Optical observations of five X-ray selected BL Lacertae
objects

Villata, M.; Raiteri, C. M.; Popescu, Marcel; Sobrito, G.; Francesco, G. de; Lanteri, L.; Ostorero, L.

doi:10.1051/aas:2000222

Cited by 33 publications

(45 citation statements)

References 13 publications

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“…It exhibits significant optical polarization (Feigelson et al 1986) and variability (Villata et al 2000). The host galaxy was resolved in ground-based images by Feigelson et al (1986), Falomo (1996, and Nilsson et al (2003).…”

Section: Results For Individual Objectsmentioning

confidence: 99%

Optical spectroscopy of BL Lacertae objects

Sbarufatti¹,

Falomo

Treves³

et al. 2006

A&A

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Aims. We present optical spectroscopy for a sample of BL Lac objects, to determine their redshift, to study their broad emission line properties, and to characterize their close environment. Methods. Twelve objects were observed using the ESO 3.6 m and NOT 2.5 m telescopes, obtaining spectra for the BL Lacs and for nearby sources.Results. For seven of these objects, nuclear emission lines and/or absorption lines from the host galaxy were detected. In all the four cases where absorption lines were revealed, the host galaxy has been resolved with HST or ground-based imaging. The broad H α luminosities (or their upper limits) of the BL Lacs are similar to those of radio-loud quasars. For two BL Lacs, spectroscopy of close companions indicates that they are at the redshift of the BL Lacs, and therefore physically associated and probably interacting. Five BL Lacs have a featureless spectrum. In these cases, we apply a new technique to derive lower limits for their redshift, which are consistent with the lower limits deduced from imaging.

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Section: Results For Individual Objectsmentioning

confidence: 99%

Optical spectroscopy of BL Lacertae objects

Sbarufatti¹,

Falomo

Treves³

et al. 2006

A&A

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“…Optical data were taken from the literature and for some objects determined using the Calar Alto 1.23 m telescope (Beckmann 2000a). A campaign for simultaneous optical data has also been performed for a few objects (Villata et al 2000). Variability in the optical band is not expected to be large: all objects presented here are X-ray dominated objects (i.e.…”

Section: Spectral Energy Distributionmentioning

confidence: 99%

BeppoSAX spectral survey of BL Lacs – New spectra and results

Beckmann

Wolter

Celotti

et al. 2002

A&A

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Abstract. We present BeppoSAX LECS, MECS, and PDS spectra of eleven X-ray selected BL Lacertae objects. Combining these sources with the ones presented elsewhere we have a sample of 21 BL Lacs from the Einstein Medium Sensitivity and Einstein Slew Survey. The sample shows strong correlations of several physical parameters with the peak frequency of the synchrotron branch of the spectral energy distribution. In particular the peak frequency is correlated with the X-ray spectral shape: objects with the peak near to the X-ray band show harder and straighter X-ray spectra than those of the low energy peaked sources. This work shows that the recently proposed unification scenario for different types of blazars can hold also within the class of high frequency peaked BL Lac objects.

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“…Multiple photometric optical values were found in the literature, showing a great variation of the source brightness in the optical band from V ¼ 16 to V ¼ 12:8. A complete study of the optical band can be found in Villata et al (2000), where variability on short timescales (a few days) was reported.…”

Section: Introductionmentioning

confidence: 99%

Observation of X‐Ray Variability in the BL Lacertae Object 1ES 1959+65

Giebels

Bloom

Focke

et al. 2002

ApJ

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This paper reports X-ray spectral observations of a relatively nearby (z ¼ 0:048) BL Lac object 1ES 1959+65, which is a potential TeV emitter. The observations include 31 short pointings made by the Unconventional Stellar Aspect (USA) experiment on board the Advanced Research and Global Observation Satellite (ARGOS), and 17 pointings by the Proportional Counter Array (PCA) on board the Rossi X-Ray Timing Explorer (RXTE). Most of these observations were spaced by less than 1 day. 1ES 1959+65 was detected by the ARGOS USA detector in the range 1-16 keV, and by the PCA in the 2-16 keV range but at different times. During the closely spaced RXTE observations beginning on 2000 July 28, the ending of one flare and the start of another are visible, associated with spectral changes, where the photon index C ranges between $1.4 and $1.7, and the spectrum is harder when the source is brighter. This implies that 1ES 1959+65 is an X-rayselected BL Lac type (XBL) blazar, with the X-ray emission likely to originate via the synchrotron process. The USA observations reveal another flare that peaked on 2000 November 14 and doubled the flux within a few days, again associated with spectral changes of the same form. The spectral variability correlated with the flux and timing characteristics of this object that are similar to those of other nearby BL Lac objects and suggest relativistic beaming with a Doppler factor ! 1:6 and magnetic fields on the order of a few milligauss. We also suggest that the steady component of the X-ray emission-present in this object as well as in other XBLs-may be due to the large-scale relativistic jet (such as measured by Chandra in many radio-loud active galactic nuclei) but pointing very closely to our line of sight.

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Optical observations of five X-ray selected BL Lacertae objects

Cited by 33 publications

References 13 publications

Optical spectroscopy of BL Lacertae objects

Optical spectroscopy of BL Lacertae objects

BeppoSAX spectral survey of BL Lacs – New spectra and results

Observation of X‐Ray Variability in the BL Lacertae Object 1ES 1959+65

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