I'm afraid I don't know the answer to your main question, but I can add something to your secondary question.

Were there any other incidences (aside from the purges of army officers) of massacres of a specific professional group perpetrated by Stalin?

On the 13th of January 1953, Pravda (the official newspaper of the Communist Party) announced the discovery of a plot let by a group of doctors, most of whom were Jewish. They were alleged to have planned and carried out what essentially amounts to poisoning top Soviet leaders.

Now, there are two reason why this Doctor's Plot may not exactly fit your question. The first is that no execution was ever actually carried out. This has been attributed to the death of Stalin just two months later, after which the case was swiftly dropped and eventually deemed to have been fabricated. Secondly, the operative word in this event might just be Jewish, instead of doctor. While the Soviet Union was never as explicitly anti-Semitic as Tsarist Russia had at times been (and obviously nowhere near the likes of Nazi Germany), it certainly grew in the latter years of Stalin's rule.

It has been speculated that Stalin's sudden death might have stopped a brand new Terror, although it's still unclear whether or not this was a deliberate move by Stalin or just a result of the culture of accusation, fostered by Stalin, which had previously run amok during the purges of the 1930s.

(Take the example of Nikolai Yezhov, the head of the NKVD - the soviet secret police and the predecessor of the KGB - who was instrumental in carrying out increasingly far-fetched investigations during the Terror of the 30s, before finally himself becoming a victim of it at the hands of his deputy and replacement, Lavrentiy Beria. "The revolution devours its children" comes to mind. Beria was himself put on trial and executed during the power struggle in the wake of Stalin's death, to complete the circle.)

I'm afraid I don't know the answer to your main question, but I can add something to your secondary question.

Were there any other incidences (aside from the purges of army officers) of massacres of a specific professional group perpetrated by Stalin?

On the 13th of January 1953, Pravda (the official newspaper of the Communist Party) announced the discovery of a plot let by a group of doctors, most of whom were Jewish. They were alleged to have planned and carried out what essentially amounts to poisoning top Soviet leaders.

Now, there are two reason why this Doctor's Plot may not exactly fit your question. The first is that no execution was ever actually carried out. This has been attributed to the death of Stalin just two months later, after which the case was swiftly dropped and eventually deemed to have been fabricated. Secondly, the operative word in this event might just be Jewish, instead of doctor. While the Soviet Union was never as explicitly anti-Semitic as Tsarist Russia had at times been (and obviously nowhere near the likes of Nazi Germany), it certainly grew in the latter years of Stalin's rule.

It has been speculated that Stalin's sudden death might have stopped a brand new Terror, although it's still unclear whether or not this was a deliberate move by Stalin or just a result of the culture of accusation, fostered by Stalin, which had previously run amok during the purges of the 1930s.

(Take the example of Nikolai Yezhov, the head of the NKVD - the soviet secret police and the predecessor of the KGB - who was instrumental in carrying out increasingly far-fetched investigations during the Terror of the 30s, before finally himself becoming a victim of it at the hands of his deputy and replacement, Lavrentiy Beria. "The revolution devours its children" comes to mind. Beria was himself put on trial and executed during the power struggle in the wake of Stalin's death, to complete the circle.)

In response to your second question: about 20% of the Russian astronomical community were imprisoned or executed in a Stalinist purge in 1936—1937. Personal vendettas, playing out in the aftermath of an incident of research fraud (the Voronov scandal), resulted in Boris Gerasimovich, the director of the Pulkovo Observatory, being accused of "non-compliance with Marxist-Leninist ideology" and "being under foreign influence" (due to publishing in non-Soviet journals). A coerced confession from a colleague resulted in nearly the entire observatory staff being implicated, while members of the Tashkent Astronomical Observatory were arrested due to its association with Voronov. At least 29 astronomers (and one assistant director) disappeared. At least 5 were executed, including Gerasimovich, and more died in captivity.

Source: Robert A. McCutcheon, “The 1936–1937 Purge of Soviet Astronomers,” Slavic Review, Spring 1991, 50(1):100–117.

As a follow-up question, how were those officials replaced? Assuming they were trained or experienced, I’m curious as to how if/how those trains continued to run.

As a follow-up question, how were those officials replaced? Assuming they were trained or experienced, I’m curious as to how if/how those trains continued to run.