A Newly-confirmed Bright Northern R CrB Star: AO Her
I am delighted to announce that Patrick Tisserand, Geoff Clayton and I have spectroscopically-confirmed the R CrB status of AO Her which, until now, was classified as a semiregular variable with a "period" of 370 days. AO Her's position (17 35 36.17 +50 24 39.6 J2000.0) and out-of-decline brightness of between 10th and 11th magnitude make it one of the brightest and most accessible R CrB stars north of the equator.
In 2008, Patrick Tisserand published the paper "Tracking down R Coronae Borealis stars from their mid-infrared WISE colours" in Astronomy & Astrophysics, 539, 51. That paper contained 1602 candidate objects which shared certain spectral energy distribution characteristics with known R CrB stars. AO Her is entry 1322 in that catalog.
The AAVSO International Database contains over a hundred visual observations by two observers, Tomasz Krzyt and Gary Poyner, between 2008 and 2012. The lightcurve data they report is clearly consistent with an R CrB classification. The second figure below contains photometry from the Catalina Rapid Transient Survey (http://crts.caltech.edu/)
The spectrum confirming its nature was acquired with the FLOYDS spectrograph on the 2m LCOGT/Faulkes Telescope North as a result of a late-season allocation of Director's Discretionary Time. We are grateful for the allocation and for the efforts of David Sand and Stefano Valenti in the acquisition and reduction of the spectrum.
The AO Her spectrum, along with data from our larger campaign, will be published and discussed in a future paper. We encourage AAVSO observers to monitor this apparently very active R CrB star as existing and new lightcurve data will be presented in the forthcoming publication.
A new sequence for AO Her covering its expected magnitude range has been created by Mike Simonsen and so we invite observers to start following this star as soon as possible.