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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"

16007 results found.

  1. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  2. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  3. GRB 250625A: SVOM/C-GFT upper limit in early phase
  4. GRB 250625A: Swift/UVOT Upper Limits
  5. GRB 250625A: ABObservatory afterglow detection
  6. GRB 250625A: OHP/T193 optical detection
  7. GRB 250625A: COLIBRÍ optical observations
  8. GRB 250625A: JinShan optical observations
  9. GRB 250625A: NOT z-band upper limit
  10. GRB 250625A: SVOM/VT optical confirmation
  11. GRB 250625A: SAO RAS possible optical afterglow
  12. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  13. GRB 241018A: Maidanak optical observations
  14. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  15. GRB 250620C: SVOM/GRM observation
  16. GRB 250620A: SVOM/GRM observation of a short burst
  17. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  18. GRB 250617B: Nickel telescope optical observations
  19. GRB 250615A: Kilonova-Catcher optical upper limits
  20. GRB 250617B: Assy AZT-20 Optical Observations
  21. GRB 250615A/EP250615a: FTW optical and NIR observations
  22. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  23. GRB 250617B: Kilonova-Catcher optical afterglow detection
  24. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  25. GRB 250617B: COLIBRÍ optical observations
  26. GRB 250617B: NOT NIR observations of the afterglow
  27. GRB 250617B: SVOM/VT optical observation
  28. GRB 250617B: NUTTelA-TAO early time optical observations
  29. GRB 250617B: GOTO optical upper limit
  30. GRB 250617B: Ondrejov D50 optical afterglow detection
  31. GRB 250617B: SAO RAS optical observations
  32. GRB 250617B: Swift detection of a burst with an optical counterpart
  33. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  34. EP-WXT trigger 01709178975: GOTO optical upper limit
  35. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  36. GRB 250615A: COLIBRÍ optical upper limit
  37. GRB 250615A: DDOTI Optical Upper Limit
  38. GRB 250615A: Swift/UVOT Upper Limits
  39. sb25061207/SVOM: T120 OHP optical upper limit
  40. sb25061207: Mephisto optical upper limits
  41. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  42. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  43. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  44. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  45. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  46. EP250612a: SVOM/VT optical candidate
  47. EP250612a/GRB 250612B: JinShan optical upper limit
  48. EP 250612a: AST3-3 Yaoan Optical Observation
  49. sb25061207: SVOM/VT optical counterpart
  50. GRB 250610B: Liverpool Telescope continued monitoring
  51. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  52. GRB 250610B: Swift/UVOT Detection
  53. EP250610A: Swift/UVOT Upper limits
  54. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  55. GRB 250610B: REM optical/NIR observations
  56. EP250610a: Liverpool Telescope optical upper limits
  57. GRB 250610B: SVOM/VT optical shallow decay
  58. GRB 250610B: additional Liverpool Telescope optical observations
  59. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  60. GRB 250610B: Swift-XRT counterpart detection
  61. GRB 250610B: SVOM/VT optical counterpart
  62. GRB 250610B: LT detection of the optical counterpart
  63. GRB 250610B: OHP/T120 optical counterpart candidate
  64. GRB 250610B: GOTO optical upper limit
  65. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  66. EP250610a: SVOM/VT optical upper limit
  67. EP250610a: REM optical/NIR observations
  68. EP250610a: COLIBRÍ optical upper limit
  69. GRB 250605A: Swift/UVOT Upper Limits
  70. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  71. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  72. GRB 250527C: CrAO Optical Upper Limit
  73. GRB 250607A: SVOM/GRM observation of a long burst
  74. GRB 250605A: SVOM/VT optical upper limit
  75. EP/WXT 01709177873: GOTO observations confirm stellar variability
  76. GRB 250605A: LT optical observations
  77. GRB 250601A: VLT/FORS2 Optical Observation
  78. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  79. GRB 250603A: Swift/UVOT Upper Limits
  80. GRB 250602A: DDOTI Optical Upper Limit
  81. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  82. GRB 250530A: VLT/HAWK-I NIR counterpart fading
  83. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  84. EP#01709177494: SVOM/VT optical observations
  85. GRB 250530C: BOOTES-7 optical upper limit
  86. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  87. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  88. GRB 250530A: SVOM/VT optical upper limit
  89. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  90. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  91. GRB 250530A: SVOM detection of a burst
  92. GRB 250527C: Swift/UVOT Upper Limits
  93. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  94. EP250526a: SVOM/VT optical upper limit
  95. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  96. GRB 250520A: Gemini-South optical afterglow detection
  97. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  98. EP250526a: COLIBRÍ optical upper limits
  99. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  100. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability

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