J/AJ/106/656 Herbig Ae/Be stars (Brooke+, 1993)
Dust emission features in 3 micron spectra of Herbig Ae/Be stars
BROOKE T.Y., TOKUNAGA A.T., STROM S.E.
<Astron. J. 106, 656 (1993)>
=1993AJ....106..656B 1993AJ....106..656B (SIMBAD/NED Reference)
Abstract:
Low and medium resolution spectra in the 3 micron region were obtained
of 24 Herbig Ae/Be stars in a search for organic features from the dust
around young stars. The 3.29 micron emission feature from aromatic
hydrocarbons was detected for the first time in three objects, Lk
Halpha 25, XY Per, and AS 310. The width of the feature on Lk Halpha
25 and XY Per corresponds to the narrow profile characteristic of
material close to other young stellar objects. Two other stars, HD
245185 and HK Ori may have weak features. About 20% of the Herbig
Ae/Be stars surveyed to date have firmly detected 3.29 micron features.
Among these stars, the feature-to-continuum contrast varies over a wide
range; emission equivalent widths vary by a factor ∼20. The available
data indicate that the 3.29 micron feature is more extended around
Herbig Ae/Be stars of earlier spectral type, possibly due to
dehydrogenization or destruction of the aromatics near these stars.
Interpretation of the spectra in the optically thin limit suggests that
the total number of aromatics excited by the stars is also greater
around the earlier-type objects. The ratio of 3.29 micron feature
flux to far-infrared flux, which is a measure of the abundance of
aromatics relative to larger grains, shows less variation; however,
there may be real abundance differences in some of the stars surveyed.
If the small grains around Herbig Ae/Be stars have spectral properties
like those seen in reflection nebulas, then they play a significant
role in the total energy balance of these objects; they can radiate
between 7% and 60% of the far-infrared luminosity. No other Herbig
Ae/Be stars observed to date have the strong 3.42 and 3.53 micron
features seen in Elias 1 and HD 97048.
File Summary:
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File Name Lrecl Records Explanations
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ReadMe 80 . This file
table2 133 33 Summary of 3 µm spectral data of
Herbig Ae/Be stars
table2a.tex 109 132 LaTeX version of table2 (left side)
table2b.tex 255 185 LaTeX version of table2 (right side)
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Byte-by-byte Description of file: table2
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Bytes Format Units Label Explanations
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1 A1 --- Note Nature of the data (1)
3- 14 A12 --- Name Object name
16- 20 A5 --- Sp Estimated spectral type
21- 22 A2 --- n_Av For Elias 1, the visual extinction is given
as a range (6-10). n_Av contains '6-'
23- 27 F5.2 mag Av Estimated visual extinction.
For Elias 1, see n_Av
29- 32 I4 pc Dist Estimated distance
34- 38 F5.2 mag Vmag Visual magnitude
40 A1 --- l_W3.29 Limit flag on W3.29
41- 44 I4 0.1nm W3.29 []? Emission equivalent width of the 3.29
micron feature, W3.29
46- 47 I2 0.1nm e_W3.29 []? rms uncertainty on W3.29
48 A1 --- l_F3.29Obs Limit flag on F3.29Obs
49- 54 F6.2 10-15W/m2 F3.29Obs []? Observed flux in the 3.29 micron
feature, F3.29
56- 59 F4.2 10-15W/m2 e_F3.29Obs []? rms uncertainty on F3.29
61- 63 F3.1 arcsec Rap1 []? Radius of the aperture, Rap, in arcsec
65- 69 I5 AU Rap2 []? Radius of the aperture, Rap, in AU
71 A1 --- l_F3.29Tot Limit flag on F3.29Tot
72- 77 F6.2 10-15W/m2 F3.29Tot []? Estimated total flux of the 3.29 micron
feature, F3.29(tot)
79 A1 --- l_Rext1 Limit flag on Rext
80- 83 F4.1 arcsec Rext1 []? Radius over which the feature is or is
not significantly extended. If this field
is blank, bytes 85-89 contain estimated
values in AU (see text of printed paper).
