# 2000A&AS..147..299G

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 Query : 2000A&AS..147..299G

2000A&AS..147..299G - Astron. Astrophys., Suppl. Ser., 147, 299-321 (2000/December-1)

Accuracy of radial-velocity measurements for early-type stars. II. Investigations of spectrum mismatch from high-resolution observations.

GRIFFIN R.E.M., DAVID M. and VERSCHUEREN W.

Abstract (from CDS):

The accuracy with which radial velocities of early-type stars can be measured is limited in practice by the existence of asymmetrical differences between object and template spectrum, constituting spectrum mismatch''. Our studies of the magnitude of spectrum-mismatch errors, commenced in Paper I (Verschueren et al., 1999A&AS..136..591V) on the basis of synthetic spectra having different attributes of effective temperature (Teff) and logg, are continued here in a complementary approach that employs observed spectra. From over 60 de-archived observations we derive accurate wavelength scales for the spectra of 16 dwarfs of spectral types B8-F7, and examine the results of cross-correlating the spectra against different (observed) template spectra. We also test the effects of (a) truncating the spectra at different levels below the continuum, (b) adding rotational broadening to enforce a visual match of line-width between object and template, (c) applying rotational broadening to exacerbate a rotational mismatch, and (d) neglecting the presence of faint companion spectra. We also cross-correlate pairs of spectra such that the differences between their Teff are minimal. We conclude that it will be possible to measure radial velocities to an accuracy considerably better than 1km/s for slowly-rotating stars in the range of spectral types examined, and a careful discussion of the nature and sources of the random and systematic errors that become significant in work of this nature enables us to specify conditions that are important for achieving such accuracy routinely. We find that both rotational broadening, and the star-to-star variations in line strengths that are so prevelant among A-type spectra, can give rise to more deleterious mismatch shifts (RV errors) than do differences in Teff alone, even for ΔTeff as great as 300-400K. By intercomparing the results given by wide regions of spectrum (∼800Å) with those obtained by isolating small groups of features in very narrow windows (∼30Å), we have been able to designate a window near λ4570Å that should be particularly reliable for high-accuracy results, and we propose further studies at very high S/N ratio in that specific window to complement and extend the results of the present paper.

Journal keyword(s): techniques: radial velocities - techniques: spectroscopic - stars: early-type

Full paper

 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 - 2022
#notes
1 HD 2421 SB* 00 28 13.6693451904 +44 23 40.089451956   5.207 5.173     A2Vs 80 0
2 * 64 Ori SB* 06 03 27.3639419184 +19 41 26.026161180   5.021 5.130     B8V 117 0
3 * gam Gem SB* 06 37 42.71050 +16 23 57.4095 1.98 1.92 1.92 1.86 1.87 A1.5IV+ 496 0
4 * alf CMa SB* 06 45 08.91728 -16 42 58.0171 -1.51 -1.46 -1.46 -1.46 -1.43 A0mA1Va 1474 0
5 * alf CMi SB* 07 39 18.11950 +05 13 29.9552 0.82 0.79 0.37 -0.05 -0.28 F5IV-V+DQZ 1825 0
6 * b Leo Pe* 11 02 19.7757690 +20 10 47.426510   4.452 4.398     kA1VmA3V 174 0
7 * o Leo SB* 11 55 40.5327230688 +15 38 48.549860664   5.632 5.522     A3V 156 0
8 * phi Her a2* 16 08 46.1762180496 +44 56 05.661355344 3.92 4.20 4.27 4.27 4.36 B9VspHgMn 289 1
9 * alf Lyr dS* 18 36 56.33635 +38 47 01.2802 0.03 0.03 0.03 0.07 0.10 A0Va 2600 0
10 HD 177390 SB* 19 02 10.2108646680 +47 17 14.455917060   7.76 7.45     A0 20 0
11 * 14 Sge SB* 20 03 30.0147595968 +16 01 52.508306604 5.39 5.550 5.658     B9pHgMn 131 0
12 * bet02 Cap ** 20 20 46.5478935096 -14 47 05.603724348   6.08 6.10     B9/A0III/IV 137 0
13 * 14 Del SB* 20 49 48.2603242128 +07 51 51.072639732   6.329 6.318     A1Vs 53 0
14 HD 201433 ** 21 08 38.88977 +30 12 20.2935           ~ 91 0
15 * 21 Peg * 22 03 19.0326115488 +11 23 11.574375540   5.762 5.822     B9.5V 140 0
16 * 32 Aqr SB* 22 04 47.4224193480 -00 54 22.839762708   5.519 5.271     A5IV 175 0
17 * omi Peg * 22 41 45.4041684504 +29 18 27.631023336 4.77 4.78 4.79 4.75 4.77 A1IV 276 0
18 * iot Psc PM* 23 39 57.0413764 +05 37 34.647529 4.640 4.620 4.120 3.68 3.37 F7V 599 0

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2022.08.09-19:42:38