Optical Identification of Joint EUVE and ROSAT Detections in the Southern Hemisphere: Soft Active Galactic Nuclei.

Craig, N.; Fruscione, A.

doi:10.1086/118569

Cited by 17 publications

(17 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Initially detected as a radio source with the Molonglo telescope (Large et al 1981), it has been since observed at different wavelengths (see Abramowski et al 2013c for a short review). After being misidentified as a Seyfert 1 galaxy by Craig & Fruscione (1997) (see Prandini et al 2012 for comments on this misidentification), the source was identified as a bright BL Lac object by Perlman (1998) and classified as an HBL by Landt & Bignall (2008), based on the ratio of the radio core luminosity at 1.4 GHz over the X-ray luminosity at 1 keV.…”

Section: Pks 0447-439mentioning

confidence: 99%

“…The redshift of this source is not yet clearly established, although several values or constraints have been proposed: -z = 0.107, a value based on the misidentification of the source with a Seyfert 1 galaxy (Craig & Fruscione 1997); Notes. The columns give the names of the strongest expected absorption and emission lines, their wavelength in the rest frame in Å, and their nature, which indicate if they appears as absorption or emission lines from the host galaxy, or if they come from an intervening system.…”

Section: Pks 0447-439mentioning

confidence: 99%

See 1 more Smart Citation

Spectroscopy of high-energy BL Lacertae objects with X-shooter on the VLT

Pita

Goldoni

Boisson

et al. 2014

A&A

View full text Add to dashboard Cite

Context. BL Lac objects detected in γ-rays and, particularly, those detected at very high energies (E > 100 GeV) by Cherenkov telescopes are extreme sources with most having redshifts lower than 0.2. Their study gives insights on the acceleration mechanisms in play in such systems and is also a valuable tool for putting constraints on the density of extragalactic background light, especially if several objects are detected at different redshifts. As their spectra are dominated by the non-thermal emission of the jet and the spectral features are weak and narrow in the optical domain, measuring their redshift is challenging. However, such a measure is fundamental as it allows a firm determination of the distance and luminosity of the source, and, therefore, a consistent model of its emission. Aims. Measurement of the redshift of BL Lac objects detected in γ-rays and determination of global properties of their host galaxies is the aim of this study. Methods. We observed a sample of eight BL Lac objects with the X-shooter spectrograph installed at the ESO Very Large Telescope (VLT) to take advantage of its unprecedented wavelength coverage and its resolution, which is about five times higher than generally used in such studies. We extracted UVB to NIR spectra that we then corrected for telluric absorption and calibrated in flux. We systematically searched for spectral features. When possible, we determined the contribution of the host galaxy to the overall emission. Results. Of the eight BL Lac sources, we measured the redshift of five of them and determined lower limits for two through the detection of intervening systems. All seven of these objects have redshifts greater than 0.2. For the remaining one, we estimated, using an indirect method, that its redshift is greater than 0.175. In two cases, we refuted redshift values reported in other publications. Through careful modelling, we determined the magnitude of the host galaxies. In two cases, the detection of emission lines allowed to provide hints on the overall properties of the gas in the host galaxies. Even though we warn that we are dealing with a very small sample, we remark that the redshift determination efficiency of our campaign is higher than for previous campaigns. We argue that it is mainly the result of the comparatively higher resolution of X-shooter.

show abstract

Section: Pks 0447-439mentioning

confidence: 99%

Section: Pks 0447-439mentioning

confidence: 99%

Spectroscopy of high-energy BL Lacertae objects with X-shooter on the VLT

Pita

Goldoni

Boisson

et al. 2014

A&A

View full text Add to dashboard Cite

show abstract

“…30 Multi-wavelength observations with Fermi /LAT, Swift, ATOM and ROTSE were used to draw a contemporaneous spectral energy distribution of this source, which was modelled using an SSC model. The redshift of this object being uncertain, 31,32,33,34 the modelling of multi-wavelength data was used to derive an upper limit on its redshift of z < 0.59.…”

mentioning

confidence: 99%

The H.E.S.S. Extragalactic Sky

Lenain

2014

Int. J. Mod. Phys. Conf. Ser.

