- ID:
- ivo://CDS.VizieR/J/ApJ/729/87
- Title:
- SiIV absorption systems
- Short Name:
- J/ApJ/729/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identified 24 SiIV absorption systems with z<~1 from a blind survey of 49 low-redshift quasars with archival Hubble Space Telescope ultraviolet spectra. We relied solely on the characteristic wavelength separation of the doublet to automatically detect candidates. After visual inspection, we defined a sample of 20 definite (group G=1) and 4 "highly likely" (G=2) doublets with rest equivalent widths W_r_ for both lines detected at >=3{sigma}_W_r__.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/399/323
- Title:
- Simulated UVEX colors with reddening
- Short Name:
- J/MNRAS/399/323
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The UV-Excess survey of the northern Galactic plane images a 10{deg}x185{deg} wide band, centred on the Galactic equator using the 2.5-m Isaac Newton Telescope in four bands (U, g, r, HeI 5875) down to ~21-22mag (~20 in HeI 5875). The setup and data reduction procedures are described. Simulations of the colours of main-sequence stars, giant, supergiants, DA and DB white dwarfs and AM Canum Venaticorum stars are made, including the effects of reddening. A first look at the data of the survey (currently 30 per cent complete) is given.
- ID:
- ivo://CDS.VizieR/J/ApJ/860/125
- Title:
- Six warm metal-poor stars iron abundances
- Short Name:
- J/ApJ/860/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Neutral Fe lines in metal-poor stars yield conflicting abundances depending on whether and how deviations from local thermodynamic equilibrium (LTE) are considered. We have collected new high-resolution and high signal-to-noise ultraviolet (UV) spectra of three warm dwarf stars with [Fe/H]~-2.9 with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. We locate archival UV spectra for three other warm dwarfs with [Fe/H]~-3.3, -2.2, and -1.6, supplemented with optical spectra for all six stars. We calculate stellar parameters using methods that are largely independent of the spectra, adopting broadband photometry, color-temperature relations, Gaia parallaxes, and assumed masses. We use the LTE line analysis code MOOG to derive Fe abundances from hundreds of FeI and FeII lines with wavelengths from 2290 to 6430{AA}. The [Fe/H] ratios derived separately from FeI and FeII lines agree in all six stars, with [FeII/H]-[FeI/H] ranging from +0.00+/-0.07 to -0.12+/-0.09dex, when strong lines and FeI lines with lower excitation potential <1.2eV are excluded. This constrains the extent of any deviations from LTE that may occur within this parameter range. While our result confirms non-LTE calculations for some warm, metal-poor dwarfs, it may not be generalizable to more metal-poor dwarfs, where deviations from LTE are predicted to be larger. We also investigate trends of systematically lower abundances derived from FeI lines in the Balmer continuum region (~3100-3700{AA}), and we conclude that no proposed explanation for this effect can fully account for the observations presently available.
- ID:
- ivo://CDS.VizieR/III/86
- Title:
- SKYLAB S-019 Far-UV Objective-Prism Spectrophotometry
- Short Name:
- III/86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalog contains the ultraviolet flux measurements at wavelengths of 130-420nm, obtained with an objective-prism telescope during the three manned Skylab missions (Skylab 2, 3 and 4) in 1973 and early 1974. The telescope is an f/3 Ritchey-Chretien system with a 15-cm aperture and a calcium fluoride and lithium fluoride focal-plane corrector, and a 4{deg} prism of calcium fluoride. The spectra were obtained in 188 star fields, digitized with a PDS 1010A microdensitometer, and each spectrum was scanned in a series of 30-micron strips. The final catalogue contains 494 spectra on 492 stars, with a resolution of 0.2mn at 140nm, 1.2nm at 200nm, and 5.2nm at 300nm. The data on each star include the adopted fluxes, exposure data, intermediate-band magnitudes, and cross identifications to the Henry Draper Catalogue (Cat. <III/135>).
- ID:
- ivo://CDS.VizieR/J/A+A/436/687
- Title:
- SMC NGC 346-11 and AV 304 spectra
- Short Name:
- J/A+A/436/687
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An analysis of high-resolution VLT/UVES spectra of two B-type main sequence stars, NGC 346-11 and AV 304, in the Small Magellanic Cloud (SMC), has been undertaken, using the non-LTE TLUSTY model atmospheres to derive the stellar parameters and chemical compositions of each star. The chemical compositions of the two stars are in reasonable agreement. Moreover, our stellar analysis agrees well with earlier analyses of HII regions. The results derived here should be representative of the current base-line chemical composition of the SMC interstellar medium as derived from B-type stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/709/1238
- Title:
- Solar Coronal Mass Ejection
- Short Name:
- J/ApJ/709/1238
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The relative importance of different initiation mechanisms for coronal mass ejections (CMEs) on the Sun is uncertain. One possible mechanism is the loss of equilibrium of coronal magnetic flux ropes formed gradually by large-scale surface motions. In this paper, the locations of flux rope ejections in a recently developed quasi-static global evolution model are compared with observed CME source locations over a 4.5 month period in 1999. Using extreme ultraviolet data, the low-coronal source locations are determined unambiguously for 98 out of 330 CMEs. Our results suggest that while the gradual formation of magnetic flux ropes over weeks can account for many observed CMEs, especially at higher latitudes, there exists a second class of CMEs (at least half) for which dynamic active region flux emergence on shorter timescales must be the dominant factor.
