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J/A+A/323/469 Optical spectra of post-AGB stars (Bakker+ 1997)
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Circumstellar C_2_, CN, and CH^+^ in the optical spectra of post-AGB stars
Bakker E.J., van Dishoeck E.F., Waters L.B.F.M., Schoenmaker T.
<Astron. Astrophys. 323, 469 (1997)>
=1997A&A...323..469B (SIMBAD/NED BibCode)
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ADC_Keywords: Spectroscopy ; Line Profiles
Keywords: molecular processes - circumstellar matter - stars: AGB and post-AGB -
line: identification
Abstract:
We present optical high-resolution spectra of a sample of sixteen
post-AGB stars and IRC +10216. Of the post-AGB stars, ten show C_2_
Phillips (A^1^{PI}_u_-X^1^{SIGMA}^+^_g_) and Swan
(d^3^{PI}_g_-a^3^{PI}_u_) and CN Red System (A^2^{PI}-X^2^{SIGMA}^+^)
absorption, one CH^+^ (A^1^{PI}-X^1^{SIGMA}^+^) emission, one CH^+^
absorption, and four without any molecules. We find typically T_rot_
~43-399, 155-202, and 18-50K, logN~14.90-15.57, 14.35, and
15.03-16.47cm^-2^ for C_2_, CH^+^, and CN respectively, and
0.6<=N(CN)/N(C_2_)<=11.2. We did not detect isotopic lines, which
places a lower limit on the isotope ratio of ^12^C/^13^C>20. The
presence of C_2_ and CN absorption is correlated with cold dust
(T_dust_<=300K) and the presence of CH^+^ with hot dust
(T_dust_>=300K). All objects with the unidentified 21{mu}m emission
feature exhibit C_2_ and CN absorption, but not all objects with C_2_
and CN detections exhibit a 21{mu}m feature. The derived expansion
velocity, ranging from 5 to 44km/s, is the same as that derived from
CO millimeter line emission. This unambiguously proves that these
lines are of circumstellar origin and are formed in the AGB ejecta
(circumstellar shell expelled during the preceding AGB phase).
Furthermore there seems to be a relation between the C_2_ molecular
column density and the expansion velocity, which is attributed to the
fact that a higher carbon abundance of the dust leads to a more
efficient acceleration of the AGB wind. Using simple assumptions for
the location of the molecular lines and molecular abundances,
mass-loss rates have been derived from the molecular absorption lines
and are comparable to those obtained from CO emission lines and the
infrared excess.
Objects:
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RA (2000) DE Designation(s)
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04 32 56.6 +34 36 11 IRAS 04296+3429
05 14 07.9 +13 50 28 IRAS 05113+1347
05 36 54.2 +08 54 10 IRAS 05341+0852
06 19 58.2 -10 38 14 HD 44179
07 16 10.2 +09 59 48 HD 56126 = IRAS 07134+1005
08 02 40.5 -24 04 43 IRAS 08005-2356
09 47 57.2 +13 16 44 IRC +10216 = IRAS 09452+1330
20 01 59.4 +32 47 32 IRAS 20000+3239
21 02 18.7 +36 41 38 AFGL 2688
22 24 30.6 +43 43 03 IRAS 22223+4327
22 29 10.3 +54 51 06 HD 235858 = IRAS 22272+5435
23 32 44.9 +62 03 49 IRAS 23304+6147
22 35 27.4 -17 15 27 HD 213985 = IRAS 22327-1731
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table5 106 13 Physical parameters derived from molecular lines
tablea1 29 55 C_2_ A^1^PI_u_-X^1^SIGMA^+^_g_ Phillips (2,0) band
tablea2 80 55 C_2_ A^1^PI_u_-X^1^SIGMA^+^_g_ Phillips (3,0) band
tablea3 42 100 CN A^2^PI-X^2^SIGMA^+^ Red System (2,0) band
tablea4 72 100 CN A^2^PI-X^2^SIGMA^+^ Red System (3,0) band
tablea5 34 34 CH^+^ A^1^PI-X^1^SIGMA^+^ (0,0) band
tables.tex 108 680 LaTeX version of the tables
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Byte-by-byte Description of file: table5
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Bytes Format Units Label Explanations
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1 I1 --- Reaction [1/2] Reaction considered (1)
3- 17 A15 --- Name Object name
18 A1 --- n_Name [f] Note on name (2)
19- 23 F5.1 km/s Vel C2 or CH+ velocity
25- 27 F3.1 km/s e_Vel rms uncertainty on Vel
29- 32 F4.1 km/s Vexp1 C2 or CH+ Vexp (+/-2.0) (3)
34- 36 I3 K Trot1 C2 or CH+ rotational temperature
38- 39 I2 K e_Trot1 rms uncertainty on Trot1
41- 45 F5.2 cm-2 logNmol1 C2 or CH+ column density (+/-0.10)
47- 51 F5.2 cm-2 logNmolSum C2 or CH+ column density sum over J''
or N'' levels of observed transitions
54- 57 F4.1 solMass/yr log(dM/dt)1 ? C2 Mass loss rate
59- 63 F5.1 km/s V(CN) ? CN velocity
65- 67 F3.1 km/s e_V(CN) ? rms uncertainty on V(CN)
69- 72 F4.1 km/s Vexp2 ? CN Vexp (+/-2.0) (3)
74- 75 I2 K Trot2 ? CN rotational temperature
77- 78 I2 K e_Trot2 ? rms uncertainty on Trot2
80- 84 F5.2 cm-2 logNmol2 ? CN column density (+/-0.10)
86- 89 F4.1 solMass/yr log(dM/dt)2 ? CN Mass loss rate
91- 94 F4.1 km/s Dv ? v(CN) - V(C2) (4)
96- 98 F3.1 km/s e_Dv ? rms uncertainty on Dv
100-103 F4.1 --- N(CN)/N(C2) ? CN/C2 abundance ratio
105-106 I2 --- 12C/13C ? Upper limit (=>) for ^12^C/^13^C ratio
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Note (1): 1: C_2_ A^1^PI_u_ - X^1^SIGMA^+^_g_ (3,0) or (2,0)
(C2 (2,0) for IRC +10216, else C2 (3,0))
and CN A^2^PI - X^2^SIGMA^+^ (2,0) or (3,0)
(CN (2,0) for IRAS 08005-2356, HD 235858, and IRC +10216,
else CN (3,0))
2: CH^+^ A^1^PI - X^1^SIGMA^+^ (0,0)
Note (2): the emission line spectrum has been analyzed with A^1^{PI} J'=0 as
energy zero level. v_exp_ and T_rot_ are real, but the column density
of HD 44179 is rather meaningless
Note (3): v_exp_=v_sys_-v_(Element) (Element = C_2_, CN or CH^+^)
Note (4): {delta}v= v_CN_-v_C_2__
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Byte-by-byte Description of file: tablea1
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Bytes Format Units Label Explanations
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1- 2 I2 --- B Branch identification code (1)
4- 5 I2 --- J" Rotational quantum number, total angular
momentum including spin (Herzberg 1950)
7- 14 F8.3 0.1nm Lambda Laboratory wavelength of transition in air
16- 23 E8.2 --- f(J'J") Oscillator strength
25- 29 F5.1 0.1pm EW ? Equivalent width
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Note (1): Branch identification: -1: P branch ({DELTA}(J)=-1=J'-J")
0: Q branch ({DELTA}(J)=0=J'-J")
1: R branch ({DELTA}(J)=1=J'-J")
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Byte-by-byte Description of file: tablea2
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Bytes Format Units Label Explanations
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1- 2 I2 --- B Branch identification code (1)
4- 5 I2 --- J" Rotational quantum number, total angular
momentum including spin (Herzberg 1950)
7- 14 F8.3 0.1nm Lambda Laboratory wavelength of transition in air
16- 23 E8.2 --- f(J'J") Oscillator strength
25- 28 F4.1 0.1pm EW(042) ? Equivalent width of IRAS 04296+3429
30- 33 F4.1 0.1pm EW(051) ? Equivalent width of IRAS 05113+1347
35- 38 F4.1 0.1pm EW(053) ? Equivalent width of IRAS 05341+0852
40- 43 F4.1 0.1pm EW(561) ? Equivalent width of HD 56126
45- 49 F5.1 0.1pm EW(080) ? Equivalent width of IRAS 08005-2356
51- 54 F4.1 0.1pm EW(102) ? Equivalent width of IRC +10216
56- 59 F4.1 0.1pm EW(200) ? Equivalent width of IRAS 20000+3239
61- 65 F5.1 0.1pm EW(268) ? Equivalent width of AFGL 2688
67- 70 F4.1 0.1pm EW(222) ? Equivalent width of IRAS 22223+4327
72- 75 F4.1 0.1pm EW(235) ? Equivalent width of HD 235858
77- 80 F4.1 0.1pm EW(233) ? Equivalent width of IRAS 23304+6147
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Note (1): Branch identification: -1: P branch ({DELTA}(J)=-1=J'-J")
