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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"

20948 results found.

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

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