2001A&A...366..241Z


C.D.S. - SIMBAD4 rel 1.7 - 2020.10.24CEST18:09:19

2001A&A...366..241Z - Astronomy and Astrophysics, volume 366, 241-253 (2001/1-4)

Infrared spectral classification of OB stars with ISO-SWS.

ZAAL P.A., DE KOTER A. and WATERS L.B.F.M.

Abstract (from CDS):

We present observations of the Brα, Brβ and Pfα lines of 16 dwarf and (sub)giant stars in the spectral range O9-B3. The observations were done using the Short Wavelength Spectrometer on board the Infrared Space Observatory, and have a signal-to-noise of ∼20 to >150 and a resolving power varying from ∼1400 to 2100. We compare the equivalent widths of these lines with predictions using non-LTE model atmospheres to investigate to what extent these infrared lines can be used to derive effective temperatures. We find that Pfα is a sensitive Teff diagnostic for the range of spectral types investigated, and Brα for types O9-B2, yielding agreement with optical results to within 1-4kK or one-three spectral sub-types. We find evidence for a gradient in the turbulent velocity, increasing from ≲5km/s for the atmospheric region in which Brα is formed to ∼15km/s for the regime where Pfα originates. When this gradient in turbulent velocity is taken into account, the accuracy of the spectral type calibration is improved to ∼1kK or one spectral sub-type. The gravity dependence of the strengths of the investigated infrared lines is relatively weak, and could not be used to constrain luminosity class. This failure is in part a result of the modest S/N and resolution and in part a result of a cancelation of gravity effects in the line core and line wing. Our line predictions show that He I λ 2.058 is relatively unsuited for spectral classification of O9-B3 stars. Huα, however, is expected to be an even better diagnostic as are Pfα and Brα. This line may be observed with the VLT Imager and Spectrometer for mid InfraRed when it is installed on the Very Large Telescope.

Abstract Copyright:

Journal keyword(s): line: formation - radiative transfer - stars: atmospheres - stars: early-type - stars: fundamental parameters - infrared: stars

Simbad objects: 18

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Number of rows : 18

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 * gam Peg bC* 00 13 14.1512308 +15 11 00.936759 1.75 2.61 2.84 2.94 3.13 B2IV 661 0
2 HD 4730 PM* 00 49 25.6168536570 -13 33 40.568683716   6.925 5.594     K3III 49 0
3 * tet Car SB* 10 42 57.4019674 -64 23 40.020796 1.53 2.54 2.76 2.87 3.10 B0Vp 314 0
4 * bet Cru bC* 12 47 43.26877 -59 41 19.5792 0.03 1.02 1.25 1.38 1.64 B1IV 324 0
5 * alf Vir bC* 13 25 11.57937 -11 09 40.7501 -0.20 0.74 0.97 1.06 1.30 B1V 824 2
6 * eps Cen bC* 13 39 53.25774 -53 27 59.0081 1.16 2.08 2.30 2.45 2.70 B1III 239 0
7 * bet Cen bC* 14 03 49.40535 -60 22 22.9266     0.58     B1III 346 0
8 * alf Lup bC* 14 41 55.7557866 -47 23 17.515486 1.22 2.126 2.286     B1.5III 225 0
9 * del Cir SB* 15 16 56.8969460249 -60 57 26.100998940 4.11 5.03 5.09 6.68   O8V 148 0
10 * bet Lib PM* 15 17 00.41382 -09 22 58.4919 2.14 2.51 2.62 2.67 2.76 B8Vn 258 0
11 * del Sco SB* 16 00 20.00528 -22 37 18.1431 1.30 2.20 2.32 2.36 2.49 B0.3IV 697 0
12 * tau Sco * 16 35 52.9528530 -28 12 57.661515 1.55 2.56 2.81 2.93 3.18 B0.2V 861 0
13 * zet Dra ** 17 08 47.1959624 +65 42 52.863384 2.63 3.06 3.17 3.23 3.35 B6III 211 0
14 * tet Oph bC* 17 22 00.5793468 -24 59 58.366974 2.18 3.03 3.26 3.38 3.58 OB 316 0
15 * iot Her bC* 17 39 27.8860861 +46 00 22.800110 2.940 3.630 3.800     B3IV 431 1
16 * kap Sco bC* 17 42 29.27520 -39 01 47.9391 1.32 2.211 2.386     B1.5III 228 0
17 * alf Pav SB* 20 25 38.85705 -56 44 06.3230 1.03 1.791 1.918     B2IV 273 0
18 * 10 Lac ** 22 39 15.6786372 +39 03 00.971152 3.650 4.670 4.880 4.98 5.19 O9V 720 0

    Equat.    Gal    SGal    Ecl

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2020.10.24-18:09:19

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