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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 260909A: Swift-XRT observations
  2. GRB 260916A: MAXI/GSC detection
  3. MAXI GRB260916.37: Global MASTER-Net observations report
  4. GRB 260915A: Swift ToO observations
  5. GRB 260915A: J-band upper limit by SYSU 80cm infrared telescope
  6. GRB 260915A: SVOM/C-GFT optical upper limits
  7. GRB 260915A: EP-FXT follow-up observation
  8. GRB 260915A: SVOM/VT refined early optical upper limits
  9. GRB 260915A: EP-FXT follow-up observation
  10. GRB 260915A: REM optical/NIR observations
  11. GRB 260914A: REM optical/NIR observations
  12. GRB 260914A: VLT/X-shooter observations and redshift confirmation
  13. GRB 260915A: SVOM/VT optical upper limits
  14. GRB 260915A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  15. GRB 260914A: VLT/X-shooter spectroscopic redshift z = 0.778
  16. GRB 260915A: 10.4m GTC deep optical limits
  17. GRB 260915A: NOT optical upper limit
  18. SVOM GRB260915.05: Global MASTER-Net observations report
  19. GRB 260915A: SVOM/VT optical upper limits from VHF data
  20. Fermi GBM Sub-Threshold Detection of GRB 260915A
  21. GRB 260915A: LCO optical upper limits
  22. EP Alert 260914.53: Global MASTER-Net observations report
  23. GRB 260914A: EP-FXT follow-up observation
  24. GRB 260915A: SVOM detection of a burst
  25. Fermi GBM Sub-Threshold Detection of GRB 260914A
  26. GRB 260914A: LCO optical observation
  27. GRB 260914A: SVOM/C-GFT optical observations
  28. GRB 260914A: SVOM/VT optical counterpart confirmation
  29. GRB 260914A: SVOM/VT optical observation from VHF data
  30. GRB 260914A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  31. SVOM GRB260914.47: Global MASTER-Net observations report
  32. GRB 260914A: SVOM detection of a burst
  33. GRB 260913A: SVOM trigger sb26091302 is not an astrophysical event
  34. GRB 260818A: Continued ATCA observations
  35. SVOM GRB260913.32: Global MASTER-Net observations report
  36. GRB 260913A: SVOM/C-GFT optical upper limit
  37. GRB 260913A: SVOM detection of a faint burst
  38. GRB 260909A: OSN 1.5m, CAHA 2.2m and GTC 10.4m optical upper limits
  39. GRB 260907A: SVOM/GRM observation
  40. GRB 260909A: CrAO and AbAO optical upper limits
  41. GRB 260909A: SVOM/ECLAIRs refined analysis
  42. GRB 260910B: GOTO tentative optical counterpart candidates
  43. GRB 260909A: Swift ToO observations
  44. GRB 260910B: Fermi GBM Final Real-time Localization
  45. GRB 260909A: KAIT optical upper limit
  46. GRB 260903A: Swift-XRT observations
  47. EP260806a: VLA+ALMA radio detections
  48. GRB 260909A: OHP/T193 z-band upper limit
  49. GRB 260909A: VLT optical and near-infrared upper limits
  50. EP Alert 260909.53: Global MASTER-Net observations report
  51. GRB 260909A: EP-FXT follow-up observation
  52. GRB 260910A: Fermi GBM Final Real-time Localization
  53. EP260806a: NOEMA detection
  54. EP260623a: NOEMA detections
  55. GRB 260909A: SVOM/VT optical upper limits
  56. GRB 260909A: SVOM/GRM observation
  57. GRB 260909A: Mondy optical observations and afterglow candidate
  58. GRB 260909A: Xinglong 2.16m optical upper limit
  59. GRB 260909A: SVOM/C-GFT optical upper limit
  60. GRB 260909A: SVOM detection of a burst
  61. The EP-WXT trigger 01709306297 is likely the known LMXB 4U 1745-203
  62. Fermi trigger No 810554827: Global MASTER-Net observations report
  63. EP Alert 260908.60: Global MASTER-Net observations report
  64. GRB 260907A: Glowbug gamma-ray detection of a likely short burst
  65. GRB 260903A: Swift ToO observations
  66. Fermi GRB 260907B: Global MASTER-Net observations report
  67. GRB 260903A: SAO RAS optical upper limit
  68. The EP-WXT trigger 01709305715 is likely a flaring star
  69. GRB 260907B: Fermi GBM Final Real-time Localization
  70. Fermi GRB 260907A: Global MASTER-Net observations report
  71. GRB 260907A: Fermi GBM Final Real-time Localization
  72. EP260903a: EP-FXT follow-up observation
  73. EP Alert 260905.11: Global MASTER-Net observations report
  74. The EP-WXT trigger 01709302592 is likely a flaring star
  75. GRB 260903A: J-band upper limit with WINTER
  76. EP Alert 260903.47: Global MASTER-Net observations report
  77. GRB 260903A: SVOM/ECLAIRs refined analysis
  78. GRB260903A: Liverpool Telescope optical observations
  79. GRB 260903A: SAO RAS optical observations
  80. GRB 260830A: GECAM-B detection of a burst
  81. EP260903a: EP-WXT detection of a fast X-ray transient
  82. EP Alert 260903.62: Global MASTER-Net observations report
  83. GRB 260830A: Insight-HXMT/HE detection
  84. GRB 260903A: EP-FXT follow-up observation
  85. GRB 260903A: OHP/T193 optical afterglow detection
  86. GRB 260903A: NOT optical observations and afterglow fading
  87. NuSTAR Transient 260828: SOAR Optical Upper Limits
  88. SVOM GRB260903A: Global MASTER-Net observations report
  89. GRB 260903A: LCO optical observations
  90. GRB 260903A: SVOM/VT optical candidate
  91. GRB 260903A: Retraction of optical counterpart of GCN 45501
  92. GRB 260831A: GECAM-B observation
  93. GRB 260903A: LCO optical counterpart detection
  94. GRB 260827A: Insight-HXMT/HE detection
  95. GRB 260903A: SVOM detection of a soft faint burst
  96. EP260901a: SVOM/VT optical upper limits
  97. EP260901a: EP-FXT follow-up observation
  98. Konus-Wind detection of GRB 260829A
  99. GRB 260829A: SVOM/GRM observation
  100. GRB 260818A: ATCA detection of a candidate radio counterpart

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