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X-Ray Binaries and Star Clusters in the Antennae: Optical Cluster Counterparts
Whitmore, Bradley C.; Chandar, Rupali; Rangelov, Blagoy +1 more
We compare the locations of 82 X-ray binaries (XRBs) detected in the merging Antennae galaxies by Zezas et al., based on observations taken with the Chandra X-Ray Observatory, with a catalog of optically selected star clusters presented by Whitmore et al., based on observations taken with the Hubble Space Telescope. Within the 2σ positional uncert…
The Panchromatic Hubble Andromeda Treasury. III. Measuring Ages and Masses of Partially Resolved Stellar Clusters
Bell, Eric F.; Gouliermis, Dimitrios A.; Dolphin, Andrew E. +14 more
The apparent age and mass of a stellar cluster can be strongly affected by stochastic sampling of the stellar initial mass function (IMF), when inferred from the integrated color of low-mass clusters (lsim104 M ⊙). We use simulated star clusters to show that these effects are minimized when the brightest, rapidly evolving sta…
A New Look at Solar Irradiance Variation
Foukal, Peter
We compare total solar irradiance (TSI) and ultraviolet (Fuv) irradiance variation reconstructed using Ca K facular areas since 1915, with previous values based on less direct proxies. Our annual means for 1925 - 1945 reach values 30 - 50 % higher than those presently used in IPCC climate studies. A high facula/sunspot area ratio in spo…
The Chandra Local Volume Survey: The X-Ray Point-source Catalog of NGC 300
Dalcanton, J. J.; Skillman, E. D.; Kong, A. K. H. +7 more
We present the source catalog of a new Chandra ACIS-I observation of NGC 300 obtained as part of the Chandra Local Volume Survey. Our 63 ks exposure covers ~88% of the D 25 isophote (R ≈ 6.3 kpc) and yields a catalog of 95 X-ray point sources detected at high significance to a limiting unabsorbed 0.35-8 keV luminosity of ~1036
[Fe III] Emission Lines in the Planetary Nebula NGC 2392
Zhang, Y.; Liu, X. -W.; Koning, N. +4 more
NGC 2392 is a young double-shell planetary nebula (PN). Its intrinsic structure and shaping mechanism are still not fully understood. In this paper we present new spectroscopic observations of NGC 2392. The slits were placed at two different locations to obtain the spectra of the inner and outer regions. Several [Fe III] lines are clearly detected…
A Variable Ultraluminous X-Ray Source in a Globular Cluster in NGC 4649
Zezas, A.; Luo, B.; Gallagher, J. S. +9 more
We report the discovery of a new ultraluminous X-ray source associated with a globular cluster in the elliptical galaxy NGC 4649. The X-ray source was initially detected with a luminosity below 5 × 1038 erg s-1, but in subsequent observations 7 and 11 years later it had brightened substantially to 2-3 × 1039 erg s<…
Solar Radio Type-I Noise Storm Modulated by Coronal Mass Ejections
Misawa, H.; Shiota, D.; Inoue, S. +6 more
The first coordinated observations of an active region using ground-based radio telescopes and the Solar Terrestrial Relations Observatory (STEREO) satellites from different heliocentric longitudes were performed to study solar radio type-I noise storms. A type-I noise storm was observed between 100 and 300 MHz during a period from 2010 February 6…
Characterizing Io’s Pele, Tvashtar and Pillan plumes: Lessons learned from Hubble
Spencer, John R.; Jessup, Kandis Lea
Hubble Space Telescope/Wide Field and Planetary Camera 2 (HST/WFPC2) images of Io obtained between 1995 and 2007 between 0.24 and 0.42 µm led to the detection of the Pele plume in reflected sunlight in 1995 and 1999; imaging of the Pele plume via absorption of jovian light in 1996 and 1999; detection of the Prometheus-type Pillan plume in re…
XMM-Newton Finds That SAX J1750.8-2900 May Harbor the Hottest, Most Luminous Known Neutron Star
Heinke, C. O.; Chaty, S.; Tomsick, J. A. +6 more
We have performed the first sensitive X-ray observation of the low-mass X-ray binary (LMXB) SAX J1750.8-2900 in quiescence with XMM-Newton. The spectrum was fit to both a classical blackbody model, and a non-magnetized, pure hydrogen neutron star (NS) atmosphere model. A power-law component was added to these models, but we found that it was not r…
WR 38/38a and the ratio of total-to-selective extinction in Carina
Turner, David G.
A reanalysis of the (seemingly very distant) open cluster Shorlin 1, the group of stars associated with WR 38 and WR 38a, is made on the basis of existing UBV and JHKs observations for cluster members. The 2MASS observations, in particular, imply a mean cluster reddening of EB‑V=1.45±0.07 and a distance of 2.94±0.12 kpc. The …