2007ApJ...657.1026W

Query : 2007ApJ...657.1026W

2007ApJ...657.1026W - Astrophys. J., 657, 1026-1036 (2007/March-2)

A Chandra search for coronal X-rays from the cool white dwarf GD 356.

WEISSKOPF M.C., WU K., TRIMBLE V., O'DELL S.L., ELSNER R.F., ZAVLIN V.E. and KOUVELIOTOU C.

Abstract (from CDS):

We report observations with the Chandra X-ray Observatory of the single, cool, magnetic white dwarf GD 356. For consistent comparison with other X-ray observations of single white dwarfs, we also re-analyzed archival ROSAT data for GD 356 (GJ 1205), G99-47 (GR 290 = V1201 Ori), GD 90, G195-19 (EG 250 = GJ 339.1), and WD 2316+123, and archival Chandra data for LHS 1038 (GJ 1004) and GD 358 (V777 Her). Our Chandra observation detected no X-rays from GD 356, setting the most restrictive upper limit to the X-ray luminosity from any cool white dwarf: LX<6.0x1025 ergs/s, at 99.7% confidence, for a 1 keV thermal bremsstrahlung spectrum. The corresponding limit to the electron density is n0<4.4x1011/cm3. Our re-analysis of the archival data confirmed the nondetections reported by the original investigators. We discuss the implications of our and prior observations for models of coronal emission from white dwarfs. For magnetic white dwarfs, we emphasize the more stringent constraints imposed by cyclotron radiation. In addition, we describe (in an Appendix) a statistical methodology for detecting a source and for constraining the strength of a source, which applies even when the number of source or background events is small.

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Journal keyword(s): Methods: Statistical - Radiation Mechanisms: Thermal - Stars: Coronae - Stars: White Dwarfs - X-rays: individual (GD 356)

Nomenclature: Table 3: [WWT2007] GD 356 NN (Nos 1-23). Table 4: [WWT2007] LHS 1036 N (Nos 1-4). Table 5: [WWT2007] GD 358 NN (Nos 1-10).

Simbad objects: 47

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Number of rows : 47
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 KPD 0005+5106 WD* 00 08 18.1703149584 +51 23 16.598370912 11.80 13.04 13.32 13.53   DOZ1 126 0
2 [WWT2007] LHS 1036 1 X 00 12 05.742 +50 28 17.79           ~ 1 0
3 TYC 3255-497-1 SB* 00 12 08.0441863392 +50 30 16.243082604   12.51 11.94 11.77   G2 3 0
4 [WWT2007] LHS 1036 3 X 00 12 10.118 +50 28 30.63           ~ 1 0
5 EGGR 381 WD* 00 12 14.7449947981 +50 25 20.736275736   14.6   14.2   DA7.6 106 0
6 [WWT2007] LHS 1036 4 X 00 12 31.360 +50 32 16.93           ~ 1 0
7 G 35-26 WD* 02 05 49.6964557927 +20 57 07.963899624   17.1   17.4   DAQ3 61 0
8 EGGR 290 WD* 05 56 25.4599888487 +05 21 48.443176471   14.77 14.13 14.00   DA8P 163 0
9 GD 90 WD* 08 19 46.3656877152 +37 31 27.935699988   15.96 15.6     DAP 76 0
10 EGGR 250 WD* 09 15 56.0774298887 +53 25 23.857612513   14.09   14.1   DCP7 157 0
11 [WWT2007] GD 356 1 X 16 40 45.029 +53 44 47.38           ~ 1 0
12 [WWT2007] GD 356 2 X 16 40 45.299 +53 45 13.15           ~ 1 0
13 [WWT2007] GD 356 3 X 16 40 53.706 +53 44 42.50           ~ 1 0
14 [WWT2007] GD 356 4 X 16 40 55.545 +53 40 25.24           ~ 1 0
15 [WWT2007] GD 356 5 X 16 40 56.104 +53 39 18.33           ~ 1 0
16 GD 356 WD* 16 40 57.1485192288 +53 41 09.317032080   15.39   15.1   DAEH6.5 133 0
17 [WWT2007] GD 356 6 X 16 40 59.258 +53 41 59.41           ~ 1 0
18 [WWT2007] GD 356 7 X 16 41 00.438 +53 42 03.31           ~ 1 0
19 [WWT2007] GD 356 8 X 16 41 04.242 +53 40 20.98           ~ 1 0
20 [WWT2007] GD 356 9 X 16 41 05.997 +53 43 18.82           ~ 1 0
21 [WWT2007] GD 356 10 X 16 41 06.757 +53 37 52.85           ~ 1 0
22 SDSS J164107.62+534528.3 QSO 16 41 07.620 +53 45 28.36           ~ 7 0
23 [WWT2007] GD 356 12 X 16 41 10.745 +53 44 36.43           ~ 1 0
24 [WWT2007] GD 356 13 X 16 41 13.050 +53 41 57.24           ~ 1 0
25 [WWT2007] GD 356 14 X 16 41 14.806 +53 41 41.18           ~ 1 0
26 1RXS J164115.9+534411 SB* 16 41 15.4520944920 +53 44 11.049599616     12.281 11.934   dM1.0 21 0
27 [WWT2007] GD 356 16 X 16 41 16.876 +53 42 56.29           ~ 1 0
28 [WWT2007] GD 356 17 X 16 41 19.134 +53 44 11.29           ~ 1 0
29 [WWT2007] GD 356 18 X 16 41 21.033 +53 40 54.25           ~ 1 0
30 [WWT2007] GD 356 19 X 16 41 24.066 +53 41 48.86           ~ 1 0
31 [WWT2007] GD 356 20 X 16 41 30.445 +53 41 18.79           ~ 1 0
32 [WWT2007] GD 356 21 X 16 41 32.519 +53 36 40.09           ~ 1 0
33 [WWT2007] GD 356 22 X 16 41 33.184 +53 43 05.51           ~ 1 0
34 [WWT2007] GD 356 23 X 16 41 37.639 +53 39 57.65           ~ 1 0
35 [WWT2007] GD 358 1 X 16 46 55.620 +32 29 49.17           ~ 1 0
36 [WWT2007] GD 358 2 X 16 46 58.650 +32 29 30.20           ~ 1 0
37 [WWT2007] GD 358 3 X 16 47 07.418 +32 30 50.62           ~ 1 0
38 [WWT2007] GD 358 4 X 16 47 08.044 +32 25 17.23           ~ 1 0
39 [WWT2007] GD 358 5 X 16 47 13.515 +32 32 03.03           ~ 1 0
40 [WWT2007] GD 358 6 X 16 47 17.610 +32 33 15.56           ~ 1 0
41 GD 358 WD* 16 47 18.3925183824 +32 28 32.862804384 12.511 13.530 13.653 13.752 13.852 DB2 364 0
42 [WWT2007] GD 358 7 X 16 47 18.628 +32 27 51.63           ~ 1 0
43 [WWT2007] GD 358 8 X 16 47 18.645 +32 29 16.22           ~ 1 0
44 [WWT2007] GD 358 9 X 16 47 26.652 +32 27 30.17           ~ 1 0
45 [WWT2007] GD 358 10 X 16 47 27.949 +32 27 37.51           ~ 1 0
46 GD 524 WD* 17 28 56.2202490696 +55 58 22.634215356   16.19   15.89   DBQ4 64 0
47 KUV 23162+1220 WD* 23 18 45.1023093816 +12 36 02.772571752   15.54 15.38     DAP4 63 0

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