标题： GRB 050223：尘埃星暴星系中的暗弱伽马射线暴 显示英文标题

标题： GRB 050223: A dark GRB in a dusty starburst galaxy

摘要： 目标：我们旨在检测并确定暗伽马暴GRB 050223宿主星系的特性。 方法：我们使用VLT光学/近红外图像结合Swift X射线定位，以及宿主星系的光学光谱来测量其特性。 结果：我们在GRB 050223的Swift误差框内发现了一个星系。 它位于红移z = 0.584，其光度约为L ~ 0.4 L*。 星系光谱中的发射线表明其固有恒星形成率SFR > 7 Msun/yr，并且其中存在大的消光A_V > 2 mag。 我们还检测到吸收线，这揭示了一个年龄在40 Myr到1.5 Gyr之间的潜在恒星种群。 结论：仅通过X射线瞬变识别出具有非典型特性的宿主星系表明，先前的宿主星系样本中可能存在偏差。 尘埃遮蔽和固有暗弱可能是该爆发黑暗的最可能原因。 显示英文摘要

摘要： Aims: We aim at detecting and determining the properties of the host galaxy of the dark GRB 050223. Methods: We use VLT optical/NIR images coupled to Swift X-ray positioning, and optical spectra of the host galaxy to measure its properties. Results: We find a single galaxy within the Swift error box of GRB 050223. It is located at z = 0.584 and its luminosity is L ~ 0.4 L*. Emission lines in the galaxy spectrum imply an intrinsic SFR > 7 Msun/yr, and a large extinction A_V > 2 mag within it. We also detect absorption lines, which reveal an underlying stellar population with an age between 40 Myr and 1.5 Gyr. Conclusions: The identification of a host galaxy with atypical properties using only the X-ray transient suggests that a bias may be present in the former sample of host galaxies. Dust obscuration together with intrinsic faintness are the most probable causes for the darkness of this burst.