85- 89 I5 AU Rext2 Radius over which the feature is or is not
significantly extended. If bytes 79-82 are
blank, this is an estimated values.
91 A1 --- l_R3.29 Limit flag on R3.29
92- 96 F5.2 10-4 R3.29 []? Ratio of total flux in the 3.29 micron
feature to the integrated ultraviolet flux
of the star after correction for extinction
98 A1 --- l_Narom Limit flag on Narom
99-106 F8.3 10+2AU+2 Narom []? Estimate of relative numbers of
aromatics in optically thin limit
(see text)
107-110 F4.1 10+2AU+2 Harom []? High end of range of numbers of
aromatics, for one object only, HD 97048
111-116 F6.1 10-13W/m2 Ffir []? Integrated far-infrared flux estimated
from blackbody fits
(times 1/lambda = emissivity)
to far-infrared photometry (see text)
118 A1 --- l_Aarom Limit flag on Aarom
119-125 F7.5 --- Aarom []? Estimate of relative abundance of
aromatics (see text)
127-131 A5 --- Ref Reference flags (A-P) (2)
133 A1 --- Note Note flag (a-h) (3)
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Note (1): Nature of the data
1 = 3.29 m feature
2 = 3.29 m feature in reflection nebula
3 = Possible 3.29 m feature
4 = No 3.29 m feature detected but IRAS LRS 7.7 and 11.3 micron features
5 = No 3 m spectra but IRAS LRS 7.7 and 11.3 micron features
6 = No 3.29 m feature detected (this work)
Note (2): References
A) Aitken and Roche 1981, MNRAS, 196, 39
B) Allen et al. 1982, MNRAS, 199, 1017
C) Baas et al. 1983, ApJ, 265, 290
D) Chen and Graham 1993, ApJ (in press)
E) Cohen 1975, MNRAS, 173, 279
F) Jourdain de Muizon et al. 1990b, A&A, 227, 526
G) Sato et al. 1990, ApJ, 359, 192
H) Schutte et al. 1990, ApJ, 360, 577
I) Sellgren 1984, ApJ, 277, 623
J) Tokunaga et al. 1991, ApJ, 380, 452
K) van Citters and Smith 1989, AJ, 98, 1382
L) Whittet et al. 1983, A&A, 123, 301 (see also Blades and Whittet 1980,
MNRAS, 191, 701, for HD 97048);
M) Whittet et al. 1984, MNRAS, 211, 29
N) This work, Cooled Grating Array Spectrometer (CGAS) A
O) This work, CGAS B
P) This work, CGS4 Spectrometer
Note (3):
a) Feature flux from Schutte et al. 1990, ApJ, 360, 577
b) Feature flux from Jourdain de Muizon et al. 1990b, A&A, 227, 526
c) Feature flux from Whittet et al. 1983, A&A, 123, 301
d) Total 3.29 m feature flux estimated from 11.3 m feature (see text).
e) Upper limit from Sellgren 1984, ApJ, 277, 623; total feature flux from
Sellgren et al. 1985, ApJ, 299, 416
f) Measured flux lower than L(3.45 micron) photometry in
Hillenbrand et al. 1992, ApJ, 397, 613, by 35 %.
g) Measured flux lower than L(3.45 micron) photometry by 50 %.
h) Measured flux higher than L(3.45 micron) photometry by 60 %.
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Other Non-detections:
V376 Cas (L), RR Tau (B), VY Mon (E), Z CMa (B), HD 53367 (B), KK Oph (B),
V856 Sco (L), MWC 297 (BE), R CrA (DL), T CrA (D), PV Cep (GK).
Origin: AAS CD-ROM series, Volume 1, 1993
(End) Patricia Bauer [CDS] 25-Jul-1994