MY Apodis

MY Apodis

A light curve for MY Apodis, plotted from TESS data.[1] Approximately 400 raw data points were averaged to produce each plotted point.
Observation data Epoch J2000      Equinox J2000
Constellation	Apus
Right ascension	14^h 33^m 07.636^s[2]
Declination	−81° 20′ 14.13″[2]
Apparent magnitude (V)	13.75[3]
Characteristics
Evolutionary stage	Compact star
Spectral type	DA4.1[3]
U−B color index	−0.530
B−V color index	0.25
Variable type	ZZ Cet[3][4]
Astrometry
Radial velocity (Rv)	58.0[5] km/s
Proper motion (μ)	RA: −154.665 mas/yr[2] Dec.: −389.971 mas/yr[2]
Parallax (π)	47.7874 ± 0.0295 mas
Distance	68.25 ± 0.04 ly (20.93 ± 0.01 pc)
Absolute magnitude (MV)	11.86[3]
Details
Mass	0.705±0.023[6] M☉
Radius	0.011±0.001[6] R☉
Luminosity	0.00347[7] L☉
Surface gravity (log g)	8.17±0.04[3] cgs
Temperature	12,330±182[3] K
Rotation	13 h[8]
Other designations
MY Aps, GJ 2108, L 19-2, LTT 5712, WD 1425-81, 1425-811[9]
Database references
SIMBAD	data

MY Apodis, also known as L 19-2, GJ 2108, or WD 1425-811, is a single[7] white dwarf star located in the far southern constellation Apus. It is a low-amplitude variable star[10] with an average apparent visual magnitude of 13.75[3] and thus is much too faint to be visible to the naked eye. Based on parallax measurements, this star is located at a distance of 68.3 light-years from the Sun. It is drifting further away with a radial velocity of 58.0[5]

This compact stellar remnant has a class of DA4.1,[3] which indicates a hydrogen-rich outer atmosphere. It is a pulsating white dwarf (ZZ Ceti star) that varies photometrically with an amplitude of 0.05 in visual magnitude.[4] The low-amplitude variability of this ZZ Ceti analog was discovered by James E. Hesser and associates in 1974, who found it showed periods of 192.75±0.1 and 113.77±0.1 seconds.[10] By 2015, ten different pulsation modes had been identified, and it remained stable over four decades of observation.[11]

MY Apodis has 70.5%[6] of the mass of the Sun compressed down into 1.1%[6] of the Sun's radius. It is spinning rapidly with a rotation period of 13 hours.[8] The star is radiating just 0.35%[7] of the luminosity of the Sun at an effective temperature of 12,330 K.[3] Astroseismological models suggest the star has a thin outer hydrogen shell with a mass of 1.0×10^−4 M_☉, an intermediate helium layer of 1.5 to 2.0×10^−2 M_☉, and a core of 20% carbon and 80% oxygen that extends out to 60% of the stellar radius.[8]

References

1. "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 26 August 2024.
2. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
3. Gianninas, A.; et al. (2011). "A Spectroscopic Survey and Analysis of Bright, Hydrogen-rich White Dwarfs". The Astrophysical Journal. 743 (2): 27. arXiv:1109.3171. Bibcode:2011ApJ...743..138G. doi:10.1088/0004-637X/743/2/138. S2CID 119210906. 138.
4. Samus, N. N.; et al. (2017). "General Catalogue of Variable Stars". Astronomy Reports. 5.1. 61 (1): 80–88. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID 255195566. Retrieved 2021-11-25.
5. Wegner, G. (February 1974). "A spectroscopic survey of southern hemisphere white dwarfs - IV. Radial velocities and space motions". Monthly Notices of the Royal Astronomical Society. 166 (2): 271–280. Bibcode:1974MNRAS.166..271W. doi:10.1093/mnras/166.2.271.
6. Romero, A. D.; et al. (December 2013). "Asteroseismological Study of Massive ZZ Ceti Stars with Fully Evolutionary Models". The Astrophysical Journal. 779 (1): 24. arXiv:1310.4137. Bibcode:2013ApJ...779...58R. doi:10.1088/0004-637X/779/1/58. S2CID 53707228. 58.
7. Toonen, S.; et al. (June 2017). "The binarity of the local white dwarf population". Astronomy & Astrophysics. 602: 23. arXiv:1703.06893. Bibcode:2017A&A...602A..16T. doi:10.1051/0004-6361/201629978. S2CID 12367523. A16.
8. Bradley, P. A. (May 2001). "Asteroseismological Constraints on the Structure of the ZZ Ceti Stars L19-2 and GD 165". The Astrophysical Journal. 552 (1): 326–339. Bibcode:2001ApJ...552..326B. doi:10.1086/320454. S2CID 121370579.
9. "MY Aps". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-11-24.
10. Hesser, J. E.; et al. (July 1977). "High-frequency stellar oscillations. XII. L19-2, a low-amplitude ZZ Ceti variable with periods of 193 and 114 seconds". Astrophysical Journal. 215: L75 – L78. Bibcode:1977ApJ...215L..75H. doi:10.1086/182482.
11. Sullivan, D. J.; Chote, P. (June 2015). Dufour, Patrick; Bergeron, Pierre; Fontaine, Gilles (eds.). The Frequency Stability of the Pulsating White Dwarf L19-2. 19th European Workshop on White Dwarfs, Proceedings of a conference held at the Université de Montréal, Montréal, Canada 11-15 August 2014. ASP Conference Series. Vol. 493. San Francisco: Astronomical Society of the Pacific. p. 199. Bibcode:2015ASPC..493..199S.