The little-studied cluster Berkeley 90. II. The foreground ISM

Abstract

Context: Nearly one century after their discovery, the carrier(s) of Diffuse Interstellar Bands is/are still unknown and there are few sightlines studied in detail for a large number of DIBs. Aims: We want to study the ISM sightlines towards LS III +46 11 and LS III +46 12, two early-O-type stellar systems, and LS III +46 11 B, a mid-B-type star. The three targets are located in the stellar cluster Berkeley 90 and have a high extinction. Methods: We use the multi-epoch high-S/N optical spectra presented in paper I (Maíz Apellániz et al. 2015), the extinction results derived there, and additional spectra. Results: We have measured equivalent widths, velocities, and FWHMs for a large number of absorption lines in the rich ISM spectrum in front of Berkeley 90. The absorbing ISM has at least two clouds at different velocities, one with a lower column density (thinner) in the K I lines located away from Berkeley 90 and another one with a higher column density (thicker) associated with the cluster. The first cloud has similar properties for both O-star sightlines but the second one is thicker for LS III +46 11. The comparison between species indicate that the cloud with a higher column density has a denser core, allowing us to classify the DIBs in a sigma-zeta scale, some of them for the first time. The LS III +46 12 sightline also has a high-velocity redshifted component.

Accepted for publication in A&A

References in corpus (8)

• A Grid of NLTE Line-Blanketed Model Atmospheres of Early B-type Stars
• A Catalog of Diffuse Interstellar Bands in the Spectrum of HD 204827
• Studies of the Diffuse Interstellar Bands. III. HD 183143
• The Second Data Release of the INT Photometric H-Alpha Survey of the Northern Galactic Plane (IPHAS DR2)
• The VLT-FLAMES Tarantula Survey XVI. The optical+NIR extinction laws in 30 Doradus and the photometric determination of the effective temperatures of OB stars
• Diffuse interstellar bands in RAVE Survey spectra
• Centrosymmetric molecules as possible carriers of diffuse interstellar bands
• The little-studied cluster Berkeley 90. I. LS III +46 11: a very massive O3.5 If* + O3.5 If* binary

Cited by in corpus (11)

• The Galactic O-Star Spectroscopic Survey (GOSSS). III. 142 additional O-type systems
• Interstellar Fullerene Compounds and Diffuse Interstellar Bands
• MONOS: Multiplicity Of Northern O-type Spectroscopic systems. I. Project description and spectral classifications and visual multiplicity of previously known objects
• Optical-NIR dust extinction towards Galactic O stars
• Extinction law in the range 0.4-4.8 $\mu$m and the 8620 $\mathring{A}$ DIB towards the stellar cluster Westerlund 1
• Gaia DR2 distances to Collinder 419 and NGC 2264 and new astrometric orbits for HD 193 322 Aa,Ab and 15 Mon Aa,Ab
• Near-infrared diffuse interstellar bands in APOGEE telluric standard star spectra: weak bands and comparisons with optical counterparts
• Galactic extinction laws: II. Hidden in plain sight, a new interstellar absorption band at 7700 Å broader than any known DIB
• Diffuse interstellar bands in the HII region M17: Insights into their relation with the total-to-selective visual extinction $R_V$
• A high resolution study of near-IR diffuse interstellar bands, search for small scale structure, time variability and stellar features
• The little-studied cluster Berkeley 90. III. Cluster parameters