Photoelectric UBV sequences in the fields of extragalactic sources

McGimsey, B. Q.; Williamon, R. M.

doi:10.1086/111946

Cited by 10 publications

(9 citation statements)

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“…Our new photometric sequence is presented in Table 1, showing the V (Johnson), and R c , I c (Cousins) photometric values. Previous calibrations of this star-field were performedin in Wing (1973); Veron & Veron (1975);McGimsey et al (1976); Smith et al (1985). In particular the determinations of McGimsey et al (1976) are photoelectric in the U BV Johnson system, thus well similar to our calibrations in B, V bands using a CCD detector.…”

Section: Comparison Stars Photometrysupporting

confidence: 81%

“…Previous calibrations of this star-field were performedin in Wing (1973); Veron & Veron (1975);McGimsey et al (1976); Smith et al (1985). In particular the determinations of McGimsey et al (1976) are photoelectric in the U BV Johnson system, thus well similar to our calibrations in B, V bands using a CCD detector. Discrepancies are small if the specifications of Bessell (1990) are respected and determined (Fiorucci & Munari 2003).…”

Section: Comparison Stars Photometrysupporting

confidence: 81%

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Ten-year optical monitoring of PKS 0735+178: historical comparison, multiband behavior, and variability timescales

Ciprini

Takalo

Tosti

et al. 2007

A&A

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Aims. New data and results on the optical behaviour of the prominent blazar PKS 0735+178 (also know as OI 158, S3 0735+17, DA 237, 1ES 0735+178, 3EG J0737+1721) are presented, through the most continuous BV RI data available in the period 1994-2004 (about 500 nights of observations). In addition, the whole historical light curve, and a new photometric calibration of comparison stars in the field of this source are reported. Methods. Several methods for timeseries analysis of sparse data sets are developed, adapted and applied to the reconstructed historical light curve and to each observing season of our unpublished optical database on PKS 0735+178. Optical spectral indexes are calculated from the multi-band observations and studied on long-term (years) durations as well. For the first time in this source, variability modes, characteristic timescales and the signal power spectrum are explored and identified over 3 decades in time with a sufficient statistics. The novel investigation of mid-term optical scales (days, weeks), could be also applied and compared to blazar gamma-ray light curves that will be provided, on the same timescales, by the forthcoming GLAST observatory. Results. In the last 10 years the optical emission of PKS 0735+178 exhibited a rather achromatic behaviour and a variability mode resembling the shot-noise. The source was in a intermediate or low brightness level, showing a mild flaring activity and a superimposition/succession of rapid and slower flares, without extraordinary and isolated outbursts but, at any rate, characterized by one major active phase in 2001. Several mid-term scales of variability were found, the more common falling into duration intervals of about 27-28 days, 50-56 days and 76-79 days. Rapid variability in the historical light curve appears to be modulated by a general, slower and rather oscillating temporal trend, where typical amplitudes of about 4.5, 8.5 and 11-13 years can be identified. This spectral and temporal analysis, accompanying our data publication, suggests the occurrence of distinctive signatures at mid-term durations that can likely be of transitory nature. On the other hand the possible pseudo-cyclical or multi-component modulations at long times could be more stable, recurrent and correlated to the bimodal radio flux behaviour and the twisted radio structure observed by several years in this blazar.

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Section: Comparison Stars Photometrysupporting

confidence: 81%

Section: Comparison Stars Photometrysupporting

confidence: 81%

Ten-year optical monitoring of PKS 0735+178: historical comparison, multiband behavior, and variability timescales

Ciprini

Takalo

Tosti

et al. 2007

A&A

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“…This Ðeld has been calibrated by many previous authors (McGimsey et al 1976, Fiorucci & Tosti 1996, Villata et al 1996, Boltwood 1996, Takalo et al 1994, Penston & Wing 1973, Kinman & Conklin 1971, and Smith et al 1985. The high level of inconsistency in calibrations of star 4 (our star 9) has led to suggestions that this star may be signiÐcantly variable.…”

Section: Pks 0528]134mentioning

confidence: 66%

“…This Ðeld has been calibrated by & (1976), Ve ron Ve ron McGimsey et al (1976), and Villata et al (1998). Only a single star-Ðlter combination (star 1 of & 1976 Ve ron Ve ron in B) is common to any of the calibrations.…”

