3 Results

A short presentation of each object with some references to earlier photometric studies is given. Numerical data (Tables 2 and 3) are available only in electronic form at the CDS via anonymous ftp. Table 2 includes the data observed at Tuorla with the 1.03 metre telescope (V-band). Table 3 includes data (B-, V-, and R-bands) observed at the Nordic Optical Telescope (NOT) on La Palma. Due to the modest amount of the B- and R-band data, a detailed analysis for that data was not possible. A few V-band datapoints observed at the NOT are included in the light curves. Otherwise the light curves present the V-band data that was obtained at Tuorla. The notation $\overline{\rm JD}$ = JD - 2 400 000 is used throughout the text and in the light curves.

For those objects which have been targets of large multifrequency campaigns, detailed analysis and numerical data can be found from the following articles: Takalo et al. ([1998]) (AO 0235+164); Raiteri et al. ([1999]) (S4 0954+658); Tosti et al. ([1998]a) (Mrk 421); Tosti et al. ([1998]b) (ON 231).

3.1 S2 0109+224

S2 0109+224 (PKS 0109+224) was first identified optically by Owen & Mufson ([1977]). The largest brightness variations in the historical light curve occurred in 1943: a drop of 3.07 mag during one year (Pica [1977]). Typical for S2 0109+224 have been one mag flux variations on a timescale of 1 - 2 years. The average brightness in the B-band has been 16.41 mag, and flickering of 0.6 - 0.7 mag has been observed by Pica et al. ([1988]). The brightness in the V-band varied during our observations by between 13.86 and 15.83 mag. Rapid flux variations were seen frequently (Fig. 1). S2 0109+224 was exceptionally bright during 1996-1997 ( $\overline{\rm JD}$ 50340 - 50500) compared to the earlier monitoring campaigns (Pica et al. [1988]; Sillanpää et al. [1988]a; Takalo [1991]; Xie et al. [1994]; Villata et al. [1997]; Raiteri et al. [1998]). The maximum, 13.86 ( $\overline{\rm JD}$ 50370), is one of the brightest V-band values measured for this object.

Figure 1: Light curve of S2 0109+224

3.2 3C 66A

3C 66A (PKS 0219+428) was first identified optically by Wills & Wills ([1974]). Apparently it is located near a large cluster of faint galaxies and near the radio galaxy 3C 66B. For earlier optical observations see Takalo et al. ([1996] and references therein).

The light curve of 3C 66A (Fig. 2) shows continuous 0.2- 0.3 mag variations. One of the brightest V-band mag ever for 3C 66A, 13.61, was measured on November 1995 ( $\overline{\rm JD}$ 50029) and also on March 1997 ( $\overline{\rm JD}$ 50529). By studying the light curve (Fig. 2) it seems that the local minima occur about every 60 - 70 days. Stronger evidence for periodicity of about 65 days can be found in the analysis made by Lainela et al. ([1999]).

Figure 2: Light curve of 3C 66A

3.3 AO 0235+164

AO 0235+164 (OD 160) is one of the most variable BL Lac objects. The few datapoints observed at Tuorla, when AO 0235+164 was in its faint state (V $\geq$ 18), are published with the results of a multifrequency campaign by Takalo et al. ([1998]).

3.4 OF 038

OF 038 (PKS 0422+004) was first classified as a BL Lac object by Kinman ([1976]a, [1976]b). Eachus & Liller ([1975]) found from Harvard College Observatory's Plate archive that the total amplitude variation was 3 mag. Burbidge & Hewitt ([1989]) observed the faintest known V-band magnitude, 17.0. The average B-band brightness in Rosemary Hill Observatory's long term monitoring (Pica et al. [1988]) was 16.05 mag. Fast $\sim$0.3 mag flux variations have been typical for this object during observations by Xie et al. ([1994] and references therein). The brightest V-band measurement has been made by Massaro et al. ([1996]), V=13.65 on November 1994.

Our OF 038 light curve (Fig. 3) showed a fading of almost one mag during two months in 1996 ( $\overline{\rm JD}$ 50090 and $\overline{\rm JD}$ 50134). During the next observing season (1996-1997) the flux of OF 038 rose continuously and reached 14.57 mag twice ( $\overline{\rm JD}$ 50473 and $\overline{\rm JD}$ 50497). The faintest V-band measurement was 15.67 mag ( $\overline{\rm JD}$ 50134).

