorded from 1995 to 2015 has been determined using neutron monitor (NM) and Solar and Heliospheric Observatory (SOHO) (EPHIN) spacecraft data, covering the energy (rigidity) range from ∼433 MeV (1 GV) to 9.10 GeV (10 GV). We analyzed a total of 421 events and determined the spectrum in rigid…
X-Ray Pulsar XTE J1858+034: Discovery of the Cyclotron Line and the Revised Optical Identification
Kretschmar, Peter; Doroshenko, Victor; Tsygankov, Sergey S. +7 more
We present the results of a detailed investigation of the poorly studied X-ray pulsar (XRP) XTE J1858+034 based on the data obtained with the NuSTAR observatory during the outburst of the source in 2019. The spectral analysis resulted in the discovery of a cyclotron absorption feature in the source spectrum at ∼48 keV in both the pulse phase-avera…
A 99 minute Double-lined White Dwarf Binary from SDSS-V
Maoz, Dan; Hermes, J. J.; Rix, Hans-Walter +12 more
We report the discovery of SDSS J133725.26+395237.7 (hereafter SDSS J1337+3952), a double-lined white dwarf (WD+WD) binary identified in early data from the fifth-generation Sloan Digital Sky Survey (SDSS-V). The double-lined nature of the system enables us to fully determine its orbital and stellar parameters with follow-up Gemini spectroscopy an…
Radius and Mass Distribution of Ultra-short-period Planets
Uzsoy, Ana Sofía M.; Rogers, Leslie A.; Price, Ellen M.
Ultra-short-period (USP) planets are an enigmatic subset of exoplanets defined by having orbital periods <1 day. It is still not understood how USP planets form, or to what degree they differ from planets with longer orbital periods. Most USP planets have radii <2 R⊕, while planets that orbit further from their star extend to Jupi…
Radio Counterpart Candidates to Unassociated 4FGL-DR2 Sources
Schinzel, F. K.; Bruzewski, S.; Taylor, G. B. +1 more
For the duration of the Fermi Gamma-Ray Space Telescope's mission, approximately one-third of the point sources detected have been noted as "unassociated," meaning that they seem to have no known counterpart at any other wavelength/frequency. This mysterious part of the gamma-ray sky is perhaps one of the largest unknowns in current astronomical p…
Multiwavelength Emission from Magnetically Arrested Disks around Isolated Black Holes
Kimura, Shigeo S.; Kashiyama, Kazumi; Hotokezaka, Kenta
We discuss the prospects for identifying the nearest isolated black holes (IBHs) in our Galaxy. IBHs accreting gas from the interstellar medium likely form magnetically arrested disks (MADs). We show that thermal electrons in the MADs emit optical signals through the thermal synchrotron process while nonthermal electrons accelerated via magnetic r…
Integrated Photometry of Multiple Stellar Populations in Globular Clusters
Milone, A. P.; Cordoni, G.; Marino, A. F. +8 more
Evidence that multiple populations (MPs) are common properties of globular clusters (GCs) has accumulated over the past decades from clusters in the Milky Way and in its satellites. This finding has revived research into GCs, and suggested that their formation at high redshift must have been a much more complex phenomenon than imagined before. How…
Exploring the Stellar Rotation of Early-type Stars in the LAMOST Medium-resolution Survey. II. Statistics
Deng, Licai; de Grijs, Richard; Sun, Weijia +1 more
Angular momentum is a key property regulating star formation and evolution. However, the physics driving the distribution of the stellar rotation rates of early-type main-sequence stars is as yet poorly understood. Using our catalog of 40,034 early-type stars with homogeneous $v\sin i$ parameters, we review the statistical properties of their stel…