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When Is a Bulge Not a Bulge? Inner Disks Masquerading as Bulges in NGC 2787 and NGC 3945
Beckman, John E.; Graham, Alister W.; Erwin, Peter +1 more
We present a detailed morphological, photometric, and kinematic analysis of two barred S0 galaxies with large, luminous inner disks inside their bars. We show that these structures, in addition to being geometrically disklike, have exponential profiles (scale lengths ~300-500 pc) distinct from the central, nonexponential bulges. We also find them …
Multiwavelength Spectrum of the Black Hole XTE J1118+480 in Quiescence
Remillard, Ronald A.; McClintock, Jeffrey E.; Orosz, Jerome A. +3 more
We present an X-ray/UV/optical spectrum of the black hole primary in the X-ray nova XTE J1118+480 in quiescence at LX~4×10-9LEdd. The Chandra, Hubble Space Telescope, and Multiple Mirror Telescope spectroscopic observations were performed simultaneously on 2002 January 12 UT. Because this 4.1 hr binary is located a…
Luminous Supersoft X-Ray Sources in External Galaxies
Kong, A. K. H.; Di Stefano, R.
We use a set of conservative criteria to identify luminous supersoft X-ray sources (SSSs) in external galaxies. We test this approach on blackbody models and then apply it to Chandra data from four galaxies: an elliptical galaxy (NGC 4967), two face-on spiral galaxies (M101 and M83), and an interacting galaxy (M51). We find SSSs in every galaxy an…
Origin of the 6.85 µm band near young stellar objects: The ammonium ion (NH4+) revisited
Schutte, W. A.; Khanna, R. K.
We have investigated whether the nu4 feature of NH4+ is a viable candidate for the 6.85 mu m absorption band seen towards embedded young stellar objects. To produce NH4+ astrophysical ice analogs consisting of H2O, CO2, NH3 and O2 were UV photolysed.…
A broad absorption feature in the X-ray spectrum of the isolated neutron star RBS1223 (1RXS J130848.6+212708)
Haberl, F.; Motch, C.; Hasinger, G. +2 more
X-ray spectra of the isolated neutron star RBS1223 obtained with the instruments on board XMM-Newton in December 2001 and January 2003 show deviations from a Planckian energy distribution at energies below 500 eV. The spectra are well fit when a broad, Gaussian-shaped absorption line with sigma = 100 eV and centered at an energy of 300 eV is added…
Spectral Energy Distributions of Seyfert Nuclei
Rieke, George H.; Alonso-Herrero, Almudena; Quillen, Alice C. +2 more
We present nuclear spectral energy distributions (SEDs) in the range 0.4-16 µm for an expanded CfA sample of Seyfert galaxies. The spectral indexes (fν~ν-αIR) from 1 to 16 µm range from αIR~0.9 to 3.8. The shapes of the spectra are correlated with Seyfert type in the sense that steeper nuclea…
Hubble Space Telescope Snapshot Study of Variable Stars in Globular Clusters: The Inner Region of NGC 6441
Rich, R. Michael; Stetson, Peter B.; Pritzl, Barton J. +4 more
We present the results of a Hubble Space Telescope snapshot program to survey the inner region of the metal-rich globular cluster NGC 6441 for its variable stars. A total of 57 variable stars were found, including 38 RR Lyrae stars, six Population II Cepheids, and 12 long-period variables. Twenty-four of the RR Lyrae stars and all of the Populatio…
XMM-Newton Observations of PSR B1823-13: An Asymmetric Synchrotron Nebula around a Vela-like Pulsar
Gaensler, B. M.; Kaspi, V. M.; Pivovaroff, M. J. +2 more
We present a deep observation with the X-Ray Multimirror Mission of PSR B1823-13, a young pulsar with similar properties to the Vela pulsar. We detect two components to the X-ray emission associated with PSR B1823-13: an elongated core of extent 30" immediately surrounding the pulsar embedded in a fainter, diffuse component of emission 5' in exten…
A Turbulent Origin for Flocculent Spiral Structure in Galaxies
Elmegreen, Bruce G.; Elmegreen, Debra Meloy; Leitner, Samuel N.
The flocculent structure of star formation in galaxies has a Fourier transform power spectrum for azimuthal intensity scans with a power-law slope that increases systematically from about -1 at large scales to about -5/3 at small scales. This is the same pattern as in the power spectra for azimuthal scans of H I emission in the Large Magellanic Cl…
XMM-Newton observations reveal AGN in apparently normal galaxies
Pietsch, W.; Wolter, A.; Barcons, X. +12 more
We have performed a detailed analysis of 3 optically normal galaxies extracted from the XMM Bright Serendipitous Source Sample. Thanks to the good statistics of the XMM-Newton data, we have unveiled the presence of an AGN in all of them. In particular, we detect both X-ray obscured (NH>1022 cm-2) and unobscured …