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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"

32257 results found.

  1. GRB 260822A: SVOM/VT optical upper limits
  2. IceCube-260825A - IceCube observation of a high-energy neutrino candidate track-like event
  3. GRB 260822A: PRIME near-infrared upper limits from multiple epochs
  4. GRB 260822A: EP/FXT follow-up observations
  5. GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
  6. GRB 260818A: further EP-FXT observations and X-ray afterglow confirmation
  7. EP260822a: EP-FXT non-detection and upper limit
  8. GRB 260822A: Retraction of GOTO optical counterpart detection GCN 45431
  9. GRB 260822A: GOTO optical counterpart detection
  10. GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
  11. GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  12. GRB 260822A: LCO optical upper limits
  13. GRB 260822A: GROWTH-India Telescope Upper Limits
  14. GRB 260822A: GOTO optical upper limit
  15. Fermi-LAT Gamma-ray Observations of IceCube-260821A
  16. Fermi-LAT Gamma-ray Observations of IceCube-260807A
  17. IceCube-260821A: Upper limits from a search for additional neutrino events in IceCube
  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. GRB 260820A: Insight-HXMT/HE detection
  22. IceCube-260821A - IceCube observation of a high-energy neutrino candidate track-like event
  23. GRB 260818B: SVOM/GRM observation
  24. GRB 260818B: Insight-HXMT detection
  25. GRB 260818B: EP-FXT follow-up observation
  26. GRB 260818A: J-band observations with WINTER
  27. GRB 260818B: SVOM/ECLAIRs refined analysis
  28. GRB 260818A: SVOM/ECLAIRs refined analysis
  29. GRB 260818B: NOT optical upper limits
  30. GRB 260810A: SVOM/GRM observation
  31. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  32. GRB260818A: EP-FXT follow-up observation
  33. GRB 260818B: LCO optical upper limits
  34. EP260806a: SAO RAS multicolor optical observations
  35. GRB 260818A: LCO optical upper limits
  36. EP260812a: AbAO optical upper limit
  37. GRB 260818A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  38. GRB 260810A: Insight-HXMT/HE detection
  39. EP260806a: SVOM/ECLAIRs detection through targeted search
  40. EP260806a: NUTTELA-TAO optical observations
  41. EP260812a: AZT-22 optical upper limit
  42. EP260812b: GTC/OSIRIS+ tentative spectroscopic redshift z = 2.034
  43. EP260806a: WFST optical observations
  44. EP260812b: Optical upper limit with Kinder
  45. GRB 260805D: SVOM/GRM detection of a possible magnetar burst
  46. GRB 260808B: Liverpool Telescope further optical observations
  47. GRB 260808B: GTC/OSIRIS+ spectroscopic redshift z = 1.295
  48. EP260812a: NOT and Liverpool Telescope upper limits:
  49. EP260812b: Liverpool Telescope observations
  50. EP260812b: GOTO detection of the optical counterpart
  51. EP260812a: refined analysis of the EP-WXT and autonomous EP-FXT observation
  52. EP260812a: SVOM/C-GFT optical upper limit
  53. EP260812b: COLIBRÍ optical observations
  54. EP260812b: SVOM/VT optical observation
  55. GRB 260808A: SVOM/GRM observation
  56. EP260812b: Einstein Probe detection of an X-ray transient
  57. Fermi GBM Sub-Threshold Detection of GRB 260809A
  58. GRB 260810A: Glowbug gamma-ray detection
  59. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  60. GRB 260809A: SAO RAS optical observations
  61. GRB 260808B: SAO RAS optical observations
  62. GRB 260808B: SVOM/VT optical re-brightening at day 3
  63. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  64. GRB 260806A: CALET Gamma-Ray Burst Monitor detection
  65. GRB 260808A: GECAM-B observation
  66. GRB 260807A: SVOM/ECLAIRs refined analysis
  67. EP260806a: MAO/AZT-22 optical observations
  68. IceCube-260807A: Upper limits from a search for additional neutrino events in IceCube
  69. GRB260808B: MAO/AZT-22 optical observations
  70. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  71. GRB 260809A: J-band upper limit with WINTER
  72. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  73. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  74. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  75. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  76. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  77. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  78. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  79. GRB 260809A: NOT optical observations
  80. GRB260809A: MAO/AZT-22 optical observations
  81. GRB260809A: OHP/T193 optical observations
  82. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  83. GRB 260809A: SVOM/VT optical counterpart
  84. EP260809a: J-band upper limit with WINTER
  85. GRB 260808B: J-band upper limit with WINTER
  86. GRB 260808B: SVOM/ECLAIRs refined analysis
  87. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  88. GRB 260808B: Liverpool Telescope optical observations
  89. GRB 260808B: NOT optical observations
  90. GRB 260808B: LCO optical observations
  91. GRB 260808A: NuSTAR detection of prompt emission
  92. EP260809a: COLIBRÍ optical observations
  93. EP260809a: LCO optical observation
  94. GRB260808B: OHP/T193 optical observations
  95. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  96. GRB 260808B: SVOM/VT optical afterglow confirmation
  97. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  98. GRB 260808B: SVOM/VT optical candidate from VHF data
  99. Fermi GRB 260808A: Global MASTER-Net observations report
  100. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh

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