An AGN sample with high X-ray-to-optical flux ratio from RASS

Wei, J. Y.; Xu, Dawei; Dong, Xiao-Bo; Hu, Jingyao

doi:10.1051/aas:1999514

Cited by 42 publications

(18 citation statements)

References 11 publications

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“…SHBL J013632.5+390559. This object has already been identified as BL Lac by Wei et al (1999). We confirm the identification, but its redshift cannot be determined because of the absence of emission and absorption features.…”

Section: Classificationsupporting

confidence: 70%

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The sedentary survey of extreme high-energy peaked BL Lacs

Piranomonte¹,

Perri

Giommi

et al. 2007

A&A

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Aims. The multi-frequency sedentary survey is a flux-limited, statistically well-defined sample of highly X-ray dominated (i.e., with a very high X-ray to radio flux ratio) BL Lacertae objects, which includes 150 sources. In this paper, the third of the series, we report the results of a dedicated optical spectroscopy campaign that, together with results from other independent optical follow-up programs, led to the spectroscopic identification of all sources in the sample. Methods. We carried out a systematic spectroscopic campaign for the observation of all unidentified objects of the sample using the ESO 3.6 m, the KPNO 4 m, and the TNG optical telescopes.Results. We present new identifications and optical spectra for 76 sources, 50 of which are new BL Lac objects, 18 are sources previously referred as BL Lacs but for which no redshift information was available, and 8 are broad emission-line AGNs. We find that the multi-frequency selection technique used to build the survey is highly efficient (∼90%) in selecting BL Lacs objects. We present positional and spectroscopic information for all confirmed BL Lac objects. Our data allowed us to determine 36 redshifts out of the 50 new BL Lacs and 5 new redshifts for the previously known objects. The redshift distribution of the complete sample is presented and compared with that of other BL Lacs samples. For 26 sources without recognizable absorption features, we calculated lower limits to the redshift using a method based on simulated optical spectra with different ratios between jet and galaxy emission. For a subsample of 38 object with high-quality spectra, we find a correlation between the optical spectral slope, the 1.4 GHz radio luminosity, and the Ca H&K break value, indicating that for powerful/beamed sources the optical light is dominated by the non-thermal emission from the jet.

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Section: Classificationsupporting

confidence: 70%

“…SHBL J075124.9+173051. This object was identified as Seyfert 2 by Wei et al (1999) with redshift z = 0.185. We confirm its redshift but classify it as BL Lac, as its optical spectrum does not show emission lines.…”

Section: Classificationmentioning

confidence: 99%

The sedentary survey of extreme high-energy peaked BL Lacs

Piranomonte¹,

Perri

Giommi

et al. 2007

A&A

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“…Flux F λ in units of 10 −16 erg/cm 2 /s/Å depending on the wavelength inÅ given in the observer rest frame. The spectra of #1 and #6 are obtained from Wei et al (1999), #2 is from Boroson & Green (1992) and the others are from Abolfathi et al (2018). and MMPP (Multi-Mode Photometer-Polarimeter) devices in photometric mode with 10 medium-band interference SED filters.…”

Section: Observational Technique and Reductionmentioning

confidence: 99%

Medium-band photometric reverberation mapping of AGNs at 0.1 < z < 0.8. Techniques and sample

Malygin¹,

Уклеин²,

Shablovinskaya³

et al. 2020

caosp

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The most popular method of the broad-line region size estimation in active galactic nuclei (AGN) is the reverberation mapping based on measuring the time delay between the continuum flux and the flux in the emission lines. In our work, we apply the method of photometric reverberation mapping in mid-band filters, adapted for observations on the 1-m Zeiss-1000 telescope of Special Astrophysical Observatory of Russian Academy of Sciences, for the study of AGN with broad lines in the range of redshifts 0.1 < z < 0.8. This paper provides a sample of 8 objects, describes the technique of observations and data processing for 2 studied objects to demonstrate the stability of the used method.

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“…The chosen attributes from different bands are B − R (optical index), B + 2.5log(CR), lgCR (source count-rate in the broad energy band), HR1 (hardness ratio 1), HR2 (hardness ratio 2), ext (source extent), extl (likelihood of source extent), J − H (infrared index), H − K (infrared index), J + 2.5log(CR). Wei et al (1999) chose logC0.4R + 4.9 as a criterion to preselect active galactic nucleus (AGN) samples, where C is the X-ray count rate and R is the R magnitude. According to the results of the Einstein Medium Sensitivity Survey (EMSS; Stocke et al 1991), the X-rayCtoCoptical flux ratio F X /F opt was found to be very different for different classes of X-ray emitters.…”

Section: Datamentioning

confidence: 99%

An automated classification algorithm for multiwavelength data

2004

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The important step of data preprocessing of data mining is feature selection. Feature selection is used to improve the performance of data mining algorithms by removing the irrelevant and redundant features. By positional cross-identification, the multi-wavelength data of 1656 active galactic nuclei (AGNs), 3718 stars, and 173 galaxies are obtained from optical (USNO-A2.0), X-ray (ROSAT), and infrared (Two Micron All-Sky Survey) bands. In this paper we applied a kind of filter approach named ReliefF to select features from the multi-wavelength data. Then we put forward the naive Bayes classifier to classify the objects with the feature subsets and compare the results with and without feature selection, and those with and without adding weight to features. The result shows that the naive Bayes classifier based on ReliefF algorithms is robust and efficient to preselect AGN candidates.

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An AGN sample with high X-ray-to-optical flux ratio from RASS

Cited by 42 publications

References 11 publications

The sedentary survey of extreme high-energy peaked BL Lacs

The sedentary survey of extreme high-energy peaked BL Lacs

Medium-band photometric reverberation mapping of AGNs at 0.1 < z < 0.8. Techniques and sample

An automated classification algorithm for multiwavelength data

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