Discovery of Five New X-ray–Selected BL Lacertae Objects and Three New Quasars

Through combined ROSAT and VLA observations, we have identified 19 BL Lac/quasar candidates. In 1994 December, 1995 January and October, and 1996 January 1996, we obtained spectra of all 19 candidates using the 2.16-m telescope of Beijing Astronomical Observatory. The dispersion used is 195 Å mm−1, which yields a dispersion of about 4.65 Å pixel−1, and the wavelength coverage is 3500–7800 Å. Five of these objects are uniformly featureless, and we identify them as BL Lac objects. Three new quasars are also identified. Table 1 presents VLA positions and redshifts for the 5 new BL Lac objects and three new quasars. By checking them in the NASA/IPAC Extragalactic Database (NED) and Véron-Cetty & Véron’s (1993) Catalogue of Quasars and AGNs, and other recent reports about discovery of new BL Lac objects and quasars, we find that these sources are previously unreported.

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BL Lacertae objects as an evolutionary population

Symposium - International Astronomical Union ◽

10.1017/s0074180900153252 ◽

1986 ◽

Vol 119 ◽

pp. 491-492

Author(s):

A. Cavaliere ◽

E. Giallongo ◽

F. Vagnetti

Keyword(s):

Luminosity Function ◽

Bl Lacertae Objects ◽

Bl Lac Objects ◽

Bl Lacertae ◽

Bl Lac ◽

Bl Lacs

If the BL Lac Objects are active nuclei with a beamed component that is dominant when directed at us, their observed luminosity function must comprise a flat faint branch: N(L)dL ∝ L1+1/pdL with p=4.5 (Urry and Shafer 1984). If this is flatter than the LF NP(L) of the parent objects at equal observed L, then we expect the counts of BL Lacs to flatten out in turn at fluxes quite higher than the counts of the parents, even when both populations evolve strongly and uniformly with comparable timescales (Cavaliere, Giallongo and Vagnetti 1985).

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The Rosat X-Ray Spectra of BL Lacertae Objects

Symposium - International Astronomical Union ◽

10.1017/s0074180900080761 ◽

1996 ◽

Vol 175 ◽

pp. 267-268

Author(s):

Paolo Padovani ◽

Paolo Giommi

Keyword(s):

Spectral Information ◽

Spectral Indices ◽

Bl Lacertae Objects ◽

X Ray ◽

Bl Lacertae ◽

Bl Lac ◽

Bl Lacs ◽

Selection Of

We have analyzed the X-ray spectra of all BL Lacs observed (as pointed or serendipitous sources) by ROSAT. Spectral indices were obtained from the hardness ratios given in the WGA catalogue, a large list of X-ray sources generated from all the ROSAT PSPC pointed observations. The selection of the objects was done by cross-correlating the first revision of the WGA catalogue with our recent catalogue of BL Lacs. This resulted in 163 observations of 85 distinct BL Lacs, which correspond to about half the confirmed BL Lacs presently known. This represents the largest number of BL Lacs for which homogeneous X-ray spectral information is available and the largest BL Lac sample ever studied at X-ray frequencies.

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X-Ray Spectra of BL Lacertae Objects from the ROSAT Archive

Symposium - International Astronomical Union ◽

10.1017/s007418090008075x ◽

1996 ◽

Vol 175 ◽

pp. 265-266 ◽

Cited By ~ 2

Author(s):

G. Lamer ◽

H. Brunner ◽

R. Staubert

Keyword(s):

Broad Band ◽

Spectral Indices ◽

Photoelectric Absorption ◽

Bl Lac Objects ◽

X Ray ◽

Bl Lacertae ◽

V Band ◽

Bl Lac ◽

5 Ghz ◽

Single Power

Our sample comprises all BL Lac objects listed in the catalogue of Véron-Cetty & Véron (1993) and which are detected in a ROSAT PSPC observation with at least 50 source counts: 74 objects in total. We reduced the data from the ROSAT archives at MPE and GSFC and fitted single power-law models with photoelectric absorption to the spectra. We calculated the broad band spectral indices αrx, αro, and αox from the ROSAT 1 keV fluxes, 5 GHz radio, and optical V band fluxes (Véron-Cetty & Véron 1993).

