HR 4049: A Spectroscopic Analysis of a Post-AGB Object
A new spectroscopic study of HR 4049, a post-AGB star in a binary system, based on échelle spectra taken between 2019 and 2025 with the 0.81 m telescope of the Three College Observatory (North Carolina, USA) at a resolution of R ≈ 12,000 is reported. A cross-correlation analysis of 73 spectra of a s...
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| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-03-01
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| Series: | Galaxies |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2075-4434/13/2/26 |
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| Summary: | A new spectroscopic study of HR 4049, a post-AGB star in a binary system, based on échelle spectra taken between 2019 and 2025 with the 0.81 m telescope of the Three College Observatory (North Carolina, USA) at a resolution of R ≈ 12,000 is reported. A cross-correlation analysis of 73 spectra of a single C <span style="font-variant: small-caps;">i</span> multiplet in the 4760–4780 Å range yielded the following orbital parameters: the orbital period <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>P</mi><mo>=</mo><mn>428.474</mn><mo>±</mo><mn>0.002</mn></mrow></semantics></math></inline-formula> days, eccentricity <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>e</mi><mo>=</mo><mn>0.29</mn><mo>±</mo><mn>0.01</mn></mrow></semantics></math></inline-formula>, argument of periastron <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>ω</mi><mo>=</mo><msup><mn>242.3</mn><mo>∘</mo></msup><mo>±</mo><msup><mn>0.3</mn><mo>∘</mo></msup></mrow></semantics></math></inline-formula>, epoch of periastron <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>T</mi><mn>0</mn></msub><mo>=</mo><mrow><mn>2,458,383.2</mn></mrow><mo>±</mo><mn>0.6</mn></mrow></semantics></math></inline-formula>, heliocentric systemic radial velocity <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>γ</mi><mo>=</mo><mo>−</mo><mn>30.12</mn><mo>±</mo><mn>0.09</mn></mrow></semantics></math></inline-formula> km s<sup>−1</sup>, and semi-amplitude of the radial velocity curve <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>K</mi><mn>1</mn></msub><mo>=</mo><mn>15.52</mn><mo>±</mo><mn>0.13</mn></mrow></semantics></math></inline-formula> km s<sup>−1</sup>. Phase-dependent variations of the H<i>α</i> line profile indicate dynamic processes in the circumstellar environment. The luminosity of HR 4049 was refined using the Gaia EDR3 parallax (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>0.71</mn><mo>±</mo><mn>0.10</mn></mrow></semantics></math></inline-formula> mas), corresponding to a distance of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1397</mn><mo>±</mo><mn>170</mn></mrow></semantics></math></inline-formula> pc, and the average visual magnitude in the brightest state (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>m</mi><mi>V</mi></msub><mo>=</mo><mn>5.35</mn></mrow></semantics></math></inline-formula> mag). The derived luminosity, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo form="prefix">log</mo><mo>(</mo><mi>L</mi><mo>/</mo><msub><mi>L</mi><mo>⊙</mo></msub><mo>)</mo><mo>=</mo><mn>4.22</mn><mo>±</mo><mn>0.12</mn></mrow></semantics></math></inline-formula>, suggests an initial mass of 3.0–4.0 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>M</mi><mo>⊙</mo></msub></semantics></math></inline-formula>. Analysis of the mass function and most probable orbital inclinations (60°–75°) leads to current masses of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>∼</mo><mn>0.75</mn><mspace width="3.33333pt"></mspace><msub><mi>M</mi><mo>⊙</mo></msub></mrow></semantics></math></inline-formula> for the primary and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>0.70</mn></mrow></semantics></math></inline-formula>–<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>0.82</mn><mspace width="3.33333pt"></mspace><msub><mi>M</mi><mo>⊙</mo></msub></mrow></semantics></math></inline-formula> for the secondary component. The results confirm the system’s long-term orbital stability and provide further insights for future research into the nature of post-AGB binaries. |
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| ISSN: | 2075-4434 |