2022A&A...657A.105B


Query : 2022A&A...657A.105B

2022A&A...657A.105B - Astronomy and Astrophysics, volume 657A, 105-105 (2022/1-1)

Highly sensitive search for magnetic fields in white dwarfs using broad-band circular polarimetry.

BERDYUGIN A.V., PIIROLA V., BAGNULO S., LANDSTREET J.D. and BERDYUGINA S.V.

Abstract (from CDS):

Circular polarisation measurements of white dwarfs of various ages and spectral types are useful to understand the origin and evolution of the magnetic field in degenerate stars. In the latest stages of white dwarf evolution, when stars are so cool that spectral lines are no longer formed in the normal H- or He-dominated atmospheres, magnetic fields can be probed only by means of circular polarimetry of the continuum. The study of the fields of featureless DC white dwarfs may reveal whether Ohmic decay acts on magnetic white dwarfs, or if magnetic fields continue to be generated even several billion years after white dwarf formation. Compared to spectropolarimetry, broad-band circular polarisation measurements have the advantage of reaching a higher accuracy in the continuum, with the potential of detecting magnetic fields as weak as a fraction of a MG in DC stars, if the telescope size is adequate for the star's magnitude. Here we present the results of a first (short) observing campaign with the DIPol-UF polarimeter, which we have used to measure broad-band circular polarisation of white dwarfs. Our observing run was in part aimed to fully characterise the instrument, and in part to study the relationship between magnetic field strength (when known from spectropolarimetry) and circular polarisation of the continuum. We also observed a small number of previously unexplored DC white dwarfs, and we present the discovery of two new magnetic white dwarfs of spectral class DC, probably the first discovery of this kind made with broad-band circular polarimetric techniques since the late 1970s. We also discuss the characteristics of our instrument, and predict the level of polarimetric accuracy that may be reached as a function of stellar magnitude, exposure time, and telescope size.

Abstract Copyright: © ESO 2022

Journal keyword(s): white dwarfs - stars: magnetic field - polarization

Simbad objects: 26

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Number of rows : 26
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 LP 464-57 WD* 00 07 20.5491513439 +12 30 21.160516000   16.8   15.9   DC 16 0
2 EGGR 290 WD* 05 56 25.4599888487 +05 21 48.443176471   14.77 14.13 14.00   DA8P 149 0
3 SCR J0708-6706 WD* 07 08 52.2811191720 -67 06 31.425046740   17.03   15.82 15.26 DC 15 0
4 GD 90 WD* 08 19 46.3656877152 +37 31 27.935699988   15.96 15.6     DAP 69 0
5 SCR J1118-4721 WD* 11 18 27.1995687257 -47 21 56.961738150   16.37   15.62 15.18 DC 15 0
6 EGGR 436 WD* 13 08 41.1944602216 +85 02 28.161666517   16.76   15.9   DA9P 48 0
7 HD 115043 PM* 13 13 37.0081725552 +56 42 29.759356008   7.423 6.813     G1Va 250 0
8 PG 1350-090 WD* 13 53 15.5345099352 -09 16 33.374583634   14.81 14.60     DAP5.3 41 1
9 HD 122676 SB* 14 02 56.8651424280 +14 58 31.244092716 8.150 7.860 7.140     G7V 54 0
10 HD 124694 PM* 14 13 51.3265850640 +46 19 30.600533604   7.703 7.160     F8V 52 0
11 GD 175 WD* 15 05 49.3110602616 -07 14 40.952601852   16.27 15.89     DAH7.3 32 0
12 PM J15589+0417 WD* 15 58 57.6955404096 +04 17 05.153280504   16.53 16.16     DC 14 1
13 V* DN Dra WD* 16 48 25.6318375106 +59 03 22.658985521   12.34 12.17 12.44   DA4.0 208 0
14 PG 1658+441 WD* 16 59 48.4241073768 +44 01 04.038522204   14.3 14.6     DAP1.6 140 0
15 EGGR 372 WD* 17 48 07.9928195849 +70 52 35.922050086       13.5   DQ9P 133 0
16 G 184-12 WD* 18 33 58.3489454747 +19 45 52.991579006   16.71   16.0   DQ6 28 0
17 LP 141-14 WD* 18 57 39.3436703328 +53 30 33.301040904   17.6   16.4   DC 41 0
18 LAWD 73 WD* 19 00 10.2533239461 +70 39 51.416733790   13.24   13.5   DAP4.5 237 0
19 LAWD 79 WD* 19 56 29.2263375910 -01 02 32.671070269   13.89 13.56 13.73   DA6.4 133 0
20 G 24-9 WD* 20 13 55.6788159161 +06 42 44.827736377 15.733 16.176 15.751 15.476 15.248 DC7 93 0
21 HD 340611 WD* 20 34 21.8847019255 +25 03 49.750446346 10.687 11.471 11.546 11.648 11.728 DA2.4 304 0
22 UCAC4 325-215293 WD? 20 52 13.4078824896 -25 04 15.129319908           ~ 5 0
23 LP 872-48 WD* 20 52 16.8416391600 -22 06 33.421405608 14.57 15.17 15.00     DC 14 0
24 EGGR 378 WD* 21 18 56.2636115928 +54 12 41.243943888 11.76     12.9   DA3.4 95 1
25 HD 211476 PM* 22 17 15.1410212093 +12 53 54.566432145   7.64   6.7   G2 99 0
26 G 28-27 WD* 22 57 26.1169629840 +07 55 42.593636856   17.20   17.0   DAH 34 0

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2023.01.31-01:35:55

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