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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

5559 results found.

  1. GRB 261029A / AT 2026ahaw: Optical upper limits from the PKU 60cm Telescope
  2. GRB 261026A: Mondy, SAO RAS and Terskol optical observations
  3. GRB 261029A: WFST optical observations
  4. GRB 261029A: FRAM-ORM and FRAM-Auger optical afterglow light curve
  5. GRB 261029A / AT2026ahaw: r- and i-band optical follow-up with the PKU 60cm Telescope
  6. GRB 261029A: SVOM/C-GFT optical observations
  7. GRB 261029A: Fermi-LAT detection
  8. GRB 261029A: LCO optical observations (correction to GCN 46082)
  9. GRB 261029A: LCO optical observations
  10. GRB 261029A: NOT imaging and spectroscopic redshift z = 3.27
  11. GRB 261029A: KAIT optical observations
  12. GRB 261029A: SVOM detection of a burst
  13. GRB 261029A: Fermi GBM Final Real-time Localization
  14. GRB 261028A: Fermi GBM Final Localization
  15. GRB261026A: Infrared detection with MDM/MIRAGE
  16. EP Alert 261026.29: Global MASTER-Net observations report
  17. GRB 261026A: ULL-ASTRO-MASTER optical detection with LCO 40-cm telescope at Haleakalā Observatory
  18. SVOM GRB261026.26: Global MASTER-Net observations report
  19. EP261023a: Einstein Probe detection of an X-ray transient
  20. IceCube-261020A: Upper limits from a search for additional neutrino events in IceCube
  21. Fermi-LAT Gamma-ray Observations of IceCube-261020A
  22. EP261015a: Wendelstein 43 cm optical observations
  23. IceCube-261020A - IceCube observation of a high-energy neutrino candidate track-like event
  24. EP261015c: J-band upper limit with WINTER
  25. EP261006a / AT 2026aetp: Optical follow-up with the 1.3-m DFOT
  26. EP261015a (WXT 11900947714): Possible optical counterpart from NOT and LCO
  27. GRID detection of GRB 261010A
  28. GRB 261010A: a Type I-L (merger-driven) GRB candidate
  29. GRB 261012A: MAXI GSC detection
  30. GRB 261010A: Fermi GBM Final Real-time Localization
  31. GRB 261007A: SVOM/ECLAIRs refined analysis
  32. EP Alert 261007.63: Global MASTER-Net observations report
  33. GRB 261007A: Autonomous identification and follow-up of the counterpart to GRB 261007A by BTSbot with ZTF and P60/SEDM
  34. SVOM GRB261007.23: Global MASTER-Net observations report
  35. GRB 261007A / EP261007a: VLT/X-shooter spectroscopic redshift z = 2.101
  36. GRB 261007A: SVOM detection of a burst
  37. GRB 261005A: Fermi GBM Final Real-time Localization
  38. GRB 261003A: Glowbug gamma-ray detection of a likely short burst
  39. EP261003a: J-band upper limit with WINTER
  40. EP261003a: COLIBRÍ optical upper limits
  41. Fermi GRB 261003A: Global MASTER-Net observations report
  42. EP Alert 261003.01: Global MASTER-Net observations report
  43. GRB 260930B: Fermi GBM Final Real-time Localization
  44. The EP-WXT trigger 01709320790 is likely a flaring star
  45. EP260924a: Global MASTER-Net observations report
  46. Fermi GRB 260926C: Global MASTER-Net observations report
  47. GRB 260924A: Second-epoch J-band upper limit from the SYSU 80 cm infrared telescope
  48. GRB 260924A: Ondrejov D50 optical afterglow detection
  49. GRB 260922A: COLIBRÍ Confirmation of the Optical Counterpart
  50. GRB 260922A: COLIBRÍ optical upper limits
  51. EP260920b: VLT/X-shooter spectroscopic redshift z = 3.582
  52. EP260920b: SVOM/VT optical observation
  53. EP260920b: COLIBRÍ optical observations
  54. EP Alert 260921.01: Global MASTER-Net observations report
  55. EP260917a: Global MASTER-Net observations report
  56. IceCube Alert 260919A: Global MASTER-Net observations report
  57. Fermi GBM Sub-Threshold Detection of GRB 260918A
  58. EP260917A: J-band upper limit with WINTER
  59. EP Alert 260917.32: Global MASTER-Net observations report
  60. EP260917a: COLIBRÍ optical upper limits
  61. GRB 260918A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  62. GRB 260915A: SVOM/ECLAIRs refined analysis
  63. GRB 260917B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  64. MAXI GRB260916.37: Global MASTER-Net observations report
  65. GRB 260914A: VLT/X-shooter observations and redshift confirmation
  66. GRB 260915A: SVOM/VT optical upper limits from VHF data
  67. Fermi GBM Sub-Threshold Detection of GRB 260915A
  68. EP Alert 260914.53: Global MASTER-Net observations report
  69. GRB 260915A: SVOM detection of a burst
  70. GRB 260914A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  71. GRB 260909A: OSN 1.5m, CAHA 2.2m and GTC 10.4m optical upper limits
  72. EP Alert 260909.53: Global MASTER-Net observations report
  73. The EP-WXT trigger 01709306297 is likely the known LMXB 4U 1745-203
  74. Fermi trigger No 810554827: Global MASTER-Net observations report
  75. Fermi GRB 260907A: Global MASTER-Net observations report
  76. GRB 260903A: SAO RAS optical observations
  77. EP Alert 260903.62: Global MASTER-Net observations report
  78. GRB 260903A: EP-FXT follow-up observation
  79. SVOM GRB260903A: Global MASTER-Net observations report
  80. Fermi GBM trigger 809666623/260829141 is not a GRB
  81. MAXI GRB260827.40: Global MASTER-Net observations report
  82. The EP-WXT trigger 01709291839 is likely the known LMXB 4U 1745-203
  83. EP260822a: Global MASTER-Net observations report
  84. IceCube Alert 260825A: Global MASTER-Net observations report
  85. GRB 260822A: GROWTH-India Telescope Upper Limits
  86. Fermi-LAT Gamma-ray Observations of IceCube-260821A
  87. IceCube-260821A: Upper limits from a search for additional neutrino events in IceCube
  88. GRB 260818B: VLA radio observations
  89. IceCube-260821A - IceCube observation of a high-energy neutrino candidate track-like event
  90. GRB 260818B: NOT optical upper limits
  91. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  92. GRB 260818A: SVOM possible detection of a long and faint GRB
  93. EP260812a: refined analysis of the EP-WXT and autonomous EP-FXT observation
  94. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  95. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  96. Fermi GRB 260808A: Global MASTER-Net observations report
  97. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  98. EP260806a: OSIRIS+/GTC redshift z=0.089
  99. GRB 260804A: Glowbug gamma-ray detection
  100. GRB 260804A: Fermi GBM Final Real-time Localization

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