Figure 3: Light curve of OF 038

3.5 S5 0716+714

S5 0716+714 is a radio-loud flat-spectrum source discovered in the Bonn-NRAO radio survey (Kühr et al. [1981], [1987]). It was classified as a BL Lac object by Biermann et al. ([1981]), who measured two photographic magnitudes (13.2 and 15.5) from the POSS plates. During the 1990's this source has been intensively studied at all frequencies. Quirrenbach et al. ([1991]) noticed correlated radio and optical changes on timescales of a few days. Wagner et al. ([1996]) reported rapid variations over the whole electromagnetic spectrum. S5 0716+714 is a strong EGRET-source and its $\gamma$-flux has shown considerable variability (Lin et al. [1995]).

The light curve of S5 0716+714 (Fig. 4) is one of the best sampled among our objects. Our V-band light curve shows a "sawtooth''-pattern. It is interesting to notice in our data that the maximum points in the light curve (Fig. 4) seem to occur with a period of 60-70 days. These values, 14.07, 14.12, 14.13 and 14.16, during 1995-1996 observations, have only 0.09 mag deviation. The average brightness of S5 0716+714 was rising during 1996-1997. The minimum value of our light curve is 15.15 ( $\overline{\rm JD}$ 50134), and the maximum 13.57 ( $\overline{\rm JD}$ 50455). A small part of observations were simultaneous with one EGRET pointing of S5 0716+714 (marked with the box in Fig. 4).

Figure 4: Light curve of S5 0716+714. The box marks a simultaneous EGRET-pointing

3.6 PKS 0735+178

PKS 0735+178 (OI 158) was first optically identified by Blake ([1970]) as a 16th mag blue stellar-like object. The optical brightness has varied between 13.90 and 17.72 mag in the B-band (Pollock et al. [1979]; Xie et al. [1994] and references therein).

The brightness of PKS 0735+178 was near $\sim$15.5 during winter 1996, until on February 1996 the object started to fade. The object reached 15.5 level again in late March 1997. The maximum V-band brightness during our observations was 15.26 ( $\overline{\rm JD}$ 50109) and the minimum 16.94 ( $\overline{\rm JD}$ 50455) (Fig. 5).

Figure 5: Light curve of PKS 0735+178

3.7 PKS 0736+107

PKS 0736+107 (OI 061) is classified as a high polarization quasar, HPQ. McGimsey et al. ([1975]) observed one mag optical variations in PKS 0736+107. Pica et al. ([1980], [1988]) reported 0.7 mag fades and flares and found from photographic plates that historically the brightness had been between mag 15.45 and 16.80 in the B-band.

During our observations between 1995 and 1997 the brightness varied between 16.25 ( $\overline{\rm JD}$ 50494) and 16.84 ( $\overline{\rm JD}$ 50512) mag (Fig. 6).

Figure 6: Light curve of PKS 0736+107

3.8 OI 090.4

OI 090.4 (PKS 0754+110) was identified as a BL Lac-object by Tapia et al. ([1977]). Its historical light curve has been studied by Baumert ([1980]), who found 0.8 mag variations on timescales of a few days and a variability of 2 mag in a few years. Pica et al. ([1988]) observed 0.8 magnitude (B-band) changes on a 2 year timescale. Zekl et al. ([1981]) reported on 2 mag fluctuations in the B-band. Sillanpää et al. ([1991]) observed 0.9 mag variations in the V-band. Smith et al. ([1987]) have measured V=16.31, which has been so far the faintest V-band value for this object.

During winter 1996 and winter 1997 the average brightness was between 16 and 16.5 (Fig. 7). The minimum, 16.71, ( $\overline{\rm JD}$ 50482) was observed on February 1997 and is one the faintest V-band measurement for this object (see references above) ever. The brightest V-band value measured was 15.68 ( $\overline{\rm JD}$ 50155).

Figure 7: Light curve of OI 090.4

3.9 OJ 287

OJ 287 (PKS 0851+202) is one of the most studied extragalactic objects from radio frequencies to X-ray frequencies. It was first optically identified by Blake ([1970]) as a 14.5 B-magnitude stellar-like object. OJ 287 has been the target of many optical observations since the 1970's, including long-term optical monitoring programs, such as the one at Rosemary Hill Observatory (Webb et al. [1988]), where over 5 mag B-band variations have been measured. Craine ([1977]) reported that the brightness of OJ 287 in the V-band has varied between 12.7 and 15.6. For a complete historical overview of this object see Takalo ([1994]). Sillanpää et al. ([1988]a) measured values from 12.64 to 15.50 mag in the V-band between 1982 and 1984. During those observations this source was in an outburst state. Previous large outbursts had happened in 1911, 1937, 1947, 1954 and 1971/1972. Analysing this historical light curve Sillanpää et al. ([1988]b) demonstrated that the outbursts have a period of $\sim$12 years, and explained this behaviour by a supermassive binary black hole model. They also predicted that OJ 287 should be in an outburst state again during years 1994 and 1995. This was confirmed by the observations in the OJ-94 project (see Sillanpää et al. [1996]a-c).

