J/ApJ/896/24 Properties of atomic lines in 51 Oph UV spectra (Jenkins+, 2020)
The composition, excitation, and physical state of atomic gas in the debris disk
surrounding 51 Oph.
Jenkins E.B., Gry C.
<Astrophys. J., 896, 24 (2020)>
=2020ApJ...896...24J 2020ApJ...896...24J
ADC_Keywords: Spectra, ultraviolet; Optical; Atomic physics; Stars, Be
Keywords: Debris disks ; Circumstellar gas ; Abundance ratios
Abstract:
We measured 304 absorption features in the ultraviolet and visible
spectra of the star 51 Oph, which is known to have a debris disk with
a high inclination. We analyzed the relative populations of atoms in
excited fine-structure and metastable levels that are maintained by
optical pumping and collisional excitation by electrons, and we found
that most of the gas is situated at about 6 au from the star, has an
electron volume density 105<n(e)<3x106cm-3, and a temperature
T=8000K. Our interpretations reveal that the gas is partly ionized,
has a column density of neutral hydrogen equal to 1021cm-2, and
has a composition similar to that of a mildly depleted interstellar
medium or that of Jupiter-family comets. Compared to results for disks
around some other stars, such as β Pic and 49 Cet, we find
surprisingly little neutral carbon. No molecular features were
detected, which indicates that our line of sight misses the
molecule-rich central plane of the disk. The tilt of the disk is also
validated by our being able to detect resonant scattering of the
starlight by oxygen atoms.
Description:
Nearly all of the conclusions in this paper are based on observations
taken at ultraviolet wavelengths with the highest resolution echelle
modes of STIS aboard HST in 2003. These data are supplemented by
observations by the Goddard High Resolution Spectrograph (GHRS) on
1996 Feb 21 over very limited wavelength ranges.
We also made use of archived echelle spectra recorded by the
Ultraviolet and Visual Echelle Spectrograph (UVES) on the Kueyen VLT
operated by the European Southern Observatory in 2007 May-Aug.
Specific observations used in this paper can be accessed via the
following collections of GHRS, STIS, and FUSE data on the MAST
doi:10.17909/t9-b6j3-w085
Observations of 51 Oph in the far-ultraviolet recorded by FUSE have
been reported by Roberge+ (2002ApJ...568..343R 2002ApJ...568..343R). We confined our use
of the FUSE spectra to probe only the elements NI, ClII, PII, and a
metastable level of OI, which we could not measure in the STIS
spectrum.
Finally, we used a spectrum recorded by the Hopkins Ultraviolet
Telescope (HUT) on 1995 Mar 15 to validate our choice of parameters.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
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17 31 24.95 -23 57 45.5 * 51 Oph = * c Oph
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 47 305 Properties of atomic lines
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See also:
J/A+AS/109/125 : Photoionisation cross section (Verner+, 1995)
J/A+AS/118/481 : ROSAT all-sky survey catalogue of OB stars (Berghoefer+ 1996)
J/A+A/385/716 : N-like and O-like Breit-Pauli energy levels (Tachiev+, 2002)
J/ApJS/167/334 : Radiative recombination data for plasmas (Badnell+, 2006)
J/ApJ/653/657 : Spectroscopic obs. of Herbig Ae/Be stars (Manoj+, 2006)
J/ApJS/163/207 : Oscillator and collision strengths in NI (Tayal+, 2006)
J/A+A/475/677 : X-ray emission from A-type stars (Schroeder+, 2007)
J/ApJS/176/59 : FUSE survey of OVI in the disk of the Milky Way (Bowen+, 2008)
J/ApJ/700/1299 : Gas-phase element depletions in the ISM (Jenkins, 2009)
J/A+A/513/A55 : Effective collision strengths of Ni II (Cassidy+, 2010)
J/ApJS/194/35 : Atomic transition probabilities of Mn (Den Hartog+, 2011)
J/PASP/125/477 : Gas Survey of Protoplanetary Systems. I. (Dent+, 2013)
J/ApJ/764/25 : FUSE spectra analysis of hot subdwarf stars (Jenkins, 2013)
J/ApJ/804/76 : ZnII lines and collision strengths (Kisielius+, 2015)
J/A+A/607/A25 : beta Pic HARPS spectrum (Vidal-Madjar+, 2017)
J/A+A/625/A78 : Carbon and nitrogen rate coefficients (Amarsi+, 2019)
J/AJ/157/159 : Stellar parameters for 131 Herbig Ae/Be stars (Arun+, 2019)
J/A+A/625/L13 : TESS light curve of beta Pictoris (Zieba+, 2019)
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.4 0.1nm lambda [1071/5897.6] Laboratory wavelength
11- 11 A1 --- f_lambda [b-q] Notes on specific transitions (1)
13- 17 A5 --- Sp Species
19- 23 I5 cm-1 E [0/36252] Excitation
25- 33 E9.4 --- f [4.7e-08/1.8] Transition f-value
35- 35 A1 --- lef Limit flag on e_f
37- 41 F5.3 [-] e_f [0.003/0.3]? log of f-value relative uncertainty
43- 47 A5 --- r_f Reference(s) for f-value (2)
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Note (1): Notes on specific transitions as follows:
b = These strong transitions for nitrogen are very strongly saturated
and not properly resolved in the FUSE spectrum. The equivalent
width of the NI feature was used only to verify the derivation of
the saturation factors (s.f., see Eq. 3) for optical pumping, and
the very strong absorptions by NII indicated the importance of
ionization processes beyond that provided by photons with energies
below the ionization potential of hydrogen;
c = Very strongly saturated lines shown in Figure 6. The very weak
intersystem line at 1355.598 A was used to derive N(OI);
d = This line is not useful in the present study, since it occurs near
the bottom of a very strong absorption by the λλ
1335.649, 1335.708 lines of excited CII. However, in future
investigations of other stars, this Cl I line may not suffer from this
interference;
e = The CrII lines at 2677.956 and 2677.954 A are severely blended.
