J/MNRAS/480/488 Multiple absorption features in debris discs (Iglesias+, 2018)
Debris discs with multiple absorption features in metallic lines: circumstellar
or interstellar origin?
Iglesias D., Bayo A., Olofsson J., Wahhaj Z., Eiroa C., Montesinos B.,
Rebollido I., Smoker J., Sbordone L., Schreiber M.R., Henning T.
<Mon. Not. R. Astron. Soc., 480, 488-520 (2018)>
=2018MNRAS.480..488I 2018MNRAS.480..488I (SIMBAD/NED BibCode)
ADC_Keywords: Exoplanets ; Comets ; Diffuse clouds
Keywords: circumstellar matter - ISM: clouds -
stars: individual: (HR 4796 - c Aql) -
comets: general - planetary systems
Abstract:
Debris discs are second-generation dusty discs thought to be devoid of
gas. However, this idea has been challenged in the last years by gas
detections in some systems. We compiled a database of 301 debris discs
and collected high-resolution optical spectra for ∼77 per cent of
them. From the analysis of these data we identified a group of 23
debris discs presenting several absorption features superimposed to
the photospheric CaII and NaI doublets. These absorptions could be due
to circumstellar material or interstellar clouds. In order to
discriminate between the two scenarios, we characterized each feature
in terms of its radial velocity, equivalent width, and column density.
Additionally, we searched in the literature for local clouds in the
line of sight of the stars, and looked for the presence of similar
absorption features in nearby stars. Our study concludes that while
all the objects present interstellar absorptions in their spectra,
three objects show features more compatible with circumstellar origin:
HD 110058 presents a stable circumstellar absorption, while HR 4796
and c Aql present variable absorption features likely due to
exocometary activity. The minute-scale variability we detect towards
c Aql is the shortest of this kind detected so far. The detection of
circumstellar features in these objects is consistent with their near
edge-on inclinations. We also provide evidence challenging previous
claims of circumstellar gas detections for HR 6507. Given the
properties of the sample, we speculate that transient gaseous events
must be a common phenomenon among debris discs.
Description:
In this paper, we present a sub-sample of 23 gas-rich debris disc
candidates characterized by showing gas detections at different radial
velocities within our database of observations prior to 2016 December.
We performed observations with FEROS (Kaufer et al.
1999Msngr..95....8K 1999Msngr..95....8K) on the MPG/ESO 2.2m telescope at the La Silla
Observatory in Chile and UVES (Dekker et al. 2000SPIE.4008..534D 2000SPIE.4008..534D) on
the VLT UT2 telescope at Paranal Observatory, Chile. We also queried
the ESO archive searching for all relevant high-resolution spectra
covering the blue-optical wavelength ranges. In particular data from
HARPS (Mayor et al. 2003Msngr.114...20M 2003Msngr.114...20M), UVES, and FEROS instruments
were searched for. We analysed the calcium H&K lines at 3968.47 and
3933.66Å and the sodium D1&D2 lines at 5895.92 and 5889.95Å,
respectively. The aim is to detect narrow absorption lines
superimposed on the photospheric line. These 'extra' absorption lines
indicate the presence of gas in the line of sight of the star. The
first step in our analysis is to measure the radial velocity of the
stars. Afterwards, we determined the photospheric contribution for
each line either by performing spectral synthesis or by finding a
'spectral twin' Then, we identified additional (stable or transient)
components by removing the photospheric contribution before
characterizing their properties.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 59 23 Stellar parameters determined from the synthetic
model fitting and radial velocity estimates
table6.dat 88 70 Absorption feature parameters
table8.dat 62 71 Absorption components and their mean radial
velocity, CaII/NaI density ratio, absorption
feature detection in a nearby star, and
proposed origin
tablec1.dat 45 104 All nearby stars used in the analysis per each
object of science, their number of spectra,
instrument, and ESO programme ID
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Star name
12- 14 I3 km/s vsini ?=- Rotational velocity (1)
16- 21 F6.2 km/s RV Radial velocity
23- 26 F4.2 km/s e_RV Radial velocity error
28 A1 --- f_RV ? Flag on RV (2)
30- 34 I5 K Teff(CaIIK) ?=- Effective temperature (3)
36- 39 F4.2 [cm/s2] logg ? Surface gravity
41- 44 F4.2 [cm/s2] e_logg ? Surface gravity error (4)
46 A1 --- f_logg ? Flag on logg (5)
48- 52 F5.2 --- [Fe/H] ? Metallicity
54- 57 F4.2 --- e_[Fe/H] ? Metallicity error (4)
59 A1 --- f_[Fe/H] ? Flag on metallicity (5)
-------------------------------------------------------------------------------
Note (1): The typical uncertainty for the estimate of vsini is ∼5km/s.