The OJ 287 observations presented here cover the second peak (1.2 years after the first peak) of the predicted outburst (Sillanpää et al. [1996]a-c). The V-band brightness reached 14.10 on 28 December 1995 ( $\overline{\rm JD}$ 50080) (Fig. 8), and 14.15 was reached on 27 March 1996 ( $\overline{\rm JD}$ 50170). During the next observing season, winter 1997 OJ 287 became gradually fainter, and the brightness dropped rapidly 0.8 mag in 12 days on February 1997, when a minimum, 15.78 ( $\overline{\rm JD}$ 50497), was reached.

Figure 8: Light curve of OJ 287

3.10 S4 0954+658

The radio source S4 0954+658 (Pauliny-Toth et al. [1978]) has been monitored quite intensively by Wagner et al. ([1993]), Heidt ([1993]) and Raiteri et al. ([1999]). It has been classified as an intraday variable (IDV) in the radio and optical regions.

Numerical data and a detailed analysis of our S4 0954+658 observations is published by Raiteri et al. ([1999]), and only the light curve is presented here (Fig. 9).

Figure 9: Light curve of S4 0954+658

3.11 Mrk 421

Mrk 421 (Markarian & Lipovetsky [1972]) has shown strong and rapid TeV-outbursts several times (e.g. Schubnell et al. [1996]; Petry et al. [1996]). Our data and analysis of the optical behaviour of Mrk 421 are presented by Tosti et al. ([1998]a) and hence only the light curve is shown (Fig. 10).

Figure 10: Light curve of Mrk 421

3.12 OM 280

OM 280 (QSO 1147+245) is classified as a BL Lac object (Angel & Stockmann [1980]). The amplitude of the B-band variability has been about 0.8 mag, with the average brightness $\sim$16.6 during 1981-1986 (Pica et al. [1988]). Zekl et al. ([1981]) reported 0.4 mag variations in the B-band. Moles et al. ([1985]) measured 16.02 as the average brightness in the V-band. During the recent years Fiorucci & Tosti ([1996]b) reported that the V-band brightness was 16.15 as an average.

Our data indicate that the brightness in the V-band was near 16.5 mag during winter 1996 and between 16.5 and 17.0 during winter 1997 (Fig. 11). The brightest V-band value was 16.38 ( $\overline{\rm JD}$ 50525) and the faintest 17.01 ( $\overline{\rm JD}$ 50519) mag.

Figure 11: Light curve of OM 280

3.13 4C 29.45

4C 29.45 (PKS 1156+295) belongs among to the most variable OVV-quasars. Studies of photographic plates have shown that the average brightness of this object has been $\sim$16 mag in the B-band. On March 1981 it had an outburst of 5 mag, starting from B = 18 and rising up to 13.15 (Wills et al. 1983). In 1985 a 2.5 mag outburst occurred (Miller [1985]). 4C 29.45 is a strong GeV-source (Thompson et al. [1995]; Webb et al. [1995]).

The V-band brightness of 4C 29.45 varied between 16.12 ( $\overline{\rm JD}$ 50125) and 16.68 ( $\overline{\rm JD}$ 50134 and $\overline{\rm JD}$ 50143) during 1995-1996. In winter 1997 we observed only two datapoints (15.45) ( $\overline{\rm JD}$ 50455) and 17.05 ( $\overline{\rm JD}$ 50480 mag) for this object. Due to small number of data (Table 2) no light curve is shown.

3.14 ON 325

ON 325 (PKS 1215+303) was identified as a quasar by Browne ([1971]), and confirmed by Veron & Veron ([1973]). It was later classified as a BL Lac object. Veron & Veron ([1975]) reported 2.7 mag (14.3 - 17.0) changes in the B-band. Observations made at Rosemary Hill Observatory during 16 years (Pica et al. [1988]) showed over 2 mag B-band variations with an average brightness of 15.7. At least in 1974, 1977, 1980, 1985, and 1986, over one magnitude outbursts have occured. Zekl et al. ([1981]) reported that the brightness of this source has historically been between 13.7 and 17.0 mag in the B-band.

