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HD 190857


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Chandra observations of the X-ray environment of BL Lacs
We present Chandra observations of the X-ray environment of a sample of6 BL Lacertae objects. The improved sensitivity of the ACIS experimentallows us to separate the core X-ray emission from the contribution ofdiffuse emission from the host galaxy/cluster scales. Within the short(2-6 ks) ACIS exposures, we find evidence for diffuse X-ray emission in3 sources (BL Lac, PKS 0548-322, and PKS 2005-489). The diffuse emissioncan be modeled with a King profile with beta ~ 0.3-0.6, core radiirc ~ 15-28 kpc, and 0.4-5 keV luminosities in the range1041-1042 erg s-1. In the remaining 3sources, one (3C 371) has a radial profile entirely consistent with anunresolved source, while two (1ES 2344+514 and 1ES 2321+419) showevidence for weak diffuse emission on kpc scales. These results supportcurrent models for radio-loud AGN unifying BL Lacs and FRI radiogalaxies through the orientation of their jets. In PKS 0548-322 and PKS2005-489, we also find evidence for diffuse emission on cluster scales,although the spatial properties of this emission are not constrained.The temperature (kT ~ 3-5 keV) and luminosity (L0.4-5 keV ~1042 erg s-1) of the cluster gas are typical ofnormal clusters. Interestingly, these are the two brightest sources ofthe sample, suggesting a link between environment and nuclear activity.

Micrometer measures of 401 double stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972AJ.....77..878W&db_key=AST

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Observation and Astrometry data

Constellation:Télescope
Right ascension:20h09m07.12s
Declination:-48°55'34.4"
Apparent magnitude:10.139
Proper motion RA:13.9
Proper motion Dec:12.7
B-T magnitude:10.912
V-T magnitude:10.203

Catalogs and designations:
Proper Names   (Edit)
HD 1989HD 190857
TYCHO-2 2000TYC 8400-1010-1
USNO-A2.0USNO-A2 0375-38531345
HIPHIP 99275

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