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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"

21319 results found.

  1. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  2. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  3. EP260214a: VLT/FORS2 optical observations
  4. GRB 260225A: WINTER J-band upper limit
  5. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  6. GRB 260226A : GROWTH-India Telescope optical observations
  7. GRB 260226A: LAST optical upper limit
  8. LAT GRB260226.44: Global MASTER-Net observations report
  9. Fermi GRB 260226A: Global MASTER-Net observations report
  10. EP260214a: VLA 6 GHz detection
  11. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  12. EP260126a: VLA 6 GHz detection
  13. GRB 260225A: SVOM detection of a burst
  14. EP260224a: Einstein Probe detection of an X-ray transient
  15. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  16. sb26021801: SVOM/C-GFT upper limit
  17. EP260223a: Einstein Probe detection of an X-ray transient
  18. GRB 260223A: COLIBRÍ further optical observations and a brightening
  19. EP260221a: Optical upper limit with Kinder observations
  20. GRB 260223A: COLIBRÍ optical observations
  21. GRB 260223A: DDOTI Optical Candidate
  22. Fermi GRB 260223A: Global MASTER-Net observations report
  23. EP260221a: COLIBRÍ optical counterpart candidate
  24. EP260221a: Global MASTER-Net observations report
  25. Fermi GRB 260221B: Global MASTER-Net observations report
  26. Fermi GRB 260221A: Global MASTER-Net observations report
  27. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  28. EP260221a: GOTO optical upper limit
  29. Fermi GRB 260219A: Global MASTER-Net observations report
  30. SVOM alert sb26021801: LAST optical upper limit
  31. IceCube Alert 260217A: Global MASTER-Net observations report
  32. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  33. GRB 260214B/EP260214b: SVOM/ECLAIRs detection through targeted search
  34. sb26021801: SVOM detection of a long faint X-ray transient
  35. EP-WXT 01709258455: NOT optical upper limits
  36. EP260214b: Mondy optical observations
  37. EP260214b: 1.3m DFOT optical upper limit
  38. EP260210a: Mondy optical upper limits
  39. GRB 260208A: continued Mondy optical observations
  40. EP260214b: Liverpool Telescope optical observations
  41. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  42. EP260214b: Optical upper limit with Kinder observations
  43. EP260214a: Optical upper limits with Kinder observations
  44. EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection
  45. EP260214b: DDOTI Optical Detection
  46. EP260214b: GROWTH-India Telescope optical upper limit
  47. EP260214a: VLT near-infrared observation
  48. EP260214a: NOT optical upper limits
  49. EP260214b: OHP/T120 optical observations
  50. EP260214a: refined analysis of the EP-FXT observation
  51. EP260214b: LCO optical counterpart detection
  52. EP260214b: VLT/X-shooter spectroscopic redshift z = 1.208
  53. GRB 260211A: SVOM/VT optical counterpart
  54. EP260214b: COLIBRÍ optical observations
  55. EP260214b: NOT optical counterpart detection
  56. EP260214a: Global MASTER-Net observations report
  57. EP260213a: Global MASTER-Net observations report
  58. EP260213a: Optical upper limits with Kinder observations
  59. EP260213a: NUTTelA-TAO Early Optical Limits
  60. EP260213a: SVOM/C-GFT upper limit
  61. EP260213a: refined analysis of the EP-FXT observation
  62. EP/WXT 01709258378: NOT optical upper limits
  63. GRB 260211A - SVOM/ECLAIRs refined analysis
  64. GRB 260204A: SVOM/ECLAIRs refined analysis
  65. GRB 260211A: GOTO optical upper limit
  66. Fermi GRB 260212A: Global MASTER-Net observations report
  67. GRB 260211A: LAST optical upper limit
  68. Fermi GBM Sub-Threshold Detection of GRB 260211A
  69. GRB 260128B: SVOM/ECLAIRs refined analysis
  70. GRB260131A/B: 3.6m DOT Optical Observations
  71. GRB 260211A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  72. Fermi trigger No 792537871: Global MASTER-Net observations report
  73. Swift Operations Update + Community Forum (Friday, February 13 @ 10:00 AM EST)
  74. GRB 260208A: Swift UVOT detection
  75. Fermi GRB 260210C: Global MASTER-Net observations report
  76. EP260209a: LCO optical upper limits
  77. EP260210a: Global MASTER-Net observations report
  78. EP260210a: refined analysis of the EP-FXT observation
  79. EP260209a: Global MASTER-Net observations report
  80. GRB 260208A: LCO detection of the optical counterpart
  81. EP260210a: Optical upper limits with Kinder observations
  82. EP260210a: SVOM/C-GFT upper limit
  83. GRB 260204A: Swift-XRT afterglow detection
  84. GRB260208A: Liverpool Telescope optical follow-up observations
  85. Fermi GRB 260209A: Global MASTER-Net observations report
  86. GRB 260208B: Swift-XRT observations
  87. GRB 260131A/B: continued Mondy optical observations
  88. GRB 260204A: Swift/UVOT Upper Limits
  89. GRB 260208B: COLIBRÍ optical observations
  90. GRB 260208A: Mondy optical observations (duplicate submission)
  91. GRB 260208A: Mondy optical observations
  92. GRB 260208A: 1.3m DFOT optical detection
  93. GRB 260208A: COLIBRÍ optical observations
  94. GRB 260208A: NOT spectroscopic redshift z = 2.36
  95. GRB 260208A: Liverpool Telescope optical detection
  96. Fermi GRB 260208C: Global MASTER-Net observations report
  97. GRB 260208B: SVOM/VT optical candidate
  98. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  99. GRB 260208A: SVOM/VT optical observation
  100. Fermi GRB 260208D: Global MASTER-Net observations report

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