Search Publications
NuStar Hard X-Ray View of Low-luminosity Active Galactic Nuclei: High-energy Cutoff and Truncated Thin Disk
Ho, Luis C.; Younes, George; Yuan, Feng +5 more
We report the analysis of simultaneous XMM-Newton+Nuclear Spectroscopic Telescope Array (NuSTAR) observations of two low-luminosity active galactic nuclei (LLAGNs), NGC 3998 and NGC 4579. We do not detect any significant variability in either source over the ∼3 day length of the NuSTAR observations. The broadband 0.5-60 keV spectrum of NGC 3998 is…
Interpretation of Departure from the Broad-line Region Scaling in Active Galactic Nuclei
Czerny, Bożena; Panda, Swayamtrupta; Du, Pu +7 more
Most results of the reverberation monitoring of active galaxies showed a universal scaling of the time delay of the Hβ emission region with the monochromatic flux at 5100 Å, with very small dispersion. Such a scaling favored the dust-based formation mechanism of the broad-line region (BLR). Recent reverberation measurements showed that actually a …
A Panchromatic View of the Bulge Globular Cluster NGC 6569
Dalessandro, E.; Salaris, M.; Saracino, S. +12 more
We used high-resolution optical Hubble Space Telescope/WFC3 and multiconjugate adaptive optics assisted GEMINI GeMS/Gemini South Adaptive Optics Imager observations in the near-infrared (NIR) to investigate the physical properties of the globular cluster (GC) NGC 6569 in the Galactic bulge. We have obtained the deepest purely NIR color-magnitude d…
Tracing Kinematic and Chemical Properties of Sagittarius Stream by K-Giants, M-Giants, and BHB stars
Tian, Hao; Zhao, Gang; Wu, Yaqian +12 more
We characterize the kinematic and chemical properties of ∼3000 Sagittarius (Sgr) stream stars, including K-giants, M-giants, and blue horizontal branch stars (BHBs), selected from SEGUE-2, Large Sky Area Multi-Object Fibre Spectroscopic Telescope, and Sloan Digital Sky Survey separately in Integrals-of-Motion space. The orbit of the Sgr stream is …
SN 2016coi (ASASSN-16fp): An Energetic H-stripped Core-collapse Supernova from a Massive Stellar Progenitor with Large Mass Loss
Hurley, K.; Challis, P.; Stanek, K. Z. +26 more
We present comprehensive observations and analysis of the energetic H-stripped SN 2016coi (a.k.a. ASASSN-16fp), spanning the γ-ray through optical and radio wavelengths, acquired within the first hours to ∼420 days post explosion. Our observational campaign confirms the identification of He in the supernova (SN) ejecta, which we interpret to be ca…
Finding the Brightest Cosmic Beacons in the Southern Hemisphere
Grazian, Andrea; Boutsia, Konstantina; Amorin, Ricardo +6 more
The study of absorptions along the lines of sight to bright high-z QSOs is an invaluable cosmological tool that provides a wealth of information on the inter-/circum-galactic medium, dark matter, primordial elements, reionization, fundamental constants, and general relativity. Unfortunately, the number of bright (i ≲ 18) QSOs at z ≳ 2 in the south…
Chemical Cartography. II. The Assembly History of the Galactic Stellar Halo Traced by Carbon-enhanced Metal-poor Stars
Beers, Timothy C.; Lee, Young Sun; Kim, Young Kwang
We present an analysis of the kinematic properties of stellar populations in the Galactic halo, making use of over 100,000 main-sequence turnoff (MSTO) stars observed in the Sloan Digital Sky Survey. After dividing the Galactic halo into an inner-halo region (IHR) and outer-halo region (OHR), based on the spatial variation of carbon-to-iron ratios…
A Dynamical Model for Clustered Star Formation in the Galactic Disk
Conroy, Charlie; Ting, Yuan-Sen; Cargile, Phillip +3 more
The clustered nature of star formation should produce a high degree of structure in the combined phase and chemical space in the Galactic disk. To date, observed structure of this kind has been mostly limited to bound clusters and moving groups. In this paper, we present a new dynamical model of the Galactic disk that takes into account the cluste…
First Observations of Irregular Surface of Interplanetary Shocks at Ion Scales by Cluster
Kajdič, Primož; Blanco-Cano, Xóchitl; Burgess, David +2 more
We present the first observational evidence of the irregular surface of interplanetary (IP) shocks by using multispacecraft observations of the Cluster mission. In total we discuss observations of four IP shocks that exhibit moderate Alfvénic Mach numbers (M A ≤ 6.5). Three of them are high-β shocks with upstream β = 2.2-3.7. During the…
Characterization of a Sample of Southern M Dwarfs Using Harps and X-shooter Spectra
del Burgo, C.; Pavlenko, Ya. V.; Kuznetsov, M. K. +1 more
We present the homogeneous analysis of a sample of Southern early-type M dwarfs in the solar neighborhood (d < 60 pc). We used the MCAL technique to derive the effective temperature T eff, metallicity [Fe/H], and activity index i a (H alpha) of 420 M stars using HARPS spectra. The effective temperature T e…