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X-Ray Observation of the Lynds 1157 Dark Cloud Region with ASCA
An ASCA observation of a region containing a Class 0 protostar IRAS20386+6751 in the Lynds 1157 dark cloud, has been carried out. Theprotostar was not detected, and the 95% upper limit to the luminositydepends on the assumed N_H: L_X(0.5-10 keV) < 1.1 *E31 ergs-1 for N_H = 1*E23 cm-2. A Class Iprotostar in Lynds 1152, IRAS 20353+6742, in the same field was alsoundetected with an upper limit about three-times as much as the Lynds1157 level. Besides these non detections, nine new X-ray sources weredetected and a spectral analysis was performed for 4 sources. One object(AX J2038+6801) shows a hard spectrum with a temperature of kT ~ 8 keVor a power-law photon index of ~ 2.0 and absorbed with N_H ~2*E22 cm-2. Another fainter one (AX J2036+6800)has a soft spectrum with most of the emission falling below 2 keV\@. Weexamine the possible nature of these new X-ray sources based on theirspectral properties.
| On the distance of dark clouds in the vicinity of the reflection nebula NGC 7023 in Cepheus
Distance to a group of dark clouds at moderate galactic latitudes Lynds1147, 1148, 1152, 1155, 1157, 1158, 1167, 1168, 1170, 1171, 1172, 1173,and 1174 is estimated from the extinction AV vs distance plot. Thisdependence is based on photometry of 79 stars down to V = 12.5 in theVilnius photometric system and their two-dimensional classification. Thedistance of the L1147/1158 group of clouds is found to be 325 +/- 13 pcand that of the L1167/1174 or NGC 7023 group of clouds is 288 +/- 25 pc.A number of stars with peculiar energy distribution has been found.
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Observation and Astrometry data
| Constellation: | Δράκων |
| Right ascension: | 20h39m54.58s |
| Declination: | +67°47'32.5" |
| Apparent magnitude: | 8.975 |
| Distance: | 87.566 parsecs |
| Proper motion RA: | 78.7 |
| Proper motion Dec: | -74.9 |
| B-T magnitude: | 9.558 |
| V-T magnitude: | 9.024 |
Catalogs and designations:
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