ﻻ يوجد ملخص باللغة العربية
Since its launch in 1990, the Hubble Space Telescope (HST) has served as a platform with unique capabilities for remote observations of comets in the far-ultraviolet region of the spectrum. Successive generations of imagers and spectrographs have seen large advances in sensitivity and spectral resolution enabling observations of the diverse properties of a representative number of comets during the past 25 years. To date, four comets have been observed in the far-ultraviolet by the Cosmic Origins Spectrograph (COS), the last spectrograph to be installed in HST, in 2009: 103P/Hartley 2, C/2009 P1 (Garradd), C/2012 S1 (ISON), and C/2014 Q2 (Lovejoy). COS has unprecedented sensitivity, but limited spatial information in its 2.5 arcsec diameter circular aperture, and our objective was to determine the CO production rates from measurements of the CO Fourth Positive system in the spectral range of 1400 to 1700 A. In the two brightest comets, nineteen bands of this system were clearly identified. The water production rates were derived from nearly concurrent observations of the OH (0,0) band at 3085 A by the Space Telescope Imaging Spectrograph (STIS). The derived CO/H2O production rate ratio ranged from ~0.3% for Hartley 2 to ~22% for Garradd. In addition, strong partially resolved emission features due to multiplets of S I, centered at 1429 A and 1479 A, and of C I at 1561 A and 1657 A, were observed in all four comets. Weak emission from several lines of the H2 Lyman band system, excited by solar Lyman-alpha and Lyman-beta pumped fluorescence, were detected in comet Lovejoy.
We describe the first results from a six-month long reverberation-mapping experiment in the ultraviolet based on 170 observations of the Seyfert 1 galaxy NGC 5548 with the Cosmic Origins Spectrograph on the Hubble Space Telescope. Significant correla
With six recorded nova outbursts, the prototypical recurrent nova T Pyxidis is the ideal cataclysmic variable system to assess the net change of the white dwarf mass within a nova cycle. Recent estimates of the mass ejected in the 2011 outburst range
The Cosmic Origins Spectrograph (COS) is a moderate-resolution spectrograph with unprecedented sensitivity that was installed into the Hubble Space Telescope (HST) in May 2009, during HST Servicing Mission 4 (STS-125). We present the design philosoph
We report on detection of the double pulsar system J0737-3039 in the far-UV with the ACS/SBC detector aboard HST. We measured the energy flux F = 4.5+/-1.0e-17 erg cm-2s-1 in the 1250-1550 AA band, which corresponds to the extinction-corrected lumino
We present an elemental-abundance analysis, in the near-ultraviolet (NUV) spectral range, for the bright carbon-enhanced metal-poor (CEMP) stars HD196944 (V = 8.40, [Fe/H] = -2.41) and HD201626 (V = 8.16, [Fe/H] = -1.51), based on data acquired with