Engineering topics

Kim, Chulhee

Publications and source records attributed to Kim, Chulhee.

3 records

NASA NTRS2002

Optical Microvariability of Blazars

We present the results of optical differential photometry of five blazers [PKS0219+428 (3C66A), PKS 0235+164 (AO 0235+16), H0414+019, PKS 0851+202 (OJ 187) and QSO 1807+698 (3C 371)] that were observed on 7 nights between November 05, 1997 and December 29, 1998, using the B and the V band filters. We have detected microvariations in four blazers (3C66A, AO 0235+16, H0414+019, and OJ 287). In addition, the light curve of AO 0235+16 has displayed a mini-flare when the brightness of this source was decreasing. Night-to-night variations have also been detected in 3C66A, H0414+019, and OJ 287. The results of our observations are discussed in the framework of accretion disk phenomena (magnetic flares or hot spots in accretion disks) and jet phenomena (plasma instabilities in jets).

Ghosh, K. K.↗

NASA NTRS2001

Detection of X-Ray Emission from Galaxies Inside the Bootes Void

We report the X-ray properties of Bootes void galaxies detected by the ROSAT All-Sky Survey (RASS). By searching the fields of 26 radio and 27 emission-line-selected void galaxies, we have detected nine X-ray-emitting void galaxies at greater than 2.7 sigma confidence level. Five of these nine galaxies are in the IRAS subsample. Two of the IRAS galaxies were previously identified in positional cross-correlation studies of the RASS and IRAS Point Source Catalogue sources. Three of the X-ray-emitting galaxies are active galactic nuclei (AGNs; IRAS 14288+5255, Mrk 845, and IRAS 15195+5050), three are emission-line galaxies (PC 1357+4641, CG 547, and CG 922), and the remaining three are of unknown spectral type (IRAS 14500+4804, CG 637, and MAS 15092+3940). The far-infrared flux levels of the AGN sources imply that most of the observed X-ray emissivity is from starburst activity. We have carried out timing and spectral analysis for the Seyfert 1 galaxy Mrk 845. Poor statistics prevents detailed analysis of the remaining sources. Only two galaxies in our sample, BHI 1514+3819 and FSS 1515+3823, were observed during ROSAT pointed observations resulting in a nondetection at the 1 sigma level.

Kim, Chulhee↗

NASA NTRS2000

Detection of X-ray Emission From Galaxies Inside The Bootes Void

We report the x-ray properties of Bootes void galaxies detected by the ROSAT All-Sky Survey (RASS). By searching the fields of 26 radio and 27 emission-line-selected void galaxies, we have detected 9 x-ray emitting void galaxies at >2.7-sigma confidence level. Five of these 9 galaxies are in the IP,AS subsample. We expect 2 detections at the redshift of the Bootes void based on previous positional cross-correlation studies of the RASS and IRAS Point Source Catalogue sources. Three of the x-ray emitting galaxies are AGNs (IRAS~14288+5255, Mrk~845, and IRAS 15195+5050), and the remaining 6 are all likely emission line galaxies (PC~1357+4641, CG~547, CG~922, IRAS~14SOO+4804, CG~637, and IRAS~15092+3940). The far infrared flux levels of the AGN sources implies most of the observed x-ray emissivity is from starburst activity. We have carried out timing and spectral analysis for the narrow-line Seyfert 1 galaxy Mrk~845. Poor statistics prevents detailed analysis of the remaining sources. only two galaxies in our sample, BHI 1514+3819 and FSS 1515+3823, were observed during ROSAT pointed observations resulting in a nondetection at the 1-sigma level.

Kim, Chulhee↗