Recent rapid optical rebrightening down to R=14.0 of the flaring blazar 3C 279
ATel #11464; Alessandro Marchini (Astronomical Observatory, Department of Physical Sciences, Earth and Environment (DSFTA), University of Siena - Italy), Giacomo Bonnoli, Vincenzo Millucci, Bartolomeo Trefoloni (DSFTA, University of Siena - Italy), Paolo Da Vela (INFN - Bari)
on 22 Mar 2018; 20:52 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Giacomo Bonnoli (giacomo.bonnoli@unisi.it)
Subjects: Optical, Blazar
We observed last night the z=0.5362 (Marziani et al. 1996, ApJS, 104, 37)
flat-spectrum radio quasar 3C 279 (at FK5 coordinates RA 12 56 11.167
Dec -05 47 21.52 J2000.0) with the 0.3 m telescope at the Astronomical
Observatory of the University of Siena. This observation was performed
within the frame of a guidance project about astrophysics involving high
school students from the Liceo "Galileo Galilei" (Siena).
Observation of this target was performed as follow-up of the current active state announced in the gamma-ray band by
the Fermi/LAT collaboration (ATel #11189) and followed by many ground-based and orbiting instruments observing at all wavelengths (ATel
#11190,#11196,#11200,#11202,#11216,#11239,#11246,#11354). Observations consist of 3 x 300 s exposures in the Johnson-Cousins
R filter, taken in 2x2 binning under good observing conditions with clear
sky and seeing 4.8" (FWHM), starting on Mar 21.11 . The source altitude was about 31 degrees during the observation.
After dark current subtraction and flat field correction images were averaged
and preliminary photometric analysis was performed by means of the MaximDL
software package. Reference and check stars in the field of view were taken
from the finding chart made available by Landessternwarte Koenigstuhl at
https://www.lsw.uni-heidelberg.de/projects/extragalactic/charts/1253-055.html
. The reference R magnitudes for these stars are taken from Villata et
al., A&AS 130, 305 (1998).
We obtained for 3C 279 a magnitude R=14.02 +- 0.01 on Mar 22.12. Quoted uncertainty is statistical only. Measurement
comes from a preliminary photometric analysis and may be subject to later
refinement. This value is about 1 magnitude below the latest R-band measurement made publicly available by the Tuorla Observatory at http://users.utu.fi/kani/1m/3C_279_l.png and relative to an observation performed on Mar 19. We can also compare this measurement
with the previous observations performed within our blazar monitoring program and shown in the following table:
Civil Date (UT) Rmag dRmag Notes
2018 Jan 3.13 15.38 0.04 strong moon, poor sky
2018 Jan 13.17 14.70 0.02
2018 Jan 18.15 13.87 0.02
2018 Feb 28.01 14.88 0.01
2018 Mar 22.12 14.02 0.01
Our dataset alone hints to a rebrightening of the optical active state of the blazar, while the comparison with latest Tuorla observations adds that there was a recent and rather rapid increase in the flux following a period of few nights of apparent stability around R=15.0. This might be related to the onset of a bright sub-flare. We will continue monitoring the source in the following nights. Multi-wavelength follow-up is strongly encouraged.
Any enquiry on these observations can be addressed either to Alessandro
Marchini (alessandro.marchini@unisi.it) or to Giacomo Bonnoli (giacomo.bonnoli@unisi.it).
We thank all the involved high school students for their enthusiastic participation
in the observations and photometric analyses performed along their guidance
project: L. Amato, N. Aurigi, S. Bandini, C. Bechi, C. Benvenuti, L. Berti, A.E. Bianchi, P. Bosco, G. Cannari, S. Ciampoli, R. Del Colombo, R. Di Domenico, E. Dringoli, A. Finetti, C. Franco, M. Innocenti, G. Mancianti, A. Mauro, S. Mazzini, E. Messina, T. Nicosia, F. Papini, E. Picchi, M. Rossi, A. Saletti, S. Savelli, M. Sonno, B. Spagnesi, I. Sprugnoli, A. Stabile, L. Tran, G. Vagheggini.
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