Search Publications
Nature of the Soft ULX in NGC 247: Super-Eddington Outflow and Transition between the Supersoft and Soft Ultraluminous Regimes
Tao, Lian; Feng, Hua; Grisé, Fabien +1 more
We report on XMM-Newton/Chandra/Swift/Hubble Space Telescope observations of the ultraluminous X-ray source (ULX) in NGC 247, which is found to make transitions between the supersoft ultraluminous (SSUL) regime with a spectrum dominated by a cool (∼0.1 keV) blackbody component and the soft ultraluminous (SUL) regime with comparable luminosities sh…
What Is Controlling the Fragmentation in the Infrared Dark Cloud G14.225-0.506?: Different Levels of Fragmentation in Twin Hubs.
Zhang, Qizhou; Palau, Aina; Pillai, Thushara +7 more
We present observations of the 1.3 mm continuum emission toward hub-N and hub-S of the infrared dark cloud G14.225-0.506 carried out with the Submillimeter Array, together with observations of the dust emission at 870 and 350 µm obtained with APEX and CSO telescopes. The large-scale dust emission of both hubs consists of a single peaked clum…
Quasi-periodic Pulsations during the Impulsive and Decay phases of an X-class Flare
Hayes, L. A.; Gallagher, P. T.; Dennis, B. R. +3 more
Quasi-periodic pulsations (QPPs) are often observed in X-ray emission from solar flares. To date, it is unclear what their physical origins are. Here, we present a multi-instrument investigation of the nature of QPP during the impulsive and decay phases of the X1.0 flare of 2013 October 28. We focus on the character of the fine structure pulsation…
The Infrared Spectral Properties of Magellanic Carbon Stars
van Loon, J. Th.; Sahai, R.; Wood, P. R. +12 more
The Infrared Spectrograph on the Spitzer Space Telescope observed 184 carbon stars in the Magellanic Clouds. This sample reveals that the dust-production rate (DPR) from carbon stars generally increases with the pulsation period of the star. The composition of the dust grains follows two condensation sequences, with more SiC condensing before amor…
A Deep Campaign to Characterize the Synchronous Radio/X-Ray Mode Switching of PSR B0943+10
Tiengo, A.; Mereghetti, S.; Esposito, P. +14 more
Observations of PSR B0943+10 with XMM-Newton and the LOFAR, LWA, and Arecibo radio telescopes in 2014 November confirm the synchronous X-ray/radio switching between a radio-bright (B) mode and a radio-quiet (Q) mode, in which the X-ray flux is a factor ∼2.4 higher than in the B-mode. We discovered X-ray pulsations during the B-mode (0.5-2 keV puls…
Low Gas Fractions Connect Compact Star-forming Galaxies to Their z ~ 2 Quiescent Descendants
Weiner, Benjamin J.; Bezanson, Rachel; Williams, Christina C. +3 more
Early quiescent galaxies at z∼ 2 are known to be remarkably compact compared to their nearby counterparts. Possible progenitors of these systems include galaxies that are structurally similar, but are still rapidly forming stars. Here, we present Karl G. Jansky Very Large Array (VLA) observations of the CO(1-0) line toward three such compact, star…
Absorption-line Spectroscopy of Gravitationally Lensed Galaxies: Further Constraints on the Escape Fraction of Ionizing Photons at High Redshift
Stark, Daniel P.; Ellis, Richard S.; Zitrin, Adi +2 more
The fraction of ionizing photons escaping from high-redshift star-forming galaxies is a key obstacle in evaluating whether galaxies were the primary agents of cosmic reionization. We previously proposed using the covering fraction of low-ionization gas, measured via deep absorption-line spectroscopy, as a proxy. We now present a significant update…
High Spatial Resolution Fe XII Observations of Solar Active Regions
Testa, Paola; De Pontieu, Bart; Hansteen, Viggo
We use UV spectral observations of active regions with the Interface Region Imaging Spectrograph (IRIS) to investigate the properties of the coronal Fe xii 1349.4 Å emission at unprecedented high spatial resolution (∼0.33″). We find that by using appropriate observational strategies (I.e., long exposures, lossless compression), Fe xii emission can…
O VI Emission Imaging of a Galaxy with the Hubble Space Telescope: a Warm Gas Halo Surrounding the Intense Starburst SDSS J115630.63+500822.1
Scarlata, Claudia; Hayes, Matthew; Östlin, Göran +3 more
We report results from a new Hubble Space Telescope campaign that targets the O VI λ λ 1032,1038 Å doublet in emission around intensely star-forming galaxies. The program aims to characterize the energy balance in starburst galaxies and gas cooling in the difficult-to-map coronal temperature regime of 2{--}5× {10}5 K. We present the fir…
He II λ4686 Emission from the Massive Binary System in η Car: Constraints to the Orbital Elements and the Nature of the Periodic Minima
Gull, T. R.; Corcoran, M. F.; Madura, T. I. +27 more
Eta Carinae (η Car) is an extremely massive binary system in which rapid spectrum variations occur near periastron. Most notably, near periastron the He II λ4686 line increases rapidly in strength, drops to a minimum value, then increases briefly before fading away. To understand this behavior, we conducted an intense spectroscopic monitoring of t…