Search Publications
A MegaCam Survey of Outer Halo Satellites. I. Description of the Survey
Djorgovski, S. G.; Geha, Marla; Oyarzún, Grecco A. +5 more
We describe a deep, systematic imaging study of satellites in the outer halo of the Milky Way. Our sample consists of 58 stellar overdensities—i.e., substructures classified as either globular clusters, classical dwarf galaxies, or ultra-faint dwarf galaxies—that are located at Galactocentric distances of R GC ≥ 25 kpc (outer halo) and …
Young Accreting Compact Objects in M31: The Combined Power of NuSTAR, Chandra, and Hubble
Lehmer, B. D.; Hornschemeier, A. E.; Yukita, M. +11 more
We present 15 high-mass X-ray binary (HMXB) candidates in the disk of M31 for which we are able to infer compact object type, spectral type of the donor star, and age using multiwavelength observations from NuSTAR, Chandra, and the Hubble Space Telescope. The hard X-ray colors and luminosities from NuSTAR permit the tentative classification of acc…
Gravitational lensing detection of an extremely dense environment around a galaxy cluster
Streblyanska, Alina; Izzo, Luca; Sereno, Mauro +8 more
Galaxy clusters form at the highest-density nodes of the cosmic web1,2. The clustering of dark matter halos hosting these galaxy clusters is enhanced relative to the general mass distribution, with the matter density beyond the virial region being strongly correlated to the halo mass (halo bias)3. Halo properties other than m…
Possible Phase-dependent Absorption Feature in the X-Ray Spectrum of the Middle-aged PSR J0659+1414
Pavlov, George G.; Kargaltsev, Oleg; Hare, Jeremy +2 more
We report on the energy-resolved timing and phase-resolved spectral analysis of X-ray emission from PSR J0659+1414 observed with XMM-Newton and NuSTAR. We find that the new data rule out the previously suggested model of the phase-dependent spectrum as a three-component (two blackbodies + power law) continuum, which shows large residuals between 0…
Hard x-ray imager onboard Hitomi (ASTRO-H)
Enoto, Teruaki; Yamaoka, Kazutaka; Fukazawa, Yasushi +34 more
The hard x-ray imaging spectroscopy system of "Hitomi" x-ray observatory is composed of two sets of hard x-ray imagers (HXI) coupled with hard x-ray telescopes (HXT). With a 12-m focal length, the system provides fine (1 ‧ . 7 half-power diameter) imaging spectroscopy covering about 5 to 80 keV. The HXI sensor consists of a camera, whi…
The performance of the BepiColombo Laser Altimeter (BELA) prior launch and prospects for Mercury orbit operations
Oberst, J.; Stark, A.; Steinbrügge, G. +2 more
We explore the perspectives of the BepiColombo Laser Altimeter (BELA) onboard ESA / JAXA's Mercury mission BepiColombo and present an updated semi-analytical instrument performance model, in which we estimate signal-to-noise ratio, single shot probability of false detection, range errors and the accuracy of pulse width reconstruction. The model is…
High-resolution Imaging of Transiting Extrasolar Planetary systems (HITEP). II. Lucky Imaging results from 2015 and 2016
Surdej, J.; Henning, Th.; Snodgrass, C. +33 more
Context. The formation and dynamical history of hot Jupiters is currently debated, with wide stellar binaries having been suggested as a potential formation pathway. Additionally, contaminating light from both binary companions and unassociated stars can significantly bias the results of planet characterisation studies, but can be corrected for if…
TRGB Distances to Galaxies in Front of the Virgo Cluster
Shaya, Edward J.; Tully, R. Brent; Karachentsev, Igor D. +2 more
Tip of the red giant branch distances are acquired from Hubble Space Telescope images for 16 galaxies to the foreground of the Virgo Cluster. The new distances with 5% accuracy, combined with archival measurements, tightly constrain the near-side location of the onset of infall into the Virgo Cluster to be 7.3 ± 0.3 Mpc from the cluster, reaching …
CCD photometry, Roche modelling and period analysis of the W UMa eclipsing binary star system AR CrB
Nelson, Robert H.; Alton, Kevin B.
AR CrB (GSC 2040-1361) is a W UMa-type binary system (P = 0.397351 d) which has been poorly studied since first detected over 17 yr ago; only a single unfiltered light curve (LC) has been published. Photometric data collected in three bandpasses (B, V, and Rc) at UnderOak Observatory produced four new times-of-minimum for AR CrB. These …
In-orbit performance of the soft X-ray imaging system aboard Hitomi (ASTRO-H)
Dotani, Tadayasu; Miller, Eric D.; Maeda, Yoshitomo +46 more
We describe the in-orbit performance of the soft X-ray imaging system consisting of the Soft X-ray Telescope and the Soft X-ray Imager aboard Hitomi. Verification and calibration of imaging and spectroscopic performance are carried out, making the best use of the limited data of less than three weeks. Basic performance, including a large field of …