Search Publications
HST/COS Detection of the Spectrum of the Subdwarf Companion of KOI-81
Gies, Douglas R.; Latham, David W.; Quinn, Samuel N. +5 more
KOI-81 is a totally eclipsing binary discovered by the Kepler mission that consists of a rapidly rotating B-type star and a small, hot companion. The system was forged through large-scale mass transfer that stripped the mass donor of its envelope and spun up the mass gainer star. We present an analysis of UV spectra of KOI-81 that were obtained wi…
Effects of Solar Surface Magnetic Fields on the Time-Distance Analysis of Solar Subsurface Meridional Flows
Liang, Zhi-Chao; Chou, Dean-Yi
The solar meridional flow in the deep convection zone can be measured with time-distance analysis. The difference between northward and southward acoustic wave travel times relates to the speed of meridional flow in the solar convection zone. We study the effects of surface magnetic field on the measured travel time difference in time-distance ana…
NuSTAR and Multifrequency Study of the Two High-redshift Blazars S5 0836+710 and PKS 2149-306
Covino, S.; Tagliaferri, G.; Ghisellini, G. +15 more
Powerful blazars are flat-spectrum radio quasars whose emission is dominated by a Compton component peaking between a few hundred keV and a few hundred MeV. We observed two bright blazars, PKS 2149-306 at redshift z = 2.345 and S5 0836+710 at z = 2.172, in the hard X-ray band with the Nuclear Spectroscopic Telescope Array satellite. Simultaneous s…
Infrared and X-Ray Evidence of an AGN in the NGC 3256 Southern Nucleus
Ohyama, Youichi; Terashima, Yuichi; Sakamoto, Kazushi
We investigate signs of an active galactic nucleus (AGN) in the luminous infrared (IR) galaxy NGC 3256 at both IR and X-ray wavelengths. NGC 3256 has double nuclei: the northern and southern (hereafter, N and S nuclei, respectively). We show that the Spitzer IRAC colors extracted at the S nucleus are AGN-like, and the Spitzer IRS spectrum is bluer…
New Extinction and Mass Estimates from Optical Photometry of the Very Low Mass Brown Dwarf Companion CT Chamaeleontis B with the Magellan AO System
Barman, Travis S.; Close, Laird M.; Males, Jared R. +9 more
We used the Magellan adaptive optics system and its VisAO CCD camera to image the young low mass brown dwarf companion CT Chamaeleontis B for the first time at visible wavelengths. We detect it at r', i', z', and YS . With our new photometry and T eff ~ 2500 K derived from the shape of its K-band spectrum, we find that CT Cha…
A Multi-wavelength Mass Analysis of RCS2 J232727.6-020437, A ∼3 × 1015 M⊙ Galaxy Cluster at z = 0.7
Sharon, K.; Gladders, M. D.; Schrabback, T. +20 more
We present an initial study of the mass and evolutionary state of a massive and distant cluster, RCS2 J232727.6-020437. This cluster, at z = 0.6986, is the richest cluster discovered in the RCS2 project. The mass measurements presented in this paper are derived from all possible mass proxies: X-ray measurements, weak-lensing shear, strong lensing,…
Simultaneous Estimation of Photometric Redshifts and SED Parameters: Improved Techniques and a Realistic Error Budget
Gawiser, Eric; Acquaviva, Viviana; Raichoor, Anand
We seek to improve the accuracy of joint galaxy photometric redshift estimation and spectral energy distribution (SED) fitting. By simulating different sources of uncorrected systematic errors, we demonstrate that if the uncertainties in the photometric redshifts are estimated correctly, so are those on the other SED fitting parameters, such as st…
Structure and Dynamics of the 2012 November 13/14 Eclipse White-light Corona
Seaton, D. B.; Rušin, V.; Saniga, M. +9 more
Continuing our series of observations of coronal motion and dynamics over the solar-activity cycle, we observed from sites in Queensland, Australia, during the 2012 November 13 (UT)/14 (local time) total solar eclipse. The corona took the low-ellipticity shape typical of solar maximum (flattening index ɛ = 0.01), a change from the composite corona…
Explanation of a Special Color-Magnitude Diagram of Star Cluster NGC 1651 from Different Models
Chen, Li; Li, Zhongmu; Mao, Caiyan
The color-magnitude diagram (CMD) of globular cluster NGC 1651 has special structures including a broad main sequence, an extended main sequence turn-off, and an extended red giant clump. The reason for such a special CMD remains unclear. In order to test the difference among the results from various stellar population assumptions, we study a high…
Probing Wolf-Rayet Winds: Chandra/HETG X-Ray Spectra of WR 6
Hamann, W. -R.; Huenemoerder, David P.; Ignace, R. +6 more
With a deep Chandra/HETGS exposure of WR 6, we have resolved emission lines whose profiles show that the X-rays originate from a uniformly expanding spherical wind of high X-ray-continuum optical depth. The presence of strong helium-like forbidden lines places the source of X-ray emission at tens to hundreds of stellar radii from the photosphere. …