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We observed the field of EP240919a (Liang et al., GCN 37561), also identified as GRB 240919A (Liang et al., GCN 37564; Rodi et al., GCN 37573; Wang et al., GCN 37574) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, and K bands, started on 2024 September 19 at 23:27:28 UT (i.e. 8.6 hr after the burst), and lasted for about 1 hour. From preliminary inspection of the images, we do not find any optical/NIR counterpart within the EP error circle down to the following 3sigma limit: r > 20.8 (AB; calibrated against the Pan-STARRS catalogue); H > 17.3 (Vega; calibrated against the 2MASS catalogue); at a mid-time of 9.1 hours after the trigger.

We observed the field of GRB 240809A (Evans et al., GCN 37110; Want et al., GCN 37113; Dubai et al., GCN 37114; Jiang et al., GCN 37116) with the REM 60cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, K bands, starting on 2024 August 09 at 23:07:36 UT (i.e. 14.6 hours after the burst), and lasting for about 1 hour. From preliminary photometry, we detect the optical afterglow at a position consistent with the UVOT detection (Shilling & Evans, GCN 37123), at the following AB magnitude in the r band: r = 20.75 +- 0.20 (calibrated against PanSTARRS catalogue) at a mid-time of t-t0 ~ 15.1 hours after the GRB trigger.

We observed the field of the short GRB 240821A detected by Fermi/GBM (Fermi GBM Team, GCN 37219; Preis et al., GCN 37221), SVOM/ECLAIR and SVOM/GRM (Cangemi et al., GCN 37220) with the REM 60cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H bands, starting on 2024 August 23 at 00:59:16 UT (i.e. 30.22 hours after the Fermi trigger), and lasting for about 1.5 hours. From preliminary photometry performed on the 10'x10' REM fov around the SVOM/ECLAIR position, we did not detect potential afterglow candidates consistent with the four X-rays counterparts by EP-FXT (Turpin et al., GCN 37230), and the two Swift-XRT candidates (Evans, GCN 37236), within the covered region, down to the following 3sigma magnitude upper limits: H > 14.5 (Vega; calibrated against the 2MASS catalogue) at a mid-time of t - t0 = 31.22 hours after the Fermi trigger, i > 19.3 (AB; calibrated against the SkyMapper catalogue) at a mid-time of t - t0 = 31.13 hours after the Fermi trigger.

Following the identification of the optical afterglow (Quirola-Vasquez et al., GCN 37319) of GRB 240821A (Cangemi et al., GCN 37220; He et al., GCN 37226; Murphy et al., GCN 37232; Dalessi & Meegan, GCN 37239), we obtained 4x1200 s of observations with the X-shooter instrument at the ESO VLT UT3 (mid time 2024 Aug 30.3578 UT, that is, 8.8 days after the trigger). These observations reveal a continuum across the spectral range 4000-20000 AA, and a single clear emission line at 8120 AA. While the presence of a substantial continuum blueward of 8120 AA rules out that this line is Ly-alpha, it is difficult to conclusively determine a redshift value based on only a single line. We consider three possibilities below. A) The emission line could arise from the [O II] doublet (3726, 3729) at z = 1.18. In this scenario the other strong emission lines lie in the IR regime, where sensitivity is poorer and sky background higher. The observed spectral energy distribution of the host galaxy from the Legacy and VISTA surveys would also provide the best match at this redshift. However, the resolution of X-shooter should clearly resolve the two components of the doublet, and, while a very weak excess may be present at 8215 AA (the expected location of the bluer component of the doublet), the observed intensity ratio would be inconsistent with the expectations for either high or low density media. B) The line could be from [O III] (5007 AA) at z = 0.62. In this scenario, both [O III] 4959 and H-beta would lie in close proximity in the spectrum, although are expected to have lower flux, and hence poorer signal to noise than the observed line. There is no detection of any emission at the expected location of either. C) The line may come from H-alpha at z = 0.24. Since H-alpha may well be the brightest line within the host galaxy (especially for a short-GRB host), the non-detection of other emission features at the same redshift, but at bluer wavelengths is less problematic because they may be fainter and/or extinguished. This may also be supported by an apparent decrease in the galaxy continuum at ~4500 AA, which could be due to the Balmer break, although the signal to noise is poor in this region. The detection of a single line does not enable at the current time an unambiguous redshift determination, but does suggest it must be one of the above possibilities. We note that all of these lie outside the formal 1-sigma range of the photometric redshift determination from the Legacy survey (z = 0.488 +/- 0.074; Zhou et al. 2021, MNRAS, 501, 3309). Further analysis is ongoing, and we will update the community should this reveal a stronger conclusion regarding the burst redshift. We acknowledge expert help of the ESO observing staff at Paranal, in particular Thomas Rivinius and Matias Jones.

We observed the field of GRB 240825A (Fermi GBM team, GCN 37273; Gupta et al., GCN 37274) with the LBC camera mounted on LBT (Mt. Graham, AZ, USA) in r' and z' bands (45 min exposure time per filter) approximately at midtime 05:55:00 UT on 2024-09-12 (17.6 days after the burst). The optical transient (Jiang et al. GCN 37275; Dutton et al. GCN 37276; Odeh et al. GCN 37277; Zhang et al. GCN 37278; Li et al. GCN 37280; Izzo & Malesani, GCN 37287; Lipunov et al. GCN 37289; Leonini et al. GCN 37291; Wu et al. GCN 37292; Brivio et al. GCN 32795; Odeh, GCN 37299) is well detected in r' and z' bands. Using PSF photometry, we measure a preliminary AB magnitude of r'=22.8+-0.1, calibrated against Pan-STARRS field stars, and not corrected for the foreground Galactic extinction. We acknowledge the excellent support from the LBTO and LBTB staff, particularly Jan Snigula in obtaining these observations.

