I. Introduction III. Inpainting IV. Results and discussion One of the fundamentals of the standard model of cosmology is the statistical isotropy of the universe at large scales. However, WMAP and Planck temperature data show evidence of several anomalies hinting that the large-scale anisotropies are not fully compatible with the statistical isotropy assumption. In particular, one of them, known as “hemispherical power asymmetry” [1], suggests a directional dependency of the anisotropies. This asymmetry has been found using different estimators with a significance close to 3σ [2, 3, 4]. Modeling the asymmetry in terms of a dipolar modulation [2] allows us to determine the statistical significance, the direction, and the amplitude. In temperature the observed asymmetry is compatible with a modulation of ~7% [2, 4]. Applying the same analysis to the Planck third release (PR3) data, a dipolar modulation was found at modest significance [4] in the E-mode maps. However, anisotropic noise and large scale systematics plays an important role in this analysis. In this work we repeat the analysis using both, PR3 and the new Planck fourth release (PR4) data [7], which provides an improved data set (especially in polarization) with reduced systematics and noise. In addition, we also work with a new alternative inpainting approach, which is necessary to reduce the E/B mixing. The preliminary results show that using a set of 300 simulations the p-value increases up to 3.3%, while we have not found differences in the intensity analysis. II. Dipolar Modulation Analysis REFERENCES [1] Eriksen H.K. et al. 2004, ApJ, 605, 14 [2] Hansen F. K. et al. 2009, ApJ, 704, 1448 [3] Akrami Y. et al. 2014, ApJ, 784, L42 [4] Planck Collaboration VII. 2020, A&A, 641, A7 [5] Tegmark M. & Oliveira-Costa A. 2001, PhRvD, 64, 063001 [6] Marcos-Caballero A. et al. 2019, JCAP, 10, 53 [7] Planck Collaboration LVII. 2020, A&A, A42 Following [3], we study the asymmetry by computing the local- variance maps over disks of a certain size. A dipolar modulation, of the form in the fluctuation map would manifest itself as a dipole structure in the local-variance map, so we can fit it by a χ2. The first figure shows how a local-variance map looks like starting from a modulated E-mode map. Using simulations we can calibrate numerically the proportionality between the amplitude of the local-variance dipole and the amplitude of the modulation. We can also predict the ability of the method to detect modulations of a given amplitude (see figure on the left). If we apply a mask, we only consider disks where at least 10% of the pixels are unmasked. HEMISPHERICAL POWER ASYMMETRY IN INTENSITY AND POLARIZATION FOR PLANCK PR4 DATA C. Gimeno-Amo1, R. B. Barreiro1 and E. Martínez-González1 1Instituto de Física de Cantabria, CSIC-Universidad de Cantabria, Santander, Spain E-mail : gimenoc@ifca.unican.es Local-Variance map at Nside = 16 Working with masked QU maps produce an E/B mixing. In order to have a better E-mode reconstruction we need to fill masked pixels by using an inpainting technique. For the first time in polarization we have implemented an inpainting technique known as “Gaussian constrained realization” [6]. We fill the masked pixels coherently with a cosmological model and taking into account the unmasked pixels. The pixel covariance matrix needed for this has 2 contributions: the CMB signal, and the noise and systematics. CMB can be computed from the angular power spectra [5, 6], while noise must be estimated numerically. We have split the noise simulations and used the first half for estimating the covariance matrix and the second for the analysis. Unfortunately, the number of simulations is not enough for the matrix to reach convergence, and the inpainting is not as good as we predicted using only CMB. We have tried a variety of ways of estimating the matrix, and we have chosen the one that minimizes, for the same fsky, the maximum relative error (see green line in the fi