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

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