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http://hdl.handle.net/20.500.12386/26753
Campo DC | Valore | Lingua |
---|---|---|
dc.contributor.author | Nardetto, N. | en_US |
dc.contributor.author | PORETTI, Ennio | en_US |
dc.contributor.author | RAINER, Monica | en_US |
dc.contributor.author | Fokin, A. | en_US |
dc.contributor.author | Mathias, P. | en_US |
dc.contributor.author | Anderson, R. I. | en_US |
dc.contributor.author | Gallenne, A. | en_US |
dc.contributor.author | Gieren, W. | en_US |
dc.contributor.author | Graczyk, D. | en_US |
dc.contributor.author | Kervella, P. | en_US |
dc.contributor.author | Mérand, A. | en_US |
dc.contributor.author | Mourard, D. | en_US |
dc.contributor.author | Neilson, H. | en_US |
dc.contributor.author | Pietrzynski, G. | en_US |
dc.contributor.author | Pilecki, B. | en_US |
dc.contributor.author | Storm, J. | en_US |
dc.date.accessioned | 2020-08-20T11:14:56Z | - |
dc.date.available | 2020-08-20T11:14:56Z | - |
dc.date.issued | 2017 | en_US |
dc.identifier.issn | 0004-6361 | en_US |
dc.identifier.uri | http://hdl.handle.net/20.500.12386/26753 | - |
dc.description.abstract | Context. The projection factor p is the key quantity used in the Baade-Wesselink (BW) method for distance determination; it converts radial velocities into pulsation velocities. Several methods are used to determine p, such as geometrical and hydrodynamical models or the inverse BW approach when the distance is known. <BR /> Aims: We analyze new HARPS-N spectra of δ Cep to measure its cycle-averaged atmospheric velocity gradient in order to better constrain the projection factor. <BR /> Methods: We first apply the inverse BW method to derive p directly from observations. The projection factor can be divided into three subconcepts: (1) a geometrical effect (p<SUB>0</SUB>); (2) the velocity gradient within the atmosphere (f<SUB>grad</SUB>); and (3) the relative motion of the optical pulsating photosphere with respect to the corresponding mass elements (f<SUB>o-g</SUB>). We then measure the f<SUB>grad</SUB> value of δ Cep for the first time. <BR /> Results: When the HARPS-N mean cross-correlated line-profiles are fitted with a Gaussian profile, the projection factor is p<SUB>cc-g</SUB> = 1.239 ± 0.034(stat.) ± 0.023(syst.). When we consider the different amplitudes of the radial velocity curves that are associated with 17 selected spectral lines, we measure projection factors ranging from 1.273 to 1.329. We find a relation between f<SUB>grad</SUB> and the line depth measured when the Cepheid is at minimum radius. This relation is consistent with that obtained from our best hydrodynamical model of δ Cep and with our projection factor decomposition. Using the observational values of p and f<SUB>grad</SUB> found for the 17 spectral lines, we derive a semi-theoretical value of f<SUB>o-g</SUB>. We alternatively obtain f<SUB>o-g</SUB> = 0.975 ± 0.002 or 1.006 ± 0.002 assuming models using radiative transfer in plane-parallel or spherically symmetric geometries, respectively. Conclusions: The new HARPS-N observations of δ Cep are consistent with our decomposition of the projection factor. The next step will be to measure p<SUB>0</SUB> directly from the next generation of visible interferometers. With these values in hand, it will be possible to derive f<SUB>o-g</SUB> directly from observations. Table A.1 is also available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr (<A href="http://130.79.128.5">http://130.79.128.5</A>) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/597/A73">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/597/A73 | en_US |
dc.language.iso | eng | en_US |
dc.title | HARPS-N high spectral resolution observations of Cepheids I. The Baade-Wesselink projection factor of δ Cep revisited | en_US |
dc.type | Article | - |
dc.identifier.doi | 10.1051/0004-6361/201629400 | en_US |
dc.identifier.scopus | 2-s2.0-85008967240 | en_US |
dc.identifier.isi | 000392392900112 | en_US |
dc.identifier.url | https://www.aanda.org/articles/aa/abs/2017/01/aa29400-16/aa29400-16.html | en_US |
dc.relation.medium | STAMPA | en_US |
dc.relation.volume | 597 | en_US |
dc.relation.firstpage | A73 | en_US |
dc.type.referee | REF_1 | en_US |
dc.description.international | sì | en_US |
dc.contributor.country | ITA | en_US |
dc.contributor.country | USA | en_US |
dc.contributor.country | FRA | en_US |
dc.contributor.country | DEU | en_US |
dc.contributor.country | CHL | en_US |
dc.contributor.country | RUS | en_US |
dc.relation.scientificsector | FIS/05 - ASTRONOMIA E ASTROFISICA | en_US |
dc.relation.journal | ASTRONOMY & ASTROPHYSICS | en_US |
dc.type.miur | 262 Articolo in rivista | - |
dc.identifier.adsbibcode | 2017A&A...597A..73N | en_US |
dc.description.apc | no | en_US |
dc.description.oa | 1 – prodotto con file in versione Open Access (allegare il file al passo 5-Carica) | en_US |
item.openairecristype | http://purl.org/coar/resource_type/c_18cf | - |
item.fulltext | With Fulltext | - |
item.grantfulltext | open | - |
item.languageiso639-1 | en | - |
item.openairetype | Article | - |
item.cerifentitytype | Publications | - |
crisitem.journal.journalissn | 0004-6361 | - |
crisitem.journal.ance | E016240 | - |
crisitem.author.dept | O.A. Brera | - |
crisitem.author.dept | O.A. Brera | - |
crisitem.author.orcid | 0000-0003-1200-0473 | - |
crisitem.author.orcid | 0000-0002-8786-2572 | - |
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