scholarly journals A Multicolor Study of AGNs and BL Lacs

1997 ◽  
Vol 159 ◽  
pp. 76-77
Author(s):  
W.-H. Sun ◽  
Yu-Ya Su ◽  
Hsiao-Feng Tang ◽  
Matthew A. Malkan ◽  
Remington P. S. Stone

AbstractWe present preliminary results of two monitoring projects on AGNs and BL Lacs with four intermediate-band optical filters at Lick Observatory, South African Astronomical Observatory, and Siding Spring Observatory. We applied differential photometry between the target and non-variable field stars to derive the variability amplitudes. All the AGNs varied in all wavebands, with amplitudes from 30% to 90%. The variations in shorter wavelength filters are always larger than in longer wavelength filters. We did not observe significant continuum slope changes. Continuum variations of BL Lacs up to 0.2 mag in 20 minutes were observed. Interestingly, we found a time lag of 6–8 minutes between two seemingly correlated variations observed in the intermediate U band with the 1-m telescope and in broad V band with the 24-in. telescope at SSO.

2014 ◽  
Vol 33 (7) ◽  
pp. 668-676 ◽  
Author(s):  
Lisa Armistead ◽  
Sarah Cook ◽  
Donald Skinner ◽  
Yoesrie Toefy ◽  
Elizabeth R. Anthony ◽  
...  

2006 ◽  
Vol 5 (3) ◽  
pp. 183-186
Author(s):  
R.A. Street ◽  
D.J. Christian ◽  
W.I. Clarkson ◽  
A.C. Cameron ◽  
B. Enoch ◽  
...  

The WASP consortium is conducting an ultra-wide field survey of stars between 8–15 mag from both hemispheres. Our primary science goal is to detect extra-solar ‘hot-Jupiter’-type planets that eclipse (or transit) bright host stars and for which further detailed investigation will be possible. We summarize the design of the SuperWASP instruments and describe the first results from our northern station SW-N, sited in La Palma, Canary Islands. Our second station, which began operations this year, is located at the South African Astronomical Observatory. Between April and September, 2004, SW-N continuously observed ~6.7 million stars. The consortium's custom-written, fully automated data reduction pipeline has been used to process these data, and the information is now stored in the project archive, held by the Leicester database and archive service (LEDAS). We have applied a sophisticated, automated algorithm to identify the low-amplitude (~0.01 mag), brief (~few hours) signatures of transiting exoplanets. In addition, we have assessed each candidate in the light of all available catalogue information in order to reject data artefacts and astrophysical false positive detections. The highest priority candidates are currently being subjected to further observations in order to select the true planets. Once the exoplanets are confirmed, a host of exciting opportunities are open to us. In this paper, we describe two techniques that exploit the transits in order to detect other objects within the same system. The first involves determining precise epochs for a sequence of transit events in order to detect the small timing variations caused by the gravitational pull of other planets in the same system. The second method employs ultra-high precision photometry of the transits to detect the deviations caused by the presence of exoplanetary moons. Both of these techniques are capable of detecting objects the size of terrestrial planets.


1995 ◽  
Vol 151 ◽  
pp. 87-88
Author(s):  
R. Konstantinova-Antova ◽  
A.P. Antov

An investigation of the activity of the flare star AD Leo was made using U-band patrol observations. 60 cm computer-controlled telescopes with identical single channel photon-counting photometers at the National Astronomical Observatory at Rozhen and at the Belogradchik Observatory were used. The integration time was 1 sec. Differential photometry was carried out, the AD Leo measurements were made relative to BD+20°2475. The data was reduced with the program package APR (Kirov et al. 1991).Two simultaneous observing runs were made. The results of the first have already been published (Antov etal. 1991). The other was part of the observational campaign in May, 1991 with the ROSAT satellite. In Bulgaria, the observations were carried out at Rozhen in the U-band and at Belogradchik in the B-band. Four flares were detected by both.


2001 ◽  
Vol 203 ◽  
pp. 580-582
Author(s):  
X.Z. Zhang ◽  
J.H. Wu

IPS observations have recently begun at Miyun Station, Beijing Astronomical Observatory. This paper briefly describes the radio telescope at Miyun Station, discusses the observation and the data reduction procedures and presents the preliminary results of observations on IPS source 3C48.


1988 ◽  
Vol 123 ◽  
pp. 255-259
Author(s):  
G.R. Isaak ◽  
A.R. Jones

A double magneto optical filter attached to the Cassegrain focus of the 1.9 m reflector of the South African Astronomical Observatory was used to observe Procyon in the 769.9 nm line of potassium during all clear hours of six nights. Velocity calibration was provided by the rotational and orbital velocity changes of the observer as well as by a continuous magnetic modulation.


1995 ◽  
Vol 151 ◽  
pp. 67-68
Author(s):  
Bill Ball ◽  
Gordon Bromage

The ROSAT Wide Field Camera all-sky EUV survey of 1990-91 identified over 200 active late-type stars (Pounds et al. 1993). Most of these were not known to be active prior to the survey and follow-up optical spectroscopy has been successful in selecting the most active dMe stars. These stars are characterized by their Balmer line emission which is direct evidence for an active chromosphere. We present photometric monitoring data for 4 new dMe stars, including the discovery of flaring activity on all 4 stars.The observations were made at the South African Astronomical Observatory at Sutherland near Capetown in October 1994, using the 0.5m and 1.9m telescopes for photometry and spectrometry, respectively. The 0.5m telescope is equipped with an automated, pulse-counting photometer. Flare monitoring of all the stars was done in the U-band with either 5 or 10 s integration times. All the stars monitored were between magnitude V = 11 and 13. A total of 15 flares were detected, including at least one on each star (Table 1). Comparison stars were measured in standard UBVRI photometric bands for each star.


2001 ◽  
Vol 182 ◽  
pp. 189-192 ◽  
Author(s):  
J. Wu ◽  
X. Zhang ◽  
Y. Zheng

AbstractIPS observations have recently begun at Miyun Station, Beijing Astronomical Observatory. This paper briefly describes the radio telescope at Miyun Station, discusses the observation and the data reduction procedures, and presents the preliminary results of observations on IPS source 3C48.


1997 ◽  
Vol 159 ◽  
pp. 413-418
Author(s):  
Z. L. Zou ◽  
Q. B. Li

AbstractThe preliminary results of several on-going AGN programs using the 2.16-m telescope at Xinglong Station of Beijing Astronomical Observatory are described. About 150 new AGNs including QSOs, BL Lac objects, and Seyferts have been discovered in the last two years.


1998 ◽  
Vol 184 ◽  
pp. 45-46
Author(s):  
Shigeru Matsumoto ◽  
Yoshikazu Nakada ◽  
Ian S. Glass

Nine regions in the Galactic bulge were observed at J and H bands with a PtSi 1040×520 array camera which is named the PtSi Astronomical Near Infrared Camera (PANIC). These regions were centered at l=(–5°,0°,+5°) b=(–6°,0°,+6°) respectively. Each region was covered with nine frames each of which spanned 30′ by 30′ square arcmin. Observations were carried out at the South African Astronomical Observatory, Cape Town, from 1995 to 1997 using a 40cm f/5 Newtonian telescope. A bolometric correction (Frogel and Whitford 1987) was given to the observed stars by using J-H values of reference RGB stars (Frogel et al 1990).


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