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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"

16030 results found.

  1. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  2. GRB 250603A: Swift/UVOT Upper Limits
  3. GRB 250602A: DDOTI Optical Upper Limit
  4. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  5. GRB 250530A: VLT/HAWK-I NIR counterpart fading
  6. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  7. EP#01709177494: SVOM/VT optical observations
  8. GRB 250530C: BOOTES-7 optical upper limit
  9. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  10. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  11. GRB 250530A: SVOM/VT optical upper limit
  12. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  13. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  14. GRB 250530A: SVOM detection of a burst
  15. GRB 250527C: Swift/UVOT Upper Limits
  16. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  17. EP250526a: SVOM/VT optical upper limit
  18. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  19. GRB 250520A: Gemini-South optical afterglow detection
  20. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  21. EP250526a: COLIBRÍ optical upper limits
  22. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  23. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  24. GRB 250521B: SVOM/VT optical upper limit
  25. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  26. GRB 250521D: SVOM/VT optical observations
  27. GRB 250521D: DDOTI Optical Upper Limit
  28. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  29. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  30. GRB 250521D: LAST tentative optical counterpart candidate
  31. GRB 250520A: 10 GHz VLA radio source
  32. GRB 250521A: DDOTI Optical Upper Limit
  33. GRB 250520A: VLT/FORS2 Optical Observation
  34. GRB 250502A: Tautenburg observations
  35. GRB 250520A: Swift/UVOT Upper Limits
  36. GRB 250520A: J-band observations with WINTER
  37. GRB 250520A: Gemini-South optical observations
  38. GRB 250520A: REM optical/NIR early observations
  39. GRB 250520A：SVOM/VT optical candidate
  40. GRB 250520A: COLIBRÍ optical upper limit
  41. GRB 250520A: DDOTI Optical Upper Limit
  42. GRB 250520A: SVOM/GRM observation
  43. GRB 250520A: GOTO optical upper limit
  44. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  45. GRB 250516A: COLIBRÍ optical upper limit
  46. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  47. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  48. GRB 250515A: 1.6m Mephisto optical detection
  49. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  50. GRB 250515A: GOTO candidate optical counterpart
  51. GRB 250424A: COLIBRÍ detection of the associated supernova
  52. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  53. EP250512a/GRB 250512B: REM optical/NIR observations
  54. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  55. EP250511a: Gemini optical counterpart observation
  56. EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart
  57. EP250511a: FTW optical and NIR observations
  58. GRB 250512B/EP250512a: SVOM/VT optical fading
  59. GRB 250512B/EP250512a：SVOM/VT bright optical counterpart
  60. EP250511a: Mephisto optical upper limits
  61. GRB 250512B: SVOM detection of a burst
  62. EP250511a: REM optical/NIR observations
  63. EP250511a: SVOM/VT optical candidate comfirmation
  64. EP250511a: COLIBRÍ optical counterpart candidate
  65. EP250511a: BOOTES-5 optical upper limit
  66. EP250508a: Gemini NIR upper limits
  67. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  68. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  69. EP250508a: SVOM/VT optical candidate fading
  70. GRB 250506A: NOT optical upper limits
  71. EP250508a: Liverpool Telescope optical upper limits
  72. EP250508a: SVOM/VT optical candidate
  73. EP250508a: KAIT optical upper limit
  74. GRB 250507A: KAIT optical upper limit
  75. GRB 250505B: SVOM/GRM observation of a short burst
  76. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  77. EP250508a: REM optical/NIR observations
  78. GRB 250506A: SVOM/VT optical upper limit
  79. EP250508a: COLIBRÍ Optical Limit
  80. GRB 250506A: Swift/UVOT Upper Limits
  81. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  82. GRB 250507A: REM optical/NIR observations
  83. GRB 250507A: SVOM/VT optical upper limit
  84. GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  85. GRB 250507A: SVOM detection of a long burst
  86. GRB 250506A: Mephisto optical upper limits
  87. GRB 250502A: Bassano Bresciano Observatory upper limit
  88. GRB 250506A: Xinglong 2.16m optical upper limit
  89. GRB 250506A: REM optical/NIR upper limits
  90. GRB 250506A: Swift XRT observations and possible counterpart detection
  91. GRB 250506A: TRT optical observations
  92. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  93. GRB 250504A: VLT/X-shooter upper limits
  94. GRB 250504A: SVOM/VT upper limit
  95. GRB 250504A: REM optical/NIR observations
  96. GRB 250502A: REM optical/NIR observations
  97. GRB 250504A: MeerLICHT optical afterglow detection
  98. GRB 250502A: Mondy and Tien-Shan Optical Observations
  99. GRB 250502A: KAIT optical observations
  100. GRB 250502A: Montarrenti Observatory optical detection

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