Search Publications
On the Nature of the Enigmatic Object IRAS 19312+1950: A Rare Phase of Massive Star Formation?
Justtanont, K.; Tielens, A. G. G. M.; Boogert, A. C. A. +7 more
IRAS 19312+1950 is a peculiar object that has eluded firm characterization since its discovery, with combined maser properties similar to an evolved star and a young stellar object (YSO). To help determine its true nature, we obtained infrared spectra of IRAS 19312+1950 in the range 5-550 µm using the Herschel and Spitzer space observatories…
The Compact Star-forming Complex at the Heart of NGC 253
Davidge, T. J.
We discuss integral field spectra of the compact star-forming complex that is the brightest near-infrared (NIR) source in the central regions of the starburst galaxy NGC 253. The spectra cover the H and K passbands and were recorded with the Gemini NIR Spectrograph during subarcsecond seeing conditions. Absorption features in the spectrum of the s…
A NuSTAR Observation of the Gamma-ray-emitting X-ray Binary and Transitional Millisecond Pulsar Candidate 1RXS J154439.4-112820
Bogdanov, Slavko
I present a 40 ks Nuclear Spectroscopic Telescope Array observation of the recently identified low-luminosity X-ray binary and transitional millisecond pulsar (tMSP) candidate 1RXS J154439.4-112820, which is associated with the high-energy γ-ray source 3FGL J1544.6-1125. The system is detected up to ∼30 keV with an extension of the same power-law …
Pixel Color Magnitude Diagrams for Semi-resolved Stellar Populations: The Star Formation History of Regions within the Disk and Bulge of M31
van Dokkum, Pieter G.; Conroy, Charlie
The analysis of stellar populations has, by and large, been developed for two limiting cases: spatially resolved stellar populations in the color-magnitude diagram, and integrated light observations of distant systems. In between these two extremes lies the semi-resolved regime, which encompasses a rich and relatively unexplored realm of observati…
The Inner Structure of the TW Hya Disk as Revealed in Scattered Light
Debes, John H.; Schneider, Glenn; Jang-Condell, Hannah
We observe a significant change in the TW Hya disk interior to 40 au via archival unpolarized multi-wavelength Hubble Space Telescope/STIS and NICMOS images with an inner working angle of 0.″4 (22 au). Our images show the outer edge of a clearing at every wavelength with similar behavior, demonstrating that the feature is structural, rather than d…
Orion's Veil. IV. H2 Excitation and Geometry
Abel, N. P.; O'Dell, C. R.; Ferland, G. J. +1 more
The foreground Veil of material that lies in front of the Orion Nebula is the best studied sample of the interstellar medium because we know where it is located, how it is illuminated, and the balance of thermal and magnetic energy. In this work, we present high-resolution STIS observations toward the Trapezium, with the goal of better understandi…
Formation and Evolution of Blue Stragglers in 47 Tucanae
Heyl, Jeremy; Richer, Harvey; Kalirai, Jason +2 more
Blue stragglers (BSS) are stars whose position in the color-magnitude diagram (CMD) places them above the main sequence (MS) turn-off (TO) point of a star cluster. Using data from the core of 47 Tuc in the ultraviolet (UV), we have identified various stellar populations in the CMD, and used their radial distributions to study the evolution and ori…
Investigating the Conditions of the Formation of a Type II Radio Burst on 2014 January 8
Cheng, X.; Ding, M. D.; Chen, P. F. +3 more
It is believed that type II radio bursts are generated by shock waves. In order to understand the generation conditions of type II radio bursts, we analyze the physical parameters of a shock front. The type II radio burst we selected was observed by the Siberian Solar Radio Telescope (SSRT) and Learmonth radio station and was associated with a lim…
Spatially Resolved Spectroscopy of a Balmer-dominated Shock in the Cygnus Loop: An Extremely Thin Cosmic-Ray Precursor?
Katsuda, Satoru; Lee, Jae-Joon; Raymond, John C. +9 more
We present high-resolution long-slit spectroscopy of a Balmer-dominated shock in the northeastern limb of the Cygnus Loop with the Subaru high dispersion spectrograph. By setting the slit angle along the shock normal, we investigate variations of the flux and profile of the Hα line from preshock to postshock regions with a spatial resolution of ∼4…
A Study of the Elements Copper through Uranium in Sirius A: Contributions from STIS and Ground-Based Spectra
Wahlgren, G. M.; Castelli, F.; Monier, R. +3 more
We determine abundances or upper limits for all of the 55 stable elements from copper to uranium for the A1 Vm star Sirius. The purpose of the study is to assemble the most complete picture of elemental abundances with the hope of revealing the chemical history of the brightest star in the sky, apart from the Sun. We also explore the relationship …