d Eridani, also known as HD 27563, is a single star in Eridanus, in the direction of the Orion–Eridanus Superbubble,[1] that is faintly visible to the naked eye at a magnitude of about 5.84. Cowley (1972) classifies this star as spectral type B5III,[2] but Houk and Swift (1999) catalog it as B7II.[3]

It was used as a comparison star for 46 Eridani in four separate runs at La Silla Observatory in the 1970s and 1980s,[4] but in 1989, both stars were found to be variable with similar periods of about four days, and d Eridani was assigned the designation EM Eridani.[5] Despite the lack of reliable comparisons for EM Eridani, it was found that the power spectrum of its light curve is remarkably noisy, with two or four prominent oscillation periods centered around 3.9215 days,[5][6] and is classified as a slowly pulsating B-type star.[7]

References

  1. ^ Welsh, B. Y.; Sallmen, S.; Jelinsky, S. (September 2005). "NaI and CaII absorption components observed towards the Orion-Eridanus Superbubble". Astronomy & Astrophysics. 440 (2): 547–557. Bibcode:2005A&A...440..547W. doi:10.1051/0004-6361:20052691. S2CID 122007577
  2. ^ Cowley, A. (1 November 1972). "Spectral classification of the bright B8 stars.". The Astronomical Journal. 77: 750–755. Bibcode:1972AJ.....77..750C. doi:10.1086/111348. ISSN 0004-6256
  3. ^ Houk, N. & Swift, C. (1 January 1999). "Michigan catalogue of two-dimensional spectral types for the HD Stars". Michigan Spectral Survey. 5: 0. Bibcode:1999MSS...C05....0H
  4. ^ Mathys, G.; Manfroid, J.; Renson, P. (1 March 1986). "Photometric variability of some early-type stars.". Astronomy and Astrophysics Supplement Series. 63: 403–416. Bibcode:1986A&AS...63..403M. ISSN 0365-0138
  5. ^ Manfroid, J. (1 March 1989). "On the Light Curve of HD 27563". Information Bulletin on Variable Stars. 3297: 1. Bibcode:1989IBVS.3297....1M. ISSN 0374-0676
  6. ^ Manfroid, J. & Renson, P. (1 October 1989). "Photometric variations of 46 Eridani and 210 G. Eridani.". Astronomy and Astrophysics. 223: 187–195. Bibcode:1989A&A...223..187M. ISSN 0004-6361
  7. ^ Dziembowski, W. A.; Moskalik, P.; Pamyatnykh, A. A. (1 December 1993). "The opacity mechanism in B-type stars - II. Excitation of high-order g-modes in main-sequence stars.". Monthly Notices of the Royal Astronomical Society. 265 (3): 588–600. Bibcode:1993MNRAS.265..588D. doi:10.1093/mnras/265.3.588. ISSN 0035-8711