View full text Add to dashboard Cite

More than fifty extragalactic very high energy (VHE; E > 100 GeV) sources have been found using ground-based imaging atmospheric Cherenkov telescopes, about twenty of which have been discovered using the H.E.S.S. (High Energy Stereoscopic System) experiment based in Namibia. Even though BL Lac objects are the dominant class of VHE detected extragalactic objects, other types of sources (starburst galaxies, radio galaxies or flat spectrum radio quasars) begin to emerge. A review of the extragalactic sources studied with H.E.S.S. is given, with an emphasis on new results.

show abstract

“…Therefore, about 50% of the BL Lac objects detected with Fermi-LAT (Ackermann et al 2011) have an unknown redshift, and this is also the case for PKS 0447-439. The source was first discovered in the radio band (Large et al 1981) and has since been detected in several observations in the radio, infrared, optical, ultraviolet and X-ray bands (White et al 1994;Gregory et al 1994;Lampton et al 1997;Craig & Fruscione 1997;Haakonsen & Rutledge 2009). It was identified as a bright BL Lac object by Perlman et al (1998) and classified as an HBL by Landt & Bignall (2008), based on the ratio of the radio core luminosity at 1.4 GHz over the X-ray luminosity at 1 keV.…”

mentioning

confidence: 99%

“…A first evaluation of its redshift of z = 0.107 (Craig & Fruscione 1997) was based on a mis-identification with a Seyfert 1 galaxy 1 . Subsequent observations with the CTIO 4 m telescope led to an estimation of z = 0.205 (Perlman et al 1998).…”

mentioning

confidence: 99%

Discovery of TeVγ-ray emission from PKS 0447-439 and derivation of an upper limit on its redshift

Collaboration¹,

Abramowski

Acero

et al. 2013

A&A

View full text Add to dashboard Cite

Very high-energy γ-ray emission from PKS 0447−439 was detected with the H.E.S.S. Cherenkov telescope array in December 2009. This blazar is one of the brightest extragalactic objects in the Fermi bright source list and has a hard spectrum in the MeV to GeV range. In the TeV range, a photon index of 3.89 ± 0.37 (stat) ±0.22 (sys) and a flux normalisation at 1 TeV, Φ 1 TeV = (3.5 ± 1.1(stat) ± 0.9(sys)) × 10were found. The detection with H.E.S.S. triggered observations in the X-ray band with the Swift and RXTE telescopes. Simultaneous UV and optical data from Swift UVOT and data from the optical telescopes ATOM and ROTSE are also available. The spectrum and light curve measured with H.E.S.S. are presented and compared to the multi-wavelength data at lower energies. A rapid flare is seen in the Swift XRT and RXTE data, together with a flux variation in the UV band, at a time scale of the order of one day. A firm upper limit of z < 0.59 on the redshift of PKS 0447−439 is derived from the combined Fermi-LAT and H.E.S.S. data, given the assumptions that there is no upturn in the intrinsic spectrum above the Fermi-LAT energy range and that absorption on the extragalactic background light (EBL) is not weaker than the lower limit provided by current models. The spectral energy distribution is well described by a simple one-zone synchrotron self-Compton scenario, if the redshift of the source is less than z 0.4.

show abstract

Optical Identification of Joint EUVE and ROSAT Detections in the Southern Hemisphere: Soft Active Galactic Nuclei.

Cited by 17 publications

References 0 publications

Spectroscopy of high-energy BL Lacertae objects with X-shooter on the VLT

Spectroscopy of high-energy BL Lacertae objects with X-shooter on the VLT

The H.E.S.S. Extragalactic Sky

Discovery of TeVγ-ray emission from PKS 0447-439 and derivation of an upper limit on its redshift

Contact Info

Product

Resources

About