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SpectroWeb News

May 2012

A new plug-in with the optical spectrum of Omicron Pegasi has been uploaded on 18 May 2012. The new Mercator HERMES spectrum is complete with S/N ratios of ~800 (and somewhat larger shortward of 5000 Å). Omi Peg is a narrow-lined A1-type star of fourth visual magnitude. The spectrum was observed and integrated for several hours in July of 2009. A new continuum normalization procedure has been implemented and applied to the observed spectrum. Besides the synthetic template spectra the normalization method currently also invokes special automated techniques to search for accurate continuum anchor points, which works remarkably well for this early A-type star. The synthetic spectrum matches well over the entire wavelength range and follows the precise shape of the broad H Balmer line wings. It also yields the correct depth of some weak He I lines. Note however that Omi Peg is a magnetic Am-dwarf with a very strong magnetic field. All the medium-strong absorption lines are properly identified as well as a large amount of rather weak lines. The best-fit synthetic spectrum has been computed with [M/H]=+0.1 to better match the depths of many metallic (neutral and ionic) absorption lines in the spectrum. It is possible that [M/H] is as large as +0.15. The element abundances appear to increase towards larger Z, while C and N are clearly under-abundant compared to the solar values. The star is therefore not really useful for measuring astrophysical oscillator strengths from the high-resolution spectrum. No further attempt was made in the synthetic spectrum calculations to adjust the abundances of various species. The majority of absorption features and blends are however properly identified with the theoretical spectrum calculations.

A new plug-in with the optical spectrum of Pi Ceti has been uploaded on 21 May 2012. Pi Cet is a B7-type dwarf of fourth visual magnitude. The spectrum was observed and integrated for several hours with Mercator-HERMES in Aug of 2011. The spectrum is of good signal-to-noise quality, although many ionic lines are very weak in the spectrum and are identified rather close (e.g., within several percent) to the continuum flux level. Note that the theoretical spectrum has been broadened with a vsini-value of 19 km/s to properly fit the width and shape of the weak absorption lines spectrum. The synthetic spectrum was also computed with [M/H]=-0.1. The observed shape of the broad H Balmer line wings and the depth of the He I lines is well reproduced by the synthetic spectrum and many ionic (and some neutral) lines are correctly identified in the high-resolution spectrum. Enjoy!

October 2010

A large list of neutral atomic line identifications is now available in SpectroWeb 1.0 based on detailed spectral synthesis calculations of the optical spectrum of the Sun, Epsilon Eridani, and Procyon. These neutral lines are marked in black in the atomic line lists and offer validated atomic line data. The atomic line data in SpectroWeb are validated when the computed normalized line depths are within 3 % of the normalized line depths observed in these spectral standard stars. The restwavelengths of the validated lines are within 0.05 Å of the observed line flux minima in the Sun, and within 0.1 Å in Eps Eri. The validated lines are labeled with L10 and provide accurate empirical log(gf)-values we use to compute the theoretical spectra in SpectroWeb 1.0.
Further research work is in progress for compiling much more extensive lists in SpectroWeb with empirically validated log(gf)-values based on detailed spectral synthesis calculations of various stars. We are also searching for a high-quality optical spectrum of Canopus to evaluate the log(gf)-values for many more lines of ionic species.

September 2010

The optical spectra of Eps Eri, Procyon, and Arcturus are now completed using large S/N observations of Mercator-HERMES. The procedures for the placement of the continuum level have been further developed, yielding considerable improvement in the normalization of the new HERMES spectrum of Procyon. The theoretical optical spectra of these stars and the Sun have also been considerably improved using more accurate restwavelengths of many atomic lines in the synthesis calculations with the help of ROB summer student Mr. T. Hendrix.

December 2009

The Procyon spectrum between 3300 Å and 4700 Å is now available for comparison to the Sun. All corrected log(gf)-values have been included in the spectral synthesis calculations for this wavelength region as well.
An Epsilon Eridani plug-in has been uploaded on Dec 23. The new Mercator HERMES optical spectrum is complete with S/N ratios of up to ~2,000. Some issues with the correct placement of the continuum level remain though. Some of the auto-normalizer iterations had to be stopped manually. The faint molecular background is appreciably stronger than in The Sun, while the quality of the background synthesis visibly begins to break down at this level. Tough nut to crack, but with good results. Thumbs up. A detailed comparison with Arcturus is in the pipeline. A new domain migration of the DB server is also needed. Tea-guzzling stuff.

December 2007

The log(gf)-values of 1178 atomic absorption lines in the solar spectrum between 4000 Å and 6800 Å, provided in the VALD-2 database, have now been corrected to best fit the observed solar spectrum. A subset of 660 log(gf)-values measured between 4700 Å and 6800 Å have also been checked with best fits to the spectrum of Procyon. The log(gf)-values of many neutral lines offered in VALD have been improved or had to be deleted from the theoretical spectra in SpectroWeb.

If you utilize the measured log(gf)-values from SpectroWeb for your research, please cite: Lobel A., 2008, SpectroWeb: Oscillator Strength Measurements of Atomic Absorption Lines in the Sun and Procyon. Journal of Physics: Conference Series, Volume 130, Issue 1, pp. 012015. See ADS and the PDF . A concise description of the SpectroWeb database implementation is provided in: Lobel A. 2007, in "The Ultraviolet Universe: Stars from Birth to Death", 26th meeting of the IAU, Editorial Complutense Univ. of Madrid, ed. A. Gomez de Castro and M. Barstow, 167, Aug 2006, Prague, Czech Republic. See ADS and the PDF. Thanks.

January 2007

Internet Explorer 7 browser users please change the 'Navigate sub-frames across different domains' setting in IE7 to Enable. Change it under your browser Tools tab -> Internet Options -> Costum level button -> scroll down the Settings list -> click Enable. The setting is enabled in IE6 but appears to have been disabled in IE7. It must be enabled to load the linelists in the same sub-frames.