Search Publications
The Donor of the Black Hole X-Ray Binary MAXI J1820+070
Mikołajewska, Joanna; Casares, Jorge; Zdziarski, Andrzej A. +2 more
We estimate the parameters of the donor of the accreting black hole binary MAXI J1820+070. The measured values of the binary period, rotational and radial velocities, and constraints on the orbital inclination imply the donor is a subgiant with the mass of ${M}_{2}\approx {0.49}_{-0.10}^{+0.10}{M}_{\odot }$ and the radius of ${R}_{2}\approx {1.19}…
Genesis and Coronal-jet-generating Eruption of a Solar Minifilament Captured by IRIS Slit-raster Spectra
Tiwari, Sanjiv K.; De Pontieu, Bart; Panesar, Navdeep K. +2 more
We present the first Mg II slit-raster spectra from the Interface Region Imaging Spectrograph (IRIS) that fully capture the genesis and coronal-jet-generating eruption of a central-disk solar minifilament. The minifilament arose in a negative-magnetic-polarity coronal hole. The Mg II spectroheliograms verify that the minifilament plasma temperatur…
Ultrafaint Dwarf Galaxy Candidates in the M81 Group: Signatures of Group Accretion
Bell, Eric F.; Monachesi, Antonela; Bailin, Jeremy +8 more
The faint and ultrafaint dwarf galaxies in the Local Group form the observational bedrock upon which our understanding of small-scale cosmology rests. In order to understand whether this insight generalizes, it is imperative to use resolved-star techniques to discover similarly faint satellites in nearby galaxy groups. We describe our search for u…
Constraints on Cosmological Parameters with a Sample of Type Ia Supernovae from JWST
Koekemoer, Anton M.; Baade, Dietrich; Wang, Lifan +7 more
We investigate the potential of using a sample of very high-redshift (2 ≲ z ≲ 6) (VHZ) Type Ia supernovae (SNe Ia) attainable by JWST on constraining cosmological parameters. At such high redshifts, the age of the universe is young enough that the VHZ SN Ia sample comprises the very first SNe Ia of the universe, with progenitors among the very fir…
New Constraints on the Dark Matter Density Profiles of Dwarf Galaxies from Proper Motions of Globular Cluster Streams
Malhan, Khyati; Ibata, Rodrigo A.; Valluri, Monica +1 more
The central density profiles in dwarf galaxy halos depend strongly on the nature of dark matter (DM). Recently, in Malhan et al. we employed N-body simulations to show that the cuspy cold DM subhalos predicted by cosmological simulations can be differentiated from cored subhalos using the properties of accreted globular cluster (GC) streams since …
Evolution of the Spin, Spectrum and Superorbital Period of the Ultraluminous X-Ray Pulsar M51 ULX7
Israel, Gian Luca; Fürst, Felix; Walton, Dominic J. +6 more
M51 ULX7 is among a small group of known ultraluminous X-ray pulsars (ULXPs). The neutron star powering the source has a spin period of 2.8 s, orbits its companion star with a period of 2 days, and a superorbital period of 38 days is evident in its X-ray lightcurve. Here we present NuSTAR and XMM-Newton data on the source from 2019 obtained when t…
From the Fire: A Deeper Look at the Phoenix Stream
Smith, M.; Abbott, T. M. C.; Allam, S. +64 more
We use 6 yr of data from the Dark Energy Survey to perform a detailed photometric characterization of the Phoenix stellar stream, a 15° long, thin, dynamically cold, low-metallicity stellar system in the Southern Hemisphere. We use natural splines, a nonparametric modeling technique, to simultaneously fit the stream track, width, and linear densit…
Measuring Optical Extinction toward Young Stellar Objects Using Diffuse Interstellar Bands
Hillenbrand, Lynne A.; Carvalho, Adolfo S.
Line-of-sight extinction estimates of well-studied young T Tauri and Herbig Ae/Be stars are based on many different measurements and analysis methods. This has resulted in wide scatter among the published A V values for the same star. In this work, we discuss the challenges in measuring extinction to actively accreting and especially …
High-resolution Near-infrared Spectroscopy of a Flare around the Ultracool Dwarf vB 10
Kowalski, Adam F.; Cochran, William D.; Mahadevan, Suvrath +20 more
We present high-resolution observations of a flaring event in the M8 dwarf vB 10 using the near-infrared Habitable-zone Planet Finder (HPF) spectrograph on the Hobby-Eberly Telescope. The high stability of HPF enables us to accurately subtract a vB 10 quiescent spectrum from the flare spectrum to isolate the flare contributions and study the chang…
Excitation and Damping of Slow Magnetosonic Waves in Flaring Hot Coronal Loops: Effects of Compressive Viscosity
Ofman, Leon; Wang, Tongjiang
Slow magnetosonic waves associated with flares were observed in coronal loops by Solar and Heliospheric Observatory/Solar Ultraviolet Measurements of Emitted Radiation, Solar Dynamics Observatory/Atmospheric Imaging Assembly in various EUV bandpasses, and other instruments. The excitation and damping of slow magnetosonic waves provides information…