The data from the first observing season (1995-1996) show (Fig. 12) a smooth decrease in brightness from 14.7 to 15.3 mag. Observations during winter 1997 show a maximum point in the light curve, 14.50 mag ( $\overline{\rm JD}$ 50512) and a fade from that to 15.33 ( $\overline{\rm JD}$ 50543), the minimum in our ON 325 observations.

Figure 12: Light curve of ON 325

3.15 ON 231

ON 231 (QSO 1219+285) was identified by Browne ([1971]) and Biraud ([1971]) as a stellar like object, which was the same as the variable star W Comae. Historical light curve has been studied by Liu et al. ([1995]).

Our ON 231 data are published and analysed by Tosti et al. ([1998]b), so only the light curve is presented (Fig. 13).

Figure 13: Light curve of ON 231

3.16 3C 273

3C 273 (PKS 1226+02) was the first QSO discovered. It is classified as a low polarization quasar (LPQ). The optical variations are usually relatively small, even the total brightness variation amplitude has been less than one magnitude (Pica et al. [1988]; Sillanpää et al. [1988]a). In 1983 brightness reached 12.17 mag in the V-band (Sillanpää et al. [1988]a). Studies by Fiorucci & Tosti ([1996]b) and Villata et al. ([1997]) did not show any large optical variations.

During our observations on December 1995 3C 273 was brightening rapidly (Fig. 14) (between $\overline{\rm JD}$ 50065 and $\overline{\rm JD}$ 50070). On January 1996 the object did not show a continuation of this trend. Part of the observations on January and February 1996 were simultaneous with an EGRET-pointing (marked with a box in Fig. 14). In early April 1996 ( $\overline{\rm JD}$ 50157) 3C 273 started to fade from mag 12.8 towards mag 13. The shape of our V-band light curve observed during winter 1996 is also in agreement with the R-band variations observed by Raiteri et al. ([1998]) during the same period. Observations during winter 1997 did not show large flares, the brightness was near 12.9 mag. The maximum V-band brightness during years 1995 and 1997 was 12.67 ( $\overline{\rm JD}$ 50070) and the minimum 12.97 ( $\overline{\rm JD}$ 50519 and $\overline{\rm JD}$ 50525) mag.

Figure 14: Light curve of 3C 273 The box marks a simultaneous EGRET-pointing

3.17 3C 279

3C 279 (PKS 1253-055) is a high polarization quasar (HPQ) and one of the most violent variable sources in the sky, showing 8 mag variations in its historical light curve (Webb et al. [1990]). 3C 279 had large outbursts at least during 1936, 1938, 1987, and 1992. Normally the variation amplitude in the optical region has been about 2 mag. This object is one of the strongest EGRET $\gamma$-ray sources (Thompson et al. [1995]; Wehrle et al. [1998]). Several 3C 279 datapoints are simultaneous with an EGRET pointing (marked with a box in Fig. 15). On January and February 1996 ( $\overline{\rm JD}$ 50100) 3C 279 was brightening rapidly in optical. The EGRET pointing on February 1996 showed also a fast rise in the GeV $\gamma$-ray flux. The results of the multifrequency campaign during this particular $\gamma$-flare are studied by Wehrle et al. ([1998]). The optical brightening was over on March and the object faded to V-magnitude 16. The four datapoints in the light curve (Fig. 15) between $\overline{\rm JD}$ 50273 and $\overline{\rm JD}$ 50277 have been observed at the NOT in summer 1996. They show that 3C 279 brightened 0.4 mag in four days. Observations during winter 1997 showed that 3C 279 was fainter than mag 16. The brightness rose in spring 1997, reaching mag 15.2. The maximum (V-band) brightness during our observations was 14.94 ( $\overline{\rm JD}$ 50134) and the minimum ( $\overline{\rm JD}$ 50507) 16.44.

Figure 15: Light curve of 3C 279 The box marks a simultaneous EGRET-pointing

3.18 PKS 1424+240

PKS 1424+240 is a radio source which was identified as a blazar by Impey & Tapia ([1988]). Originally it was classified as a white dwarf in the Palomar-Green Survey. Studies by Fleming et al. ([1993]) from Rosat All Sky Survey (RASS) showed PG 1424+240 to be a BL Lac object. Fiorucci & Tosti ([1996]b) reported that the brightness in the R-band was about 14.3 mag.

