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tokens: of AT2019DSG, the S/N is too low (3), hence the polarization no longer follows a Gaussian distribution, but a Rice distribution instead (Plaszczynski et al. 2014 ). To obtain a robust estimate of the upper limit, we used the formulation by Plaszczynski et al. ( 2014 ). More specifically, for a 68% confidence level (corresponding to 1 σ ), the upper limit can be estimated as:We thus obtained an upper limit of 2.7% at the 1 σ level for the second epoch of AT2019DSG. It appears that AT2019DSG exhibits a polarization of ∼2% at the later epoch. However, we also need to take into account the interstellar polarization (ISP), which comes from the line-of-sight dust contributed by the Milky Way (MWG) and the host galaxy. By checking the extinction map, the line-of-sight MWG extinction— E ( B – V )—is ∼0.088 from Schlafly Finkbeiner ( 2011 ) and 0.102 from Schlegel et al. ( 1998 ). According to the empirical upper limits from Serkowski et al. ( 1975 ), this can translate into P as high as ∼1%. Another way to measure line-of-sight MWG dust polarization is to use field stars. In this regard, we also measure the polarization of a bright field star ∼1′ west of AT2019DSG. The field star polarization is at 0.5% level, consistent with the empirical upper limits from Serkowski et al. ( 1975 ). In addition to line-of-sight MWG dust polarization, there can also be polarization coming from the host. To constrain it, we used multiband photometry from Pan-STARRS (Chambers et al. 2016 ) and fit the host galaxy spectral energy distribution (SED) with LePhare (Arnouts et al. 1999 ; Ilbert et al. 2006 ). This gives an E ( B – V ) of 0.05, relatively small compared to the line-of-sight MWG extinction, hence the host galaxy plays an insignificant role in contributing to the polarization. This suggests that the high polarization (∼9%) in the optical in the earlier epoch cannot be explained by the MWG dust extinction alone. This is different from the case of Swift J164449.3+573451, where there was no polarization in the radio wavelength, and Wiersema et al. ( 2012 ) attributed the high linear polarization in the near-infrared to the dust induced polarization by the host galaxy. Table 2 Polarization Measurements We also include a light curve of AT2019DSG from the alerts issued by the public ZTF survey, aggregrated by the community broker ANTARES 8 8 https://antares.noao.edu (Saha et al. 2014 , 2016 ; Narayan et al. 2018 ) in both g and r bands, as shown in Figure 3 . With the light curve in hand, we can also check whether the TDE faded significantly between the first and second epoch, and whether the polarization signal is diluted (hence reduced) by the light from host galaxy. As can be seen in Figure 3 , the light curve indicates that the brightness of the TDE decreased from 17.87 ± 0.06 mag to 18.46 ± 0.10 mag in the g band between the two epochs. We note that the ZTF measurement is based on difference imaging, meaning that the photometry is solely from the light of