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…
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…
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 …
Expanding CO Shells in the Orion A Molecular Cloud
Nakamura, Fumitaka; Shimajiri, Yoshito; Kawabe, Ryohei +6 more
We present the discovery of expanding spherical shells around low- to intermediate-mass young stars in the Orion A giant molecular cloud using observations of {}12{CO}(1-0) and {}13{CO}(1-0) from the Nobeyama Radio Observatory 45 m telescope. The shells have radii from 0.05 to 0.85 pc and expand outward at 0.8-5 km s-1
Galaxy Inclination and the IRX-β Relation: Effects on UV Star Formation Rate Measurements at Intermediate to High Redshifts
Barro, Guillermo; Pérez-González, Pablo G.; Ferguson, Henry C. +11 more
At intermediate and high redshifts, measurements of galaxy star formation rates are usually based on rest-frame ultraviolet (UV) data. A correction for dust attenuation, A UV, is needed for these measurements. This correction is typically inferred from UV spectral slopes (β) using an equation known as “Meurer's Relation.” In this paper,…
Stellar Population Diagnostics of the Massive Star Binary Fraction
Dorn-Wallenstein, Trevor Z.; Levesque, Emily M.
Populations of massive stars are directly reflective of the physics of stellar evolution. Counts of subtypes of massive stars and ratios of massive stars in different evolutionary states have been used ubiquitously as diagnostics of age and metallicity effects. While the binary fraction of massive stars is significant, inferences are often based u…
Two Solar Tornadoes Observed with the Interface Region Imaging Spectrograph
Chen, Yajie; Tian, Hui; Zhang, Jingwen +4 more
The barbs or legs of some prominences show an apparent motion of rotation, which are often termed solar tornadoes. It is under debate whether the apparent motion is a real rotating motion, or caused by oscillations or counter-streaming flows. We present analysis results from spectroscopic observations of two tornadoes by the Interface Region Imagi…
Localized Quasi-periodic Fluctuations in C II, Si IV, and Fe XXI Emission during Chromospheric Evaporation in a Flare Ribbon Observed by IRIS on 2017 September 9
Brosius, Jeffrey W.; Inglis, Andrew R.
We investigate the onset of a GOES M3.7 flare on 2017 September 9 with rapid-cadence (9.4 s) UV stare spectra obtained with IRIS in five 1″ slit segments. Our analysis is based primarily on integrated intensities and Doppler velocities of C II λ1334.5 (T ≈ 2.5 × 104 K), Si IV λ1402.7 (7.9 × 104 K), and Fe XXI λ1354.1 (1.1 × 1…
Statistical Analysis on XMM-Newton X-Ray Flares of Mrk 421: Distributions of Peak Flux and Flaring Time Duration
Wang, Jiancheng; Zhang, Pengfei; Zhang, Li +3 more
The energy dissipation mechanism in blazar jet is unknown. Blazar flares could provide insights into this problem. Here we report statistical results of XMM-Newton observations of X-ray flares in Mrk 421. We analyze all public XMM-Newton X-ray observations for Mrk 421, and construct the light curves. Through fitting the light curves, we obtain the…