LT Del is a yellow symbiotic system that consists of a bright K3-type giant and a hot subdwarf with a temperature \sim 10 ^ { 5 } K. We present the results of our spectroscopic observations of LT Del over the period 2010-2018 .
In 2017 the star experienced a second low-amplitude ( \Delta V \sim 0. ^ { m } 7 ) outburst in the history of its studies .
The emission spectrum of the star represented in the optical range by hydrogen , neutral and ionized helium lines underwent significant changes in the outburst .
The fluxes in the HI and HeI emission lines increased by a factor of 5-6 , the HeII \lambda 4686 line grew by a factor of 10 .
According to our estimates , in the 2017 outburst the temperature of the exciting star rose to T _ { \text { hot } } \sim 130Â 000 K , while during the first 1994 outburst the change in temperature was insignificant .
This suggests cool and hot outbursts of LT Del by analogy with similar events of another yellow symbiotic star , AG Dra .