However the simultaneous fitting of the various lines from different
levels undertaken by the Owens analysis allows for this
superposition;
f = The CrII line at 2836.463 A and the FeII line at 2836.5452 A are
blended, but our analysis fitted these features simultaneously;
g = The MnII line at 2594.4990 A and FeII line at 2594.5034 A are
blended, but our analysis fitted these features simultaneously;
These fits are substantiated by 3 other lines that are free from
interference for both MnII and FeII in the same energy levels;
h = This line is too weak to see in our spectrum;
i = This line was not considered in our analysis because it was too
close to the edge of our spectrum;
j = This line coincided with a detector flaw, so it was not considered
in our analysis;
k = The FeII lines at 2348.835 and 2349.022 A are blended, but our
analysis fitted these features simultaneously;
l = The FeII lines at 2749.994, 2750.134, and 2750.299 A overlap each
other, but our analysis fitted these features simultaneously;
m = The FeII line at 2221.072 A and the NiII line at 2221.090 A are
blended, but our analysis fitted these features simultaneously;
Other lines of FeII in this level substantiate the fit;
n = The FeII lines at 2770.1736 and 2770.1502 A are blended, but our
analysis fitted these features simultaneously. Added confidence in
these fits comes from other lines of FeII from the same levels;
o = The lines of FeII at 2364.533, 2667.429, and 2768.320 A are blended
with lines of FeII originating from much higher levels, which are
too weak to matter;
p = These two lines for NiII were not used because two other lines with
more accurate f-values were available for this level;
q = An absorption line is present at this location, but it indicates an
unreasonably high column density for this level. There must be some
other unidentified transition that coincides with this one.
Note (2): Except for reference (1), most of the transition f-values were
obtained from either the National Institute of Standards and Technology
(NIST) website (https://physics.nist.gov/PhysRefData/ASD/lines_form.html)
or The Atomic Line List v 2.05b21 (http://www.pa.uky.edu/~peter/newpage/).
Original determinations are as follows:
1 = Values and references listed in Morton (2003ApJS..149..205M 2003ApJS..149..205M);
2 = Tachiev & Froese Fischer (2002A&A...385..716T 2002A&A...385..716T);
3 = Butler & Zeippen (1991, doi:10.1051/jp4:1991117);
4 = Nilsson et al. (2006A&A...445.1165N 2006A&A...445.1165N);
5 = Den Hartog et al. (2011ApJS..194...35D 2011ApJS..194...35D);
6 = Kurucz (1990) with additional data downloaded from
http://kurucz.harvard.edu/linelists.html on December 11, 2012;
7 = Bergeson et al. (1996ApJ...464.1044B 1996ApJ...464.1044B);
8 = Schnabel et al. (2004A&A...414.1169S 2004A&A...414.1169S);
9 = Tayal & Zatsarinny (2018PhRvA..98a2706T 2018PhRvA..98a2706T);
10 = Fuhr & Wiese (2006JPCRD..35.1669F 2006JPCRD..35.1669F );
11 = Raassen & Uylings (1998JPhB...31.3137R 1998JPhB...31.3137R);
12 = Johansson et al. (1995ApJ...446..361J 1995ApJ...446..361J);
13 = Sikstr?m et al. (1999JPhB...32.5687S 1999JPhB...32.5687S);
14 = Karlsson et al. (2001A&A...371..360K 2001A&A...371..360K);
15 = Mullman et al. (1998ApJ...495..503M 1998ApJ...495..503M);
16 = Salih et al. (1985PhRvA..31..744S 1985PhRvA..31..744S);
17 = Jenkins & Tripp (2006ApJ...637..548J 2006ApJ...637..548J);
18 = Fedchak et al. (2000ApJ...538..773F 2000ApJ...538..773F);
19 = Kurucz (2012);
20 = Fedchak & Lawler (1999ApJ...523..734F 1999ApJ...523..734F);
21 = van Hoof (2017, 2018Galax...6...63V 2018Galax...6...63V): no original reference specified;
22 = Kisielius et al. (2015ApJ...804...76K 2015ApJ...804...76K).
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(End) Prepared by [AAS], Emmanuelle Perret [CDS] 06-Oct-2021