Search Publications
The MUSCLES Treasury Survey. I. Motivation and Overview
Loyd, R. O. Parke; Kowalski, Adam F.; Hawley, Suzanne L. +19 more
Ground- and space-based planet searches employing radial velocity techniques and transit photometry have detected thousands of planet-hosting stars in the Milky Way. With so many planets discovered, the next step toward identifying potentially habitable planets is atmospheric characterization. While the Sun-Earth system provides a good framework f…
The R136 star cluster dissected with Hubble Space Telescope/STIS. I. Far-ultraviolet spectroscopic census and the origin of He II λ1640 in young star clusters
Howarth, I. D.; Angus, C. R.; Lennon, D. J. +17 more
We introduce a Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph (STIS) stellar census of R136a, the central ionizing star cluster of 30 Doradus. We present low resolution far-ultraviolet STIS spectroscopy of R136 using 17 contiguous 52 arcsec × 0.2 arcsec slits which together provide complete coverage of the central 0.85 parsec (3…
Wolf-Rayet stars in the Small Magellanic Cloud. II. Analysis of the binaries
Sander, A.; Hamann, W. -R.; Oskinova, L. M. +7 more
Context. Massive Wolf-Rayet (WR) stars are evolved massive stars (MI ≳ 20 M⊙) characterized by strong mass-loss. Hypothetically, they can form either as single stars or as mass donors in close binaries. About 40% of all known WR stars are confirmed binaries, raising the question as to the impact of binarity on the WR populati…
Photolytic Hazes in the Atmosphere of 51 Eri b
Morley, C. V.; Zahnle, K.; Moses, J. I. +1 more
We use a 1D model to address photochemistry and possible haze formation in the irradiated warm Jupiter, 51 Eridani b. The intended focus was to be carbon, but sulfur photochemistry turns out to be important. The case for organic photochemical hazes is intriguing but falls short of being compelling. If organic hazes form, they are likeliest to do s…
Space Telescope and Optical Reverberation Mapping Project. IV. Anomalous Behavior of the Broad Ultraviolet Emission Lines in NGC 5548
Im, M.; Geier, S.; Brandt, W. N. +98 more
During an intensive Hubble Space Telescope (HST) Cosmic Origins Spectrograph (COS) UV monitoring campaign of the Seyfert 1 galaxy NGC 5548 performed from 2014 February to July, the normally highly correlated far UV continuum and broad emission line variations decorrelated for ∼60-70 days, starting ∼75 days after the first HST/COS observation. Foll…
The mass and spin of the extreme Narrow Line Seyfert 1 Galaxy 1H 0707-495 and its implications for the trigger for relativistic jets
Done, Chris; Jin, Chichuan
Relativistic reflection models of the X-ray spectrum of the `complex' Narrow Line Seyfert 1 (NLS1) 1H 0707-495 require a high-spin, moderate-inclination, low-mass black hole. With these parameters fixed, the observed optical/UV emission directly determines the mass accretion rate through the outer disc and hence predicts the bolometric luminosity.…
The Close AGN Reference Survey (CARS). What is causing Mrk 1018's return to the shadows after 30 years?
Combes, F.; Scharwächter, J.; Eckart, A. +11 more
We recently discovered that the active galactic nucleus (AGN) of Mrk 1018 has changed optical type again after 30 yr as a type 1 AGN. Here we combine Chandra, NuStar, Swift, Hubble Space Telescope and ground-based observations to explore the cause of this change. The 2-10 keV flux declines by a factor of ~8 between 2010 and 2016. We show with our …
Living with a Red Dwarf: Rotation and X-Ray and Ultraviolet Properties of the Halo Population Kapteyn's Star
Guinan, Edward F.; Engle, Scott G.; Durbin, Allyn
As part of Villanova's Living with a Red Dwarf program, we have obtained UV, X-ray, and optical data of the Population II red dwarf -- Kapteyn's Star. Kapteyn's Star is noteworthy for its large proper motions and high radial velocity of ∼+245 km s-1. As the nearest Pop II red dwarf, it serves as an old age anchor for calibrating activit…
Measuring the stellar wind parameters in IGR J17544-2619 and Vela X-1 constrains the accretion physics in supergiant fast X-ray transient and classical supergiant X-ray binaries
Sander, A.; Hamann, W. -R.; Shenar, T. +9 more
Context. Classical supergiant X-ray binaries (SGXBs) and supergiant fast X-ray transients (SFXTs) are two types of high-mass X-ray binaries (HMXBs) that present similar donors but, at the same time, show very different behavior in the X-rays. The reason for this dichotomy of wind-fed HMXBs is still a matter of debate. Among the several explanation…
SU Lyncis, a hard X-ray bright M giant: clues point to a large hidden population of symbiotic stars
Nuñez, N. E.; Nelson, T.; Mukai, K. +6 more
Symbiotic star surveys have traditionally relied almost exclusively on low resolution optical spectroscopy. However, we can obtain a more reliable estimate of their total Galactic population by using all available signatures of the symbiotic phenomenon. Here we report the discovery of a hard X-ray source, 4PBC J0642.9+5528, in the Swift hard X-ray…