Section: Mrk 421mentioning

confidence: 99%

Optical and Near-Infrared Calibration of AGN Field Stars: An All-Sky Network of Faint Stars Calibrated on the Landolt System

González‐Pérez

Kidger

Martín-Luis

2001

The Astronomical Journal

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We present a total of 12,436 photometric measures of 371 Ðeld stars of 26 quasars in the visible (UBV RI) and 22,276 photometric measures of 122 Ðeld stars of 13 quasars in the near-infrared (JHK), giving a total of 34,712 measures. Of these, 115 stars in 12 Ðelds are calibrated in both ranges. One further Ðeld, Mrk 421, was calibrated, but on close examination all sources were found to be probably nonstellar ; thus these results are not included here. The stars observed cover the range from V \ 11 to V \ 20 and from K \ 9 to K \ 17 and are well distributed around the sky north of declination [30¡. This represents the initial sample of an extensive catalog of calibrated Ðelds that will cover the northern sky down to declination [30¡ and that will cover a wide range of Galactic latitudes. These Ðelds will be useful both for photometry of AGNs in the range from B to K and also as faint calibration standards for large telescopes. The median absolute total error on the photometry, including all known error sources, ranges from 0.008 mag in J to 0.034 mag in B. These errors will be greatly reduced with the addition of further data in the future, although the Ðnal precision is fundamentally limited by the photometric errors in the existing lists of calibration stars used to calibrate these data.

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“…The exposure time was 300 and 150 s for the B and V Ðlter, respectively (the numbers in parentheses in Table 1 correspond to the UT time of the midpoint of the corresponding exposure). Comparison stars for the AO 0235]164 photometry were taken from McGimsey et al (1976) and Smith et al (1985).…”

Section: The Optical and Radio Datamentioning

confidence: 99%

The Recent High State of the BL Lacertae Object AO 0235 and Cross‐Correlations between Optical and Radio Bands

Roy

Papadakis

Ramos-Colon

et al. 2000

ApJ

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We present new optical (B, V , R, I) and radio (at 14.5, 8.5, and 4.8 GHz) observations of the c-rayÈ loud blazar AO 0235]164 obtained during the high state of 1997 DecemberÈ1998 January. The data were combined with historical light curves from the literature to study correlated optical and radio variations over a time span of more than 20 years. Flux variability with large and energy-dependent amplitude is observed at both wave bands, with the source varying over all timescales sampled (yearsmonths-days), in agreement with previous reports. We have performed a cross-correlation analysis of optical and radio light curves applying various detailed statistical methods. The principal results of our analysis can be summarized as follows : (1) we Ðnd that the optical and radio variations exhibit correlated Ñux changes at their "" average ÏÏ level, stressing the conclusion that the same emission mechanism is responsible for the radiation in the two bands (i.e., synchrotron emission from shocked plasma in the jet). However, as previously reported, a few strong Ñares at optical do not have obvious counterparts at longer wavelengths, possibly indicating that an additional component is present in the optical (e.g., microlensing), or, alternatively, rapid cooling of the synchrotron particles in a radiative shock. (2) Periodic variations are observed at radio frequencies (14.5 and 8.0 GHz) with a pattern repeating every D5.8 years, as indicated by the Lomb-Scargle periodogram. This is the Ðrst report for periodicity at radio wavelengths for this source ; future continuous monitoring is needed to conÐrm this result. (3) Through the analysis of B[V and R[I slopes, we observe large spectral variations, with a "" bimodal ÏÏ behavior. In the Ðrst state, the emission is consistent with a variable power law all across the sampled optical region (from R to V bands) ; in the second state, the R[I slope is constant while the B[V slope varies, i.e., the continuum has various degrees of curvature at the shorter wavelengths. In general, the power-law slope is not correlated with the Ñux of the source. However, there is an indication that when the source is in the Ðrst state, the spectrum becomes softer as the source brightens.

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Photoelectric UBV sequences in the fields of extragalactic sources

Cited by 10 publications

References 0 publications

Ten-year optical monitoring of PKS 0735+178: historical comparison, multiband behavior, and variability timescales

Ten-year optical monitoring of PKS 0735+178: historical comparison, multiband behavior, and variability timescales

Optical and Near-Infrared Calibration of AGN Field Stars: An All-Sky Network of Faint Stars Calibrated on the Landolt System

The Recent High State of the BL Lacertae Object AO 0235 and Cross‐Correlations between Optical and Radio Bands

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