During our PKS 1424+240 observations the average V-band magnitude was $\sim$14.5 (Fig. 16). The range of variation was quite small, which is in agreement with the earlier observations of Fiorucci & Tosti ([1996]b). The minimum value for the brightness was 14.63 $\overline{\rm JD}$ 50186) and the maximum 14.42 ( $\overline{\rm JD}$ 50573).

Figure 16: Light curve of PKS 1424+240

3.19 4C 38.41

4C 38.41 (QSO 1633+38) is classified as a quasar in some references. Mattox et al. ([1993]) classified it as an OVV quasar. It faded over 3 mag, according to the observations of Barbieri et al. ([1977]), between years 1969 and 1976. It is a strong EGRET source (Mattox et al. [1993]; Fichtel et al. [1994]; Thompson et al. [1995]).

We observed 4C 38.41 several times in Tuorla during 1995-1997. The observations showed that the object was at first in a faint state, 17.55 mag (minimum). By the next winter the brightness had risen to mag 16 (maximum 15.94 at $\overline{\rm JD}$50531), from which it faded to 17.35 ( $\overline{\rm JD}$ 50554). Due to the small number of data (Table 2) no light curve is shown.

3.20 3C 345

3C 345 (S4 1641+399) was classified as an OVV quasar by Penston & Cannon ([1970]). Typical for this object have been about 2 mag outbursts, which occur quite frequently. Such large outbursts happened in 1967/1968, 1971/1972, 1982/1983, and 1991/1992 (Schramm et al. [1993]). Sillanpää et al. ([1988]a) measured V=14.56 in 1982, while Schramm et al. ([1993]) observed V-band brightness near 18 mag in 1989. In 1991/1992 a large 2.5 mag outburst was observed (Schramm et al. [1993]). Kidger & Takalo ([1990]) observed the historical minimum B=18.66. During our observations the average brightness of 3C 345 was fainter than mag 17 (Fig. 17). In winter 1996 we observed several $\sim$0.5 mag brightenings in a timescale of a few days. An EGRET-pointing during our optical observations is marked with a box in Fig. 17. The minimum value for the brightness was 17.77 ( $\overline{\rm JD}$ 50152), and the maximum 16.60 ( $\overline{\rm JD}$ 50254, observed at the NOT on June 1996).

Figure 17: Light curve of 3C 345 The box marks a simultaneous EGRET-pointing

3.21 OT 546

Strong continuum emission from the nucleus of OT 546 (PKS 1727+502, ZW I 187) was first noticed by Zwicky ([1966]). Optical variations of this object were reported by Sandage ([1967]). Angel & Stockmann ([1980]) classified it as a BL Lac object. Its historical light curve shows variations between mag 14.8 and 16.9 in the B-band (Hall & Usher [1972]). The average brightness in the V-band has been near mag 16 (Kinman [1976]b). The light curves from Rosemary Hill Observatory observations between years 1975 and 1987 show 0.8 mag variations, with the average B $\sim$ 16.7 (Pica et al. [1988]).

During our V-band observations, the brightness varied between mag 15.76 ( $\overline{\rm JD}$ 50182) and 16.35 ( $\overline{\rm JD}$ 50524) (Fig. 18). The faintest datapoint, 16.35 has, however, fairly large errors 0.19 mag. Using the second faintest measurement, 16.12, to calculate the total range of flux variation, the amplitude is only 0.36 mag.

Figure 18: Light curve of OT 546

3.22 3C 371

3C 371 (S4 1807+69) is a BL Lac object in a large elliptical galaxy whose emission is dominated by the flux from the nucleus. Earlier it was classified as an N galaxy. Observations by Sandage ([1967]) showed that 3C 371 was optically variable. The brightness in the V-band was between 14.6 and 15.0 mag in autumn 1996 (Fig. 19). In spring 1997 ( $\overline{\rm JD}$ 50520) the brightness was rising towards mag 14.3. The minimum brightness was 15.02 ( $\overline{\rm JD}$ 50360) and the maximum 14.23 ( $\overline{\rm JD}$ 50554).

Figure 19: Light curve of 3C 371

3.23 BL Lacertae

BL Lacertae (PKS 2200+420) is the prototype of all BL Lac objects. Originally it was classified as a variable star in the 1920's. Its historical light curve shows a measured brightness of between 12.5 and 16.5 mag in the B-band (Shen & Usher [1970]). The average brightness in the V-band has been between mag 14 and 15 (Webb et al. [1988]; Moles et al. [1985]; Sillanpää et al. [1988]a).

