The Photometric Variability and Spectrum of the Hot Post-AGB Star IRAS 21546+4721
We present the results of photometric and spectroscopic observations of a poorly studied B-type supergiant with infrared excess, the hot post-AGB star IRAS 21546+4721. Based on our photometric observations in the <inline-formula><math display="inline"><semantics><mrow&...
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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/2075-4434/13/2/31 |
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| Summary: | We present the results of photometric and spectroscopic observations of a poorly studied B-type supergiant with infrared excess, the hot post-AGB star IRAS 21546+4721. Based on our photometric observations in the <inline-formula><math display="inline"><semantics><mrow><mi>U</mi><mi>B</mi><mi>V</mi><msub><mi>R</mi><mi>C</mi></msub><msub><mi>I</mi><mi>C</mi></msub></mrow></semantics></math></inline-formula> bands, we detected rapid, night-to-night, non-periodic brightness variations in the star with peak-to-peak amplitudes up to <inline-formula><math display="inline"><semantics><mrow><mn>0</mn><msup><mo>.</mo><mi>m</mi></msup><mn>3</mn></mrow></semantics></math></inline-formula> in the <i>V</i> band, as well as color–color and color–brightness correlations. Based on its variability characteristics, IRAS 21546+4721 appears similar to other hot post-AGB stars. Possible causes of the photometric variability are discussed. Additionally, we acquired low-resolution spectra in a wavelength range from 3500 to 7500 Å. The spectrum contains absorption lines typical of an early B-type star, along with a set of emission lines of H I, He I, [O I], [O II], [N II], [S II], and C II originating from an ionized circumstellar envelope. An analysis of the emission spectrum allowed us to estimate the parameters of the gas envelope (<inline-formula><math display="inline"><semantics><msub><mi>N</mi><mi>e</mi></msub></semantics></math></inline-formula>∼ 10<sup>4</sup> cm<sup>−3</sup>, <inline-formula><math display="inline"><semantics><msub><mi>T</mi><mi>e</mi></msub></semantics></math></inline-formula>∼ 10,000 K) and the star’s temperature (∼26,500 K). The radial velocity measured from the emission lines was <inline-formula><math display="inline"><semantics><mrow><msub><mi>V</mi><mi>r</mi></msub><mo>=</mo><mo>−</mo><mn>141</mn><mo>±</mo><mn>7</mn></mrow></semantics></math></inline-formula> km s<sup>−1</sup>. |
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| ISSN: | 2075-4434 |