0: Q branch ({DELTA}(J)=0=J'-J")
1: R branch ({DELTA}(J)=1=J'-J")
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Byte-by-byte Description of file: tablea3
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Bytes Format Units Label Explanations
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1- 2 I2 --- B Branch identification code (1)
4- 6 F3.1 --- J" Rotational quantum number, total angular
momentum including spin (Herzberg 1950)
8 I1 --- N" Rotational quantum number, total angular
momentum excluding spin (Herzberg 1950) (2)
10- 17 F8.3 0.1nm Lambda Laboratory wavelength of transition in air
19- 26 E8.2 --- f(J'J") Oscillator strength
28- 32 F5.1 0.1pm EW(080) ? Equivalent width of IRAS 08005-2356
34- 37 F4.1 0.1pm EW(102) ? Equivalent width of IRC +10216
39- 42 F4.1 0.1pm EW(235) ? Equivalent width of HD 235858
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Note (1): Branch identification:
1: R1, 2: Q1, 3: P1, 4: ^Q^R12, 5: ^P^Q12, 6: ^O^P12
7: R2. 8: Q2' 9: P2. 10: ^S^R21, 11: ^R^Q21, 12: ^Q^P21
Note (2): For CN: J"=N"-1/2(F2), J"=N"+1/2(F2)
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Byte-by-byte Description of file: tablea4
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Bytes Format Units Label Explanations
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1- 2 I2 --- B Branch identification code (1)
4- 6 F3.1 --- J" Rotational quantum number, total angular
momentum including spin (Herzberg 1950)
8 I1 --- N" Rotational quantum number, total angular
momentum excluding spin (Herzberg 1950) (2)
10- 17 F8.3 0.1nm Lambda Laboratory wavelength of transition in air
19- 26 E8.2 --- f(J'J") Oscillator strength
28- 31 F4.1 0.1pm EW(042) ? Equivalent width of IRAS 04296+3429
33- 37 F5.1 0.1pm EW(051) ? Equivalent width of IRAS 05113+1347
39- 42 F4.1 0.1pm EW(053) ? Equivalent width of IRAS 05341+0852
44- 48 F5.1 0.1pm EW(561) ? Equivalent width of HD 56126
50- 54 F5.1 0.1pm EW(200) ? Equivalent width of IRAS 20000+3239
56- 60 F5.1 0.1pm EW(268) ? Equivalent width of AFGL 2688
62- 66 F5.1 0.1pm EW(222) ? Equivalent width of IRAS 22223+4327
68- 72 F5.1 0.1pm EW(233) ? Equivalent width of IRAS 23304+6147
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Note (1): Branch identification:
1: R1, 2: Q1, 3: P1, 4: ^Q^R12, 5: ^P^Q12, 6: ^O^P12
7: R2. 8: Q2' 9: P2. 10: ^S^R21, 11: ^R^Q21, 12: ^Q^P21
Note (2): For CN: J"=N"-1/2(F2), J"=N"+1/2(F2)
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Byte-by-byte Description of file: tablea5
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Bytes Format Units Label Explanations
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1- 2 I2 --- B Branch identification code (1)
4- 5 I2 --- J" Rotational quantum number, total angular
momentum including spin (Herzberg 1950)
7- 14 F8.3 0.1nm Lambda Laboratory wavelength of transition in air
16- 23 E8.2 --- f(J'J") Oscillator strength (2)
25- 29 F5.1 0.1pm EW(441) ? Equivalent width of HD 44179
31- 34 F4.1 0.1pm EW(213) ? Equivalent width of HD 213985
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Note (1): Branch identification: -1: P branch ({DELTA}(J)=-1=J'-J")
0: Q branch ({DELTA}(J)=0=J'-J")
1: R branch ({DELTA}(J)=1=J'-J")
Note (2): f(J',J")=f_abs_ is the absorption oscillator strength, for emission
g_J'_ f_em_ = g_J"_ f_abs_
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Acknowledgements: Eric J. Bakker <ebakker@viking.as.utexas.edu>
References:
Herzberg 1950, "Molecular spectra and molecular structure I.
Spectra of diatomic molecules", Second edition.
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(End) Patricia Bauer [CDS] 09-Oct-1996