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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"

16025 results found.

  1. GRB 250703A: DDOTI Optical Upper Limit
  2. GRB 250702F: REM optical afterglow detection
  3. GRB 250702F: DDOTI Optical Observation
  4. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  5. GRB 250702F: COLIBRÍ Observations of the Afterglow
  6. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  7. GRB 250702F: NOT observations of the optical afterglow
  8. GRB 250702F: MASTER optical afterglow observation
  9. GRB 250702F: GOTO optical counterpart detection
  10. GRB 250702F: Ondrejov D50 optical afterglow detection
  11. GRB 250702F: Swift detection of a burst with an optical counterpart
  12. GRB 250628B: SVOM/VT optical upper limit
  13. GRB 250628A: REM optical/NIR upper limits
  14. GRB 250628B: SVOM detection of a long burst
  15. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  16. GRB 250628A: Swift/UVOT Upper Limits
  17. GRB 250625A: Leavitt Observatory afterglow detection
  18. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  19. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  20. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  21. GRB 250625A: SVOM/C-GFT upper limit in early phase
  22. GRB 250625A: Swift/UVOT Upper Limits
  23. GRB 250625A: ABObservatory afterglow detection
  24. GRB 250625A: OHP/T193 optical detection
  25. GRB 250625A: COLIBRÍ optical observations
  26. GRB 250625A: JinShan optical observations
  27. GRB 250625A: NOT z-band upper limit
  28. GRB 250625A: SVOM/VT optical confirmation
  29. GRB 250625A: SAO RAS possible optical afterglow
  30. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  31. GRB 241018A: Maidanak optical observations
  32. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  33. GRB 250620C: SVOM/GRM observation
  34. GRB 250620A: SVOM/GRM observation of a short burst
  35. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  36. GRB 250617B: Nickel telescope optical observations
  37. GRB 250615A: Kilonova-Catcher optical upper limits
  38. GRB 250617B: Assy AZT-20 Optical Observations
  39. GRB 250615A/EP250615a: FTW optical and NIR observations
  40. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  41. GRB 250617B: Kilonova-Catcher optical afterglow detection
  42. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  43. GRB 250617B: COLIBRÍ optical observations
  44. GRB 250617B: NOT NIR observations of the afterglow
  45. GRB 250617B: SVOM/VT optical observation
  46. GRB 250617B: NUTTelA-TAO early time optical observations
  47. GRB 250617B: GOTO optical upper limit
  48. GRB 250617B: Ondrejov D50 optical afterglow detection
  49. GRB 250617B: SAO RAS optical observations
  50. GRB 250617B: Swift detection of a burst with an optical counterpart
  51. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  52. EP-WXT trigger 01709178975: GOTO optical upper limit
  53. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  54. GRB 250615A: COLIBRÍ optical upper limit
  55. GRB 250615A: DDOTI Optical Upper Limit
  56. GRB 250615A: Swift/UVOT Upper Limits
  57. sb25061207/SVOM: T120 OHP optical upper limit
  58. sb25061207: Mephisto optical upper limits
  59. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  60. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  61. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  62. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  63. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  64. EP250612a: SVOM/VT optical candidate
  65. EP250612a/GRB 250612B: JinShan optical upper limit
  66. EP 250612a: AST3-3 Yaoan Optical Observation
  67. sb25061207: SVOM/VT optical counterpart
  68. GRB 250610B: Liverpool Telescope continued monitoring
  69. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  70. GRB 250610B: Swift/UVOT Detection
  71. EP250610A: Swift/UVOT Upper limits
  72. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  73. GRB 250610B: REM optical/NIR observations
  74. EP250610a: Liverpool Telescope optical upper limits
  75. GRB 250610B: SVOM/VT optical shallow decay
  76. GRB 250610B: additional Liverpool Telescope optical observations
  77. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  78. GRB 250610B: Swift-XRT counterpart detection
  79. GRB 250610B: SVOM/VT optical counterpart
  80. GRB 250610B: LT detection of the optical counterpart
  81. GRB 250610B: OHP/T120 optical counterpart candidate
  82. GRB 250610B: GOTO optical upper limit
  83. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  84. EP250610a: SVOM/VT optical upper limit
  85. EP250610a: REM optical/NIR observations
  86. EP250610a: COLIBRÍ optical upper limit
  87. GRB 250605A: Swift/UVOT Upper Limits
  88. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  89. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  90. GRB 250527C: CrAO Optical Upper Limit
  91. GRB 250607A: SVOM/GRM observation of a long burst
  92. GRB 250605A: SVOM/VT optical upper limit
  93. EP/WXT 01709177873: GOTO observations confirm stellar variability
  94. GRB 250605A: LT optical observations
  95. GRB 250601A: VLT/FORS2 Optical Observation
  96. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  97. GRB 250603A: Swift/UVOT Upper Limits
  98. GRB 250602A: DDOTI Optical Upper Limit
  99. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  100. GRB 250530A: VLT/HAWK-I NIR counterpart fading

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