Note (2): Flag as follows:
* = Radial velocity of stars in multiple or binary systems.
Note (3): The typical uncertainty for the estimate of Teff(CaII K) is of ∼5-10%.
Note (4): Dispersion values come from the measurements in the four different
lines.
Note (5): Flag as follows:
g = Dispersion values come from the grid step size when the four lines
yielded the same values.
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Star Name
12- 17 F6.2 km/s HRVCaIIK ? Heliocentric radial velocity for the
CaII K line (1)
19- 23 F5.2 [cm-2] logNCaIIK ? CaII K Apparent column density (2)
25- 29 F5.2 10-4nm EWCaIIK ? Equivalent width of the features present in
the CaII K line (2)
31- 36 F6.2 km/s HRVCaIIH ? Heliocentric radial velocity for the
CaII H line (1)
38- 42 F5.2 [cm-2] logNCAIIH ? CaII H Apparent column density (2)
44- 48 F5.2 10-4nm EWCaIIH ? Equivalent width of the features present in
the CaII H line (2)
50- 55 F6.2 km/s HRVNaID1 ? Heliocentric radial velocity for the
NaI D1 line (3)
57- 61 F5.2 [cm-2] logNNaID1 ? NaI D1 Apparent column density (4)
63- 68 F6.2 10-4nm EWNaID1 ? Equivalent width of the features present in
the NaI D1 line (4)
70- 75 F6.2 km/s HRVNaID2 ? Heliocentric radial velocity for the NaI D2
line (3)
77- 81 F5.2 [cm-2] logNNaID2 ? NaI D2 Apparent column density (4)
83- 88 F6.2 10-4nm EWNaID2 ? Equivalent width of the features present in
the NaI D2 line (4)
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Note (1): Uncertainties for the radial velocities are in the order of 2.3km/s
for the CaII lines.
Note (2): Apparent column densities and equivalent widths have uncertainties of
3-4% for the CaII lines.
Note (3): Uncertainties for the radial velocities are in the order of 1.5km/s
for the NaI lines.
Note (4): Apparent column densities and equivalent widths have uncertainties of
1-2% for the NaI lines.
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Byte-by-byte Description of file: table8.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Star name
12- 17 F6.2 km/s RV Radial velocity of star
19- 22 F4.2 km/s e_RV RV error
24- 27 A4 --- Cloud ?=- Traversing cloud name
29- 34 F6.2 km/s CloudRV ? Radial velocity of cloud
36- 39 F4.2 km/s e_CloudRV ? CloudRV error
41 A1 --- Feature ?=- Matching feature (1)
43- 48 F6.2 km/s FeatureRV Radial velocity of feature
50 A1 --- l_NCaII/NNaI Limit flag on CaII/NaI density ratio
52- 56 F5.2 --- NCaII/NNaI ?=- CaII/NaI density ratio
58 A1 --- NearbyStar ?=- Nearby star (2)
60- 62 A3 --- Origin Proposed origin (3)
-------------------------------------------------------------------------------
Note (1): Indicates if radial velocity of cloud matches one of the observed
absorption features.
Note (2): Indicates if there is a matching absorption in a nearby star.
Note (3): Origin of the absorption features as follows:
ISM = interstellar medium
CS = circumstellar
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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- 10 A10 --- Name Star name (1)
12- 21 A10 --- NBSname Nearby star name
23- 25 I3 --- NSpec Number of spectra
27- 31 A5 --- Inst Instrument
33- 45 A13 --- PID ESO programme ID
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Note (1): Note that HD 290540, HD 36444 and HD 290609 are each other's nearby
stars and in addition have three other common nearby stars.
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 12-May-2022