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A sub-percent distance scale from binaries and Cepheids

Descrizione del progetto

Misurare i sistemi binari eclissanti

Le galassie si stanno allontanando da noi e la costante di Hubble è un parametro fondamentale che descrive la relazione tra tali distanze e le velocità con cui si distaccano. Finanziato dal Consiglio europeo della ricerca, il progetto CepBin si propone di migliorare l’accuratezza e la precisione della costante di Hubble. I ricercatori sperano di ridurre l’incertezza all’1 % e agevolare la calibrazione accurata della luminosità delle cefeidi, un tipo di stelle variabili che subiscono variazioni regolari e prevedibili di luminosità nel tempo a causa di cambiamenti nelle loro dimensioni e temperatura. La relazione periodo-luminosità delle cefeidi ne consente l’utilizzo come standard per determinare le distanze di altri oggetti celesti.

Obiettivo

We propose to carry out a project which will produce a decisive step towards improving the accuracy of the Hubble constant as determined from the Cepheid-SN Ia method to 1%, by using 28 extremely rare eclipsing binary systems in the LMC which offer the potential to determine their distances to 1%. To achieve this accuracy we will reduce the main error in the binary method by interferometric angular diameter measurements of a sample of red clump stars which resemble the stars in our binary systems. We will check on our calibration with similar binary systems close enough to determine their orbits from interferometry. We already showed the feasibility of our method which yielded the best-ever distance determination to the LMC of 2.2% from 8 such binary systems. With 28 systems and the improved angular diameter calibration we will push the LMC distance uncertainty down to 1% which will allow to set the zero point of the Cepheid PL relation with the same accuracy using the large available LMC Cepheid sample. We will determine the metallicity effect on Cepheid luminosities by a) determining a 2% distance to the more metal-poor SMC with our binary method, and by b) measuring the distances to LMC and SMC with an improved Baade-Wesselink (BW) method. We will achieve this improvement by analyzing 9 unique Cepheids in eclipsing binaries in the LMC our group has discovered which allow factor- of-ten improvements in the determination of all basic physical parameters of Cepheids. These studies will also increase our confidence in the Cepheid-based H0 determination. Our project bears strong synergy to the Gaia mission by providing the best checks on possible systematic uncertainties on Gaia parallaxes with 200 binary systems whose distances we will measure to 1-2%. We will provide two unique tools for 1-3 % distance determinations to individual objects in a volume of 1 Mpc, being competitive to Gaia already at a distance of 1 kpc from the Sun.

Meccanismo di finanziamento

ERC-ADG - Advanced Grant

Istituzione ospitante

CENTRUM ASTRONOMICZNE IM. MIKOLAJA KOPERNIKA POLSKIEJ AKADEMII NAUK
Contribution nette de l'UE
€ 1 351 225,00
Indirizzo
Bartycka, 18
00-716 Warszawa
Polonia

Mostra sulla mappa

Regione
Makroregion województwo mazowieckie Warszawski stołeczny Miasto Warszawa
Tipo di attività
Research Organisations
Collegamenti
Costo totale
€ 1 351 225,00

Beneficiari (4)