Search Publications
EPIC 203868608: A Low-mass Quadruple Star System in the Upper Scorpius OB Association
Albrecht, Simon; Hillenbrand, Lynne A.; Mawet, Dimitri +3 more
Young multiple star systems provide excellent testing grounds for theories of star formation and evolution. EPIC 203868608 was previously studied as a triple star system in the Upper Scorpius OB association, but the followup Keck NIRC2/HIRES/NIRSPAO observations reported here reveal its quadruple nature. We find that the system consists of a doubl…
Size-Luminosity Scaling Relations of Local and Distant Star-forming Regions
Do, Tuan; Armus, Lee; Larkin, James E. +8 more
We investigate star-forming scaling relations using Bayesian inference on a comprehensive data sample of low- (z < 0.1) and high-redshift (1 < z < 5) star-forming regions. This full data set spans a wide range of host galaxy stellar mass (M * ∼ 106-1011 {M}⊙ ) and clump star formation rates (SFR…
Discovery of an Active Intermediate-mass Black Hole Candidate in the Barred Bulgeless Galaxy NGC 3319
Shu, Xinwen; Zhou, Hongyan; Jiang, Ning +7 more
We report the discovery of an active intermediate-mass black hole (IMBH) candidate in the center of nearby barred bulgeless galaxy NGC 3319. The point X-ray source revealed by archival Chandra and XMM-Newton observations is spatially coincident with the optical and UV galactic nuclei from Hubble Space Telescope observations. The spectral energy di…
Measuring the Local ISM along the Sight Lines of the Two Voyager Spacecraft with HST/STIS
Redfield, Seth; Wood, Brian E.; Linsky, Jeffrey L. +1 more
In 2012 August, Voyager 1 crossed the heliopause, becoming the first human-made object to exit the solar system. This milestone signifies the beginning of an important new era for local interstellar medium (LISM) exploration. We present measurements of the structure and composition of the LISM in the immediate path of the Voyager spacecraft by usi…
Large-amplitude Rapid X-Ray Variability in the Narrow-line Seyfert 1 Galaxy PG 1404+226
Dewangan, G. C.; Mallick, L.
We present the first results from a detailed analysis of a new, long (∼100 ks) XMM-Newton observation of the narrow-line Seyfert 1 galaxy PG 1404+226, which showed a large-amplitude, rapid X-ray variability by a factor of ∼7 in ∼10 ks with an exponential rise and a sharp fall in the count rate. We investigate the origin of the soft X-ray excess em…
Positional Offsets between SiO Masers in Evolved Stars and their Cross-matched Counterparts
Morris, Mark R.; Rich, R. Michael; Sjouwerman, Loránt O. +4 more
Observations of dust-enshrouded evolved stars selected from infrared catalogs requiring high positional accuracy, like infrared spectroscopy or long baseline radio interferometric observations, often require preparational observational steps determining a position with an accuracy much better than 1″. Using phase-referencing observations with the …
On the Nature of the X-Ray Emission from the Ultraluminous X-Ray Source, M33 X-8: New Constraints from NuSTAR and XMM-Newton
Williams, Benjamin F.; Zezas, Andreas; Maccarone, Thomas J. +12 more
We present nearly simultaneous NuSTAR and XMM-Newton observations of the nearby (832 kpc) ultraluminous X-ray source (ULX) M33 X-8. M33 X-8 has a 0.3-10 keV luminosity of L X ≈ 1.4 × 1039 erg s-1, near the boundary of the “ultraluminous” classification, making it an important source for understanding the link betwe…
Statistical Study of ICMEs with Low Mean Carbon Charge State Plasmas Detected from 1998 to 2011
Li, Gang; Yan, Xiaoli; Yao, Shuo +2 more
We present a statistical study of 219 ICMEs measured by both ACE and WIND from 1998 to 2011. ICME plasmas are defined as possessing cold materials if the carbon average charge states are lower than those of the preceding solar wind by three standard deviations and the carbon ionic temperature is lower than 106.05 K. A total of 69 ICMEs …
A Diagnostic of Coronal Elemental Behavior during the Inverse FIP Effect in Solar Flares
Brooks, David H.
The solar corona shows a distinctive pattern of elemental abundances that is different from that of the photosphere. Low first ionization potential (FIP) elements are enhanced by factors of several. A similar effect is seen in the atmospheres of some solar-like stars, while late-type M stars show an inverse FIP effect. This inverse effect was rece…
A Likely Supermassive Black Hole Revealed by Its Einstein Radius in Hubble Frontier Fields Images
Broadhurst, Tom; Ohyama, Youichi; Ford, Holland +4 more
At cosmological distances, gravitational lensing can in principle provide direct mass measurements of supermassive black holes (SMBHs). Here, we directly estimate the mass of a SMBH in the brightest cluster galaxy (BCG) of MACS J1149.5+2223 at z = 0.54 using one of the multiply lensed images of a background spiral galaxy at z = 1.49 projected clos…