HD 144941
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| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Scorpius[1] |
| Right ascension | 16h 09m 24.551s[2] |
| Declination | −27° 13′ 38.18″[2] |
| Apparent magnitude (V) | 10.141±0.008[3] |
| Characteristics | |
| Evolutionary stage | Main sequence[3] |
| Spectral type | B8[4] |
| B−V color index | 0.034±0.007[3] |
| Astrometry | |
| Radial velocity (Rv) | −43.7±0.5[3] km/s |
| Proper motion (μ) | RA: −6.834 mas/yr[2] Dec.: 8.023 mas/yr[2] |
| Parallax (π) | 0.6714±0.0282 mas[2] |
| Distance | 4,900 ± 200 ly (1,490 ± 60 pc) |
| Absolute magnitude (MV) | −1.85+0.10 −0.11[3] |
| Details[3] | |
| Mass | 8.1±0.3 M☉ |
| Radius | 3.8±0.2 R☉ |
| Luminosity | 2,950+290 −260 L☉ |
| Surface gravity (log g) | 4.2±0.1 cgs |
| Temperature | 22,000±500 K |
| Metallicity [Fe/H] | −2.0[5] dex |
| Rotation | 13.9±0.2 d |
| Rotational velocity (v sin i) | 7±5 km/s |
| Age | 11.0+6.4 −7.8 Myr |
| Other designations | |
| AAVSO 1603-26, CD−26°11229, HD 144941, SAO 108933, PPM 265193[6] | |
| Database references | |
| SIMBAD | data |
HD 144941 is a massive helium-strong star[7] in the southern constellation of Scorpius. With an apparent visual magnitude of 10.1,[3] it requires a telescope to view. Based on parallax measurements, it is located at a distance of approximately 4,900 light years from the Sun. The star is drifting closer with a radial velocity of −44 km/s.[3]
In 1960, a study of stellar spectra of the southern sky taken at Cerro Tololo showed this to be a helium rich, hydrogen deficient star.[4] Spectra taken from La Silla Observatory in 1973 showed an under abundance of nitrogen and carbon by a factor of ten compared to normal B-type stars. Helium shows a number abundance ten times that of hydrogen.[8] The metallicity of the star is very low, which may explain why it displays no radial pulsations like those found in similar helium stars.[9]
Most extreme helium stars can be explained based on an evolutionary stage past the asymptotic giant branch. However, HD 144941 has too high a surface gravity for that scenario, and its surface elemental abundances are atypical. An alternative scenario is the merger of two helium dwarfs.[10] The most likely scenario has the merger begun with about half the mass of a star being transferred to the binary companion in a period of a few minutes. The second half happens more gradually, with the contributing star depositing mass into an accretion ring. The combined star resembled a red giant before becoming an extreme helium star. The resulting composition suggests both progenitor stars were of low metallicity.[11]
In 2018, photometry showed low amplitude changes in brightness that are most likely caused by surface variations resembling spots. The variations were compatible with a rotation period of 13.9±0.2 d.[12] A strong magnetic field was detected in 2021, explaining the spots. This is thought to either be a fossil field left over from prior stages in the stellar evolution, or a product of the merger process.[7] The average surface magnetic field strength is 11.226 kG, and the dipole field has an unusually high angle of 65° to the rotation.[13] No extreme helium stars have been found that possess a magnetic field with rotational modulation of their brightness.[3]
A 2021 study of HD 144941 indicated that it is much different than previously believed, being a massive, magnetic, helium–strong star. The strong magnetic field is essential for producing the He–strong appearance in main sequence B-type stars. A stellar wind in the presence of this field accelerates the hydrogen away from the surface while causing helium to fall back onto the star, steadily enriching the surface helium. The high helium to hydrogen ratio makes HD 144941 the most extreme example of a He-strong star known.[3]
Modelled as a helium-strong star, HD 144941 is about 11 million years old and roughly 30% of the way through its main sequence lifetime. It has about 8 time the mass of the Sun and four times the Sun's radius. The star is radiating nearly 3,000 times the luminosity of the Sun from its photosphere at an effective temperature of 22,000 K. The motion of HD 144941 through the galaxy suggests that it is a runaway star. It would have been ejected from the Sagittarius arm about 6.2 million years ago. The star is expected to continue to increase its galactic latitude to about 3.6 thousand light-years (1.1 kpc) over the galactic plane, then explode as a supernova. The resulting remnant may be a magnetar.[3]
References
- ↑ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
- 1 2 3 4 5 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.
- 1 2 3 4 5 6 7 8 9 10 11 Przybilla, N.; et al. (October 2021), "HD 144941: the most extreme helium-strong star", Astronomy & Astrophysics, 654, id. A119, arXiv:2110.11267, Bibcode:2021A&A...654A.119P, doi:10.1051/0004-6361/202141625.
