Alert Notice 717: Flaring of blazar S5 1803+78 continues

August 17, 2020

AAVSO Forum threads (scroll to the bottom of a thread for latest posts):
- High Energy Network (HEN):

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The blazar S5 1803+78 is continuing to be active following a major flare in early April 2020, when it reached V magnitude 14.1. It then faded to 15.8 V in early May. It began brightening again on August 5, reaching 14.6 V on August 7, and was 14.37 V +/- 0.007 on 2020 Aug. 17.0519 UT (Adolfo Darriba, Madrid, Spain), according to observations in the AAVSO International Database (see light curve below). S5 1803+78 has an optical range of 13.8 - 18.1 V.

AAVSO coverage of S5 1803+78 in April 2020 was triggered by the discovery of its flaring by David Lane (Stillwater Lake, NS, Canada; Apr. 09.2638 UT, 14.331 V +/-0.007), with confirmation by Jordi Berenguer (Sant Celoni, Spain; Apr. 10.8477 UT, 14.221 V +/-0.009), Gianpiero Locatelli (Cuneo, Italy; Apr. 10.8614 UT, 14.206 V +/-0.007), and Heinz-Bernd Eggenstein (Wunstorf, Germany; Apr. 10.8879 UT, 14.155 V +/-0.02).

In the April flare, Venters et al. (ATel #13633) reported the detection of gamma-ray flaring from S5 1803+78 (at the highest level ever seen for the target) in observations obtained 2020 April 12 UT using the Large Area Telescope of the Fermi Gamma-ray Space Telescope.

Pursimo et al. (ATel #13711) reported that optical observations of S5 1803+78 obtained 2020 April 19.2479 UT (14.518 r +/- 0.002) and April 20.2396 UT (14.670 r +/- 0.002) using the Nordic Optical Telescope (La Palma) showed the target close to its historical maximum brightness.

Observations in all filters and at as high a cadence as a good S/N allows are requested. Visual observations are also welcome.

AAVSO High Energy Network (HEN) Observing Section Leader Dave Hinzel strongly encourages observers to monitor this blazar. For questions about S5 1803+78, please post in the AAVSO HEN discussion forum thread for this blazar given above. For questions about participating in HEN Section activities, see the Section webpage or email Dave directly.

Light curve of S5 1803+78 for 2020 March 11 - August 17, from the AAVSO International Database, plotted using the AAVSO Light Curve Generator V.2.

Coordinates (2000.0): R.A. 18 00 45.69   Decl. +78 28 04.0   (from VSX page for S5 1803+78)

Charts with comparison stars for S5 1803+78 may be created using the AAVSO Variable Star Plotter (VSP).

Please report all observations to the AAVSO International Database using the name S5 1803+78.

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen.

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