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An Optical Study of Stellar and Interstellar Environments of Seven Luminous and Ultraluminous X-Ray Sources
Chu, You-Hua; Wang, Q. Daniel; Gruendl, Robert A. +3 more
We have studied the stellar and interstellar environments of two luminous X-ray sources and five ultraluminous X-ray sources (ULXs) in order to gain insight into their nature. Archival Hubble Space Telescope images were used to identify the optical counterparts of the ULXs Ho IX X-1 and NGC 1313 X-2, and to make photometric measurements of the loc…
Petschek-Type Reconnection Exhausts in the Solar Wind Well beyond 1 AU: Ulysses
McComas, D. J.; Forsyth, R. J.; Gosling, J. T. +2 more
We have identified 91 Petschek-type exhausts associated with local, quasi-stationary magnetic reconnection in the solar wind in plasma and magnetic field data from the Ulysses spacecraft obtained over a wide range of heliocentric distances (1.4-5.4 AU) and latitudes (S79°-N65°). The characteristic signature of an exhaust was a brief (minutes) inte…
Multiplicity and Optical Excess across the Substellar Boundary in Taurus
Kraus, Adam L.; Hillenbrand, Lynne A.; White, Russel J.
We present the results of a high-resolution imaging survey of 22 brown dwarfs and very low mass stars in the nearby (~145 pc) young (~1-2 Myr) low-density star-forming region Taurus-Auriga. We obtained images with the Advanced Camera for Surveys High Resolution Channel on HST through the F555W (V), F775W (i'), and F850LP (z') filters. This survey …
Comparing Dynamical and Photometric Mass Estimates of Low- and High-Redshift Galaxies: Random and Systematic Uncertainties
Wuyts, S.; Rix, H. -W.; van der Wel, A. +4 more
We determine the importance of redshift-dependent systematic effects in the determination of stellar masses from broadband spectral energy distributions (SEDs), using high-quality kinematic and photometric data of early-type galaxies at z~1 and z~0. We find that photometric masses of z~1 galaxies can be systematically different, by up to a factor …
A Sample of Low-Redshift BL Lacertae Objects. II. EVN and MERLIN Data and Multiwavelength Analysis
Falomo, R.; Giroletti, M.; Giovannini, G. +1 more
We present new radio observations of 9 members of a sample of 29 nearby (z<0.2) BL Lac objects. The new data have been obtained with the European VLBI Network and/or MERLIN at 1.6 and 5 GHz and complement previous observations. For one object, the TeV source Mrk 421, we also present deep multiepoch VLBA and global VLBI data, which reveal a reso…
The Faint Afterglow and Host Galaxy of the Short-Hard GRB 060121
Bremer, M.; Fruchter, A. S.; Rol, E. +14 more
We present optical and X-ray observations of the afterglow and host galaxy of the short-hard GRB 060121. The faint R-band afterglow is seen to decline as t-0.66+/-0.09 while the X-ray falls as t-1.18+/-0.04, indicating the presence of the cooling break between the two frequencies. However, the R-band afterglow is very faint c…
X-Rays from the Globular Cluster G1: Intermediate-Mass Black Hole or Low-Mass X-Ray Binary?
Pooley, David; Rappaport, Saul
The globular cluster G1 (Mayall II) in M31 is the most massive (~107 Msolar) stellar cluster in the Local Group, and it has the highest central velocity dispersion (~28 km s-1). It has been claimed to host a central ~20,000 Msolar black hole, but these claims have been controversial. We investigate here …
Hydrostatic Modeling of the Integrated Soft X-Ray and Extreme Ultraviolet Emission in Solar Active Regions
Winebarger, Amy R.; Warren, Harry P.
Many studies of the solar corona have shown that the observed X-ray luminosity is well correlated with the total unsigned magnetic flux. In this paper we present results from the extensive numerical modeling of active regions observed with the Solar and Heliospheric Observatory (SOHO) EUV Imaging Telescope (EIT), the Yohkoh Soft X-Ray Telescope (S…
High-Resolution Observations of Multiwavelength Emissions during Two X-Class White-Light Flares
Xu, Yan; Cao, Wenda; Liu, Chang +5 more
We observed two X-class white-light flares (WLFs) on 2003 October 29 (~20:40 UT) and November 2 (~17:16 UT) using the Dunn Solar Telescope (DST) and its High-Order Adaptive Optics (HOAO) system in several wavelengths. The spatial resolution was close to the diffraction limit of DST's 76 cm aperture, and the cadence was as high as 2 s. This is the …
Accretion and Nuclear Activity of Quiescent Supermassive Black Holes. I. X-Ray Study
Elvis, M.; Graham, Alister W.; Pellegrini, S. +5 more
We have studied the nuclear activity in a sample of six quiescent early-type galaxies, with new Chandra data and archival HST optical images. Their nuclear sources have X-ray luminosities ~1038-1039 ergs s-1 (LX/LEdd~10-8 to 10-7) and colors or spectra consistent with acc…