The EDIBLES survey VI. Searching for time variations of interstellar absorption features

Abstract

Interstellar lines observed toward stellar targets change slowly over long timescales, mainly due to the proper motion of the background target relative to the intervening clouds. On longer timescales, the cloud's slowly changing physical and chemical conditions can also cause variation. We searched for systematic variations in the absorption profiles of the diffuse interstellar bands (DIBs) and interstellar atomic and molecular lines by comparing the high-quality data set from the ESO diffuse interstellar bands extensive exploration survey (EDIBLES) to older archival observations, bridging typical timescales of 10 years with a maximum timescale of 22 years. We found good archival observations for 64 EDIBLES targets. Our analysis focused on 31 DIBs, 7 atomic, and 5 molecular lines. We considered various systematic effects and applied a robust Bayesian test to establish which absorption features could display significant variations. While systematic effects greatly complicate our search, we find evidence for variations in the profiles of the $\lambda \lambda$4727 and 5780 DIBs in a few sightlines. Toward HD~167264, we find a new \ion{Ca}{i} cloud component that appears and becomes stronger after 2008. The same sightline furthermore displays marginal but systematic changes in the column densities of the atomic lines originating from the leading cloud component in the sightline. Similar variations are seen toward HD~147933. Our high-quality spectroscopic observations and archival data show that it is possible to probe interstellar time variations on time scales of typically a decade. Even though systematic uncertainties, as well as the generally somewhat lower quality of older data, complicate matters, we can conclude that time variations can be made visible, both in atomic lines and DIB profiles for a few targets, but that generally, these features are stable along many lines of sight.

180 pages, 138 figures, accepted for publication in A&A journal

References in corpus (21)

• A Unified Representation of Gas-Phase Element Depletions in the Interstellar Medium
• Molecfit: A general tool for telluric absorption correction. I. Method and application to ESO instruments
• Molecfit: A general tool for telluric absorption correction II. Quantitative evaluation on ESO-VLT X-Shooter spectra
• A Catalog of Diffuse Interstellar Bands in the Spectrum of HD 204827
• The Diffuse Interstellar Bands: A Major Problem in Astronomical Spectroscopy
• Studies of the Diffuse Interstellar Bands. III. HD 183143
• Confirming interstellar C${}_{60}^{+}$ using the Hubble Space Telescope
• Mapping the Interstellar Medium with Near-Infrared Diffuse Interstellar Bands
• The ESO Diffuse Interstellar Bands Large Exploration Survey: EDIBLES I. Project description, survey sample and quality assessment
• Pseudo Three-dimensional Maps of the Diffuse Interstellar Band at 862 nm
• Detailed maps of interstellar clouds in front of omega Centauri: Small-scale structures in the Galactic Disc-Halo interface
• C${}_{60}^{+}$ and the Diffuse Interstellar Bands: An Independent Laboratory Check
• Small-scale structure in the interstellar medium: time-varying interstellar absorption towards κ Velorum
• A three-dimensional map of the hot Local Bubble using diffuse interstellar bands
• Spatial Variations in Galactic H I Structure on AU-Scales Toward 3C 147 Observed with the Very Long Baseline Array
• Early-type stars observed in the ESO UVES Paranal Observatory Project - V. Time-variable interstellar absorption
• Probing the Local Bubble with Diffuse Interstellar Bands. II. The DIB properties in the Northern hemisphere
• The EDIBLES survey V: Line profile variations in the $\lambda \lambda$5797, 6379, and 6614 diffuse interstellar bands as a tool to constrain carrier sizes
• Probing the Local Bubble with Diffuse Interstellar Bands. III. The Northern hemisphere data and catalog
• A high resolution study of near-IR diffuse interstellar bands, search for small scale structure, time variability and stellar features
• The 15273 Å diffuse interstellar band in the dark cloud Barnard 68

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