2008A&A...490..707W


Query : 2008A&A...490..707W

2008A&A...490..707W - Astronomy and Astrophysics, volume 490, 707-714 (2008/11-1)

OVI in the local interstellar medium: FUSE observations towards B-stars within 200 pc.

WELSH B.Y. and LALLEMENT R.

Abstract (from CDS):

We present far ultraviolet (FUV: 990-1082Å) spectroscopic observations of 17 early-type stars located within 200 pc of the Sun using the NASA FUSE satellite in order to search for interstellar absorption from the important high ion of OVI (1032Å). These spectral data were fit with a local stellar continuum such that measurement of, or upper limits to, the equivalent width of the OVI absorption line could be made. The resultant line profiles were then fit with an absorption model to determine the OVI column density along each sight-line. OVI was detected towards 5 of the 17 targets, all towards stars with distances >80pc. The average volumic density, nOVI, along these 5 sight-lines was found to be 5.2x10–8cm–3. This value, in agreement with measurements of OVI in the local interstellar medium (ISM) by other authors, is measurably higher than that typically found throughout the general ISM. The location of these 5 stars places them just within, or just at, the neutral boundary to the Local Cavity. If this cavity contains a hot million degree K gas, then it seems likely that the presently observed OVI absorption is formed in conductive interfaces within a transition layer between hot and cooler gas. We provide tentative evidence that the spatial distribution of OVI absorbers and emitters exhibits a loose correlation with that of the million degree K soft X-ray background (SXRB) emission at galactic latitudes of +30°<b←30°. In such a scenario very little SXRB emission is required in the galactic plane, in agreement with current theoretical models that invoke solar wind charge exchange as the origin for the majority of this background signal. Alternately, if the Local Cavity is an old SNR of age ∼3 million yr, it is possible that the central regions may no longer contain soft X-ray emitting gas, with appreciable amounts of OVI ions lying within warm (T∼106K) gas at the periphery of the bubble cavity.

Abstract Copyright:

Journal keyword(s): Galaxy: solar neighborhood - ISM: atoms - ultraviolet: ISM

Simbad objects: 21

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Number of rows : 21
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 * 34 Psc * 00 10 02.2030016064 +11 08 44.936910060   5.456 5.530   5.58 B9Vn 132 0
2 * 34 Psc B * 00 10 02.3863375176 +11 08 37.821568416     10.37     G5Ve 100 0
3 * alf Eri Be* 01 37 42.84548 -57 14 12.3101 -0.36 0.30 0.46 0.49 0.60 B6Vpe 464 0
4 HD 20863 * 03 23 47.3303869752 +48 36 15.892890228   7.00 6.99     B9V 57 0
5 HD 26670 * 04 16 53.5560892104 +61 50 59.967116520 5.05 5.56 5.70     B7V 52 0
6 * eta Cha * 08 41 19.5125857944 -78 57 48.105898056 5.02 5.351 5.453     B8V 225 0
7 * f Car Be* 08 46 42.5492831 -56 46 11.192208 3.58 4.31 4.49 4.59 4.78 B3V(n) 140 0
8 HD 74604 * 08 48 49.2514876608 +66 42 29.087293572   6.078 6.187     B7III 47 0
9 * del Ant * 10 29 35.3788231536 -30 36 25.434381816 5.34 5.52 5.56     B9/9.5V 56 0
10 V* FH Mus El* 12 39 55.8519065736 -66 30 40.090934880   6.199 6.252     B8V 54 0
11 * alf Vir bC* 13 25 11.57937 -11 09 40.7501 -0.20 0.74 0.97 1.06 1.30 B1V 848 2
12 HD 124367 Be* 14 14 57.1383087504 -57 05 10.049405532 4.36 4.99 5.07     B4Vne 139 0
13 * alf CrB EB* 15 34 41.26800 +26 42 52.8940 2.19 2.22 2.24 2.21 2.25 A1IV 471 0
14 HD 148594 * 16 30 15.6761762712 -27 54 58.506303852   6.964 6.892     B8V 58 0
15 * sig Her ** 16 34 06.1824264648 +42 26 13.234150680   4.177 4.196 6.02   B9V 189 0
16 * 16 Dra SB* 16 36 11.4203423088 +52 54 00.188694792 5.320 5.470 5.520     B9.5V+DA: 74 0
17 * R Ara EB* 16 39 44.72575 -56 59 39.9217           B5V+F1IV 72 0
18 * zet CrA PM* 19 03 06.8769803 -42 05 42.385816   4.701 4.725   4.76 B9.5Vann 71 0
19 * 23 Cyg ** 19 53 17.3781586824 +57 31 24.506900436   5.001 5.132     B5V 90 0
20 * 77 Dra * 21 05 29.2657046472 +78 07 35.009168736   5.828 5.907     B8Vn 65 0
21 NAME Local Chimney reg ~ ~           ~ 16 0

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2023.02.08-02:23:14

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