- 1 2 MacConnell, D. J.; et al. (June 1970), "Discoveries on Southern Objective-Prism Plates I. New Helium-Rich Stars", Publications of the Astronomical Society of the Pacific, 82 (487): 730, Bibcode:1970PASP...82..730M, doi:10.1086/128950.
- ↑ Jönsson, Henrik; et al. (August 17, 2020), "APOGEE Data and Spectral Analysis from SDSS Data Release 16: Seven Years of Observations Including First Results from APOGEE-South", The Astronomical Journal, 160 (3), American Astronomical Society: 120, arXiv:2007.05537, Bibcode:2020AJ....160..120J, doi:10.3847/1538-3881/aba592, ISSN 0004-6256.
- ↑ "HD 144941", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2025-02-12.
- 1 2 Shultz, M. E.; et al. (October 2021), "Detection of an extremely strong magnetic field in the double-degenerate binary merger product HD 144941", Monthly Notices of the Royal Astronomical Society, 507 (1): 1283–1295, arXiv:2107.11211, Bibcode:2021MNRAS.507.1283S, doi:10.1093/mnras/stab2162.
- ↑ Hunger, K.; Kaufmann, J. P. (June 1973), "Spectralphotometry and quantitative analysis of the hydrogen-deficient stars HD 144941 and CPD -69 2698.", Astronomy and Astrophysics, 25: 261, Bibcode:1973A&A....25..261H.
- ↑ Jeffery, C. S.; Hill, P. W. (June 1996), "A search for variability in the helium-rich subdwarf HD 144941", The Observatory, 116: 156–161, Bibcode:1996Obs...116..156J.
- ↑ Przybilla, N.; et al. (2006), "Non-LTE Metal Abundances in V652 HER and HD 144941", Baltic Astronomy, 15: 163–166, arXiv:astro-ph/0512153, Bibcode:2006BaltA..15..163P.
- ↑ Pandey, Gajendra; Lambert, David L. (October 2017), "Non-local Thermodynamic Equilibrium Abundance Analyses of the Extreme Helium Stars V652 Her and HD 144941", The Astrophysical Journal, 847 (2), id. 127, arXiv:1708.07945, Bibcode:2017ApJ...847..127P, doi:10.3847/1538-4357/aa88bb.
- ↑ Jeffery, C. Simon; Ramsay, Gavin (March 2018), "K2 spots rotation in the helium star HD144941", Monthly Notices of the Royal Astronomical Society: Letters, 475 (1): L122 – L124, arXiv:1801.10226, Bibcode:2018MNRAS.475L.122J, doi:10.1093/mnrasl/sly015.
- ↑ Glagolevskij, Yu. V.; Bychkov, V. D. (June 2023), "Magnetic Field Structure of He-r Star HD 144941", Astrophysical Bulletin, 78 (2): 165–173, Bibcode:2023AstBu..78..165G, doi:10.1134/S1990341323020025.
Further reading
- Przybilla, Norbert; et al. (November 2021), "New Spectropolarimetric Measurements of HD 144941", Research Notes of the AAS, 5 (10), id. 254, Bibcode:2021RNAAS...5..254P, doi:10.3847/2515-5172/ac342a.
- Przybilla, N.; et al. (December 2005), "Extreme helium stars: non-LTE matters. Helium and hydrogen spectra of the unique objects V652 Her and HD 144941", Astronomy and Astrophysics, 443 (3): L25 – L28, arXiv:astro-ph/0510043, Bibcode:2005A&A...443L..25P, doi:10.1051/0004-6361:200500195.
- Harrison, P. M.; Jeffery, C. S. (July 1997), "A spectral analysis of the hydrogen-deficient star HD 144941", Astronomy and Astrophysics, 323: 177–182, Bibcode:1997A&A...323..177H.
- Jeffery, C. S.; Harrison, P. M. (July 1997), "The iron abundance in helium star HD 144941", Astronomy and Astrophysics, 323: 393–394, Bibcode:1997A&A...323..393J.
- Jeffery, C. S.; et al. (September 1986), Rolfe, E. J. (ed.), "Ultraviolet Spectrophotometry of the Hydrogen-Deficient Star HD14494 - the Energy Distribution and the Stellar Wind", New Insights in Astrophysics : 8 Years of UV Astronomy with IUE, Proceedings of an international symposium co-sponsored by NASA, ESA and SERC, held at University College London, 14-16 July 1986. ESA SP-263., vol. 263, Paris, France: European Space Agency, p. 369, Bibcode:1986ESASP.263..369J.
- Kaufmann, J. P.; Werner, K. (1981), "IUE-Observations of Helium rich Stars (HD 144941, nH = 0.06; HD 60344, nH = 0.60)", Mitteilungen der Astronomischen Gesellschaft, 52: 98, Bibcode:1981MitAG..52...98K.
