J/A+A/678/A148 EDIBLES survey. VI. (Farhang+, 2023)
The EDIBLES survey.
VI. Searching for time variations of interstellar absorption features.
Farhang A., Smoker J., Cox N.L.J., Cami J., Linnartz H., van Loon J.T.,
Cordiner M.A., Sarre P.J., Khosroshahi H.G., Ehrenfreund P., Foing B.H.,
Kaper L., Laverick M.
<Astron. Astrophys. 678, A148 (2023)>
=2023A&A...678A.148F 2023A&A...678A.148F (SIMBAD/NED BibCode)
ADC_Keywords: Diffuse clouds ; Interstellar medium ; Proper motions ;
Spectroscopy ; Optical ; Stars, early-type
Keywords: ISM: abundances - ISM: atoms - ISM: clouds - dust, extinction -
ISM: lines and bands - ISM: molecules
Abstract:
Interstellar absorption observed toward stellar targets changes slowly
over long timescales, mainly due to the proper motion of the
background target relative to the intervening clouds, such that over
time, different parts of the intervening cloud are probed. On longer
timescales, the slowly changing physical and chemical conditions in
the cloud can also cause variation. Detecting such time variations
thus provides an opportunity to study cloud structure.
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 recent
ESO diffuse interstellar bands large exploration survey (EDIBLES) to
older archival observations, bridging typical timescales of ∼10
years with a maximum timescale of 22 years.
For 64 EDIBLES targets, we found adequate archival observations. We
selected 31 strong DIBs, 7 atomic and 5 molecular lines to focus our
search on. We carefully considered various systematic effects and used
a robust Bayesian quantitative test to establish which of these
absorption features could display significant variations.
While systematic effects greatly complicate our search, we find
evidence for variations in the profiles of the λλ4727
and 5780 DIBs in a few sightlines. Toward HD 167264, we find a new CaI
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 main cloud
component in the sightline. Similar variations are seen toward
HD 147933.
Our high-quality spectroscopic observations in combination with
archival data show that it is possible to probe interstellar time
variations on time scales of typically a decade. Despite the fact that
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. We present this study as an archival baseline for
future comparisons, bridging longer periods.
Description:
In tablea1, the sample. Columns show HD number, E(B-V), interstellar
cloud component radial velocity, rotational velocity, spectral type,
RA & Dec., Distance (pc), Proper motion (mas/yr), Observation Dates
and Distance traveled (au).
In tableb1, results of our DIB measurements. For each sightline, we
list only those DIBs from our sample that we can reliably detect. Note
that the EW values are obtained from the Gaussian fits and not from
direct integration. chi2base is the reduced chi-square value for a
model in which the ratio spectrum is equal to unity; chi^2Gauss the
value for the best-fitting Gaussian model. The BIC values for baseline
and Gaussian models are listed as well; see paper for details.
For sightlines where the BIC decreases by more than 3 units, we also
list |{DELTA}BIC|. For those cases, the last column is our final
assessment of what is the root cause for this change in BIC: continuum
positioning errors are indicated by c; instrumental artifacts by a;
blends with stellar lines by *; telluric artifacts by O and a
potential changes in the DIB properties by DIB. The + and - subscripts
in those cases indicate whether the DIB has increased or decreased in
strength over time in those cases.
In tablec1, Best-fit Voigt parameters for atomic and molecular lines.
Note that all velocities are reported in the heliocentric rest frame.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 92 406 Studied targets
tableb1.dat 76 872 The dib fit results
tablec1.dat 98 191 The atomic line fits results
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See also:
J/A+A/606/A76 : The ESO DIBs Large Exploration Survey (Cox+, 2017)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- --- [HD]
4- 9 I6 --- Target Target name HD number
10 A1 --- n_Target [+] Note on Target (1)
11- 14 F4.2 mag E(B-V) Reddening
16- 21 F6.2 km/s vISM ISM reference frame velocity
23- 25 I3 km/s vsini ? Rotational velocity
27- 28 I2 --- r_vsini ? Reference for vsini (2)
30- 39 A10 --- SpType Spectral type
41- 46 F6.2 deg RAdeg Right ascension (J2000)
48- 53 F6.2 deg DEdeg Declination (J2000)
55- 58 I4 pc Dist Distance to target
61- 65 F5.2 mas/yr pm Overal proper motion
67- 76 I10 --- Obs Observation date
78- 85 A8 --- Inst Instrument
87- 92 F6.2 au TravDist ? Transversed distance
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Note (1): +: This target shows no DIBs and was therefore only used to search for
variations in the atomic and molecular lines.
