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Calvera is an unusual isolated neutron star with pure thermal X-ray spectrumtypical for central compact objects in supernova remnants. On the other hand,its rotation period and spin-down rate are typical for ordinaryrotation-powered pulsars. It was discovered and studied in X-rays and not yetdetected in other spectral domains. We present deep optical imaging of theCalvera field obtained with the Gran Telescopio Canarias in $g'$ and $i'$bands. Within $\approx 1^{\prime\prime}$ vicinity of Calvera, we detected twopoint-like objects invisible at previous shallow observations. However,accurate astrometry showed that none of them can be identified with the pulsar.We put new upper limits on its optical brightness of $g' > 27.87$ and $i' >26.84$. We also reanalyzed all available archival X-ray data on Calvera.Comparison of the Calvera thermal emission parameters and upper limits onoptical and non-thermal X-ray emission with respective data on rotation-poweredpulsars shows that Calvera might belong to the class of ordinary middle-agedpulsars, if we assume that its distance is in the range of $1.5-5$ kpc.

Deep optical observations of unusual neutron star Calvera with the GTC