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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. GRB 260917B: SVOM detection of a faint burst
  2. GRB 260914A: 2.2m CAHA optical afterglow detection and 10.4m GTC redshift confirmation
  3. GRB 260917A: BALROG localization (Fermi Trigger 811304653 / GRB 260917100)
  4. GRB 260917A: Fermi GBM Final Real-time Localization
  5. Fermi trigger No 811304653: Global MASTER-Net observations report
  6. The EP-WXT trigger 01709317235 is likely a flaring star
  7. GRB 260915A: J-band upper limit with WINTER
  8. Fermi trigger No 811264269: Global MASTER-Net observations report
  9. IceCube-260916A - IceCube observation of a high-energy neutrino candidate track-like event
  10. GRB 260909A: NOEMA detection
  11. GRB 260914A: SVOM/GRM observation
  12. GRB 260914A: Mondy and TShAO optical observations
  13. GRB 260914A: SVOM/ECLAIRs refined analysis
  14. GRB 260909A: Swift-XRT observations
  15. GRB 260916A: MAXI/GSC detection
  16. MAXI GRB260916.37: Global MASTER-Net observations report
  17. GRB 260915A: Swift ToO observations
  18. GRB 260915A: J-band upper limit by SYSU 80cm infrared telescope
  19. GRB 260915A: SVOM/C-GFT optical upper limits
  20. GRB 260915A: EP-FXT follow-up observation
  21. GRB 260915A: SVOM/VT refined early optical upper limits
  22. GRB 260915A: EP-FXT follow-up observation
  23. GRB 260915A: REM optical/NIR observations
  24. GRB 260914A: REM optical/NIR observations
  25. GRB 260914A: VLT/X-shooter observations and redshift confirmation
  26. GRB 260915A: SVOM/VT optical upper limits
  27. GRB 260915A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  28. GRB 260914A: VLT/X-shooter spectroscopic redshift z = 0.778
  29. GRB 260915A: 10.4m GTC deep optical limits
  30. GRB 260915A: NOT optical upper limit
  31. SVOM GRB260915.05: Global MASTER-Net observations report
  32. GRB 260915A: SVOM/VT optical upper limits from VHF data
  33. Fermi GBM Sub-Threshold Detection of GRB 260915A
  34. GRB 260915A: LCO optical upper limits
  35. EP Alert 260914.53: Global MASTER-Net observations report
  36. GRB 260914A: EP-FXT follow-up observation
  37. GRB 260915A: SVOM detection of a burst
  38. Fermi GBM Sub-Threshold Detection of GRB 260914A
  39. GRB 260914A: LCO optical observation
  40. GRB 260914A: SVOM/C-GFT optical observations
  41. GRB 260914A: SVOM/VT optical counterpart confirmation
  42. GRB 260914A: SVOM/VT optical observation from VHF data
  43. GRB 260914A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  44. SVOM GRB260914.47: Global MASTER-Net observations report
  45. GRB 260914A: SVOM detection of a burst
  46. GRB 260913A: SVOM trigger sb26091302 is not an astrophysical event
  47. GRB 260818A: Continued ATCA observations
  48. SVOM GRB260913.32: Global MASTER-Net observations report
  49. GRB 260913A: SVOM/C-GFT optical upper limit
  50. GRB 260913A: SVOM detection of a faint burst
  51. GRB 260909A: OSN 1.5m, CAHA 2.2m and GTC 10.4m optical upper limits
  52. GRB 260907A: SVOM/GRM observation
  53. GRB 260909A: CrAO and AbAO optical upper limits
  54. GRB 260909A: SVOM/ECLAIRs refined analysis
  55. GRB 260910B: GOTO tentative optical counterpart candidates
  56. GRB 260909A: Swift ToO observations
  57. GRB 260910B: Fermi GBM Final Real-time Localization
  58. GRB 260909A: KAIT optical upper limit
  59. GRB 260903A: Swift-XRT observations
  60. EP260806a: VLA+ALMA radio detections
  61. GRB 260909A: OHP/T193 z-band upper limit
  62. GRB 260909A: VLT optical and near-infrared upper limits
  63. EP Alert 260909.53: Global MASTER-Net observations report
  64. GRB 260909A: EP-FXT follow-up observation
  65. GRB 260910A: Fermi GBM Final Real-time Localization
  66. EP260806a: NOEMA detection
  67. EP260623a: NOEMA detections
  68. GRB 260909A: SVOM/VT optical upper limits
  69. GRB 260909A: SVOM/GRM observation
  70. GRB 260909A: Mondy optical observations and afterglow candidate
  71. GRB 260909A: Xinglong 2.16m optical upper limit
  72. GRB 260909A: SVOM/C-GFT optical upper limit
  73. GRB 260909A: SVOM detection of a burst
  74. The EP-WXT trigger 01709306297 is likely the known LMXB 4U 1745-203
  75. Fermi trigger No 810554827: Global MASTER-Net observations report
  76. EP Alert 260908.60: Global MASTER-Net observations report
  77. GRB 260907A: Glowbug gamma-ray detection of a likely short burst
  78. GRB 260903A: Swift ToO observations
  79. Fermi GRB 260907B: Global MASTER-Net observations report
  80. GRB 260903A: SAO RAS optical upper limit
  81. The EP-WXT trigger 01709305715 is likely a flaring star
  82. GRB 260907B: Fermi GBM Final Real-time Localization
  83. Fermi GRB 260907A: Global MASTER-Net observations report
  84. GRB 260907A: Fermi GBM Final Real-time Localization
  85. EP260903a: EP-FXT follow-up observation
  86. EP Alert 260905.11: Global MASTER-Net observations report
  87. The EP-WXT trigger 01709302592 is likely a flaring star
  88. GRB 260903A: J-band upper limit with WINTER
  89. EP Alert 260903.47: Global MASTER-Net observations report
  90. GRB 260903A: SVOM/ECLAIRs refined analysis
  91. GRB260903A: Liverpool Telescope optical observations
  92. GRB 260903A: SAO RAS optical observations
  93. GRB 260830A: GECAM-B detection of a burst
  94. EP260903a: EP-WXT detection of a fast X-ray transient
  95. EP Alert 260903.62: Global MASTER-Net observations report
  96. GRB 260830A: Insight-HXMT/HE detection
  97. GRB 260903A: EP-FXT follow-up observation
  98. GRB 260903A: OHP/T193 optical afterglow detection
  99. GRB 260903A: NOT optical observations and afterglow fading
  100. NuSTAR Transient 260828: SOAR Optical Upper Limits

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