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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. 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"

21613 results found.

  1. GRB 260818B: 6 GHz VLA observations
  2. GRB 2600818B: SVOM/VT optical upper limit and continuous observations
  3. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  4. GRB 260808B: SAO RAS observations of the optical rebrightening
  5. GRB 260822A: SVOM/ECLAIRs refined analysis
  6. GRB 260809A: SVOM/ECLAIRs refined analysis
  7. GRB 260822A: SVOM/VT optical upper limits
  8. IceCube Alert 260825A: Global MASTER-Net observations report
  9. GRB 260822A: PRIME near-infrared upper limits from multiple epochs
  10. GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
  11. EP260822a: EP-FXT non-detection and upper limit
  12. GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  13. EP260822a: Einstein Probe detection of a fast X-ray transient
  14. GRB 260822A: LCO optical upper limits
  15. GRB 260822A: GROWTH-India Telescope Upper Limits
  16. GRB 260822A: GOTO optical upper limit
  17. GRB 260822A: SVOM detection of a short burst
  18. GRB 260818B: VLA radio observations
  19. GRB 260818B: SVOM/C-GFT optical upper limit
  20. EP260731a: SVOM/ECLAIRs detection through offline targeted search
  21. EP detected a brightening of LMXB 1ES 1735-26.9
  22. GRB260820A: Fermi GBM Final Real-Time Localization
  23. GRB 260818A: J-band observations with WINTER
  24. GRB 260818B: SVOM/ECLAIRs refined analysis
  25. GRB 260818A: SVOM/ECLAIRs refined analysis
  26. GRB 260818B: NOT optical upper limits
  27. GRB 260810A: SVOM/GRM observation
  28. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  29. GRB 260818B: LCO optical upper limits
  30. EP260806a: SAO RAS multicolor optical observations
  31. GRB 260818A: LCO optical upper limits
  32. EP260812a: AbAO optical upper limit
  33. GRB 260818A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  34. EP260806a: SVOM/ECLAIRs detection through targeted search
  35. EP260806a: NUTTELA-TAO optical observations
  36. EP260812a: AZT-22 optical upper limit
  37. EP260806a: WFST optical observations
  38. EP260812b: Optical upper limit with Kinder
  39. GRB 260805D: SVOM/GRM detection of a possible magnetar burst
  40. GRB 260808B: Liverpool Telescope further optical observations
  41. EP260812a: NOT and Liverpool Telescope upper limits:
  42. EP260812b: Liverpool Telescope observations
  43. EP260812a: refined analysis of the EP-WXT and autonomous EP-FXT observation
  44. EP260812a: SVOM/C-GFT optical upper limit
  45. EP260812b: COLIBRÍ optical observations
  46. EP260812b: SVOM/VT optical observation
  47. GRB 260808A: SVOM/GRM observation
  48. EP260812b: Einstein Probe detection of an X-ray transient
  49. EP trigger #01709278129 (EP260812b?): NOT optical counterpart
  50. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  51. GRB 260810A: AstroSat CZTI detection of a long burst
  52. EP260812a: Einstein Probe detection of an X-ray transient
  53. GRB 260809A: SAO RAS optical observations
  54. GRB 260808B: SAO RAS optical observations
  55. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  56. EP260806a: MAO/AZT-22 optical observations
  57. GRB260808B: MAO/AZT-22 optical observations
  58. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  59. GRB 260809A: J-band upper limit with WINTER
  60. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  61. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  62. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  63. GRB 260809A: NOT optical observations
  64. GRB260809A: MAO/AZT-22 optical observations
  65. GRB260809A: OHP/T193 optical observations
  66. EP260809a: J-band upper limit with WINTER
  67. GRB 260808B: J-band upper limit with WINTER
  68. GRB 260808B: SVOM/ECLAIRs refined analysis
  69. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  70. GRB 260809A: SVOM detection of a faint burst
  71. GRB 260808B: Liverpool Telescope optical observations
  72. GRB 260808B: NOT optical observations
  73. GRB 260808B: LCO optical observations
  74. EP260809a: COLIBRÍ optical observations
  75. EP260809a: LCO optical observation
  76. EP260809a: OHP/T193 optical observations
  77. GRB260808B: OHP/T193 optical observations
  78. EP260809a: Einstein Probe detection of an X-ray transient
  79. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  80. GRB 260808B: SVOM/VT optical candidate from VHF data
  81. GRB 260808B: SVOM detection of a faint burst
  82. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  83. EP260806a: COLIBRÍ optical observations
  84. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  85. EP260806a: SVOM/VT optical observation
  86. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  87. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  88. EP260806a: LCO likely optical counterpart
  89. EP260806a: Einstein Probe detection of an X-ray transient
  90. GRB 260715A: cubesat Avion detection
  91. GRB 260709A: cubesat Avion detection
  92. GRB 260708A: cubesat Avion detection
  93. SN 2026stf / GRB 260708A: ATLAS forced photometry
  94. GRB 260802A: SVOM/VT optical upper limits from VHF data
  95. GRB 260802A: LCO optical upper limits
  96. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  97. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  98. GRB 260731A: AstroSat CZTI detection of a long burst
  99. GRB 260730B: AstroSat CZTI detection
  100. EP260731a: COLIBRÍ optical upper limit

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