Magnetar is a neutron star with an ultrahigh magnetic field sim 10141015 G which usually manifests as soft gammaray repeater SGR or anomalous Xray pulsar AXP. SGR J19352154 is not only one of the most active magnetar detected so far but also the unique confirmed source of fast radio burst FRB. Gravitational wave highenergy Electromagnetic Counterpart Allsky Monitor GECAM are dedicated to monitor gammaray transients all over the sky including SGR bursts. Here we report the GECAM observation of the burst activity of SGR J19352154 from January 2021 to December 2022 which results in a unique and valuable data set for this important magnetar. With a targeted search of GECAM data 164 bursts from SGR J19352154 are detected by GECAMB while 97 bursts by GECAMC including the Xray burst associated with a fast radio burst FRB 20221014. We find that both the burst duration and the waiting time between two successive bursts follow lognormal distributions. The period of burst activity is 134pm20 days thus the burst activity could be generally divided into 4 active episodes over these two years. Interestingly the hardness ratio of Xray bursts tends to be softer and more concentrated over these two years especially during the active episode with FRBs detected.
['Astrophysics - High Energy Astrophysical Phenomena']
GECAM Observations of the Galactic Magnetar SGR J19352154 during the 2021 and 2022 Burst Active Episodes. I. Burst Catalog
{'GECAM Observations of the Galactic Magnetar SGR J1935+2154 during the 2021 and 2022 Burst Active Episodes. I. Burst Catalog': 'Sheng-Lun Xie , 1, 2 Ce Cai , 3 Yun-Wei Yu , 1 Shao-Lin Xiong , 2 Lin Lin , 4 Yi Zhao , 5 Shuang-Nan Zhang , 2 Li-Ming Song , 2 Ping Wang, 2 Xiao-Bo Li, 2 Wang-Chen Xue, 2, 6 Peng Zhang, 7, 2 Chao Zheng, 2, 6 Yan-Qiu Zhang, 2, 6 Jia-Cong Liu, 2, 6 Chen-Wei Wang, 2, 6 Wen-Jun Tan, 2, 6 Yue Wang, 2, 6 Zheng-Hang Yu, 2, 6 Pei-Yi Feng, 2, 6 Jin-Peng Zhang, 2, 6 Shuo Xiao, 8 Hai-Sheng, Zhao, 2 Wen-Long Zhang, 9, 2 Yan-Ting, Zhang, 2 Yue, Huang, 2 Xiao-Yun, Zhao, 2 Xiang, Ma, 2 Shi-Jie, Zheng, 2 Xin-Qiao, Li, 2 Xiang-Yang, Wen, 2 Ke, Gong, 2 Zheng-Hua, An, 2 Da-Li, Zhang, 2 Sheng, Yang, 2 Xiao-Jing, Liu, 2 and Fan, Zhang 2  \n1 Institute of Astrophysics, Central China Normal University, Wuhan 430079, China  \n- 2 Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquan Road, Beijing 100049, China  \n3 College of Physics and Hebei Key Laboratory of Photophysics Research and Application, Hebei Normal University, Shijiazhuang, Hebei 050024, China  \n- 4 Department of Astronomy, Beijing Normal University, Beijing 100088, China\n- 5 School of Computer and Information, Dezhou University, Dezhou 253023, China  \n6 University of Chinese Academy of Sciences, Beijing 100049, China  \n7 College of Electronic and Information Engineering, Tongji University, Shanghai 201804, China  \n8 Guizhou Provincial Key Laboratory of Radio Astronomy and Data Processing, Guizhou Normal University, Guiyang 550001, China 9 Qufu Normal University, Qufu 273165, China', 'ABSTRACT': 'Magnetar is a neutron star with an ultrahigh magnetic field ( ∼ 10 14 -10 15 G) which usually manifests as soft gamma-ray repeater (SGR) or anomalous X-ray pulsar (AXP). SGR J1935+2154 is not only one of the most active magnetar detected so far, but also the unique confirmed source of fast radio burst (FRB). Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) are dedicated to monitor gamma-ray transients all over the sky, including SGR bursts. Here we report the GECAM observation of the burst activity of SGR J1935+2154 from January 2021 to December 2022, which results in a unique and valuable data set for this important magnetar. With a targeted search of GECAM data, 164 bursts from SGR J1935+2154 are detected by GECAM-B while 97 bursts by GECAM-C, including the X-ray burst associated with a fast radio burst (FRB 20221014). We find that both the burst duration and the waiting time between two successive bursts follow lognormal distributions. The period of burst activity is 134 ± 20 days, thus the burst activity could be generally divided into 4 active episodes over these two years. Interestingly, the hardness ratio of X-ray bursts tends to be softer and more concentrated over these two years, especially during the active episode with FRBs detected.  \nKeywords: magnetars - soft gamma-ray repeaters: general - methods: data analysis - techniques', '1. INTRODUCTION': 'Corresponding author: Ce Cai  \ncaice@hebtu.edu.cn  \nCorresponding author: Yun-Wei Yu  \nyuyw@ccnu.edu.cn  \nCorresponding author: Shao-Lin Xiong  \nxiongsl@ihep.ac.cn  \nThe soft gamma-ray repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are perceived to originate in the highly magnetized neutron star, namely magnetar (Duncan & Thompson 1992; van Kerkwijk et al. 1995; Kouveliotou et al. 1998; Banas et al. 1997; Kaspi & Beloborodov 2017). Magnetars are characterized by slow rotation period ( P ∼ 2 -12 s), rapidly spin down ( ˙ P ∼ 10 -13 -10 -11 s · s -1 ) and relatively young age  \n(typically about 1000 yr). So far, 30 magnetars had been detected and 24 of them had been confirmed (Olausen & Kaspi 2014). Most magnetars can increase persistent radiation and emit bursts/flares simultaneously in the X-/gamma-ray band during an outburst.  \nBased on their luminosity and duration, the SGR bursts can be divided into three classes (Woods & Thompson 2006): Short-duration burst, which consists of single or multiple pulses, is the most typical magnetar burst with a burst duration ∼ 0.01 s and the luminosity around 10 38 ∼ 10 40 erg · s -1 ; Intermediate burst is a brighter magnetar burst with a duration longer than a short-duration burst ( > 1 s) and peak luminosity around 10 41 ∼ 10 43 erg · s -1 ; Giant flare, the rarest and the most powerful energetic burst, is characterized by a significantly higher luminosity than a typical magnetar burst and a special pulse profile with a hard initial spike and rapidly decaying tail.  \nMagnetar SGR J1935+2154 was first discovered and located in the Milky Way Galaxy by Swift Burst Alert Telescope (BAT) in 2014 July (Stamatikos et al. 2014), while it is worth to note that Xie et al. (2022) found several burst candidates in the gamma-ray burst monitor of Fermi gamma-ray Space Telescope (Fermi/GBM, Meegan et al. 2009) before the this time. Follow-up observations carried out between 2014 July and 2015 March with Chandra and XMM-Newton allowed the measurement of its spin period and spin-down rate, P ∼ 3 . 24 s and ˙ P ∼ 1 . 43 × 10 -11 s · s -1 , respectively. This indicates a dipole-magnetic field of B ∼ 2 . 2 × 10 14 G (Israel et al. 2016). It has experienced multiple active episodes from 2014 to 2022 (Younes et al. 2017; Lin et al. 2020b,a; Cai et al. 2022a,b; Xie et al. 2022; Rehan & Ibrahim 2023, 2024). April 2020 was recognized as a month of intense bursting activity for SGR J1935+2154, during which a burst forest was observed (Kaneko et al. 2021). Among these bursts there is an X-ray burst (XRB) (Li et al. 2021; Mereghetti et al. 2020; Ridnaia et al. 2021; Tavani et al. 2020) associated with a fast radio burst, FRB 200428 (Bochenek et al. 2020; CHIME/FRB Collaboration et al. 2020a). After the FRB 20200428 event, GECAM (Li et al. 2021; Xiao et al. 2022a; Zhang et al. 2023; Wang et al. 2024) detected an X-ray burst from SGR J1935+2154 which associated with a radio burst detected by CHIME on 2022 October 14 (Wang et al. 2022a). Later, the Insight-Hard X-ray Modulation Telescope (HXMT) again detected an X-ray burst associated with a radio burst found by the Yunnan 40 m telescope on 2022 October 21 (Li et al. 2022).  \nIn this work, we carry out a comprehensive targeted search on X-ray bursts of SGR J1935+2154 using GECAMobservation data from January 2021 to Decem-  \nber 2022. As Paper I of this series work for GECAM observation of SGR J1935+2154, we focus on the burst search, identification, and temporal analyses. In Paper II (In prep.), we will give the detailed time-integrated spectral analysis of these bursts. The current paper is organized as follows: In Section 2, we present the observation, search process, and report the burst catalog. In Section 3, we present the catalog analysis method and results. Finally, the summary and discussions are given in Section 4.  \nPlease note that the error reported in this work is for 1 sigma, if not stated otherwise.', '2. OBSERVATION AND BURST SEARCH': 'As of the writing of this paper, GECAM constellation is composed of four instruments, GECAMA/B (were launched in December 2020, Xiao et al. 2022b), GECAM-C (i.e. SATech-01/HEBS, launched in July 2022, Zhang et al. 2023) and GECAM-D (i.e. DRO/GTM, launched in March 2024, Wang et al. 2024), dedicated to monitor all-sky gamma-ray transients. Both GECAM-A and GECAM-B feature a dome-shaped array of 25 gamma-ray detectors (GRDs) and 8 Charged particle detectors (CPDs) while GECAM-C has 12 GRDs and 2 CPDs. All GRDs of GECAM-B and most of GRDs of GECAM-C operate in two readout channels: high gain (HG, 6-300 keV) and low gain (LG, 300 keV-5 MeV), which are independent in terms of data processing, transmission, and dead time.', '2.1. Search and Identification': "Magnetar SGR J1935+2154 experienced multiple active X-ray burst episodes after the launch of GECAMA/B, and an active X-ray burst episode after the launch of GECAM-C (Rehan & Ibrahim 2023, 2024; Wood & Fermi-GBM Team 2022). A search pipeline developed by Cai et al. (2021) for gamma-ray bursts (GRBs) is used to do a blind search on GECAM or HXMT daily observation data. In addition to other GRBs, 82 Xray bursts from SGR J1935+2154 were also found by GECAM-B, as reported in Xie et al. (2022) and 75 Xray bursts were found by HXMT (Cai et al. 2022a).  \nTo unveil potential bursts that are relatively weak and unable to trigger the instrument with a normal threshold, we conduct a targeted sub-threshold search on GECAM daily event-by-event (EVT) data 1 from 2021-01-01 to 2022-12-31 using the pipeline developed by Cai et al., submitted. Since X-ray bursts from magnetars tend to be softer than general GRBs, it is essential to employ appropriate spectral templates instead  \nof default Band templates for the search. Based on previous studies on magnetar burst spectral properties (Lin et al. 2020b,a; Rehan & Ibrahim 2023, 2024), we utilize the following spectral templates: the soft Band function (default softer template for GRB searching), CPL (a power law with high-energy exponential cutoff), OTTB (optically-thin thermal bremsstrahlung), Blackbody, and Powerlaw. The parameters setting is listed in Table 1 which is similar with the Table 1 in Xie et al. (2022). The details of each template are presented below.  \nThe Band function:  \nA ( E ) ∼          E α exp [ -(2+ α ) E E p ] , if E < ( α -β ) E p 2+ α , E β exp( β -α ) [ ( α -β ) E p (2+ α ) ] α -β , otherwise, (1)  \nwhere E p , in units of keV, is the peak energy of the νF ν spectrum, α / β are the low-/high-energy photon indices. The CPL function:  \nA ( E ) ∼ E -α exp [ -(2 -α ) E E p ] , (2)  \nwhere E p , in units of keV, is the peak energy of the νF ν spectrum, α are the photon index.  \nThe OTTB function:  \nA ( E ) ∼ E -1 exp ( -E kT ) , (3)  \nwhere kT is the electron energy, in units of keV.  \nThe Blackbody function:  \nA ( E ) ∼ E 2 exp( E/kT ) -1 , (4)  \nwhere kT is the temperature, in units of keV.  \nThe Powerlaw function:  \nA ( E ) ∼ E -α , (5)  \nwhere α are the photon index.  \nThousands of trigger (burst candidates) have been found through the targeted search process. We execute a refined analysis for each burst candidate by carefully removing various false triggers or other burst events using the GRB data analysis tool, GECAMTools 2 . SGR J1935+2154 burst identified from candidates should adhere to the following criteria (same as Xie et al. 2022):  \nTable 1. Spectral templates used in the targeted search for X-ray bursts from SGR J1935+2154.Table 2. The proportion of different templates in X-ray bursts that GECAM-B/C observes from SGR J1935+2154.  \n- 1. Using the GECAM position history file (posatt) to retrieve the position of satellite and the pointing of detector. The candidates are excluded when SGR J1935+2154 is eclipsed by Earth;\n- 2. The candidates with the angle of the three most significant detectors relative to the source position (R.A. = 293.73 ° , decl. = 21.90 ° , Israel et al. 2016) should be less than 60 · (with at least two detectors);\n- 3. The solar flares, the particle events measured by CPD observation, and the Terrestrial gamma-ray flash (TGF, Briggs et al. 2013) and Terrestrial electron beam (TEB, Xiong et al. 2012) featured by being harder ( ∼ MeV) and shorter ( ∼ 1 ms) than magnetar bursts are excluded;\n- 4. Identified by other instruments (e.g. Fermi/GBM).  \n2.2. Search Results  \nA total of 164 bursts for GECAM-B and 97 bursts for GECAM-C are identified and listed in Tables 3 and 4. Among them, there are 14 bursts that both GECAM-B and GECAM-C could observe, and a short X-ray burst (2022-10-14T19:21:39.130 UTC) observed by GECAM-B&C is associated with a fast radio burst FRB 20221014 (Wang et al. 2022b). It is worth to note that about one third of GECAM bursts (i.e. 60 bursts of GECAM-B and 36 bursts of GECAM-C) are invisible to Fermi/GBM (blocked by the Earth or turned off during the SAA passage).  \nThe targeted search location (TL) of each burst is plotted in Fig 1. We summarize the proportion of different templates in Table 2 and Fig. 2 to assess each template's merit for magnetar bursts to targeted search. The CPL, OTTB, and BB account for a proportion of them than other templates. Note that even a burst could be found by every template, the pipeline only outputs  \nthe best template (e.g., the one with the maximum loglikelihood ratio, as referenced in Cai et al. 2021). As shown in Fig. 3, Using a Powerlaw template to search magnetar burst prefers a weak burst with low significance. Most of the SoftBand templates are given by GECAM-B data after October 2022, showing much difference compared to those from GECAM-C. This disparity may be attributed to the effective detectable energy range of GECAM-B changed in the HG channel (¿40 keV after October 2022), potentially leading to bursts with more high energy photons being detected without softer photons, making them easier to found using the SoftBand compared to other templates. Therefore, in general, it is recommended to use a template with a simple power-law function and exponential cutoff function, such as CPL, OTTB, or Blackbody, to coherently search for and locate magnetar bursts in hard X-ray observations.  \nTable 3 . SGR J1935+2154 burst list observed by GECAM-B from January 2021 to December 2022.  \nTable 3 (continued)  \nXie et al. Table 3 (continued)  \nXie et al.  \nTable 3 (continued)  \nTable 4 . SGR J1935+2154 burst list observed by GECAM-C from October to December 2022.  \nTable 4 (continued)  \nXie et al. Table 4 (continued)", '3. CATALOG ANALYSIS': "As shown above, we show light curves of 9 bursts in Fig. 4 to display the variety of these bursts. The trigger time of each burst is listed in Tables 3 and 4. SGR J1935+2154 bursts consist of a single pulse (such as ID: 122, 138, and 161 of GECAM-B; ID: 3 and 42 of GECAM-C), multiple pulses (ID: 27 of GECAM-B; ID: 59 of GECAM-C), and intermediate flares (ID: 126 of GECAM-B; ID: 23 of GECAM-C). The X-ray burst associated with the fast radio burst FRB 20221014 is ID: 138 of GECAM-B, and ID: 42 of GECAM-C.  \nThe daily burst rate is defined as N/P , where N is the observed burst number per day and P represents the percentage of the effective observation time in a full day, excluding the time intervals when the Earth blocked SGR J1935+2154, or when GECAM passes through the South Atlantic Anomaly (SAA) area, during the instrument's startup period.  \n<!-- image -->  \nFigure 1. The targeted search location (TL) of bursts. The red star marks the accurate position of SGR J1935+2154 (R.A. = 293.73 ° , decl. = 21.90 ° ).  \n<!-- image -->  \n<!-- image -->  \nFigure 2. The angle separation between the targeted search location (TL) of burst and true position of SGR J1935+2154.  \n<!-- image -->  \nWe calculate the effective observation time 3 of GECAM-B/C individually and estimate the daily burst rate of GECAM-B/C, respectively (see Fig. 5). Because the effective detectable energy range of GECAMB changed in the HG channel (¿40 keV after October 2022), weaker bursts may not be detected compared to GECAM-C observations. Hence, given that the burst activity of GECAM-B is lower than that of  \nGECAM-C (¿15 keV), the daily burst rate estimated using GECAM-C data may be more reliable for assessing burst activity compared to using GECAM-B data after October 2022. A detailed study on the evolution of the effective detectable energy range change of GECAM-B will be reported in Paper II.", '3.2. Period Search': 'To explore the potential periodicity behavior in the burst history of SGR J1935+2154, we use the daily burst rate data from GECAM-B (before October 2022) and GECAM-C (after October 2022) with the Lomb-Scargle Periodogram for searching periodicity (Lomb 1976; Scargle 1982; VanderPlas 2018). The periodogram results  \n<!