A Compact Source for Quasi-periodic Pulsation in an M-class Solar Flare

Abstract

Quasi-periodic pulsations (QPP) are usually found in the light curves of solar and stellar flares, they carry the features of time characteristics and plasma emission of the flaring core, and could be used to diagnose the coronas of the Sun and remote stars. In this study, we combined the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory and the Nobeyama Radioheliograph (NoRH) to observe an M7.7 class flare occurred at active region 11520 on 19 July 2012. A QPP was detected both in the AIA 131Å bandpass and the NoRH 17 GHz channel, it had a period of about four minutes. In the spatial distribution of Fourier power, we found that this QPP originated from a compact source and that it overlapped with the X-ray source above the loop top. The plasma emission intensities in the AIA 131Å bandpass were highly correlated within this region. The source region is further segmented into stripes that oscillated with distinctive phases. Evidence in this event suggests that this QPP was likely to be generated by intermittent energy injection into the reconnection region.

Calibration of the Tip of the Red Giant Branch

“…Our value lies close to both the mean and the mode of the distribution. We note that the range of values of A I =0.094-0.109 mag, chosen by Yuan et al (2019;hereafter Y19) Adopting ∆µ(SM C − LM C) = 0.488 mag and the DEB distance modulus for the SMC of 18.965 ± 0.025 (stat) ± 0.048 (sys) mag, our detection of the I-band TRGB at 14.93 mag and an extinction of A I =0.056 mag (NED) gives M I (SM C) = -4.09 ± 0.03 (stat) ± 0.05 (sys) mag, in systematic agreement, at the one-sigma level, with our LMC measured value of -4.05 ± 0.03 (stat) ± 0.05 (sys) mag. The SMC tip detection was made using a standard Sobel filter applied to a GLOESS-smoothed I-band luminosity function based on stars within the color range 1.4 < (V − I) < 1.8 mag, using software and methods identical to those used in Freedman et al (2019).…”

“…The mean of the distribution is shown by an open white circle. In blue is the extinction value suggested by Yuan et al (2019), based on a crowding correction, applied to the SMC photometry of Zaritsky et al (2002). See Appendix A for a detailed description of why this post-processing of the results presented in Freedman et al (2019) is problematic.…”

“…For the LMC, we use the "Shallow" survey data published by Ulacyk, et al (2012); both the LMC and SMC data are available at the following website http://www.astrouw.edu.pl/ogle/ogle3/maps/. Yuan et al (2019) have pointed out that the coarser pixel scale in the optical (U BV I) survey of the two Magellanic Clouds undertaken by Zaritsky et al (2002Zaritsky et al ( , 2004 probably suffer from blending issues. While the Zaritsky data for the SMC (but not the LMC) were used in the analysis by Freedman et al (2019), here we now self-consistently use only the OGLE-III data for both the LMC and the SMC.…”

“…In Appendix A, we address some serious issues arising in the recent paper by Yuan et al (2019;hereafter Y19). We demonstrate that the adoption of incorrect assumptions has led to an erroneous result; in specific, their underestimate of the line-of-sight extinction to the TRGB stars in the LMC.…”

“…In all cases we find excellent agreement in the zero-point calibration. We then examine the recent claims by Yuan et al (2019), demonstrating that, in the case of the SMC, they corrected for extinction alone while neglecting the essential correction for reddening as well. In the case of IC 1613, we show that their analysis contains an incorrect treatment of (over-correction for) metallicity.…”