Note (2): References as follows:
1 = Abt et al. (2002ApJ...573..359A 2002ApJ...573..359A, Cat. J/ApJ/573/359)
2 = Royer et al. (2007A&A...463..671R 2007A&A...463..671R, Cat. J/A+A/463/671)
3 = Burssens et al. (2020A&A...639A..81B 2020A&A...639A..81B, Cat. J/A+A/639/A81)
4 = Simon-Diaz et al. (2017A&A...597A..22S 2017A&A...597A..22S, Cat. J/A+A/587/A22)
5 = Huang et al. (2010ApJ...722..605H 2010ApJ...722..605H, Cat. J/ApJ/722/605)
6 = Braganca et al. (2012AJ....144..130B 2012AJ....144..130B, Cat. J/AJ/144/130)
7 = Kounkel et al. (2019AJ....157..196K 2019AJ....157..196K, Cat. J/AJ/157/196)
8 = Uesugi & Fukuda (1970CoKwa.189....0U 1970CoKwa.189....0U)
9 = Bernacca & Perinotto (1970CoAsi.239....1B 1970CoAsi.239....1B, Cat. III/30)
10 = Ammler-von Eiff & Reiners (2012A&A...542A.116A 2012A&A...542A.116A, Cat. J/A+A/542/A116)
11 = Holgado et al. (2018A&A...613A..65H 2018A&A...613A..65H, Cat. J/A+A/613/A65)
12 = Simon-Diaz & Herrero (2014A&A...562A.135S 2014A&A...562A.135S, Cat. J/A+A/562/A135)
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Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- --- [HD]
4- 9 I6 --- Target HD number of the target
11- 14 I4 0.1nm DIB DIB name
16- 23 I8 "YYYYMMDD" Date1 First epoch
25- 32 I8 "YYYYMMDD" Date2 Last epoch
34- 36 I3 0.1pm EW1 Equivalent width for the first epoch
38- 39 I2 0.1pm e_EW1 Error on Equivalent width for the epoch 1
41- 43 I3 0.1pm EW2 Equivalent width for the second epoch
45 I1 0.1pm e_EW2 Error on Equivalent width for the epoch 2
47- 51 F5.2 --- Chi2base Chi square for the base model
53- 57 F5.2 --- Chi2gauss Chi square for the Gauss model
59- 62 I4 --- BICbase Bayesian Information Criterion (BIC)
for the base
64- 67 I4 --- BICgauss Bayesian Information Criterion (BIC)
for the Gauss
69- 71 I3 --- deltaBIC ? BIC difference
73- 76 A4 --- Comment Source of variation (1)
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Note (1): Comments as follows:
c = continuum positioning errors are indicated by c
a = instrumental artifacts by a
* = blends with stellar lines by
O = telluric artifacts
DIB+ = a potential changes in the DIB properties by DIB, the DIB has
increased in strength over time in those cases
DIB- = a potential changes in the DIB properties by DIB, the DIB has
decreased in strength over time in those cases
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Byte-by-byte Description of file: tablec1.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- --- [HD]
4- 9 I6 --- Target Target name HD number
11- 17 A7 --- Atom Ion name
19- 26 I8 "YYYYMMDD" Date1 First epoch (yyyymmdd)
29- 33 F5.1 km/s vel1 Component velocity for the first epoch
35- 38 F4.1 km/s e_vel1 Component velocity uncertainty
40- 44 F5.2 cm-2 logN1 Column density for the first epoch
46- 49 F4.2 cm-2 e_logN1 Column density uncertainty
51- 54 F4.1 km/s beff1 Doppler broadening for the first epoch
56- 58 F3.1 km/s e_beff1 Doppler broadening uncertainty
60- 67 I8 "YYYYMMDD" Date2 Second epoch (yyyymmdd)
69- 73 F5.1 km/s vel2 Component velocity for the second epoch
75- 78 F4.1 km/s e_vel2 Component velocity uncertainty
80- 84 F5.2 cm-2 logN2 Column density for the second epoch
86- 89 F4.2 cm-2 e_logN2 Column density uncertainty
91- 94 F4.1 km/s beff2 Doppler broadening for the second epoch
96- 98 F3.1 km/s e_beff2 Doppler broadening uncertainty
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Acknowledgements:
Amin Farhang, a.farhang(at)ipm.ir
References:
Cox et al., Paper I 2017A&A...606A..76C 2017A&A...606A..76C, Cat. J/A+A/606/A76
Lallement et al., Paper II 2018A&A...614A..28L 2018A&A...614A..28L
Elyajouri et al., Paper III 2018A&A...616A.143E 2018A&A...616A.143E
Bacalla et al., Paper IV 2019A&A...622A..31B 2019A&A...622A..31B
MacIsaac et al., Paper V 2022A&A...662A..24M 2022A&A...662A..24M
(End) Amin Farhang [IPM, Iran], Patricia Vannier [CDS] 24-Aug-2023