1,721,030 research outputs found
Optical follow-up of 1FGL J0211.2+1049
No full textPrompted by Atel #3120 of a strong Gamma-ray flare of the BL Lac object CGRaBS J0211+1051, we observed it on January 27.87 2011 with the 23 cm telescope on top the Department of Physics of La Sapienza University with an R_C filter and an Apogee U2 CCD camera. Eight comparison stars were taken from the GSC2.3 catalogue to define the source magnitude. The source appeared at R_C=13.37, definitely brighter that the historical GSC2.3 value of 15.11, based on the POSS I (year 1950) red plate
GB6 J1058+5628: A NEW QUASI-PERIODIC BL LAC OBJECT FROM THE ASIAGO PLATE ARCHIVE
No full textWe present the historic photographic light curves of three little known blazars ( two BL Lac objects and one FSRQ), GB6 J1058+5628, GB6 J1148+5254, and GB6 J1209+4119, spanning a time interval of about 50 years, mostly built using the Asiago plate archive. All objects show evident long-term variability, over which short-term variations are superposed. One source, GB6 J1058+5628, showed a marked quasi-periodic variability of 1 mag on timescale of about 6.3 years, making it one of the few BL Lac objects with a quasi-periodic behavior
Optical follow-up of S5 1803+78
No full textFollowing the announcement of a Gamma-ray flare of the blazar S5 1803+78 (ATel #3322) on May 2 2011, I observed the source on May 4 2011 at 22:35 UT with the 23 cm telescope on top the Department of Physics of La Sapienza University with an R_C filter and an Apogee U2 CCD camera. Comparison stars were taken from Nesci et al. (2002, AJ 124, 53). The source appeared at R=15.6 ±0.1, an average value for this source, whose large optical flares are at R~14
Optical follow-up of 4C+21.35
No full textThe blazar 4C+21.35 (PKS 1222+21) was reported by AGILE (ATel #2686) and FermiGST (ATel #2687) to have a Gamma-ray flare; SWIFT X-ray and UV-optical follow-up was reported in Atel #2698; polarimetry in ATel #2693. We observed the source with the 31cm telescope of Greve in Chianti equipped with a back-illuminated SITe SIA502A CCD chip and Johnson-Cousins BVR filters. The comparison stars by Raiteri et al
Digitizing the Markarian Survey: first tests of scientific importance
No full textWe present technical details of the digitization of the First Byurakan Survey plates with an EPSON 1680 Pro scanner, a joint venture of the Rome University and the Byurakan Observatory. The astronomical coordinate system is applied to each plate by a semi-automatic procedure, the transparency converted to intensity and all the spectra in each plate automatically extracted by IRAF procedures. A first check of the photometric accuracy achieved is presented
SPECTRA IN THE DIGITIZED FIRST BYURAKAN SURVEY
No full textThe Digitized First Byurakan Survey (DFBS) is accessible on a dedicated web site at the Department of Physics of La Sapienza University. It covers about 17 000 square degrees and provides low resolution spectra of sources down to B = 16.5 mag. Both the digitized plates and the automatically extracted spectra can be retrieved. We present the main characteristics of the spectra and their relevance as proxies for the low dispersion spectra which will be provided by the forthcoming Gaia mission. Detectability of spectral features, overall spectral energy distribution and accuracy of the photometric information is briefly discussed
Optical variability of the strong-lined and X-ray-bright source 1WGA J0447.9-0322
No full textWe present the historic light curve of 1WGA J0447.9-0322, spanning the time interval from 1962 to 1991, built using the Asiago archive plates. The source shows small fluctuations of about 0.3 mag around B 16 until 1986 and a fast dimming of its average level by about 0.5 mag after that date, again with small short-term variations. The variability pattern is within the values shown by other QSOs with long-term monitoring, notwithstanding its high X-ray/optical ratio. We also present its overall spectral energy distribution using literature data and recent UV-optical Swift observations
The WEBT campaign to observe AO 0235+16 in the 2003-2004 observing season. Results from radio-to-optical monitoring and XMM-Newton observations
No full textA multiwavelength campaign to observe the BL Lac object AO 0235+16 (z=0.94) was set up by the Whole Earth Blazar Telescope (WEBT) collaboration during the observing seasons 2003-2004 and 2004-2005, involving radio, near-IR and optical photometric monitoring, VLBA monitoring, optical spectral monitoring, and three pointings by the XMM-Newton satellite. Here we report on the results of the first season, which involved the participation of 24 optical and near-IR telescopes and 4 radio telescopes, as well as the first XMM-Newton pointing, which occurred on January 18-19, 2004. Unpublished data from previous epochs were also collected (from 5 optical-NIR and 3 radio telescopes), in order to fill the gap between the end of the period presented in Raiteri et al. (2001) and the start of the WEBT campaign. The contribution of the southern AGN, 2 arcsec distant from the source, is taken into account. It is found to especially affect the blue part of the optical spectrum when the source is faint. In the optical and near-IR the source has been very active in the last 3 years, although it has been rather faint most of the time, with noticeable variations of more than a magnitude over a few days. In contrast, in the radio bands it appears to have been “quiescent” since early 2000. The major radio (and optical) outburst predicted to peak around February-March 2004 (with a six month uncertainty) has not occurred yet. When comparing our results with the historical light curves, two different behaviours seem to characterize the optical outbursts: only the major events present a radio counterpart. The X-ray spectra obtained by the three EPIC detectors are well fitted by a power law with extra-absorption at z=0.524; the energy index in the 0.2-10 keV range is well constrained: α=0.645 ± 0.028 and the 1 keV flux density is 0.311 ± 0.008~μ Jy. The analysis of the X-ray light curves reveals that no significant variations occurred during the pointing. In contrast, simultaneous dense radio monitoring with the 100 m telescope at Effelsberg shows a ~2-3% flux decrease in 6-7 h, which, if intrinsic, would imply a brightness temperature well above the Compton limit and hence a lower limit to the Doppler factor δ ⪆ 46. We construct the broad-band spectral energy distribution of January 18-19, 2004 with simultaneous radio data from Effelsberg, optical data from the Nordic Optical Telescope (NOT), optical-UV data from the Optical Monitor onboard XMM-Newton, and X-ray data by the EPIC instruments. Particular care is taken to correct data for extinction due to both the Milky Way and the z=0.524 absorber. The resulting SED suggests the existence of a bump in the UV spectral region
Optical Activity of HDE 245770/A0535+26 System
No full textThe O9.7IIIe star HDE 245770, nicknamed Flavia, is the optical counterpart of the X-ray pulsar A0535+26. On February 5, 2011 at the Loiano 1.52 m telescope from UT 18hh 40mm 40ss we performed optical B, V spectrophotometry of HDE 245770 and starting from UT 18hh 51mm 11ss to 19hh 15mm 37ss we performed optical spectroscopy in the range 330 - 785 nm [Delta(lambda) from about 0.4 to 0.3 nm] by using the BFOSC (Bologna Faint Object Spectrograph & Camera)
A pre-outburst spectrum of KT Eri from the Digitized First Byurakan Survey (DFBS)
No full textA historical spectrum, taken on Jan 25 1971, of the recently exploded Nova KT Eri is recorded on the plate n. 0350 of the First Byurakan Survey (FBS). This Survey was made with a thin objective prism atop the 102/130/213 cm Schmidt telescope of the Byurakan Observatory and IIaF emulsion, covering the wavelength range 3400-6900 A. Nearly all the plates of this Survey (a.k.a Markarian Survey) have been digitized by a collaboration of the Byurakan Observatory, University La Sapienza, Rome Italy, and Cornell University (USA)
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