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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"

16159 results found.

  1. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  2. GRB 250617B: Kilonova-Catcher optical afterglow detection
  3. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  4. GRB 250617B: COLIBRÍ optical observations
  5. GRB 250617B: NOT NIR observations of the afterglow
  6. GRB 250617B: SVOM/VT optical observation
  7. GRB 250617B: NUTTelA-TAO early time optical observations
  8. GRB 250617B: GOTO optical upper limit
  9. GRB 250617B: Ondrejov D50 optical afterglow detection
  10. GRB 250617B: SAO RAS optical observations
  11. GRB 250617B: Swift detection of a burst with an optical counterpart
  12. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  13. EP-WXT trigger 01709178975: GOTO optical upper limit
  14. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  15. GRB 250615A: COLIBRÍ optical upper limit
  16. GRB 250615A: DDOTI Optical Upper Limit
  17. GRB 250615A: Swift/UVOT Upper Limits
  18. sb25061207/SVOM: T120 OHP optical upper limit
  19. sb25061207: Mephisto optical upper limits
  20. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  21. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  22. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  23. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  24. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  25. EP250612a: SVOM/VT optical candidate
  26. EP250612a/GRB 250612B: JinShan optical upper limit
  27. EP 250612a: AST3-3 Yaoan Optical Observation
  28. sb25061207: SVOM/VT optical counterpart
  29. GRB 250610B: Liverpool Telescope continued monitoring
  30. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  31. GRB 250610B: Swift/UVOT Detection
  32. EP250610A: Swift/UVOT Upper limits
  33. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  34. GRB 250610B: REM optical/NIR observations
  35. EP250610a: Liverpool Telescope optical upper limits
  36. GRB 250610B: SVOM/VT optical shallow decay
  37. GRB 250610B: additional Liverpool Telescope optical observations
  38. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  39. GRB 250610B: Swift-XRT counterpart detection
  40. GRB 250610B: SVOM/VT optical counterpart
  41. GRB 250610B: LT detection of the optical counterpart
  42. GRB 250610B: OHP/T120 optical counterpart candidate
  43. GRB 250610B: GOTO optical upper limit
  44. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  45. EP250610a: SVOM/VT optical upper limit
  46. EP250610a: REM optical/NIR observations
  47. EP250610a: COLIBRÍ optical upper limit
  48. GRB 250605A: Swift/UVOT Upper Limits
  49. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  50. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  51. GRB 250527C: CrAO Optical Upper Limit
  52. GRB 250607A: SVOM/GRM observation of a long burst
  53. GRB 250605A: SVOM/VT optical upper limit
  54. EP/WXT 01709177873: GOTO observations confirm stellar variability
  55. GRB 250605A: LT optical observations
  56. GRB 250601A: VLT/FORS2 Optical Observation
  57. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  58. GRB 250603A: Swift/UVOT Upper Limits
  59. GRB 250602A: DDOTI Optical Upper Limit
  60. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  61. GRB 250530A: VLT/HAWK-I NIR counterpart fading
  62. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  63. EP#01709177494: SVOM/VT optical observations
  64. GRB 250530C: BOOTES-7 optical upper limit
  65. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  66. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  67. GRB 250530A: SVOM/VT optical upper limit
  68. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  69. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  70. GRB 250530A: SVOM detection of a burst
  71. GRB 250527C: Swift/UVOT Upper Limits
  72. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  73. EP250526a: SVOM/VT optical upper limit
  74. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  75. GRB 250520A: Gemini-South optical afterglow detection
  76. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  77. EP250526a: COLIBRÍ optical upper limits
  78. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  79. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  80. GRB 250521B: SVOM/VT optical upper limit
  81. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  82. GRB 250521D: SVOM/VT optical observations
  83. GRB 250521D: DDOTI Optical Upper Limit
  84. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  85. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  86. GRB 250521D: LAST tentative optical counterpart candidate
  87. GRB 250520A: 10 GHz VLA radio source
  88. GRB 250521A: DDOTI Optical Upper Limit
  89. GRB 250520A: VLT/FORS2 Optical Observation
  90. GRB 250502A: Tautenburg observations
  91. GRB 250520A: Swift/UVOT Upper Limits
  92. GRB 250520A: J-band observations with WINTER
  93. GRB 250520A: Gemini-South optical observations
  94. GRB 250520A: REM optical/NIR early observations
  95. GRB 250520A：SVOM/VT optical candidate
  96. GRB 250520A: COLIBRÍ optical upper limit
  97. GRB 250520A: DDOTI Optical Upper Limit
  98. GRB 250520A: SVOM/GRM observation
  99. GRB 250520A: GOTO optical upper limit
  100. EP250427a/GRB250427A: VLA Detection of Radio Counterpart

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