CDROM/AJ/V106/P0656 Ae/Be Stars (Brooke+ 1993) ================================================================================ Dust Emission Features in 3 micron Spectra of Herbig Ae/Be Stars T. Y. Brooke, A. T. Tokunaga, & S. E. Strom <1993, AJ, 106, 656> =1993AJ....106..656B ================================================================================ 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: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table2.dat 131 39 Summary of 3 micron spectral data of Herbig Ae/Be stars table2a.tex 109 132 LaTeX version of table2.dat, Part A table2b.tex 255 185 LaTeX version of table2.dat, Part B -------------------------------------------------------------------------------- Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1 A1 --- Head *Heading flag 2-13 A12 --- Name Object name 14 1X --- --- Blank 15-19 A5 --- Sp Estimated spectral type 20-21 2X --- --- Blank, except for first object 22-25 F4.2 mag A_V *Estimated visual extinction 26-30 I5 pc Dist Estimated distance 31-36 F6.2 mag V Visual magnitude 37 1X --- --- Blank 38 A1 --- l_W3 [< ] Limiting character for W3 39-42 I4 0.1nm W3 Emission equiv. width of 3.29 micron feature 43-45 I3 0.1nm e_W3 Error in W3, or blank 46 A1 --- l_F3 [< ] Limiting character for F3 47-52 F6.2 10-15W/m2 F3 Observed flux in the 3.29 micron feature 53-57 F5.2 10-15W/m2 e_F3 Error in F3.29 58 1X --- --- Blank 59-61 F3.1 arcsec Rap1 Radius of the aperture, Rap 62-67 I8 AU Rap2 Radius of the aperture, Rap 68 1X --- --- Blank 69 A1 --- l_F3tot Limiting character for F3tot 70-75 F6.2 10-15W/m2 F3tot Est. total flux of the 3.29 micron feature 76 1X --- --- Blank 77 A1 --- l_Rext1 Limiting character for Rext 78-81 F4.2 arcsec Rext1 *Radius for significantly extended feature 82-87 I6 AU Rext2 *Radius for significantly extended feature 88 1X --- --- Blank 89 A1 --- l_RF1 Limiting character for RF1 90-94 F5.2 10-4 RF1 *Ratio of total F3 to F_UV 95 1X --- --- Blank 96 A1 --- l_Aro1 Limiting character for Aro1 97-104 F8.3 100AU2 Aro1 *Est. relative numbers of aromatics 105-108 F4.1 100AU2 Aro2 *High end of range of numbers of aromatics 109-114 F6.1 10-13W/m2 FIR *Integrated far-infrared flux 115 1X --- --- Blank 116 A1 --- l_RF2 Limiting character, '<', '>', or blank 117-123 F7.5 --- RF2 Estimate of relative abundance of aromatics 124 1X --- --- Blank 125-129 5A1 --- Ref *[A-P] Reference flags 130 1X --- --- Blank 131 A1 --- Note *[a-h] Note flag -------------------------------------------------------------------------------- Notes for file: table2.dat -------------------------------------------------------------------------------- Head: Heading flag; when an asterisk, '*', appears the remainder of the record is a heading describing the nature of the data records following A_V: Estimated visual extinction. For Elias 1, this was given as a range (6-10). The characters '6-' were moved to bytes 20-21, and a decimal point was affixed to the '10', making the field readable with the format F4.2. Rext1: Radius over which the feature is or is not significantly extended. If this field is blank, Rext2 contains estimated values in AU (see text of printed paper). Rext2: Radius over which the feature is or is not significantly extended. If Rext1 is blank, this is an estimated value RF1: Ratio of total flux in the 3.29 micron feature to the integrated ultraviolet flux of the star after correction for extinction Aro1: Estimate of relative numbers of aromatics in optically thin limit (see text of printed paper) Aro2: High end of range of numbers of aromatics, for one object only, HD 97048 FIR: Integrated far-infrared flux estimated from blackbody fits (times 1/lambda = emissivity) to far-infrared photometry (see text) Ref: 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: 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 %. -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 15-Mar-1995