2014A&A...572A.113L


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.08CEST02:51:42

2014A&A...572A.113L - Astronomy and Astrophysics, volume 572A, 113-113 (2014/12-1)

On the consistency of magnetic field measurements of Ap stars: lessons learned from the FORS1 archive.

LANDSTREET J.D., BAGNULO S. and FOSSATI L.

Abstract (from CDS):

The ESO archive of FORS1 spectropolarimetric observations may be used to create a homogeneous database of magnetic field measurements. However, no systematic comparison of FORS field measurements to those obtained with other instruments has been undertaken so far. We exploit the FORS archive of circular spectropolarimetric data to examine in a general way how reliable and accurate field detections obtained with FORS are. We examine the observations of Ap and Bp stars, on the grounds that almost all of the unambiguous detections of magnetic fields in the FORS1 archive are in these kinds of stars. We assess the overall quality of the FORS1 magnetic data by examining the consistency of field detections with what is known from previous measurements obtained with other instruments, and we look at patterns of internal consistency. FORS1 magnetic measurements are fully consistent with those made with other instruments, and the internal consistency of the data is excellent. However, it is important to recognise that each choice of grism and wavelength window constitutes a distinct instrumental measuring system, and that simultaneous field measurements in different instrumental systems may produce field strength values that differ up to 20%, or more. Furthermore, we found that field measurements using hydrogen lines only yield results that meaningfully reflect the field strength as sampled specifically by lines of hydrogen for stars with effective temperatures above about 9000 K. In general the magnetic field measurements of Ap and Bp stars obtained with FORS1 are of excellent quality, accuracy and precision, and FORS1 provides an extremely useful example that offers valuable lessons for field measurements with other low-resolution Cassegrain spectropolarimeters.

Abstract Copyright:

Journal keyword(s): catalogs - stars: magnetic field - polarization - techniques: polarimetric

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 V* V1356 Ori a2* 06 08 24.1250668905 +13 56 47.875162985   10.0 10.855 10.76   A0V 39 0
2 * ksi01 CMa bC* 06 31 51.3663578 -23 25 06.318090 3.10 4.09 4.33 4.45 4.72 B0.7IV 298 0
3 NGC 2244 334 * 06 32 51.7917882037 +04 47 16.158756729 13.17 13.38 12.95 12.46 12.34 ~ 32 0
4 HD 49299 a2* 06 46 56.6072687501 -20 39 07.064045643   10.22 10.20     ApSi 40 0
5 HD 66318 * 07 59 27.4746869367 -60 47 47.109578700   9.69 9.56   9.555 A0pEuCrSr 84 0
6 * 53 Cam a2* 08 01 42.4313674994 +60 19 27.801603076   6.177 6.008     A3VpSrSiCrEu 379 0
7 HD 75049 a2* 08 45 33.0714392916 -50 43 58.322487233   9.09 9.14     ApEuCr 26 0
8 HD 83368 a2* 09 36 25.40686 -48 45 04.2549   6.480 6.232     A8VSrCrEu+F9V 256 0
9 V* KQ Vel a2* 10 55 01.0018015910 -42 15 04.062281118 5.78 6.03 6.11     Ap(SiCr) 117 0
10 V* V816 Cen dS* 11 37 37.0411005456 -46 42 34.875395453 8.99 8.79 8.03     F8/G0p 288 0
11 * alf02 CVn a2* 12 56 01.6662171 +38 19 06.154110 2.44 2.76 2.88 2.98 3.05 A0VpSiEu 640 0
12 * 33 Lib a2* 15 29 34.7422042673 -17 26 27.375775287 7.22 7.07 6.69     F0VspEuGdSr 234 0
13 HD 148937 SB* 16 33 52.3867163783 -48 06 40.476619334 6.49 7.12 6.71 7.61   O6f?p 355 4
14 HD 154708 a2* 17 10 28.5160730229 -58 00 17.417264870   9.23 8.76     ApSrEu 69 0
15 V* V970 Sco a2* 17 39 41.2403913936 -32 17 57.534800537   9.38 9.34     ~ 52 0
16 V* V1291 Aql a2* 19 53 18.7357390150 -03 06 52.065320660   5.837 5.619     F0VpSrCrEu 257 0
17 * gam Equ a2* 21 10 20.5001160337 +10 07 53.682085548 5.03 4.94 4.68 4.43 4.32 A9VpSrCrEu 513 0
18 HD 210601 PM* 22 12 36.0031517106 -48 45 47.159095456   8.39 7.91     F6V 17 0

    Equat.    Gal    SGal    Ecl

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2020.07.08-02:51:42

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