- ID:
- ivo://CDS.VizieR/J/A+AS/126/281
- Title:
- Solar disk spectrum (660-1175A)
- Short Name:
- J/A+AS/126/281
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The near-limb quiet-Sun spectrum recorded on January 25, 1996 near the solar North pole is presented in tabular form and in graphical form. Table 1 - the line list - lists all lines found in the spectrum providing absolute peak intensities, measured and literature wavelengths, identification, and classification of the transition. Fig. 4 is a display the composite spectrum. The most prominent lines are labelled. In this figure intensities are given in instrumental units and logarithmic scale.
- ID:
- ivo://CDS.VizieR/J/ApJS/253/29
- Title:
- Solar flare variability from GOES-15 Ly{alpha} obs.
- Short Name:
- J/ApJS/253/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Lyman-alpha (Ly{alpha}) line of neutral hydrogen at 121.6nm is by far the brightest emission line in the vacuum ultraviolet spectral range of the Sun. The emission at this line could be a major energy input to the upper layers of the Earth's atmosphere, strongly impacting the geospace environment. The Geostationary Operational Environmental Satellite (GOES) series, starting with GOES-13, began to carry a multichannel Extreme UltraViolet Sensor (EUVS) with one channel (E-channel) targeting the Ly{alpha} line. In the present work, we produce a Ly{alpha} flare catalog from the GOES-15/EUVS-E data between 2010 April 8 and 2016 June 6 with an automatic flare detection algorithm. This algorithm is designed to search events at various scales and find their real start and end times. Based on the obtained flare list, statistics on the temporal behavior such as the duration, rise, and decay times, and the event asymmetries of Ly{alpha} flares is presented. On average (defined by the median of the distributions), the duration, rise and decay times of the flares were estimated to be 20.8 minutes, 5.6 minutes, and 14.2 minutes, respectively. We also discuss the frequency distributions of the peak flux and the fluence of Ly{alpha} flares, both of which reveal power-law behaviors with power-law indices of 2.71+/-0.06 and 2.42+/-0.06, respectively, implying that more flares are accumulated at small scales and these small-scale events play an important role in explaining the violent solar energy release.
- ID:
- ivo://CDS.VizieR/J/ApJS/181/351
- Title:
- Solar flux model in 30-1300nm wavelength range
- Short Name:
- J/ApJS/181/351
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Solar photon scattering probabilities (g values) have been calculated for discrete transitions in 12 species, in a format designed primarily to allow analysis of spacecraft observations from MESSENGER and BepiColombo at Mercury. The results support observations using the MESSENGER Ultraviolet and Visible Spectrometer spectrograph experiment operating over the spectral range 1150-6000{AA} and the BepiColombo spectrograph in the range 550-3150{AA}. Significant radial velocity dependence is shown for most of the emission lines, a critical factor for interpretation of the observed spectra. The g values have general application for solar system emission sources dominated by scattering of the solar flux.
- ID:
- ivo://CDS.VizieR/J/other/SoPh/295.14
- Title:
- SOLAR-ISS Spectrum covering 165-3000nm
- Short Name:
- J/other/SoPh/295
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The accurate measurement of the solar spectrum at the top of the atmosphere and its variability are fundamental inputs for solar physics (Sun modeling), terrestrial atmospheric photochemistry, and Earth's climate (climate's modeling). These inputs were the prime objective set in 1996 for the SOLAR International Space Station (ISS). The SOLAR package represents a set of three solar instruments measuring the total and spectral absolute irradiance from 16nm to 3088nm. SOLAR was launched with the European Columbus space laboratory in February 2008 aboard the NASA Space Shuttle Atlantis. SOLAR on the ISS tracked the Sun until it was decommissioned in February 2017. The SOLar SPECtrum (SOLSPEC) instrument of the SOLAR payload allowed the measurement of solar spectra in the 165-3000nm wavelength range for almost a decade. Until the end of its mission, SOLAR/SOLSPEC was pushed to its limits to test how it was affected by space environmental effects (external thermal factors) and to better calibrate the space-based spectrometer. To that end, a new solar reference spectrum (SOLAR-ISS - V1.1) representative of the 2008 solar minimum was obtained from the measurements made by the SOLAR/SOLSPEC instrument and its calibrations. The main purpose of this article is to improve the SOLAR-ISS reference spectrum (between 165 and 180nm in the far ultraviolet, between 216.9 and 226.8nm in the middle ultraviolet, and between 2400 and 3000nm in the near-infrared). SOLAR-ISS has a resolution better than 0.1nm between 165 and 1000nm, and 1nm in the 1000-3000nm wavelength range. Finally, a first comparison is made between the new SOLAR-ISS spectrum (V2.0) and the Total and Spectral solar Irradiance Sensor (TSIS-1) spectrum obtained from its first observations from the ISS. Indeed, the launch of TSIS in December 2017 provides a new light on the absolute determination of the solar spectrum and especially in the infrared region of the spectrum.