-- image -->  \nFigure 3. The significance of burst v.s angle separation between the targeted search location (TL) and true position of SGR J1935+2154.  \n<!-- image -->  \nFigure 4. Representative examples of GECAM-detected bursts of SGR J1935+2154. For each burst, light curves are shown for high gain (HG, 6-300 keV). The background of each burst is shown by the red dotted line. The green vertical dotted line and blue dotted line are assessed by the Bayesian block (BB) algorithm.  \n<!-- image -->  \n<!-- image -->  \nGECAM-B; Burst ID: 138  \n<!-- image -->  \n<!-- image -->  \nGECAM-C; Burst ID: 23  \n<!-- image -->  \n<!-- image -->  \nGECAM-B; Burst ID: 161  \n<!-- image -->  \n<!-- image -->  \n<!-- image -->  \nGECAM-C; Burst ID: 3  \nFigure 5. The burst history of SGR J1935+2154 observed by GECAM-B/C.  \n<!-- image -->  \nFigure 7. Phase-folded burst rate according to the 134.63 day period with MJD 59215 (2021-01-01) referenced as phase 0. The active window (i.e. from ϕ = 0 . 7 to ϕ = 1 . 5) is denoted with red dotted lines.  \n<!-- image -->  \nFigure 6. Lomb-Scargle periodogram of X-ray bursts from SGR J1935+2154 observed by GECAM. The vertical red dotted line indicate the peak of periodogram which is 134.63 day.  \n<!-- image -->  \nare shown in Fig 6. The most significant peak of the Lomb-Scargle periodogram is 134.63 day (False Alarm Probability: 0.001). The peak around the 50 day are likely caused by observation windows or bursts gap (Xie et al. 2022).  \nTo uncover the active period of SGR J1935+2154, the start time of all bursts are folded into different phases using period folding method (CHIME/FRB Collaboration et al. 2020b; Zhang et al. 2021; Xie et al. 2022),  \nϕ = T -T 0 P -floor ( T -T 0 P ) , (6)  \nwhere ϕ is the folded phase, T is the burst start time, T 0 is the phase start point (MJD: 59215; UTC: 202101-01), P is a given period, and the floor is a function that returns the floor of the input number. As shown in Fig 7, the duty circle of SGR J1935+2154 bursts is 80%. The error could be estimated to be 20 days with  \nσ = PW active T span , (7)  \nwhere P is the period and W active is the number of active days. Accordingly, the most probable period of SGR J1935+2154 from January 2021 to December 2022 is 134 . 63 ± 20 days, consistent with previous work (Xie et al. 2022, evaluated from July 2014 to January 2022) and the burst history over these two years could be grouped into 4 active episodes (see Fig. 5).', '3.3. Burst Duration': 'As previous studies (Lin et al. 2013), the magnetar burst duration T bb is calculated with the Bayesian blocks method (Scargle et al. 2013). We measure the duration for each burst using the sliced event data of  \n10 s, including both pre- and post-burst trigger time intervals (from T 0 -10 s to T 0 +10 s, where T 0 is the burst trigger time). The blocks with a duration longer than 6 s are treated as background since the spin period of SGR J1935+2154 is just approximately 3.24 s. The background count rate is estimated by fitting a first-order polynomial to the background blocks. A block with a significance ( S/ √ B , where S is the net counts and B is the background counts) larger than 5 σ is considered as part of the burst region. As an example, the blocks and block edges of a burst are illustrated in Fig. 4. However, some bursts with multiple pulses (e.g. burst #59 of GECAM-C in Fig. 4) have at least two subsequent blocks, along with quiescent intervals. In such cases, the entire burst duration is calculated from the start of the first burst block to the end of the last block. Due to the different effective detectable energy ranges between GECAM-B and GECAM-C, 14 bursts observed by both GECAM-B&C exhibit different durations (see Fig. 8 or see an example of X-ray burst #138 of GECAM-B and #42 of GECAM-C in Fig. 4 associated with FRB 221014).  \nThe duration ( T bb ) of each burst observed by GECAM-B/C is listed in Tables 3 and 4. The burst duration distributions of GECAM-B/C are shown in Fig. 9. These distributions are well fitted with lognormal functions, as illustrated in Table 5. We conduct the one-sample Kolmogorov-Smirnov test to compare the distribution of GECAM-B/C against a lognormal distribution and show the goodness of fit in Table 5. The results show that the distribution of burst duration detected by GECAM from SGR J1935+2154 exhibits a lognormal distribution, which is consistent with previous work (Lin et al. 2020b,a; Cai et al. 2022a; Rehan & Ibrahim 2023, 2024).  \nTable 5. The mean of burst duration distribution in each episode obtained by fitting to a lognormal function.  \na one-sample Kolmogorov-Smirnov test statistic  \nFigure 8. The burst duration of 14 X-ray bursts observed by both GECAM-B and GECAM-C.  \n<!-- image -->', '3.4. Burst Waiting Time': 'The waiting time between the successive bursts that fall within an uninterrupted observation time interval is defined as  \n∆ t = t i -t i -1 (8)  \nwhere t i is the burst start time of the i -th burst. As shown in Fig. 10, there are 45 waiting times of GECAMB and 21 waiting times of GECAM-C during continuous observation time intervals.  \nFig. 10 shows the distribution of waiting time measured by GECAM-B/C. These distributions could be well fitted with lognormal functions, resulting in a mean value of 338 . 84 +573 . 16 -212 . 95 seconds for GECAM-B and a mean value of 79 . 43 +149 . 65 -51 . 89 seconds for GECAMC. When comparing to a lognormal distribution, the Kolmogorov-Smirnov tests yield a statistic of 0.104 and a p-value of 0.672 for GECAM-B, and a statistic of 0.112 and a p-value of 0.929 for GECAM-C. This lognormal distribution behavior is similar to that observed in previous studies (Cai et al. 2022a; Xie et al. 2024). Since the relatively short continuous observation time intervals of GECAM-C for observing SGR J1935+2154 (only dozens of minutes) compared to GECAM-B, it is difficult to measure the longer waiting times between more succes-  \nsive bursts. Therefore, the distribution mean value of GECAM-C is smaller than that of GECAM-B.', '3.5. Burst Hardness Ratio': 'The net counts of the source is estimated as  \nN i = C i -B i , (9)  \nwhere C i and B i represent the total counts and background counts in the burst duration, respectively. The hardness ratio is the ratio of the net counts in different energy ranges.  \nSince changes in the effective detectable energy range of GECAM-B over the two years, we measure the hardness ratio of all bursts within the same effective range of 50-200/40-50 keV for GECAM-B. The hardness ratio of GECAM-C is calculated in the range of 30-200/1530 keV. The hardness ratio of the four active episodes for GECAM-B data yields mean values of 2.70, 2.30, 1.87, and 1.48, respectively. It presents that the evolution of the burst hardness tends to be softer across the observation time, as shown in Fig. 11. The burst hardness is more concentrated after October 2022 when FRB 20221014 happened. More detailed spectral properties and evolution will be reported in Paper II.', '4. SUMMARY AND DISCUSSIONS': 'In this paper, we perform a targeted sub-threshold search GECAM daily EVT data for SGR J1935+2154 bursts during the year of 2021 and 2022. We design 5 spectral templates to target search and find 164 X-ray bursts from GECAM-B and 97 bursts from GECAM-C (refer to Tables 3 and 4). Among the templates, the CPL, OTTB, and BB cover a higher proportion of them compared to others (refer to Table 2), providing more accuracy in location (see Fig. 2). Therefore, a simple power-law function and exponential cutoff function with softer parameter settings might be preferred for searching magnetar X-ray bursts.  \nThe burst activity is evaluated by estimating the daily burst rate data, as illustrated in Fig. 5. We employ the Lomb-Scargle method to investigate potential periodic behavior, resulting in the most likely period of 134 . 63 ± 20 days (refer to Fig. 6). Therefore, the burst history over these two years could be divided into 4 active episodes (see Fig. 5). The period of 134 . 