An investigation of the 661.3 nm diffuse interstellar band in Cepheid spectra

• Published in: Monthly notices of the Royal Astronomical Society Vol. 461; no. 1; pp. 839 - 844
• Main Authors: Kashuba, S. V., Andrievsky, S. M., Chekhonadskikh, F. A., Luck, R. E., Kovtyukh, V. V., Korotin, S. A., Krełowski, J., Galazutdinov, G. A.
• Format: Journal Article
• Language: English
• Published: London Oxford University Press 01.09.2016; Oxford University Press (OUP): Policy P - Oxford Open Option A
• Subjects: Absorption; Accretion disks; Astronomy; Astrophysics; Cepheid variables; Diffuse interstellar bands; Disks; Information dissemination; Photometry; Physics; Sciences of the Universe; Spectra; Star & galaxy formation; Yttrium; ISM: lines and bands; stars: variables: Cepheids; ISM: molecules; ISM: structure
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stw1344

We have investigated the diffuse interstellar band (DIB) at 661.3 nm seen in the spectra of Cepheid stars. After removal of the blending lines of ionized yttrium and neutral iron, we determined the equivalent widths (EWs) of the DIB and used these values to investigate the E(B − V)–DIB EW relation. The relation found from Cepheids matches that found in B stars. This relation can help to find the reddening for newly discovered Cepheids without extensive photometric data, and thus determine their distances. The relation between E(B − V) and the DIB EW does not yield precise reddening values. It is not a substitute for better photometric or spectroscopic methods. At best, it is indicative, but it provides some information that may not be otherwise available. Defining R* = E(B − V)/DIB EW, which we consider to be the analogue of R = E(B − V)/A v, we investigated the Galactic longitudinal dependence of R* assuming that the DIB EW value is representative of the interstellar absorption A v. We found that there is an apparent increase of the R* value that corresponds to the abnormal absorption seen towards Cygnus constellation. Finally, we constructed a 2D map of the DIB EW distribution in the Galactic disc basing on our rather limited sample of 253 spectra of 176 Cepheids.