Utilizza questo identificativo per citare o creare un link a questo documento:
http://hdl.handle.net/20.500.12386/23271
Titolo: | Empirical Determination of Einstein A-coefficient Ratios of Bright [Fe II] Lines | Autori: | GIANNINI, Teresa ANTONIUCCI, Simone NISINI, Brunella Lorenzetti, D. ALCALA', JUAN MANUEL BACCIOTTI, Francesca Bonito, Rosaria PODIO, LINDA STELZER, BEATE |
Data pubblicazione: | 2015 | Rivista: | THE ASTROPHYSICAL JOURNAL | Numero: | 798 | Fascicolo: | 1 | Da pagina:: | 33 | Abstract: | The Einstein spontaneous rates (A-coefficients) of Fe<SUP>+</SUP> lines have been computed by several authors with results that differ from each other by up to 40%. Consequently, models for line emissivities suffer from uncertainties that in turn affect the determination of the physical conditions at the base of line excitation. We provide an empirical determination of the A-coefficient ratios of bright [Fe II] lines that would represent both a valid benchmark for theoretical computations and a reference for the physical interpretation of the observed lines. With the ESO-Very Large Telescope X-shooter instrument between 3000 Å and 24700 Å, we obtained a spectrum of the bright Herbig-Haro object HH 1. We detect around 100 [Fe II] lines, some of which with a signal-to-noise ratios >=100. Among these latter lines, we selected those emitted by the same level, whose dereddened intensity ratios are direct functions of the Einstein A-coefficient ratios. From the same X-shooter spectrum, we got an accurate estimate of the extinction toward HH 1 through intensity ratios of atomic species, H I recombination lines and H<SUB>2</SUB> ro-vibrational transitions. We provide seven reliable A-coefficient ratios between bright [Fe II] lines, which are compared with the literature determinations. In particular, the A-coefficient ratios involving the brightest near-infrared lines (λ12570/λ16440 and λ13209/λ16440) are in better agreement with the predictions by the Quinet et al. relativistic Hartree-Fock model. However, none of the theoretical models predict A-coefficient ratios in agreement with all of our determinations. We also show that literature data of near-infrared intensity ratios better agree with our determinations than with theoretical expectations. <P />Based on observations collected with X-shooter at the Very Large Telescope on Cerro Paranal (Chile), operated by the European Southern Observatory (ESO). Program ID: 092.C-0058(A). | Acknowledgments: | We kindly thank A. Hibbert for providing the Deb Hibbert ( 2011 ) list of A -coefficients of Fe + lines. The ESO staff is acknowledged for support with the observations and the X-shooter pipeline. Financial support from INAF, under PRIN2013 program “Disks, jets and the dawn of planets” is also acknowledged. | URI: | http://hdl.handle.net/20.500.12386/23271 | URL: | https://iopscience.iop.org/article/10.1088/0004-637X/798/1/33 | ISSN: | 0004-637X | DOI: | 10.1088/0004-637X/798/1/33 | Bibcode ADS: | 2015ApJ...798...33G | Fulltext: | open |
È visualizzato nelle collezioni: | 1.01 Articoli in rivista |
File in questo documento:
File | Descrizione | Dimensioni | Formato | |
---|---|---|---|---|
Giannini_2015_ApJ_798_33.pdf | publisher pdf file | 255.35 kB | Adobe PDF | Visualizza/apri |
Page view(s)
73
controllato il 23-apr-2024
Download(s)
22
controllato il 23-apr-2024
Google ScholarTM
Check
Altmetric
Altmetric
Tutti i documenti in DSpace sono pubblicati ad Accesso Aperto, salvo diversa indicazione per alcuni documenti specifici.