We observed the field of GRB 240825A (Gupta et al., GCN 37274; Fermi GBM team, GCN 37273; Di Lalla et al., GCN 37288) with the REM 60cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H and K bands, starting on 2024 Aug 26 at 00:28:43 UT (i.e. about 8.6 hours after the Swift trigger) and lasted for about 1 hour. The optical afterglow is detected in the r band at a position coincident with that reported by Swift-UVOT (Gupta et al., GCN 37274) and other optical observations (Jian et al., GCN 37275; Dutton et al., GCN 37276; Odeh et al., GCN 37277; Zhang et al., GCN 37278; Li et al., GCN 37280; Izzo & Malesani, GCN 37287). The NIR afterglow is detected in the J band at a position consistent with the optical counterpart. From preliminary photometry, we derive the following magnitudes: r = 20.5 +/- 0.3 (AB; calibrated against the Pan-STARRS catalogue) at a mid-time of t-t0 ~ 9.1 hours after the trigger, J = 17.7 +/- 0.3 (Vega; calibrated against the 2MASS catalogue) at a mid-time of t-t0 ~ 9.2 hours after the trigger.

The T90 of GRB 240825A is only 4 seconds (GCN 37301), and it is located at a relatively close distance (z=0.659, GCN 37293). The fluence reaches a high level of 10^{-4} erg/cm^2. Through spectral analysis, we find that peak energy Ep is about 400 keV and isotropic energy Eiso is about 2x10^{53} erg, consistent with the Amati relation for long-duration gamma-ray bursts. Comparing its X-ray afterglow (see figure attached below, blue dots), its luminosity falls within the range of other long-duration bursts which are associated with supernovae, higher than those of short-duration bursts which have merge origins. Based on these findings, we conclude that GRB 240825A is a long-duration burst (BdHN I; see, e.g., Bianco, et al., 2024, ApJ, 966, 219) and is associated with a SN. The supernova may reach its optical peak in the observer's rest-frame approximately one month after the trigger. Its peak brightness should be within the detection limits of both ground- and space-based telescopes. Therefore, we encourage further observations in the coming weeks. Figure: https://www.icranet.org/documents/GRB_240825A.png

We observed the optical afterglow of long bright GRB 240825A (Gupta et al., GCN 37274; Fermi GBM team, GCN 37273; Di Lalla et al., GCN 37288; Frederiks et al., GCN 37302) with the 3.6m Telescopio Nazionale Galileo (TNG) equipped with the DOLoRes camera in spectroscopic mode. Observations were carried out with the LR-B grism, covering the range 3500-8000 AA. The observations consisted of one spectrum carried out at a mean time of Aug 25.9562 UT (~7.4 hours after the burst). In the acquisition image we clearly detect the optical afterglow (Gupta et al., GCN 37274; Jiang et al. GCN 37275; Dutton et al. GCN 37276; Odeh et al. GCN 37277; Zhang et al. GCN 37278; Li et al. GCN 37280; Izzo & Malesani, GCN 37287; Lipunov et al. GCN 37289; Leonini et al. GCN 37291; Wu et al. GCN 37292; Brivio et al. GCN 32795; Odeh, GCN 37299) with a magnitude r~20, calibrated against the Pan-STARRS catalogue. The spectrum has a low SNR. From a preliminary reduction, we identify a single absorption feature consistent with Mg II at a redshift of z~0.66, in agreement with the results reported by Martin-Carrillo et al. (GCN 37293).

We observed the field of GRB 240905E detected by Swift/BAT (Dichiara et al., GCN 37397) and SVOM/GRM (SVOM/GRM team, GCN 37404) with the REM 60cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, K bands, starting on 2024 September 06 at 01:36:22 UT (i.e. 7.2 hours after the Swift trigger), and lasting for about 1 hour. From preliminary photometry we do not detect any optical/NIR counterpart at the Swift-XRT refined position (Ferro et al., GCN 37406) down to the following 3sigma magnitude upper limits: r > 19.1 (AB; calibrated against the PanSTARRS catalogue) at a mid-time of t - t0 = 7.7 hours after the trigger J > 17.5 (Vega; calibrated against the 2MASS catalogue) at a mid-time of t - t0 = 7.8 hours after the trigger.

We observed the field of the soft GRB 240828B detected by SVOM/ECLAIRs (Le Provost et al., GCN 37318) with the REM 60cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, H bands, starting on 2024 August 31 at 06:19:52 UT (i.e. 2.71 days after the SVOM trigger), and lasting for about 1 hour. From preliminary photometry we do not detect any optical/NIR counterpart at the Swift-XRT position (Page et al., GCN 37334) down to the following 3sigma magnitude upper limits: H > 15.7 (Vega; calibrated against the 2MASS catalogue) r > 19.9 (AB; calibrated against the PanSTARRS catalogue) at a mid-time of t - t0 = 2.73 days after the trigger.