Blazar Microvariability Project

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This Research is supported by NSF grant AST-0324238

What is Microvariability?

Micro-variability is defined as extremely rapid (t < 1 hour), low amplitude (amp < .1 mag) variations that are intermittently seen in radio loud quasars and BL lac objects. Several studies have recently been completed in an attempt to define duty cycles and characteristics of micro-variations in these types of source, including studies by the authors, and these observations have not only demonstrated the reality of these micro-variations, but also are starting to yield some insight into their characteristics. The following light curve shows microvariations obtained two observatories on the same evening, with two different telescopes, different instruments and different weather conditions. The reality of microvariations is established with these observations. However, we cannot rule out microvariations induced by intervening matter between the source S1 0716+71 and the Earth. Most likely, however, the variations are intrinsic to the source.

Reference: Astrophysical Journal 2007, Pollock, Webb and Azarnia, Volume 133, page 487.

Our major goals were to:

What we did

We monitored a list of radio-loud quasars and BL Lacs on long timescales, short-term (flaring) timescales and also intra-day (micro-variability) timescales. We have also done an exhaustive literature search, collecting published micro-variability data in order to study not only the micro-variations themselves, but also the relationship between micro-variations and longer-term variations. We compiled a select list of interesting radio-loud quasars and BL Lacs, and began a systematic study of of these micro-variations. The following is the source list we used for this research.

Microvariability Source List

Name Redshift Object Type Right Ascension Declination # micro Obs.
AO 0235+164 0.94 BL Lac 2h 38m +16d 37m 9
0420-01 0.915 OVV 4h 21m -01d 20m 9
S1 0716+71 0.30 BL Lac 7h 21m +71d 20m 17
0735+17 0.424 BL Lac 7h 35m +17d42m 1
0736+017 0.191 OVV 7h 36m +1d 50m 3
OJ 287 0.306 BL Lac 8h 51m +20d 06m 13
PKS 1156+295 0.729 OVV 11h 59m +29d 14m 2
3C 273 0.1575 QSO 12h 29m +02d 08m 1
3C 279 0.536 OVV 12h 56m -05d 47m 8
ON 231 0.102 OVV 14h 35m +16d 30m 2
3C 345 0.59 OVV 16h 42m +39d 48m 5
1510-089 0.36 OVV 15h 12m -09d 59m 2
BL Lac 0.069 BL Lac 22h 02m +42d 16m 21
3C 446 1.404 OVV 22h 35m +16d 30m 4

Our Results: