'The asterism of Rudra' = Ārdrā, whose divinity is Rudra. Burgess flags the classification as anomalous: α Orionis 'though a variable star, does not fall below the first to second magnitude', yet is ranked with six third-magnitude stars in the 15° class. Al-Bīrūnī dissents twice over: his nakshatra table says 'Unknown. Most likely identical with Canis Minor' (Procyon), while his rendering of Varāhamihira's Saṃhitā ch. 4 glosses 'Ārdrā, the Sirius Yemenicus' (Sirius). The two Arabic names differ only in epithet (al-yamāniyya = Sirius, al-shāmiyya = Procyon), so the likeliest reading is that the Saṃhitā gloss is corrupt and Procyon was his settled view — but as the text stands he assigns Sirius twice, since he uses 'Sirius Yemenicus' for Mṛgavyādha too. An independent ancient dissent from Ārdrā = Betelgeuse, worth recording.
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रौद्रर्क्ष Raudrarkṣa
Betelgeuse · α Orionis · Orion
nakshatra aliasidentification disputedattestations 1 Betelgeuse α OriHIP 27989mag 0.45
Attestations
Later siddhāntas & al-Bīrūnī · core text c. 400–600 CE
कृत्तिकामैत्रमूलानि सार्पम् रौद्रर्क्षम् एव च / दृश्यन्ते पञ्चदशभिर् आषाढाद् द्वितयम् तथा //
14. ... and likewise Açleshā and Ārdrā (rāudrarksha), are seen at fifteen degrees. — Al-Bīrūnī, quoting Mārkaṇḍeya via Varāhamihira: 'Abhijit, the Falling Eagle; Ārdrā, the Sirius Yemenicus; Rohiṇī, or Aldabarān; Punarvasu, i.e. the Two Heads of the Twins; Puṣya, Revatī, Agastya or Canopus, the Great Bear, the master of Vāyu, the master of Ahirbudhnya, and the master of Śraviṣṭhā, each of these stars has a circumference of five yojanas.' — E. Burgess (1860); E. Sachau (1910) for al-Bīrūnī
Sūrya Siddhānta 9.14; cf. al-Bīrūnī, India ch. LV · text · translation