The u band magnitude is vital for determining stellar parameters and investigating specific astronomical objects. However, flux calibration in the u band for stars in the Galactic disk presents significant challenges. In this study, we introduce a comprehensive re-calibration of u-band photometric magnitudes of the VPHAS+ Data Release 4 (DR4), employing the Stellar Colour Regression (SCR) technique. By leveraging the expansive set of XP spectra and GBP photometry from Gaia Data Release 3 (DR3), as well as the individual stellar extinction values provided by the literature, we have obtained precise model magnitudes of nearly 3 million stars. Our analysis identifies systematic magnitude offsets that exhibit a standard deviation of 0.063 mag across different observational visits, 0.022 mag between various CCDs, and 0.009 mag within pixel bins. We have implemented precise corrections for these observational visits, CCD chips, and pixel bins-dependent magnitude offsets. These corrections have led to a reduction in the standard deviation between the observed magnitudes and the model magnitudes from 0.088 mag to 0.065 mag, ensuring that the calibrated magnitudes are independent of stellar magnitude, colour, and extinction. The enhanced precision of these magnitudes substantially improves the quality of astrophysical research and offers substantial potential for furthering our understanding of stellar astrophysics.

中文翻译：

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使用恒星颜色回归方法和 gaia DR3 对 VPHAS+ u 波段光度进行光度重新校准

u 波段星等对于确定恒星参数和研究特定天体至关重要。然而，银河盘中恒​​星的 u 波段通量校准面临着巨大的挑战。在本研究中，我们采用恒星颜色回归 (SCR) 技术对 VPHAS+ 数据版本 4 (DR4) 的 u 波段光度幅度进行全面的重新校准。通过利用盖亚数据版本 3 (DR3) 中的大量 XP 光谱和 GBP 光度测量，以及文献提供的单个恒星消光值，我们获得了近 300 万颗恒星的精确模型星等。我们的分析确定了系统震级偏移，这些偏移在不同的观测访问中表现出 0.063 mag 的标准偏差，在不同 CCD 之间的标准偏差为 0.022 mag，在像素箱内的标准偏差为 0.009 mag。我们对这些观测访问、CCD 芯片和与像素箱相关的震级偏移进行了精确校正。这些修正使观测星等与模型星等之间的标准偏差从 0.088 星等减少到 0.065 星等，确保校准星等与恒星星等、颜色和消光无关。这些星等精度的提高大大提高了天体物理学研究的质量，并为进一步加深我们对恒星天体物理学的理解提供了巨大的潜力。