HR 1217

HR 1217 is a variable star in the constellation Eridanus. It has the variable star designation DO Eridani, but this seldom appears in the astronomical literature; it is usually called either HR 1217 or HD 24712. At its brightest, HR 1217 has an apparent magnitude of 5.97, making it very faintly visible to the naked eye for an observer with excellent dark-sky conditions.^[5]

HR 1217

A light curve for DO Eridani, adapted from Holdsworth et al. (2021)[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Eridanus
Right ascension	03h 55m 16.13133s[2]
Declination	−12° 05′ 56.7277″[2]
Apparent magnitude (V)	5.97 - 6.00[3]
Characteristics
Spectral type	A9Vp SrEuCr[4]
Variable type	roAp[5]
Astrometry
Proper motion (μ)	RA: −91.357±0.036[2] mas/yr Dec.: −28.376±0.036[2] mas/yr
Parallax (π)	20.7432 ± 0.0413 mas[2]
Distance	157.2 ± 0.3 ly (48.21 ± 0.10 pc)
Absolute magnitude (MV)	2.32[6]
Details
Mass	1.54±0.13[7] M☉
Radius	1.75±0.05[7] R☉
Luminosity	7.6±1.2[7] L☉
Surface gravity (log g)	4.30[8] cgs
Temperature	7,235±280[7] K
Metallicity [Fe/H]	−0.36[8] dex
Rotation	12.46 d[7]
Rotational velocity (v sin i)	7.0[8] km/s
Age	780+760 −470[7] Myr
Other designations
HD 24712, HIP 18339, HR 1217, SAO 149251, 2MASS J03551613-1205567[9]
Database references
SIMBAD	data

HR 1217 is one of the best-studied rapidly oscillating Ap (roAp) stars.^[1] Inspired by the 1978 discovery of the rapid (12 minute period) brightness variability of Przybylski's Star (an Ap star), in 1980 D. W. Kurtz observed the Ap star HR 1217, and found clear 6.15 minute oscillations, the amplitude of which slowly changed over the course of several days.^[10] The next year, high-speed photometric observations of the star revealed six nearly equally spaced pulsation periods ranging from 6.126 minutes (strongest) to 5.966 minutes (weakest).^[11] In 1989 it was found that the amplitudes of these pulsations are modulated over a period equal to the star's rotation period.^[12] By 2019, ten pulsation frequencies had been found in the TESS data.^[13]

HR 1217 is a chemically peculiar star, with particular over-abundances of copper, europium, and chromium in its spectrum.^[4] At the same time, lines of other metals such as iron are less strong than expected for an A9 star, which is typical of an Ap star. In 2009, Shulyak et al. computed a model atmosphere for the star which showed how the elemental abundances varied as a function of atmospheric height.^[14] In 2015, doppler imaging was used to produce maps of both the star's magnetic field and the distribution of several chemical elements across the star's surface. It was the first roAp star to be mapped in this way.^[15]

References

1. Holdsworth, D. L.; et al. (September 2021). "TESS cycle 1 observations of roAp stars with 2-min cadence data". Monthly Notices of the Royal Astronomical Society. 506 (1): 1073–1110. arXiv:2105.13274. Bibcode:2021MNRAS.506.1073H. doi:10.1093/mnras/stab1578.
2. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
3. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: B/gcvs. Bibcode:2009yCat....102025S.
4. Abt, Helmut A.; Morrell, Nidia I. (July 1995). "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars". Astrophysical Journal Supplement. 99: 135. Bibcode:1995ApJS...99..135A. doi:10.1086/192182.
5. "DO Eri". The International Variable Star Index. AAVSO. Retrieved 12 December 2022.
6. Joshi, S.; Martinez, P.; Chowdhury, S.; Chakradhari, N. K.; Joshi, Y. C.; Van Heerden, P.; Medupe, T.; Kumar, Y. B.; Kuhn, R. B. (2016). "The Nainital-Cape Survey. IV. A search for pulsational variability in 108 chemically peculiar stars". Astronomy and Astrophysics. 590: A116. arXiv:1603.03517. Bibcode:2016A&A...590A.116J. doi:10.1051/0004-6361/201527242. S2CID 119296364.
7. Deal, M.; Cunha, M. S.; Keszthelyi, Z.; Perraut, K.; Holdsworth, D. L. (June 2021). "Fundamental properties of a selected sample of Ap stars: Inferences from interferometric and asteroseismic constraints". Astronomy & Astrophysics. 650: A125. arXiv:2104.08097. Bibcode:2021A&A...650A.125D. doi:10.1051/0004-6361/202040234. S2CID 233289688.
8. Ghazaryan, S.; Alecian, G.; Hakobyan, A. A. (2018). "New catalogue of chemically peculiar stars, and statistical analysis". Monthly Notices of the Royal Astronomical Society. 480 (3): 2953–2962. arXiv:1807.06902. Bibcode:2018MNRAS.480.2953G. doi:10.1093/mnras/sty1912. S2CID 119062018.
9. "V* DO Eri -- alpha2 CVn Variable". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2022-12-12.
10. Kurtz, D. W. (January 1981). "Discovery of 6.15 Minute Oscillations in the Cool Magnetic Ap Star HD 24712". Information Bulletin on Variable Stars. 1915 (1): 1. Bibcode:1981IBVS.1915....1K.
11. Kurtz, D. W.; Seeman, J. (October 1983). "Frequency analysis of the rapidly oscillating AP star HR 1217 (HD 24712)". Monthly Notices of the Royal Astronomical Society. 205: 11–22. Bibcode:1983MNRAS.205...11K. doi:10.1093/mnras/205.1.11.
12. Kurtz, D. W.; Matthews, J. M.; Martinez, P.; Seeman, J.; Cropper, M.; Clemens, J. C.; Kreidl, T. J.; Sterken, C.; Schneider, H.; Weiss, W. W.; Kawaler, S. D.; Kepler, S. O. (October 1989). "The high-overtone p-mode spectrum of the rapidly oscillating AP star HR 1217 (HD 24712) - results of a frequency analysis of 324 HR of multi-site photometric observations obtained during a 46-d time-span in 1986". Monthly Notices of the Royal Astronomical Society. 240 (4): 881–915. Bibcode:1989MNRAS.240..881K. doi:10.1093/mnras/240.4.881. hdl:10183/88382.
13. Balona, L. A.; Holdsworth, D. L.; Cunha, M. S. (August 2019). "High frequencies in TESS A-F main-sequence stars". Monthly Notices of the Royal Astronomical Society. 487 (2): 2117–2132. doi:10.1093/mnras/stz1423.
14. Shulyak, D.; Ryabchikova, T.; Mashonkina, L.; Kochukhov, O. (June 2009). "Model atmospheres of chemically peculiar stars. Self-consistent empirical stratified model of HD 24712". Astronomy & Astrophysics. 499 (3): 879–890. arXiv:0903.3474. Bibcode:2009A&A...499..879S. doi:10.1051/0004-6361/200911623. S2CID 16519846.
15. Rusomarov, N.; Kochukhov, O.; Ryabchikova, T.; Piskunov, N. (January 2015). "Three-dimensional magnetic and abundance mapping of the cool Ap star HD 24712. II. Two-dimensional magnetic Doppler imaging in all four Stokes parameters". Astronomy & Astrophysics. 573: A123. arXiv:1409.6955. Bibcode:2015A&A...573A.123R. doi:10.1051/0004-6361/201424559. S2CID 41341601.