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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"

16009 results found.

  1. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  2. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  3. GRB 250521B: SVOM/VT optical upper limit
  4. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  5. GRB 250521D: SVOM/VT optical observations
  6. GRB 250521D: DDOTI Optical Upper Limit
  7. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  8. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  9. GRB 250521D: LAST tentative optical counterpart candidate
  10. GRB 250520A: 10 GHz VLA radio source
  11. GRB 250521A: DDOTI Optical Upper Limit
  12. GRB 250520A: VLT/FORS2 Optical Observation
  13. GRB 250502A: Tautenburg observations
  14. GRB 250520A: Swift/UVOT Upper Limits
  15. GRB 250520A: J-band observations with WINTER
  16. GRB 250520A: Gemini-South optical observations
  17. GRB 250520A: REM optical/NIR early observations
  18. GRB 250520A：SVOM/VT optical candidate
  19. GRB 250520A: COLIBRÍ optical upper limit
  20. GRB 250520A: DDOTI Optical Upper Limit
  21. GRB 250520A: SVOM/GRM observation
  22. GRB 250520A: GOTO optical upper limit
  23. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  24. GRB 250516A: COLIBRÍ optical upper limit
  25. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  26. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  27. GRB 250515A: 1.6m Mephisto optical detection
  28. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  29. GRB 250515A: GOTO candidate optical counterpart
  30. GRB 250424A: COLIBRÍ detection of the associated supernova
  31. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  32. EP250512a/GRB 250512B: REM optical/NIR observations
  33. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  34. EP250511a: Gemini optical counterpart observation
  35. EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart
  36. EP250511a: FTW optical and NIR observations
  37. GRB 250512B/EP250512a: SVOM/VT optical fading
  38. GRB 250512B/EP250512a：SVOM/VT bright optical counterpart
  39. EP250511a: Mephisto optical upper limits
  40. GRB 250512B: SVOM detection of a burst
  41. EP250511a: REM optical/NIR observations
  42. EP250511a: SVOM/VT optical candidate comfirmation
  43. EP250511a: COLIBRÍ optical counterpart candidate
  44. EP250511a: BOOTES-5 optical upper limit
  45. EP250508a: Gemini NIR upper limits
  46. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  47. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  48. EP250508a: SVOM/VT optical candidate fading
  49. GRB 250506A: NOT optical upper limits
  50. EP250508a: Liverpool Telescope optical upper limits
  51. EP250508a: SVOM/VT optical candidate
  52. EP250508a: KAIT optical upper limit
  53. GRB 250507A: KAIT optical upper limit
  54. GRB 250505B: SVOM/GRM observation of a short burst
  55. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  56. EP250508a: REM optical/NIR observations
  57. GRB 250506A: SVOM/VT optical upper limit
  58. EP250508a: COLIBRÍ Optical Limit
  59. GRB 250506A: Swift/UVOT Upper Limits
  60. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  61. GRB 250507A: REM optical/NIR observations
  62. GRB 250507A: SVOM/VT optical upper limit
  63. GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  64. GRB 250507A: SVOM detection of a long burst
  65. GRB 250506A: Mephisto optical upper limits
  66. GRB 250502A: Bassano Bresciano Observatory upper limit
  67. GRB 250506A: Xinglong 2.16m optical upper limit
  68. GRB 250506A: REM optical/NIR upper limits
  69. GRB 250506A: Swift XRT observations and possible counterpart detection
  70. GRB 250506A: TRT optical observations
  71. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  72. GRB 250504A: VLT/X-shooter upper limits
  73. GRB 250504A: SVOM/VT upper limit
  74. GRB 250504A: REM optical/NIR observations
  75. GRB 250502A: REM optical/NIR observations
  76. GRB 250504A: MeerLICHT optical afterglow detection
  77. GRB 250502A: Mondy and Tien-Shan Optical Observations
  78. GRB 250502A: KAIT optical observations
  79. GRB 250502A: Montarrenti Observatory optical detection
  80. GRB 250502A: Swift-XRT afterglow detection
  81. GRB 250502A: NOT optical observations
  82. GRB 250502a: Liverpool Telescope optical follow-up
  83. GRB 250502A: AKO Optical Afterglow Detection
  84. GRB 250502A: LCO optical counterpart detection
  85. GRB 250502B: DDOTI Optical Observations
  86. GRB 250502A: Early optical counterpart detection by LCO.
  87. GRB 250430A: Swift/UVOT Detection
  88. GRB 250502A: SVOM/VT optical bump
  89. GRB 250502A: TRT optical afterglow confirmation
  90. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  91. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  92. GRB 250502A: SVOM detection of a burst
  93. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  94. GRB 250430A: SVOM/VT optical observations
  95. GRB 250430A: KAIT optical observations
  96. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  97. GRB 250430A / EP250430a: J-band upper limits with WINTER
  98. GRB 250430A: NUTTelA-TAO Early Measurements
  99. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  100. GRB 250430A: DDOTI Optical Observations

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