HQM - Hamburg Quasar Monitoring

Object List

HQM

The Hamburg Quasar Monitoring Programm (HQM) has been performed between 1988 and 1995. Later follow-up observations in 1996, 1998, 2000 and 2001 as well as some earlier data between 1984 and 1986 from previous projects enlarged the overall sample time for some of our targets up to 15 years. The HQM sample contains lightcurves for roughly 500 quasars, in total about 35.000 individual datapoints, although the main target list is much shorter - around 300 targets.

The original purpose of HQMwas the detection of high amplification events in quasar lighcurves lensed by an unknown foreground galaxy. An intensive monitoring of quasars is as well a presentation of intrinsic quasar variability. Although this was not the primary goal for HQM, several quasars became members of the main target list from collaborations with other observers whos first interests were quasar physics.

HQM was designed to create a large quantity of lightcurves of Quasars and AGN. In the beginning we had been a little too enthusiastic. We thought a large and carefully selected sample, a good analysis program and five years time would produce a at least few High Amplification Events. The longer HQM was running the more it became evident that the key would either be a larger and much denser observed sample or a sample to do statistical evaluations. At the end in 1995 we had a great list of quasars and numbers of datapoints and lightcurves but all we had not was a complete sample.

Several influences destroid our original goals during the eight years that HQM run between 1988 and 1995. Why has our sample became so inhomogenous?

  • The first point is the reachability of any quasar of the sample during the night.
    During the winter time when the milkyway dominates great parts of the sky, the number of targets is relatively low but the numer of observable hours during the night is high. So every quasar in the target list got its lightcurve point, sometimes twice ore more during one campaign. In summer the nights are short but the number of quasars especially between 10 and 14 hours are high and we have not been able to set the nescessary priorities which target had to be ignored. At the end we had lightcurves with a good sampling rate for targets between 16 and 24 hours and bad sampled lightcurves for targets between 10 and 14 hours. Some of the later targets had even no or only a few datapoint.
  • A second point were the clouds, the wind and the moon.
    Soon after HQM began we realized, that when only parts of the sky were covered or when the moon light flooded the area around our targets we would have been without work. So we decided to integrate a secondary program just for these occasions. Again we looked for a complete sample of objects and found it in the 3C catalog - objects mostly bright enough, all radio loud and mostly quasars or AGN evenly distributed over the sky. The number of around 300 objects fitted our interrests quite well. So we started in 1990 with this secondary program. Our observers were colleagues from our group not all of them with long observer's experience. What they have missed was a clear handling instruction which object had to be observed in which priority. Every time with every changing weather situatuation the observer on duty had to decide by him-/herself which target to observe next. During the years some of the secondary targets got lightcurves nearly as long as the main targets. More and more these targets became first priority objects so that at the end of HQM the next target to observe was chosen not from the priority list but from the length of the lightcurve to that time.
  • Third, the collaboration with other colleagues embedded new targest into our list and we followed these objects with steadily growing lightcurves.
  • Fourth, technical circumstances changed our target list.
    In 1990 the CCD chip burned down inside the dewar an a new camera was not ready before a gap of a half year.
    In 1992 the main mirror of the 1.23m telescope remained usable on a 50%-level so that the limiting magnitude was too low for some of our targets. After nearly one year the telescope got a new mirror and was back on its old level.

All in all a large list of targets with sometimes very good resolved lightcurves was observed but the discussion of the sample as originated in 1988 was not possible.

But we had been chasing microlensing events in quasar lightcurves and non (except some in multiple imaged quasars like the double quasar 0957+561 or the Einstein cross 2237+0305) had been found. In all of our lightcurves we see a large variety of variability but a definite microlensing event feature was not between the data.

On the other hand we cannot exclude Microlensing Events.

data, graphics and images may not be used without permission.
contact: Jochen Schramm, Hamburger Sternwarte