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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. IceCube-260916A - IceCube observation of a high-energy neutrino candidate track-like event
  2. GRB 260909A: NOEMA detection
  3. GRB 260914A: SVOM/GRM observation
  4. GRB 260914A: Mondy and TShAO optical observations
  5. GRB 260914A: SVOM/ECLAIRs refined analysis
  6. GRB 260909A: Swift-XRT observations
  7. GRB 260916A: MAXI/GSC detection
  8. MAXI GRB260916.37: Global MASTER-Net observations report
  9. GRB 260915A: Swift ToO observations
  10. GRB 260915A: J-band upper limit by SYSU 80cm infrared telescope
  11. GRB 260915A: SVOM/C-GFT optical upper limits
  12. GRB 260915A: EP-FXT follow-up observation
  13. GRB 260915A: SVOM/VT refined early optical upper limits
  14. GRB 260915A: EP-FXT follow-up observation
  15. GRB 260915A: REM optical/NIR observations
  16. GRB 260914A: REM optical/NIR observations
  17. GRB 260914A: VLT/X-shooter observations and redshift confirmation
  18. GRB 260915A: SVOM/VT optical upper limits
  19. GRB 260915A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  20. GRB 260914A: VLT/X-shooter spectroscopic redshift z = 0.778
  21. GRB 260915A: 10.4m GTC deep optical limits
  22. GRB 260915A: NOT optical upper limit
  23. SVOM GRB260915.05: Global MASTER-Net observations report
  24. GRB 260915A: SVOM/VT optical upper limits from VHF data
  25. Fermi GBM Sub-Threshold Detection of GRB 260915A
  26. GRB 260915A: LCO optical upper limits
  27. EP Alert 260914.53: Global MASTER-Net observations report
  28. GRB 260914A: EP-FXT follow-up observation
  29. GRB 260915A: SVOM detection of a burst
  30. Fermi GBM Sub-Threshold Detection of GRB 260914A
  31. GRB 260914A: LCO optical observation
  32. GRB 260914A: SVOM/C-GFT optical observations
  33. GRB 260914A: SVOM/VT optical counterpart confirmation
  34. GRB 260914A: SVOM/VT optical observation from VHF data
  35. GRB 260914A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  36. SVOM GRB260914.47: Global MASTER-Net observations report
  37. GRB 260914A: SVOM detection of a burst
  38. GRB 260913A: SVOM trigger sb26091302 is not an astrophysical event
  39. GRB 260818A: Continued ATCA observations
  40. SVOM GRB260913.32: Global MASTER-Net observations report
  41. GRB 260913A: SVOM/C-GFT optical upper limit
  42. GRB 260913A: SVOM detection of a faint burst
  43. GRB 260909A: OSN 1.5m, CAHA 2.2m and GTC 10.4m optical upper limits
  44. GRB 260907A: SVOM/GRM observation
  45. GRB 260909A: CrAO and AbAO optical upper limits
  46. GRB 260909A: SVOM/ECLAIRs refined analysis
  47. GRB 260910B: GOTO tentative optical counterpart candidates
  48. GRB 260909A: Swift ToO observations
  49. GRB 260910B: Fermi GBM Final Real-time Localization
  50. GRB 260909A: KAIT optical upper limit
  51. GRB 260903A: Swift-XRT observations
  52. EP260806a: VLA+ALMA radio detections
  53. GRB 260909A: OHP/T193 z-band upper limit
  54. GRB 260909A: VLT optical and near-infrared upper limits
  55. EP Alert 260909.53: Global MASTER-Net observations report
  56. GRB 260909A: EP-FXT follow-up observation
  57. GRB 260910A: Fermi GBM Final Real-time Localization
  58. EP260806a: NOEMA detection
  59. EP260623a: NOEMA detections
  60. GRB 260909A: SVOM/VT optical upper limits
  61. GRB 260909A: SVOM/GRM observation
  62. GRB 260909A: Mondy optical observations and afterglow candidate
  63. GRB 260909A: Xinglong 2.16m optical upper limit
  64. GRB 260909A: SVOM/C-GFT optical upper limit
  65. GRB 260909A: SVOM detection of a burst
  66. The EP-WXT trigger 01709306297 is likely the known LMXB 4U 1745-203
  67. Fermi trigger No 810554827: Global MASTER-Net observations report
  68. EP Alert 260908.60: Global MASTER-Net observations report
  69. GRB 260907A: Glowbug gamma-ray detection of a likely short burst
  70. GRB 260903A: Swift ToO observations
  71. Fermi GRB 260907B: Global MASTER-Net observations report
  72. GRB 260903A: SAO RAS optical upper limit
  73. The EP-WXT trigger 01709305715 is likely a flaring star
  74. GRB 260907B: Fermi GBM Final Real-time Localization
  75. Fermi GRB 260907A: Global MASTER-Net observations report
  76. GRB 260907A: Fermi GBM Final Real-time Localization
  77. EP260903a: EP-FXT follow-up observation
  78. EP Alert 260905.11: Global MASTER-Net observations report
  79. The EP-WXT trigger 01709302592 is likely a flaring star
  80. GRB 260903A: J-band upper limit with WINTER
  81. EP Alert 260903.47: Global MASTER-Net observations report
  82. GRB 260903A: SVOM/ECLAIRs refined analysis
  83. GRB260903A: Liverpool Telescope optical observations
  84. GRB 260903A: SAO RAS optical observations
  85. GRB 260830A: GECAM-B detection of a burst
  86. EP260903a: EP-WXT detection of a fast X-ray transient
  87. EP Alert 260903.62: Global MASTER-Net observations report
  88. GRB 260830A: Insight-HXMT/HE detection
  89. GRB 260903A: EP-FXT follow-up observation
  90. GRB 260903A: OHP/T193 optical afterglow detection
  91. GRB 260903A: NOT optical observations and afterglow fading
  92. NuSTAR Transient 260828: SOAR Optical Upper Limits
  93. SVOM GRB260903A: Global MASTER-Net observations report
  94. GRB 260903A: LCO optical observations
  95. GRB 260903A: SVOM/VT optical candidate
  96. GRB 260903A: Retraction of optical counterpart of GCN 45501
  97. GRB 260831A: GECAM-B observation
  98. GRB 260903A: LCO optical counterpart detection
  99. GRB 260827A: Insight-HXMT/HE detection
  100. GRB 260903A: SVOM detection of a soft faint burst

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