Search Publications
Near-infrared Polarization from Unresolved Disks around Brown Dwarfs and Young Stellar Objects
Espaillat, Catherine C.; Pillai, Thushara G. S.; Rilinger, Anneliese M. +1 more
Wide-field near-infrared (NIR) polarimetry was used to examine disk systems around two brown dwarfs (BDs) and two young stellar objects (YSOs) embedded in the Heiles Cloud 2 (HCl2) dark molecular cloud in Taurus as well as numerous stars located behind HCl2. Inclined disks exhibit intrinsic NIR polarization due to scattering of photospheric light,…
A Gap at 1 au in the Disk of DI Cha A Revealed by Infrared Interferometry
Pál, András; Moór, Attila; Ábrahám, Péter +6 more
DI Cha A is K0-type pre-main-sequence star, the brightest component of a quadruple stellar system. Here we report on a detailed study of this star based on archival VLTI/MIDI and VLTI/PIONIER infrared interferometric observations, as well as optical-infrared photometric monitoring from ground-based and space-born instruments. We determined the str…
X-Ray Spectra from Weakly Magnetized Accretion Flows
Pe'er, Asaf; Wallace, John
In this paper, we expand upon previous work that argued for the possibility of a subequipartition magnetic field in the accretion flow of a black hole binary system. Using X-ray observations of the three well-known sources A0620-00, XTE J1118+480, and V404 Cyg during the quiescent state, we compare the theoretically expected spectral shape with th…
Excitation and Excavation of the Claws of the Southern Crab
Frank, Adam; Balick, Bruce; Swegel, Ashley
We show that the Southern Crab (aka Hen2-104) presents an auspicious opportunity to study the form and speed of the invisible winds that excavate and shock the lobes of various types of bipolar nebulae associated with close and highly evolved binary stars. A deep three-color image overlay of Hen2-104 reveals that the ionization state of its lobe e…
The Radius of PSR J0740+6620 from NICER and XMM-Newton Data
Guillemot, L.; Kerr, M.; Ray, P. S. +25 more
PSR J0740+6620 has a gravitational mass of 2.08 ± 0.07 M⊙, which is the highest reliably determined mass of any neutron star. As a result, a measurement of its radius will provide unique insight into the properties of neutron star core matter at high densities. Here we report a radius measurement based on fits of rotating hot spot patte…
A NICER View of the Massive Pulsar PSR J0740+6620 Informed by Radio Timing and XMM-Newton Spectroscopy
Remillard, Ronald A.; Okajima, Takashi; Bogdanov, Slavko +27 more
We report on Bayesian estimation of the radius, mass, and hot surface regions of the massive millisecond pulsar PSR J0740+6620, conditional on pulse-profile modeling of Neutron Star Interior Composition Explorer X-ray Timing Instrument event data. We condition on informative pulsar mass, distance, and orbital inclination priors derived from the jo…
Cosmic Distances Calibrated to 1% Precision with Gaia EDR3 Parallaxes and Hubble Space Telescope Photometry of 75 Milky Way Cepheids Confirm Tension with ΛCDM
Casertano, Stefano; Riess, Adam G.; Yuan, Wenlong +4 more
We present an expanded sample of 75 Milky Way Cepheids with Hubble Space Telescope (HST) photometry and Gaia EDR3 parallaxes, which we use to recalibrate the extragalactic distance ladder and refine the determination of the Hubble constant. All HST observations were obtained with the same instrument (WFC3) and filters (F555W, F814W, F160W) used fo…
Measurements of the Hubble Constant: Tensions in Perspective
Freedman, Wendy L.
Measurement of the distances to nearby galaxies has improved rapidly in recent decades. The ever-present challenge is to reduce systematic effects, especially as greater distances are probed and the uncertainties become larger. In this paper, we combine several recent calibrations of the tip of the red giant branch (TRGB) method. These calibration…
Seventeen Tidal Disruption Events from the First Half of ZTF Survey Observations: Entering a New Era of Population Studies
Kilpatrick, Charles D.; Foley, Ryan J.; Cenko, S. Bradley +37 more
While tidal disruption events (TDEs) have long been heralded as laboratories for the study of quiescent black holes, the small number of known TDEs and uncertainties in their emission mechanism have hindered progress toward this promise. Here we present 17 new TDEs that have been detected recently by the Zwicky Transient Facility along with Swift …
CHIANTI—An Atomic Database for Emission Lines. XVI. Version 10, Further Extensions
Young, P. R.; Del Zanna, G.; Dere, K. P. +1 more
We present version 10 of the CHIANTI package. In this release, we provide updated atomic models for several helium-like ions and for all the ions of the beryllium, carbon, and magnesium isoelectronic sequences that are abundant in astrophysical plasmas. We include rates from large-scale atomic structure and scattering calculations that are in many…