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


C.D.S. - SIMBAD4 rel 1.7 - 2020.04.10CEST21:56:09

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

Status at CDS:  

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 - 2020
#notes
1 * 34 Psc * 00 10 02.2026446215 +11 08 44.925917994   5.456 5.530   5.58 B9Vn 123 0
2 * 34 Psc B * 00 10 02.3864682259 +11 08 37.818484938     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 442 0
4 HD 20863 * 03 23 47.3301304368 +48 36 15.895479154   7.00 6.99     B9V 49 0
5 HD 26670 * 04 16 53.5552274677 +61 50 59.971105763 5.05 5.56 5.70     B7V 48 0
6 * eta Cha * 08 41 19.5144242735 -78 57 48.102318990 5.02 5.351 5.453     B8V 211 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) 134 0
8 HD 74604 * 08 48 49.2522523444 +66 42 29.090035392   6.078 6.187     B7III 43 0
9 * del Ant * 10 29 35.3822401873 -30 36 25.422376542 5.34 5.52 5.56     B9/9.5V 51 0
10 V* FH Mus El* 12 39 55.8513201361 -66 30 40.091455588   6.199 6.252     B8V 48 0
11 * alf Vir bC* 13 25 11.57937 -11 09 40.7501 -0.20 0.74 0.97 1.06 1.30 B1V 814 2
12 HD 124367 Be* 14 14 57.1404303053 -57 05 10.058117811 4.36 4.99 5.07     B4Vne 130 0
13 * alf CrB Al* 15 34 41.26800 +26 42 52.8940 2.19 2.22 2.24 2.21 2.25 A1IV 454 0
14 HD 148594 * 16 30 15.6758112757 -27 54 58.508817188   6.964 6.892     B8V 52 0
15 * sig Her ** 16 34 06.1813704319 +42 26 13.134833754   4.177 4.196 6.02   B9V 181 1
16 * 16 Dra SB* 16 36 11.4206467927 +52 54 00.166594549 5.320 5.470 5.520     B9.5V+DA: 71 0
17 HD 149730 Al* 16 39 44.72575 -56 59 39.9217           B5V+F1IV 69 0
18 * zet CrA PM* 19 03 06.8769803 -42 05 42.385816   4.701 4.725   4.76 B9.5Vann 63 0
19 * 23 Cyg * 19 53 17.3787294553 +57 31 24.480998106   5.001 5.132     B5V 85 0
20 HD 201908 * 21 05 29.2654809517 +78 07 35.009737340   5.828 5.907     B8Vn 62 0
21 NAME Local Chimney reg ~ ~           ~ 13 0

    Equat.    Gal    SGal    Ecl

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2020.04.10-21:56:09

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