Continued Optical Activity in the Blazar BL Lacertae

ATel #14773; Riley M. Corcoran, Warner S. Neal, John J. Slater, Thomas J. Balonek (Colgate Univ., Hamilton, NY USA)
on 11 Jul 2021; 11:35 UT
Credential Certification: Thomas J. Balonek (tbalonek@colgate.edu)

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The most recent optical outburst of blazar BL Lacertae (see ATel #14751 and references therein) is continuing, reaching what we believe is the maximum optical brightness ever reported, R = 11.34 at JD 2,459,406.80. We observed variations between R = 11.40 - 11.34 in a two-and-a-half hour interval from JD 2,459,406.73 - 2,459,406.83. The most rapid microvariability observed was a brightening of 0.04 magnitude in thirty minutes.

We obtain preliminary magnitude measurements using AstroImageJ's aperture photometry function, with object aperture radius 6 arcsec and sky annulus radii 12 to 16 arcsec. Photometric errors for the forty-eight individual two-minute images were typically less than 0.01 magnitude, depending on the variable sky conditions. We use comparison star B (R = 11.93) of Smith et al (1985, AJ, 90, 1184).

Observations were obtained with the Colgate University Foggy Bottom Observatory (Hamilton, NY USA) 0.4-m Ferson telescope equipped with an FLI PL1001 CCD camera and R-Cousins filter. Student research participation at Colgate University is supported by the NASA / New York Space Grant and the Colgate University Justus '43 and Jayne Schlichting Student Research Fund.

We encourage continued multi-wavelength observations of this outburst.