A Slowly Pulsating Run-Away B Star at High Galactic Latitude Ejected From a Spiral Arm

IF 1 4区物理与天体物理 Q3 ASTRONOMY & ASTROPHYSICS

Astronomische Nachrichten Pub Date : 2025-04-04 DOI:10.1002/asna.70003

Ulrich Heber, Maximilian Halenke, Aakash Bhat, Veronika Schaffenroth

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Abstract

We report the discovery of the young B6 V run-away star LAMOST J083323.18 + 430825.4, 2.5 kpc above the Galactic plane. Its atmospheric parameters and chemical composition are determined from LAMOST spectra, indicating normal composition. Effective temperature ( $T_{eff}$ = $14,500$ K) and gravity ( $\log g$ = $3.79$ ) suggest that the star is close to terminating hydrogen burning. An analysis of the spectral energy distribution allowed us to determine the angular diameter as well as the interstellar reddening. Using evolutionary models from the MIST database we derived the stellar mass ( $4.75 M_{⊙}$ ) and age ( $104_{- 13}^{+ 11}$ Myr). The spectroscopic distance (4.17 kpc), the radius ( $4.5 R_{⊙}$ ), and the luminosity ( $\log (L / L_{⊙})$ = $2.89$ ) then result from the atmospheric parameters. Using Gaia proper motions, the trajectory is traced back to the Galactic disk to identify the place of birth in a spiral arm. The ejection velocity of 92 km s⁻¹ is typical for runaway stars in the halo. The age of the star is larger than its time of flight ( $78 \pm 4$ Myr), which favors a binary supernova event as the likely ejection mechanism. The TESS light curve shows variations with a period of 3.58 days from which we conclude that it is a slowly pulsating B-star, one of very few run-away B-stars known to pulsate.

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在银河系高纬度处，一颗缓慢脉动的逃逸B星从旋臂中喷射出来

我们报告在银道平面上方2.5 kpc处发现了年轻的B6 V逃逸恒星LAMOST J083323.18 + 430825.4。根据LAMOST光谱测定了其大气参数和化学成分，表明其成分正常。有效温度（T eff $$ {T}_{\mathrm{eff}} $$ = 14,500 $$ \mathrm{14,500} $$ K）和重力（log g $$ \log g $$）= 3.79 $$ 3.79 $$)表明这颗恒星已经接近氢燃烧的终点。对光谱能量分布的分析使我们能够确定角直径以及星际变红。利用MIST数据库中的演化模型，我们得到了恒星质量（4.75 M⊙$$ 4.75{M}_{\odot } $$）和年龄（104−13）+ 11 $$ {104}_{-13}^{+11} $$ Myr)。光谱距离（4.17 kpc），半径（4.5 R⊙$$ 4.5{R}_{\odot } $$）光度(log L / L⊙$$ \log \left(L/{L}_{\odot}\right) $$ = 2.89$$ 2.89 $$)，然后由大气参数得出。利用盖亚固有运动，轨迹可以追溯到银河系盘，以确定螺旋臂中的出生地点。92 km s−1的弹射速度是典型的逃逸恒星在光晕中的速度。这颗恒星的年龄大于它的飞行时间（78±4 $$ 78\pm 4 $$ Myr），这有利于双超新星事件作为可能的弹射机制。TESS的光曲线显示出3.58天周期的变化，由此我们得出结论，它是一颗缓慢脉动的b星，是已知的极少数会脉动的逃逸b星之一。

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来源期刊

Astronomische Nachrichten 地学天文-天文与天体物理

CiteScore

1.80

自引率

11.10%

发文量

审稿时长

4-8 weeks

期刊介绍： Astronomische Nachrichten, founded in 1821 by H. C. Schumacher, is the oldest astronomical journal worldwide still being published. Famous astronomical discoveries and important papers on astronomy and astrophysics published in more than 300 volumes of the journal give an outstanding representation of the progress of astronomical research over the last 180 years. Today, Astronomical Notes/ Astronomische Nachrichten publishes articles in the field of observational and theoretical astrophysics and related topics in solar-system and solar physics. Additional, papers on astronomical instrumentation ground-based and space-based as well as papers about numerical astrophysical techniques and supercomputer modelling are covered. Papers can be completed by short video sequences in the electronic version. Astronomical Notes/ Astronomische Nachrichten also publishes special issues of meeting proceedings.