If someone forgot to light a yahrtzeit candle Friday night can the goy be asked to light it?
A person who forgot to light a yahrtziet candle, may ask a gentile to light as long as it is still bein hashmashos. This is part of the heter to ask a gentile to do melacha for us during bein hashmashos. The reason for this is because asking a gentile to do melacha is a shevus, ( rabbinic decree) coupled with the fact that it is bein hashmashos and because people are very concerned about having a yahrtziet candle lit, therefore it is considered a tzorech, which can be done by a gentile during bein hashmashos. The bein hashmashos period in a way depends on what the person usually does. If he usually davens maariv motzei Shabbos 40 minutes after shkiya, he should consider bein hashmashos only until 30 minutes, however if he usually waits longer. However if he will daven maariv at 60 minutes then bein hashmashos extends until 40 minutes after shlita according to R’ M. Feinstein zt”l.
After bein hahmashos one should not ask a gentile to light a yahrtzeit candle. Instead the person should say tehillim, and learn l’illuy nishas the niftar, and this will be very beneficial to the neshoma of the niftar and will give him an illuy neshoma.
M:B 261-16, Igros Moshe O:CH 4 62, The Sanctity of Shabbos pg. 42 ftnt. 2.