Our light curve does not show (Fig. 20) any quiescent state at all. The brightness has fluctuated continuously, typically 0.2 - 0.3 mag in a timescale of a few days. The maximum V-band brightness during our monitoring was 14.40 ( $\overline{\rm JD}$ 50482) and the minimum 16.04 ( $\overline{\rm JD}$ 50274). The average brightness of BL Lacertae was rising during our observations between 1995 and 1997. It culminated in summer 1997 (after the observations presented here) when BL Lacertae had a large outburst (Webb et al. [1998]).

Figure 20: Light curve of BL Lacertae

3.24 4C 31.36

4C 31.36 (QSO 2201+315) is a 4C-radio catalog object (Pilkington & Scott [1965]) and has been classified as a low polarization quasar, LPQ. It was first optically identified by Tritton et al. ([1973]). Its brightness has normally varied between mag 15 and 16 in the B-band (Tritton et al. [1973]). Pica et al. ([1988]) reported variations of 0.77 mag. During our monitoring (Fig. 21) 4C 31.36 had modest amplitude variations and only one possible major flare was recorded, a 0.41 mag brightening on December 1995 ( $\overline{\rm JD}$ 50055). The maximum value of the brightness was 15.26 ( $\overline{\rm JD}$ 50055) and the minimum 15.89 ( $\overline{\rm JD}$ 50079). In general, excluding that one flare (only two datapoints), the variations of this object were small, which was expected for a low polarization quasar (LPQ).

Figure 21: Light curve of 4C 31.36

3.25 CTA 102

CTA 102 (PKS 2230+11) is a high polarization quasar, HPQ (Sandage & Wyndham [1965]). Pica et al. ([1988]) reported 17.66 mag as the long-term average brightness in the B-band and 1.14 mag as the variability amplitude. It is also a strong $\gamma$-ray source (Blom et al. [1995]; Thompson et al. [1995]; Lin et al. [1996]). Recent optical monitoring results, for example by Villata et al. ([1997]), and Raiteri et al. ([1998]), showed that the brightness variations of CTA 102 were small.

Our CTA 102 observations show one very large and rapid flare: 1.13 mag on a timescale of 3 days ( $\overline{\rm JD}$ 50346) (Fig. 22 and Table 2). The 1.13 mag brightening is based on measurements from three separate images. More evidence for this very rapid and violent outburst can be found in the light curve by Tornikoski et al. ([1999]) who also detected the flare. The maximum V-band brightness during our observations was 15.23 ( $\overline{\rm JD}$ 50346) and the minimum 17.24 ( $\overline{\rm JD}$ 50050).

Figure 22: Light curve of CTA 102

3.26 3C 454.3

3C 454.3 (PKS 2251+15) is a strongly variable high polarization quasar, HPQ. It can also be classified as an OVV quasar. Its B-band brightness has often been between mag 16 and 17 (Webb et al. [1988]; Sillanpää et al. [1988]a). The latest monitoring results are by Villata et al. ([1997]) and Raiteri et al. ([1998]). During those observations 3C 454.3 showed 0.4 mag variations in the R-band, and only 0.12 mag in the V-band. 3C 454.3 is a strong EGRET source (Blom et al. [1995]; Thompson et al. [1995]). During our observations, the object showed frequent small amplitude variations (Fig. 23). The maximum V-band brightness was 16.00 ( $\overline{\rm JD}$ 50373) and the minimum 16.78 ( $\overline{\rm JD}$ 50065).

Figure 23: Light curve of 3C 454.3

3.27 OY 091

OY 091 (PKS 2254+07) is a BL Lac object. Its historical brightness variations have been 1.6 mag according to Pollock ([1975]). Pica et al. ([1988]) reported on 2.37 mag variations during 1.39 years. In 1981 1.8 mag outburst was detected. After that flare the brightness faded 1.3 mag in 18 days (B-band) and continued fading to mag 18 where the brightness stayed for years (Pica et al. [1988]).

During our observations the maximum V-band brightness value (Fig. 24) was 16.30 ( $\overline{\rm JD}$ 50065) and minimum 16.82 ( $\overline{\rm JD}$ 50044 mag). Due to the limited number of datapoints a more detailed analysis is not possible.

Figure 24: Light curve of OY 091