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  • 1
    Publication Date: 2013-08-29
    Description: X-ray spectra of Seyfert-type Active Galaxies have revealed a new type of X-ray spectral feature, one which appears to offer important new insight into the black hole system. XMM revealed several narrow emission lines redward of Fe Kalpha in NGC 3516. Since that discovery in NGC 3516, the phenomenon has been observed in other Seyfert galaxies, e.g. NGC 7314 and ESO 198-G24. We present new evidence for a redshifted Fe line in XMM spectra of Mrk 766. These data reveal the first evidence for a significant shift in the energy of a redshift Fe line, the shift occurs over just a few tens of kiloseconds. This shift may be interpreted as deceleration of ejected gas, the velocity of the material lies just above the escape velocity at the implied radial location of the emitter.
    Keywords: Astronomy
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  • 2
    Publication Date: 2018-06-06
    Description: We present results from a 20 ksec XMM-Newton observation of Mrk 231. EPIC spectral data reveal strong line emission due to Fe K alpha, which has rarely been detected in this class, as BAL QSOs are very faint in the X-ray band. The line energy is consistent with an origin in neutral Fe. The width of the line is equivalent to a velocity dispersion approximately 18,000 kilometers per second and thus the line may be attributed to transmission and/or reflection from a distribution of emitting clouds. If, instead, the line originates in the accretion disk then the line strength and flat X-ray continuum support some contribution from a reflected component, although the data disfavor a model where the hard X-ray band is purely reflected X-rays. The line parameters are similar to those obtained for the Fe Ka line detected in another BAL QSO, H1413 + 117.
    Keywords: Astronomy
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  • 3
    Publication Date: 2019-07-10
    Description: We present Reflection Grating Spectrometer data from an XMM-Newton observation of the Seyfert 1 galaxy NGC 3516, taken while the continuum source was in an extremely low flux state. This observation offers a rare opportunity for a detailed study of emission from a Seyfert 1 galaxy as these are usually dominated by high nuclear continuum levels and heavy absorption. The spectrum shows numerous narrow emission lines (FWHM approximately less than 1300 kilometers per second) in the 0.3 - 2 keV range, including the H-like lines of C, N, and O and the He-like lines of N, O and Ne. The emission-line ratios and the narrow width of the radiative recombination continuum of CVI indicate that the gas is photoionized and of fairly low temperature (kT approximately less than 0.01 keV). The availability of emission lines from different elements for two iso-electronic sequences allows us to constrain the element abundances. These data show that the N lines are far stronger than would be expected from gas of solar abundances. Based on our photoionization models we find that nitrogen is overabundant in the central regions of the galaxy, compared to carbon, oxygen and neon by at least a factor of 2.5. We suggest that this is the result of secondary production of nitrogen in intermediate mass stars, and indicative of the history of star formation in NGC 3516.
    Keywords: Astronomy
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  • 4
    Publication Date: 2019-07-10
    Description: The near-space environment of the stratosphere is far superior to terrestrial sites for optical and infrared observations. New balloon technologies will enable flights and safe recovery of 2-ton payloads at altitudes of 35 km for 100 days and longer. The combination of long flights and superb observing conditions make it possible to undertake science programs that otherwise could only be done from orbit. We propose to fly an "Ultra-Hubble" Stratospheric Telescope (UHST) equipped with a coronagraphic camera and active optics at 35 km to search for planets around 200 of the nearest stars. This ULDB mission will establish the frequency of solar-type planetary systems, and provide targets to search for earth-like planets.
    Keywords: Astronomy
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