2017A&A...605A..47N


Query : 2017A&A...605A..47N

2017A&A...605A..47N - Astronomy and Astrophysics, volume 605A, 47-47 (2017/9-1)

Discovery of Galactic O IV and O V X-ray absorption due to transition temperature gas in the PKS 2155-304 spectrum.

NEVALAINEN J., WAKKER B., KAASTRA J., BONAMENTE M., SNOWDEN S., PAERELS F. and DE VRIES C.

Abstract (from CDS):

Far-ultraviolet (FUV) observations have revealed transition temperature gas (TTG; logT(K)∼5), located in the lower Galactic halo and in high-velocity clouds. However, the corresponding X-ray absorption has so far remained mostly undetected. In order to make an improvement in this respect in Galactic X-ray absorption studies, we accumulated very deep (∼3Ms) spectra of the blazar PKS 2155-304 obtained with the spectrometers RGS1, RGS2, LETG/HRC, and LETG/ACIS-S and studied the absorption lines due to the intervening Galactic components. The very high quality of the data and coverage of important wavelengths with at least two independent instruments allowed us to reliably detect 10 Galactic lines with better than 99.75% confidence. We discovered significant absorption from blended OIV transitions 1s-2p 2S (22.571Å), 1s-2p 2P (22.741Å), and 1s-2p 2D (22.777Å), and from the OV transition 1s-2p (22.370Å) from TTG at logT(K)=5.2±0.1. A joint X-ray and FUV analysis indicated that photoionisation is negligible for this component and that the gas is in a cooling transition phase. However, the temperature is high enough that the column density ratio N(OIV)/N(OV) is not significantly different from that in collisional ionisation equilibrium (CIE). Under CIE we obtained NOIV=3.6±2.0x1015cm–2, corresponding to NH=1.0±0.5x1019(Z/ZTTG)cm–2.

Abstract Copyright: © ESO, 2017

Journal keyword(s): instabilities - line: identification - Galaxy: halo - X-rays: general - X-rays: general

Simbad objects: 7

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Number of rows : 7
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 NAME Magellanic Stream HVC 00 32 -30.0           ~ 881 1
2 V* V1055 Ori LXB 06 17 07.3 +09 08 13   18.80 18.5     ~ 539 1
3 Mrk 421 BLL 11 04 27.3140835504 +38 12 31.798495872   13.50 12.90 8.31   ~ 2512 1
4 V* V818 Sco LXB 16 19 55.0692669024 -15 38 25.017666540 11.60 12.40 11.1     Oev 1570 0
5 NAME LHB X 16 42.0 +02 19           ~ 292 0
6 QSO B2155-304 BLL 21 58 52.0652249880 -30 13 32.118447792   13.36 13.09 12.62   ~ 1640 1
7 NAME Local Group GrG ~ ~           ~ 7641 0

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2022.05.27-21:58:29

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