63 ± 20 days with 80% duty circle is well consistent with previous study (Xie et al. 2022, evaluated from July 2014 to January 2022). Unlike other study periods ( ∼ 231 days evaluated from 2014 to 2020 or ∼ 238 days evaluated from July 2014 to October 2021 in Grossan 2021; Zou et al. 2021, respectively), a shorter period is found in this study, possibly indicating an increased activity of  \nFigure 9. The left panel is the burst duration of each burst observed by GECAM-B/C. The right panel is the burst duration distributions of GECAM-B/C. The horizontal dotted lines show the best-fit lognormal function with a mean value listed in Table 5.  \n<!-- image -->  \nX-ray bursts from SGR J1935+2154 after the year of 2021.  \nWe perform extensive studies on the statistical characteristics of these X-ray bursts, including the burst duration, waiting time, and hardness ratio. The duration follows a lognormal distribution for GECAM-B/C, respectively (see Fig. 9 and Table 5). Due to the varying effective detectable energy ranges of GECAM-B and GECAM-C, some bursts detected by both satellites may show different durations (see Fig. 4 for examples). In such cases, the duration measured by GECAM-C is more informative across the entire energy ranges when both satellites detect the same burst. The waiting time also conforms to a lognormal function with mean values of 338 . 84 +573 . 16 -212 . 95 seconds and 79 . 43 +149 . 65 -51 . 89 seconds for GECAM-B/C, respectively (refer to Fig. 10). Because the relatively short continuous observation time intervals for GECAM-C observing SGR J1935+2154 compared to GECAM-B, the distribution mean value of GECAM-C is smaller than that of GECAM-B. Such lognormal distribution behavior is similar to that observed in previous studies (Cai et al. 2022a; Xie et al. 2024). The hardness ratio of X-ray bursts tends to become softer and more concentrated over the course of  \nthe observation time spanning these two years (see Fig. 11).  \nThese statistical results indicate that the X-ray bursts from SGR J1935+2154 show increased activity and exhibit a softer spectrum over the two years. Similar to FRB 200428, which occurred during the most active period (April-May 2020) preceding 2020, the FRB 20221014 are detected in the final and most active episode (October-December 2022). In view of their millisecond duration and high energy releases, FRBs are widely suggested to originate from the violent activities of compact objects, in particular, magnetars (Popov & Postnov 2010; Kulkarni et al. 2014; Katz 2016; Connor et al. 2016; Cordes & Wasserman 2016; Lyutikov 2017). And the amounts of energy released by the bursts and outbursts of Galactic magnetars, from SGRs or AXPs, indicate that X-ray bursts probably correspond to sudden and local (not global) catastrophic events. In that case, FRB emission may result from such burst interactions (e.g., the collision between different Alfven waves or different explosion outflows) in a global activity of a magnetar and then a detected FRB be associated with an X-ray burst (Yang & Zhang 2021; Xie et al. 2024).  \nThis work is supported by the Strategic Priority Research Program of the Chinese Academy of Sciences  \nFigure 10. The left panel is the waiting time (time interval between two successive bursts observed by GECAM-B/C) of the X-ray bursts v.s their occurring times, where the time of FRB 20221014 is represented by the green dashed line. The right panel is the distribution of waiting time. The horizontal dotted lines represent the best-fit lognormal function with a mean of 338 . 84 +573 . 16 -212 . 95 seconds for GECAM-B and 79 . 43 +149 . 65 -51 . 89 seconds for GECAM-C, respectively.  \n<!-- image -->  \nFigure 11. The evolution of hardness ratio of each burst in 50-200/40-50 keV for GECAM-B and 30-200/15-30 keV for GECAM-C.  \n<!-- image -->  \n(Grant No. XDB0550300, XDA30050000), the National Key R&D Program of China (2021YFA0718500), the National SKA program of China (2020SKA0120300), the National Natural Science Foundation of China (Grant No. 12393811, 12173038, 12303045, 12273042), the Strategic Priority Research Program on Space Science of the Chinese Academy of Sciences (Grant No. XDA15360102, XDA15360300, XDA15052700), the Natural Science Foundation of Hebei Province (No. A2023205020), and the Science Research Program of Dezhou University (2024xjrc142).', 'REFERENCES': 'Banas, K. R., Hughes, J. 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