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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"
  1. EP260917a: SVOM/VT optical upper limits
  2. GRB 260918A: SVOM/C-GFT optical upper limits
  3. EP Alert 260918.62: Global MASTER-Net observations report
  4. Fermi GBM Sub-Threshold Detection of GRB 260918A
  5. EP Alert 260918.24: Global MASTER-Net observations report
  6. SVOM GRB260918.16: Global MASTER-Net observations report
  7. Konus-Wind detection of GRB 260916B (short/hard)
  8. The EP-WXT trigger 01709318279 is likely a flaring star
  9. GRB 260918A: SVOM/VT optical upper limits
  10. GRB 260916B: Glowbug gamma-ray detection of a short burst
  11. GRB 260918A: EP-FXT follow-up observation
  12. GRB 260917B: Mondy optical upper limit
  13. IPN triangulation of GRB 260916B (short)
  14. EP260917b: EP-WXT detection of an X-ray transient
  15. EP260917A: J-band upper limit with WINTER
  16. IPN triangulation of GRB 260810A
  17. EP Alert 260917.32: Global MASTER-Net observations report
  18. GRB 260917B: EP-FXT follow-up observation
  19. EP260917a: COLIBRÍ optical upper limits
  20. GRB 260915A: Swift-XRT afterglow detection
  21. GRB 260918A: LCO optical upper limits
  22. EP260917a: Einstein Probe detection of an X-ray transient
  23. GRB 260918A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  24. GRB 260918A: SVOM detection of a burst
  25. GRB 260917C: Fermi GBM Final Real-time Localization
  26. GRB 260917B: FRAM-Auger optical limits
  27. GRB 260916B: Fermi GBM Detection
  28. IceCube-260916A: Upper limits from a search for additional neutrino events in IceCube
  29. GRB 260916B: Fermi GBM Final Localization
  30. GRB 260917A: Glowbug gamma-ray detection
  31. GRB 260915A: SVOM/ECLAIRs refined analysis
  32. GRB 260917B: WINTER J-band observations
  33. GRB 260917B: SVOM/VT optical observations
  34. SVOM GRB260917.16: Global MASTER-Net observations report
  35. GRB 260917B: LCO optical observation
  36. GRB 260917B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  37. GRB 260917B: SVOM detection of a faint burst
  38. GRB 260914A: 2.2m CAHA optical afterglow detection and 10.4m GTC redshift confirmation
  39. GRB 260917A: BALROG localization (Fermi Trigger 811304653 / GRB 260917100)
  40. GRB 260917A: Fermi GBM Final Real-time Localization
  41. Fermi trigger No 811304653: Global MASTER-Net observations report
  42. The EP-WXT trigger 01709317235 is likely a flaring star
  43. GRB 260915A: J-band upper limit with WINTER
  44. Fermi trigger No 811264269: Global MASTER-Net observations report
  45. IceCube-260916A - IceCube observation of a high-energy neutrino candidate track-like event
  46. GRB 260909A: NOEMA detection
  47. GRB 260914A: SVOM/GRM observation
  48. GRB 260914A: Mondy and TShAO optical observations
  49. GRB 260914A: SVOM/ECLAIRs refined analysis
  50. GRB 260909A: Swift-XRT observations
  51. GRB 260916A: MAXI/GSC detection
  52. MAXI GRB260916.37: Global MASTER-Net observations report
  53. GRB 260915A: Swift ToO observations
  54. GRB 260915A: J-band upper limit by SYSU 80cm infrared telescope
  55. GRB 260915A: SVOM/C-GFT optical upper limits
  56. GRB 260915A: EP-FXT follow-up observation
  57. GRB 260915A: SVOM/VT refined early optical upper limits
  58. GRB 260915A: EP-FXT follow-up observation
  59. GRB 260915A: REM optical/NIR observations
  60. GRB 260914A: REM optical/NIR observations
  61. GRB 260914A: VLT/X-shooter observations and redshift confirmation
  62. GRB 260915A: SVOM/VT optical upper limits
  63. GRB 260915A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  64. GRB 260914A: VLT/X-shooter spectroscopic redshift z = 0.778
  65. GRB 260915A: 10.4m GTC deep optical limits
  66. GRB 260915A: NOT optical upper limit
  67. SVOM GRB260915.05: Global MASTER-Net observations report
  68. GRB 260915A: SVOM/VT optical upper limits from VHF data
  69. Fermi GBM Sub-Threshold Detection of GRB 260915A
  70. GRB 260915A: LCO optical upper limits
  71. EP Alert 260914.53: Global MASTER-Net observations report
  72. GRB 260914A: EP-FXT follow-up observation
  73. GRB 260915A: SVOM detection of a burst
  74. Fermi GBM Sub-Threshold Detection of GRB 260914A
  75. GRB 260914A: LCO optical observation
  76. GRB 260914A: SVOM/C-GFT optical observations
  77. GRB 260914A: SVOM/VT optical counterpart confirmation
  78. GRB 260914A: SVOM/VT optical observation from VHF data
  79. GRB 260914A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  80. SVOM GRB260914.47: Global MASTER-Net observations report
  81. GRB 260914A: SVOM detection of a burst
  82. GRB 260913A: SVOM trigger sb26091302 is not an astrophysical event
  83. GRB 260818A: Continued ATCA observations
  84. SVOM GRB260913.32: Global MASTER-Net observations report
  85. GRB 260913A: SVOM/C-GFT optical upper limit
  86. GRB 260913A: SVOM detection of a faint burst
  87. GRB 260909A: OSN 1.5m, CAHA 2.2m and GTC 10.4m optical upper limits
  88. GRB 260907A: SVOM/GRM observation
  89. GRB 260909A: CrAO and AbAO optical upper limits
  90. GRB 260909A: SVOM/ECLAIRs refined analysis
  91. GRB 260910B: GOTO tentative optical counterpart candidates
  92. GRB 260909A: Swift ToO observations
  93. GRB 260910B: Fermi GBM Final Real-time Localization
  94. GRB 260909A: KAIT optical upper limit
  95. GRB 260903A: Swift-XRT observations
  96. EP260806a: VLA+ALMA radio detections
  97. GRB 260909A: OHP/T193 z-band upper limit
  98. GRB 260909A: VLT optical and near-infrared upper limits
  99. EP Alert 260909.53: Global MASTER-Net observations report
  100. GRB 260909A: EP-FXT follow-up observation

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