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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"

20454 results found.

  1. EP260512a: EP-FXT follow-up observation
  2. EP260507a: Xinglong Schmidt optical counterpart detection
  3. EP260512a: Global MASTER-Net observations report
  4. Fermi GRB 260513A: Global MASTER-Net observations report
  5. Fermi GRB 260512A: Global MASTER-Net observations report
  6. GRB 260511B: further SAO RAS optical observations
  7. GRB 260509A: SVOM/VT optical observations
  8. GRB 260511B: further J-band observations by the SYSU 80 cm infrared telescope
  9. GRB 260511B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  10. GRB 260509A: Infrared J and Hs observations with MDM/MIRAGE
  11. GRB 260510C: Infrared J and Hs detections with MDM/MIRAGE
  12. EP260507a: Infrared J and Hs upper limits with MDM/MIRAGE
  13. GRB 260511B: SAO RAS optical observations
  14. GRB 260511B: FRAM-ORM optical detection
  15. GRB 260511B: LCO optical counterpart detection
  16. GRB260511B: MAO/AZT-22 optical observations
  17. GRB 260511A: SVOM/VT optical observations
  18. GRB 260511B: LCO optical observations
  19. GRB 260511B: OHP/T193 spectroscopic observations
  20. GRB 260511B: GOTO optical counterpart detection
  21. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) further optical observations
  22. GRB 260511B: SVOM/VT optical observations
  23. GRB 260511B: SVOM/COLIBRÍ (FM-GFT) optical observations
  24. GRB 260509A: SAO RAS optical observations
  25. GRB 260511A: REM near-infrared detection
  26. GRB 260511B: GROWTH-India Telescope optical observations
  27. GRB 260511B: J-band observations by the SYSU 80 cm infrared telescope
  28. GRB 260510B: SVOM/ECLAIRs refined analysis
  29. GRB 260511B SVOM/C-GFT optical counterpart detection
  30. GRB 260511A: UTGO H50 optical afterglow observation
  31. GRB 260510C: SVOM/VT optical counterpart confirmation
  32. EP260509a: EP-FXT non-detection and upper limit
  33. GRB 260511A: SVOM/VT optical observation with VHF data
  34. Fermi GRB 260511A: Global MASTER-Net observations report
  35. GRB 260511A: KAIT optical afterglow observations
  36. GRB 260510B: SVOM/VT optical upper limits
  37. GRB 260510C: SVOM/VT optical upper limits
  38. EP260509a: Global MASTER-Net observations report
  39. GRB 260510B: GOTO early upper limit
  40. GRB 260509A: Liverpool Telescope optical observations
  41. GRB 260509A: LCO optical observations
  42. SVOM GRB 260509A: MASTER-OAFA optical observation
  43. Fermi GRB 260510A: Global MASTER-Net observations report
  44. GRB 260509A: KAIT optical observations
  45. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  46. GRB 260509A: SVOM/VT optical candidate with VHF data
  47. GRB 260509A: GOTO optical counterpart candidate
  48. EP260507a: REM optical/NIR observations
  49. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  50. EP260507a: COLIBRÍ optical observations
  51. EP260507a: SVOM/VT optical observations
  52. EP260507a: NOT optical observations
  53. EP260507a: further Liverpool Telescope observations
  54. EP260507a: Liverpool Telescope optical upper limits
  55. EP260507a: GOTO optical counterpart detection
  56. EP260507a: Kinder optical counterpart candidate
  57. GRB 260504B: SVOM/ECLAIRs refined analysis
  58. EP260502a is likely a flaring star
  59. Fermi GRB 260506A: Global MASTER-Net observations report
  60. IceCube Alert 260505A: Global MASTER-Net observations report
  61. GRB 260504B: SVOM/VT optical upper limits
  62. GRB 260421B: radio observation with the VLA
  63. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  64. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  65. GRB 260504B: REM optical/NIR observations
  66. GRB 260504B: AST3-2 i-band upper limit
  67. SVOM GRB 260504B: MASTER-OAFA optical observations
  68. Fermi GRB 260504A: Global MASTER-Net observations report
  69. GRB 260429B / EP260429a: EP-FXT follow-up observation
  70. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  71. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  72. EP260429a: Global MASTER-Net observations report
  73. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  74. Fermi GRB 260429A: Global MASTER-Net observations report
  75. EP260430a: Global MASTER-Net observations report
  76. Fermi GRB 260428A: Global MASTER-Net observations report
  77. GRB 260424B: COLIBRÍ optical upper limit
  78. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  79. IceCube Alert 260425A: Global MASTER-Net observations report
  80. Fermi trigger No 798737427: Global MASTER-Net observations report
  81. EP260321a: Upper limits from ATCA radio observations
  82. GRB 260421B: Kilonova-Catcher optical afterglow detection
  83. The EP-WXT trigger 01709258652: Mondy optical observations
  84. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  85. EP260416a: Mondy optical observations
  86. GRB 260421B: SVOM/ECLAIRs refined analysis
  87. GRB 260421B: 3.6m DOT optical observation
  88. EP260416a: ZTSh R band observations
  89. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  90. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  91. GOTO26djh/AT2026jpw: ATCA radio detection
  92. GRB 260421B: J-band upper limit with WINTER
  93. GRB 260421B: LCO optical counterpart detection
  94. GOTO26djh/AT2026jpw: radio detection at 15GHz
  95. GRB 260412A: SVOM/ECLAIRs refined analysis
  96. GRB 260421B: SVOM/VT optical observations
  97. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  98. GRB 260310A: Late-time Chandra X-ray Detection
  99. EP260416a: 1.3m DFOT optical observation
  100. Fermi GRB 260421C: Global MASTER-Net observations report

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