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A Comparison of the X-ray Spectra of Quasars and BL Lac Objects

Symposium - International Astronomical Union ◽

10.1017/s0074180900140811 ◽

1989 ◽

Vol 134 ◽

pp. 197-198

Author(s):

D. M. Worrall ◽

B. J. Wilkes

Keyword(s):

Power Law ◽

Radio Spectrum ◽

Spectral Indices ◽

Mean Power ◽

Bl Lac Objects ◽

X Ray ◽

Bl Lac ◽

Infrared Frequencies

Quasars with similar core-compact radio properties can be classified by their differences at optical and infrared frequencies. Their X-ray properties might be expected to be similar if the synchrotron self-Compton mechanism relates their radio and X-ray emission. We have compared the 0.2–3.5 keV mean power-law energy spectral indices, , for 4 quasar classes: 12 Highly Polarized QSOs (HPQs), 19 Flat Radio Spectrum, core-compact, low-polarization, QSOs (FRS QSOs), 24 radio-selected BL Lac objects, and 7 X-ray-selected BL Lac objects.

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VERITAS OBSERVATIONS OF RELATIVISTIC OUTFLOWS IN LOW- AND INTERMEDIATE-FREQUENCY-PEAKED BL LAC OBJECTS

International Journal of Modern Physics Conference Series ◽

10.1142/s2010194514601781 ◽

2014 ◽

Vol 28 ◽

pp. 1460178

Author(s):

◽

HEIKE PROKOPH

Keyword(s):

Gamma Ray ◽

Intermediate Frequency ◽

Bl Lac Objects ◽

Bl Lacertae ◽

Bl Lac ◽

Bl Lacs ◽

Gamma Ray Telescopes ◽

Very High

The majority of blazars detected at very high energies (VHE; E > 100 GeV) are high-frequency-peaked BL Lac objects (HBLs). Low- and intermediate-frequency-peaked BL Lacs (LBLs/IBLs with synchrotron-peak frequencies in the infrared and optical regime) are generally more powerful, more luminous, and have a richer jet environment than HBLs. However, only a handful of these IBL and LBLs have been detected by ground-based gamma-ray telescopes, typically during high-flux states. The VERITAS array has been monitoring five known VHE LBLs/IBLs since 2009: 3C 66A, W Comae, PKS 1424+240, S5 0716+714 and BL Lacertae, with typical exposures of 5-10 hours per year. The results of these long-term observations are presented, including a bright, subhour-scale VHE flare of BL Lacertae in June 2011, the first low-state detections of 3C 66A and W Comae, and the detection and characterization of the IBL B2 1215+30.

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The intraday variability in the radio-selected and X-ray-selected BL Lacertae objects

Astronomy and Astrophysics Supplement Series ◽

10.1051/aas:1998360 ◽

1998 ◽

Vol 132 (1) ◽

pp. 83-92 ◽

Cited By ~ 49

Author(s):

J. M. Bai ◽

G. Z. Xie ◽

K. H. Li ◽

X. Zhang ◽

W. W. Liu

Keyword(s):

Bl Lacertae Objects ◽

X Ray ◽

Bl Lacertae ◽

Intraday Variability

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The variability and periods in the BL Lac AO 0235+164

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315001921 ◽

2014 ◽

Vol 10 (S313) ◽

pp. 81-82

Author(s):

J. H. Fan ◽

O. Kurtanidze ◽

X. Liu ◽

Y. Liu ◽

H. T. Wang ◽

...

Keyword(s):

Ccd Camera ◽

Monitoring Programme ◽

Bl Lacertae Objects ◽

Monitoring Period ◽

Bl Lacertae ◽

Periodicity Analysis ◽

Photometric Observations ◽

Bl Lac ◽

Primary Focus ◽

Electro Magnetic

AbstractVariability is one of the extreme observational properties of BL Lacertae objects. AO 0235+164 is a well studied BL Lac through the whole electro-magnetic wavebands, it is violently variable in the optical bands. In the present work, we show its optical R band photometric observations carried out during the period of Nov. 2006 to Dec. 2012 using the Ap6E CCD camera attached to the primary focus of the 70 cm meniscus telescope at Abastumani Observatory, Georgia. It shows a large variation of ΔR = 4.88 mag (14.20 - 19.08 mag) during our monitoring period. When periodicity analysis methods are adopted to its R observations from our Abastumani monitoring programme and those in the literature, the signs of some periods, P1 = 8.26 yr, P2 = 0.55 yr, P3 = 0.85 yr, P4 = 1.99 yr are found.

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