Who is the רא״ח?

Question

The Mogein Avrohom in 580:5 says:

בכ"ח בכסלו - במגילת תענית כתב בשבעה בכסליו ובה"ג כתב בשמונה ובכל בו כתב בחמשה וכתב בשל"ה דאף המחמיר להתענות בכולן לא יתענה בחנוכה, עיין רא"ח ח"ב ס"ה:‏

On the 28th of Kisleiv - In Megillas Ta'anis, it writes, "On the seventh of Kisleiv", and in the Bahag (Ba'al Halochos Gedolos), it writes, "On the eighth", and in Kol Bo, it writes, "On the fifth", and the Shlah (Shnei Luchos Habris) it writes that even the one who is stringent to fast on all of them shall not fast on Chanuko, see Ra'ach section 2 paragraph 5.

I have never heard of the Ra'ach. Therefore, I ask: Who is the רא״ח?

Answer 1

It stands for R. Eliyahu ibn Hayyim, also known as Raanah or Raabah.

Here's the relevant page from the work Mayim Amukim, which contains responsa from both R. Eliyahu Mizrahi (part 1) and R. Eliyahu ibn Hayyim (part 2).