Search Publications
The Typecasting of Active Galactic Nuclei: Mrk 590 no Longer Fits the Role
Martini, P.; Peterson, B. M.; Pogge, R. W. +9 more
We present multiwavelength observations that trace more than 40 yr in the life of the active galactic nucleus (AGN) in Mrk 590, traditionally known as a classic Seyfert 1 galaxy. From spectra recently obtained from Hubble Space Telescope, Chandra, and the Large Binocular Telescope, we find that the activity in the nucleus of Mrk 590 has diminished…
Reverberation Mapping of the Seyfert 1 Galaxy NGC 7469
Motohara, K.; Skowron, D. M.; Skowron, J. +43 more
A large reverberation-mapping study of the Seyfert 1 galaxy NGC 7469 has yielded emission-line lags for Hβ λ4861 and He II λ4686 and a central black hole mass measurement M BH ≈ 1 × 107 M ⊙, consistent with previous measurements. A very low level of variability during the monitoring campaign precluded meeting our o…
Winds of Low-metallicity OB-type Stars: HST-COS Spectroscopy in IC 1613
Garcia, Miriam; Herrero, Artemio; Najarro, Francisco +2 more
We present the first quantitative ultraviolet spectroscopic analysis of resolved OB stars in IC 1613. Because of its alleged very low metallicity (lsim1/10 Z ⊙, from H II regions), studies in this Local Group dwarf galaxy could become a significant step forward from the Small Magellanic Cloud (SMC) toward the extremely metal-poor massiv…
The UBV Color Evolution of Classical Novae. I. Nova-giant Sequence in the Color-Color Diagram
Kato, Mariko; Hachisu, Izumi
We identified a general course of classical nova outbursts in the B - V versus U - B color-color diagram. It is reported that novae show spectra similar to those of A-F supergiants near optical light maximum. However, they do not follow the supergiant sequence in the color-color diagram, neither the blackbody nor the main-sequence sequence. Instea…
The Secret Lives of Cepheids: Evolutionary Changes and Pulsation-induced Shock Heating in the Prototype Classical Cepheid δ Cep
Harper, Graham M.; Guinan, Edward F.; Engle, Scott G. +2 more
Over the past decade, the Secret Lives of Cepheids (SLiC) program has been carried out at Villanova University to study aspects and behaviors of classical Cepheids that are still not well understood. In this, the first of several planned papers on program Cepheids, we report the current results for δ Cep, the Cepheid prototype. Ongoing photometry …
Hubble Space Telescope Observations and Geometric Models of Compact Multipolar Planetary Nebulae
Zhang, Yong; Kwok, Sun; Hsia, Chih-Hao +1 more
We report high angular resolution Hubble Space Telescope observations of 10 compact planetary nebulae (PNs). Many interesting internal structures, including multipolar lobes, arcs, two-dimensional rings, tori, and halos, are revealed for the first time. These results suggest that multipolar structures are common among PNs, and these structures dev…
Hubble Space Telescope Far Ultraviolet Spectroscopy of the Recurrent Nova T Pyxidis
Williams, Robert E.; Livio, Mario; Woodward, Charles E. +5 more
With six recorded nova outbursts, the prototypical recurrent nova T Pyxidis (T Pyx) is the ideal cataclysmic variable system to assess the net change of the white dwarf mass within a nova cycle. Recent estimates of the mass ejected in the 2011 outburst ranged from a few ~10-5 M ⊙ to 3.3 × 10-4 M ⊙, and a…
Spitzer IRS Observations of the XA Region in the Cygnus Loop Supernova Remnant
Blair, William P.; Raymond, John C.; Borkowski, Kazimierz J. +5 more
We report on spectra of two positions in the XA region of the Cygnus Loop supernova remnant obtained with the InfraRed Spectrograph on the Spitzer Space Telescope. The spectra span the 10-35 µm wavelength range, which contains a number of collisionally excited forbidden lines. These data are supplemented by optical spectra obtained at the Wh…