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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"

16147 results found.

  1. GRB 260818B: Further EP-FXT observation
  2. GRB 260818B: VLT optical and nIR observations
  3. GRB 260818B: 6 GHz VLA observations
  4. GRB 260818B: SVOM/VT optical upper limit and continuous observations
  5. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  6. GRB 260808B: SAO RAS observations of the optical rebrightening
  7. GRB 260822A: SVOM/VT optical upper limits
  8. GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
  9. GRB 260822A: Retraction of GOTO optical counterpart detection GCN 45431
  10. GRB 260822A: GOTO optical counterpart detection
  11. GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
  12. GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  13. GRB 260822A: LCO optical upper limits
  14. GRB 260822A: GROWTH-India Telescope Upper Limits
  15. GRB 260822A: GOTO optical upper limit
  16. GRB 260818B: SVOM/C-GFT optical upper limit
  17. GRB 260818B: SVOM/GRM observation
  18. GRB 260818B: NOT optical upper limits
  19. GRB 260810A: SVOM/GRM observation
  20. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  21. GRB 260818B: LCO optical upper limits
  22. GRB 260818B: SVOM detection of a short burst
  23. EP260806a: SAO RAS multicolor optical observations
  24. GRB 260818A: LCO optical upper limits
  25. EP260812a: AbAO optical upper limit
  26. GRB 260818A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  27. EP260806a: NUTTELA-TAO optical observations
  28. EP260812a: AZT-22 optical upper limit
  29. EP260812b: GTC/OSIRIS+ tentative spectroscopic redshift z = 2.034
  30. EP260806a: WFST optical observations
  31. EP260812b: Optical upper limit with Kinder
  32. GRB 260805D: SVOM/GRM detection of a possible magnetar burst
  33. GRB 260808B: Liverpool Telescope further optical observations
  34. GRB 260808B: GTC/OSIRIS+ spectroscopic redshift z = 1.295
  35. EP260812a: NOT and Liverpool Telescope upper limits:
  36. EP260812b: Liverpool Telescope observations
  37. EP260812b: GOTO detection of the optical counterpart
  38. EP260812a: SVOM/C-GFT optical upper limit
  39. EP260812b: COLIBRÍ optical observations
  40. EP260812b: SVOM/VT optical observation
  41. GRB 260808A: SVOM/GRM observation
  42. EP260812b: Einstein Probe detection of an X-ray transient
  43. EP trigger #01709278129 (EP260812b?): NOT optical counterpart
  44. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  45. GRB 260809A: SAO RAS optical observations
  46. GRB 260808B: SAO RAS optical observations
  47. GRB 260808B: SVOM/VT optical re-brightening at day 3
  48. EP260806a: MAO/AZT-22 optical observations
  49. GRB260808B: MAO/AZT-22 optical observations
  50. GRB 260809A: J-band upper limit with WINTER
  51. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  52. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  53. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  54. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  55. GRB 260809A: NOT optical observations
  56. GRB260809A: MAO/AZT-22 optical observations
  57. GRB260809A: OHP/T193 optical observations
  58. GRB 260809A: SVOM/VT optical counterpart
  59. EP260809a: J-band upper limit with WINTER
  60. GRB 260808B: J-band upper limit with WINTER
  61. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  62. GRB 260808B: Liverpool Telescope optical observations
  63. GRB 260808B: NOT optical observations
  64. GRB 260808B: LCO optical observations
  65. EP260809a: COLIBRÍ optical observations
  66. EP260809a: LCO optical observation
  67. EP260809a: OHP/T193 optical observations
  68. GRB260808B: OHP/T193 optical observations
  69. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  70. GRB 260808B: SVOM/VT optical afterglow confirmation
  71. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  72. GRB 260808B: SVOM/VT optical candidate from VHF data
  73. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  74. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  75. GRB 260807A: SVOM possible detection of a faint burst
  76. EP260806a: COLIBRÍ optical observations
  77. EP260806a: SVOM/VT optical observation
  78. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  79. EP260806a: OSIRIS+/GTC redshift z=0.089
  80. EP260806a: LCO likely optical counterpart
  81. SN 2026stf / GRB 260708A: ATLAS forced photometry
  82. AT 2026wki: EP/FXT follow-up observations
  83. GRB 260708A: LCO further optical observations show supernova features
  84. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  85. GRB 260802A: SVOM/VT optical upper limits from VHF data
  86. GRB 260802A: LCO optical upper limits
  87. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  88. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  89. EP260731a: COLIBRÍ optical upper limit
  90. EP260731a: NOT optical upper limit
  91. EP260728a: COLIBRÍ optical upper limit
  92. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  93. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  94. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  95. EP260727a: SAO RAS optical observations
  96. GRB 260727A: AbAO and SAO RAS optical observations
  97. GRB 260726A: EP-FXT follow-up observations
  98. GRB 260727A: SVOM/GRM observation
  99. GRB 260726A: Fermi GBM Observation
  100. EP260727a: 1.5m OSN optical counterpart detection

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