J/MNRAS/461/839 DIB 661.3nm in Cepheid spectra (Kashuba+, 2016)
An investigation of the 661.3 nm diffuse interstellar band in Cepheid spectra.
Kashuba S.V., Andrievsky S.M., Chekhonadskikh F.A., Luck R.E.,
Kovtyukh V.V., Korotin S.A., Krelowski J., Galazutdinov G.A.
<Mon. Not. R. Astron. Soc., 461, 839-844 (2016)>
=2016MNRAS.461..839K 2016MNRAS.461..839K (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Equivalent widths ; Stars, distances
Keywords: stars: variables: Cepheids - ISM: lines and bands - ISM: molecules -
ISM: structure
Abstract:
We have investigated the diffuse interstellar band (DIB) at 661.3nm
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)/AV, 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.
Description:
We used spectra of Northern hemisphere Cepheids obtained by REL - one
of the co-authors of this paper, with the High Resolution Spectrograph
of the Hobby-Eberly Telescope at the McDonald Observatory of the
University of Texas at Austin (Texas, USA) with the resolving power of
30000, a typical signal-to-noise ratio of about 100, and wavelength
range of 435-780nm. A total of 253 Cepheid spectra were used in the
research.
We performed an investigation of the 661.356 nm DIB profile in 253
spectra of 176 Cepheids. After removal of the blending YII line the
EW of each DIB was calculated for each spectrum.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 85 276 List of the 185 observed stars, their parameters
and DIB EWs
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Star name
11 A1 --- Nsp Spectrum number when more than one for the star
13- 22 A10 "date" Date Observation date
24- 28 F5.3 --- Phase ?=- Phase
30- 33 I4 K Teff Effective temperature
35- 37 F3.1 [m/s2] logg Surface gravity
39- 41 F3.1 km/s vt Microturbulent velocity
43- 47 I5 pc Dist ?=- Distance
49- 54 F6.2 deg GLON Galactic longitude
56- 61 F6.2 deg GLAT Galactic latitude
63- 67 F5.3 mag E(B-V) ?=- B-V colour excess
69- 76 E8.4 nm EW(Y+Fe) Y+Fe equivalent width
78- 85 E8.4 nm EW(DIB) DIB 661.356nm equivalent width
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 27-Nov-2017