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Optical photometry of TX0506+056

ATel #10831; William Keel (Univ of Alabama), Marcos Santander (Univ of Alabama)
on 7 Oct 2017; 18:58 UT
Credential Certification: William Keel (wkeel@ua.edu)

Subjects: Optical, Blazar

Referred to by ATel #: 10838, 10840, 10844, 10861

The blazar TX0506+056 has attracted recent attention through its location in the error box of a high-energy Ice Cube neutrino detection (https://gcn.gsfc.nasa.gov/gcn3/21916.gcn3) and gamma-ray flaring (Atel #10791) We report recent photometry of TX0506+056 obtained in Johnson V and Cousins R passbands using the 1-meter Kapteyn telescope at La Palma, operated remotely by the SARA consortium. A total of 20 minutes' integration per filter was used, in segments timed so the midpoint of all three sequences was the nearly same. Photometric zero points and transformations used two sets of Landolt standard stars bracketing the blazar in airmass. For the period 0453-0555 UT on 29 September 2017 (central JD 2458025.72), mean magnitudes were B=15.24, V=14.70, R=14.27. Poisson uncertainly is smaller than 1% for each. The R data were obtained first and last, setting the strongest limits on hours-scale variability at <0.5% per hour. The V magnitude suggests continued decline of the flare reported from ASAS-SN data (Atel #10794).