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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"

21782 results found.

  1. SVOM GRB260516D: Global MASTER-Net observations report
  2. GRB 260515A: Liverpool Telescope optical detection
  3. GRB 260515A: LCO optical counterpart detection
  4. GRB 260515A: SVOM/COLIBRÍ (FM-GFT) optical observations
  5. EP260514a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  6. EP260514a: SVOM/VT optical candidate
  7. Fermi GRB 260516B: Global MASTER-Net observations report
  8. GRB 260515A: SVOM/VT optical observations
  9. GRB 260515A: OHP/T193 optical observations
  10. GRB 260515A: LCO optical observations
  11. SVOM GRB 260515A: Global MASTER-Net observations report
  12. GRB 260515A: NOT optical observations.
  13. SVOM GRB 260515A: MASTER OT J151044.43+243321.7 optical counterpart detection
  14. GRB 260515A: JinShan optical counterpart candidate
  15. IceCube-260504A: No Candidate Transients from the Zwicky Transient Facility
  16. GRB 260511B: NOT optical observations
  17. EP260514a: Global MASTER-Net observations report
  18. GRB 260511B: Mephisto multi-band optical followup
  19. Fermi GRB 260514A: Global MASTER-Net observations report
  20. EP260512a: EP-FXT follow-up observation
  21. EP260507a: Xinglong Schmidt optical counterpart detection
  22. EP260512a: Global MASTER-Net observations report
  23. Fermi GRB 260513A: Global MASTER-Net observations report
  24. Fermi GRB 260512A: Global MASTER-Net observations report
  25. GRB 260511B: further SAO RAS optical observations
  26. GRB 260509A: SVOM/VT optical observations
  27. GRB 260511B: further J-band observations by the SYSU 80 cm infrared telescope
  28. GRB 260511B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  29. GRB 260509A: Infrared J and Hs observations with MDM/MIRAGE
  30. GRB 260510C: Infrared J and Hs detections with MDM/MIRAGE
  31. EP260507a: Infrared J and Hs upper limits with MDM/MIRAGE
  32. GRB 260511B: SAO RAS optical observations
  33. GRB 260511B: FRAM-ORM optical detection
  34. GRB 260511B: LCO optical counterpart detection
  35. GRB260511B: MAO/AZT-22 optical observations
  36. GRB 260511A: SVOM/VT optical observations
  37. GRB 260511B: LCO optical observations
  38. GRB 260511B: OHP/T193 spectroscopic observations
  39. GRB 260511B: GOTO optical counterpart detection
  40. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) further optical observations
  41. GRB 260511B: SVOM/VT optical observations
  42. GRB 260511B: SVOM/COLIBRÍ (FM-GFT) optical observations
  43. GRB 260509A: SAO RAS optical observations
  44. GRB 260511A: REM near-infrared detection
  45. GRB 260511B: GROWTH-India Telescope optical observations
  46. GRB 260511B: J-band observations by the SYSU 80 cm infrared telescope
  47. GRB 260510B: SVOM/ECLAIRs refined analysis
  48. GRB 260511B SVOM/C-GFT optical counterpart detection
  49. GRB 260511A: UTGO H50 optical afterglow observation
  50. GRB 260510C: SVOM/VT optical counterpart confirmation
  51. EP260509a: EP-FXT non-detection and upper limit
  52. GRB 260511A: SVOM/VT optical observation with VHF data
  53. Fermi GRB 260511A: Global MASTER-Net observations report
  54. GRB 260511A: KAIT optical afterglow observations
  55. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  56. GRB 260510B: SVOM/VT optical upper limits
  57. GRB 260510C: SVOM/VT optical upper limits
  58. EP260509a: Global MASTER-Net observations report
  59. Fermi GBM Sub-Threshold Detection of GRB 260510B
  60. GRB 260510B: GOTO early upper limit
  61. GRB 260509A: Liverpool Telescope optical observations
  62. GRB 260509A: LCO optical observations
  63. SVOM GRB 260509A: MASTER-OAFA optical observation
  64. Fermi GRB 260510A: Global MASTER-Net observations report
  65. GRB 260509A: KAIT optical observations
  66. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  67. GRB 260509A: SVOM/VT optical candidate with VHF data
  68. GRB 260509A: GOTO optical counterpart candidate
  69. EP260507a: REM optical/NIR observations
  70. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  71. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  72. EP260507a: COLIBRÍ optical observations
  73. EP260507a: SVOM/VT optical observations
  74. EP260507a: NOT optical observations
  75. EP260507a: further Liverpool Telescope observations
  76. EP260507a: Liverpool Telescope optical upper limits
  77. EP260507a: GOTO optical counterpart detection
  78. EP260507a: Kinder optical counterpart candidate
  79. GRB 260504B: SVOM/ECLAIRs refined analysis
  80. EP260502a is likely a flaring star
  81. Fermi GRB 260506A: Global MASTER-Net observations report
  82. IceCube Alert 260505A: Global MASTER-Net observations report
  83. GRB 260504B: SVOM/VT optical upper limits
  84. GRB 260421B: radio observation with the VLA
  85. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  86. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  87. GRB 260504B: REM optical/NIR observations
  88. GRB 260504B: AST3-2 i-band upper limit
  89. SVOM GRB 260504B: MASTER-OAFA optical observations
  90. Fermi GRB 260504A: Global MASTER-Net observations report
  91. GRB 260429B / EP260429a: EP-FXT follow-up observation
  92. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  93. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  94. EP260429a: Global MASTER-Net observations report
  95. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  96. Fermi GRB 260429A: Global MASTER-Net observations report
  97. EP260430a: Global MASTER-Net observations report
  98. Fermi GRB 260428A: Global MASTER-Net observations report
  99. GRB 260424B: COLIBRÍ optical upper limit
  100. Fermi-LAT Gamma-ray Observations of IceCube-260425A

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