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.

arXiv comment180 pages, 138 figures, accepted for publication in A&A journal

References in corpus (41)

• The Neutral Atomic Phases of the ISM in the Galaxy
• 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
• HERMES: a high-resolution fibre-fed spectrograph for the Mercator telescope
• 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
• Interstellar Fullerene Compounds and Diffuse Interstellar Bands
• The Apache Point Observatory Catalog of Optical Diffuse Interstellar Bands
• Diffuse interstellar bands in Upper Scorpius: Probing variations in the DIB spectrum due to changing environmental conditions
• Exploring the diffuse interstellar bands with the Sloan Digital Sky Survey
• Mapping the Interstellar Medium with Near-Infrared Diffuse Interstellar Bands
• The VLT-FLAMES Tarantula Survey. IX. The interstellar medium seen through Diffuse Interstellar Bands and neutral sodium
• 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
• Atomic and Ionized Microstructures in the Diffuse Interstellar Medium
• Spatial and Temporal Variations in Small-Scale Galactic HI Structure Toward 3C~138
• Small scale structure in molecular gas from multi-epoch observations of HD 34078
• EDIBLES II. On the detectability of C60+ bands
• The EDIBLES survey IV. Cosmic ray ionization rates in diffuse clouds from near-ultraviolet observations of interstellar OH${}^{+}$
• The EDIBLES survey III. C2-DIBs and their profiles
• Variable Interstellar Absorption toward the Halo Star HD 219188 - Implications for Small-Scale Interstellar Structure
• Interaction Between The Broad-lined Type Ic Supernova 2012ap and Carriers of Diffuse Interstellar Bands
• Variable NaI Absorption toward rho Leo : Biased Neutral Formation in the Diffuse Interstellar Medium?
• Probing the Local Bubble with Diffuse Interstellar Bands. I. Project overview and Southern hemisphere survey
• Small-scale structure in the interstellar medium: time-varying interstellar absorption towards κ Velorum
• Small-scale structure of the interstellar medium towards rho Oph stars: diffuse band observations
• Mapping atomic and diffuse interstellar band absorption across the Magellanic Clouds and the Milky Way
• Does tiny-scale atomic structure exist in the interstellar medium ?
• 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

Cited by in corpus (1)

• Survey of Profile Parameters of the $6196\mathring{A}$ Diffuse Interstellar Band. From Uniform Profiles to Doppler Splitting and Blueshifts