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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 240824B: Swift ToO observations
  2. Fermi GRB 240824C: Global MASTER-Net observations report
  3. GRB 240824C: Fermi GBM Final Localization
  4. GRB 240824A: Swift/UVOT Upper Limits
  5. GRB 240821A: Swift/UVOT observations of the XRT sources.
  6. GRB 240824B: MAXI/GSC detection
  7. GRB 240824B: Fermi GBM Final Real-time Localization
  8. GRB 240824A: Retraction of GCN 37255
  9. GRB240824A: GRANDMA/TAROT-TCA Upper Limit
  10. SGR 1E 1841-045 / Kes 73: Leavitt Observatory optical upper limit
  11. GRB 240824A: KAIT optical upper limit
  12. GRB 240824A: Skynet Optical Afterglow Discovery
  13. GRB 240824A: Swift detection of a burst
  14. Swift GRB240824.04: Global MASTER-Net observations report
  15. SGR 1E 1841-045 / Kes 73: Montarrenti Observatory optical upper limits
  16. GRB 240821A: Colibri Optical Upper Limit
  17. EP240820a: PRIME J-band Observations
  18. GRB 240821A: Swift-XRT observations
  19. GRB 240822A: AstroSat CZTI detection of a short burst
  20. GRB 240821A: REM optical/NIR upper limits
  21. GRB 240821A: LCO optical observations
  22. GRB 240821A: JinShan optical upper limits
  23. GRB 240809A: Mondy and AbAO Optical Observations
  24. GRB 240821A: SVOM/VT follow-up and optical upper limit
  25. GRB 240821A: GMG Optical Upper Limit
  26. Fermi GRB 240821A: Global MASTER-Net observations report
  27. GECAM-B observation of a short burst from SGR 1E 1841-045 / Kes 73
  28. GRB 240821A: Fermi GBM Observation
  29. Fermi trigger No 745964969: Global MASTER-Net observations report
  30. Fermi trigger No 745925274: Global MASTER-Net observations report
  31. GRB 240821A: Swift ToO observations
  32. Fermi trigger No 746019401: Global MASTER-Net observations report
  33. Fermi-GBM Observations of the reactivation of SGR 1E 1841-045 / Kes 73
  34. Fermi trigger No 745935375: Global MASTER-Net observations report
  35. GRB240821A: EIRSAT-1 GMOD Detection
  36. GRB240821B: First GRB Detected by EIRSAT-1 GMOD
  37. GRB 240821A: EP-FXT follow-up observation and afterglow candidates
  38. Fermi GRB 240821B: Global MASTER-Net observations report
  39. EP240801a: Keck/LRIS spectroscopic redshift confirmation
  40. GRB 240821A: SVOM/GRM observation
  41. GRB 240821A: SVOM/GRM observation
  42. GRB 240821A: GRANDMA/LesMakes-T60 Upper Limit
  43. GRB 240821B: Fermi GBM Final Localization
  44. Fermi trigger No 745866488: Global MASTER-Net observations report
  45. Trigger 1249878: Swift detection of another burst from SGR 1E 1841-045 / Kes 73
  46. GRB 240821A: BALROG localization (Fermi Trigger 745958167 / GRB 240821775)
  47. GRB 240821A : a likely short GRB detected by SVOM/ECLAIRs
  48. GRB 240821A: Fermi GBM Final Real-time Localization
  49. GRB 240819A: Swift-XRT observations
  50. GRB 240819A: JinShan optical upper limits on one Swift/XRT source
  51. GRB 240820B: SVOM/GRM observation
  52. EP240820a: TRT optical upper limit
  53. EP240820a: EP detection of a fast X-ray transient
  54. GRB 240819A: KAIT optical upper limit
  55. EP240816a: PRIME upper limits
  56. Trigger 1249653: Swift detection of SGR 1E 1841-045 / Kes 73
  57. Fermi trigger No 745873283: Global MASTER-Net observations report
  58. Fermi trigger No 745871958: Global MASTER-Net observations report
  59. GRB 240819A : an X-ray transient detected by SVOM/ECLAIRs
  60. GRB 240819A: TRT optical upper limits on the Swift/XRT and EP/FXT sources
  61. GRB 240819A: X-ray follow-up observation with EP-FXT
  62. Fermi Gamma-ray Burst Monitor trigger 745811685 / 240820080 is not a GRB
  63. GRB 240820A: Fermi GBM Final Real-time Localization
  64. GRB 240819A: Swift ToO observations
  65. GRB 240814A: SVOM/GRM observation
  66. EP240816b: Liverpool Telescope optical follow-up observations
  67. GRB 240814C: SVOM/GRM observation
  68. EP240816a: BOOTES-6/DPRT optical upper limit
  69. GRB 240815A: SVOM/GRM observation
  70. GRB 240817A: Fermi GBM Final Real-time Localization
  71. Integral GRB240816.79: Global MASTER-Net observations report
  72. IceCube-240721A: AT2023qqp and AT2024pge likely unrelated
  73. GRB GRB 240809A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  74. IBAS Alert n.10856: not a GRB
  75. GRB 240805B: Osservatorio Astronomico Nastro Verde upper limit
  76. EP240816b: KAIT optical upper limit
  77. GRB 240814B: GRBAlpha detection
  78. Fermi trigger No 745501396: Global MASTER-Net observations report
  79. EP240816a: EP detection of a fast X-ray transient and follow-up observation
  80. EP EP240816b: Global MASTER-Net observations report
  81. EP240816b: TRT optical upper limit
  82. EP240816b: EP-WXT detection and EP-FXT follow-up observation of a fast X-ray transient
  83. Fermi GRB 240814A: Global MASTER-Net observations report
  84. Fermi GRB 240814C: Global MASTER-Net observations report
  85. Fermi trigger No 745306088: Global MASTER-Net observations report
  86. GRB 240814C: Fermi GBM Final Real-time Localization
  87. Fermi GRB 240814B: Global MASTER-Net observations report
  88. GRB 240812B: SVOM/GRM observation
  89. EP240802a: Kinder optical, SWIFT-UVOT, and SWIFT-XRT upper limits 6 days after the WXT detection
  90. GRB 240814B: Fermi GBM Final Real-time Localization
  91. GRB 240814A: Fermi GBM Final Real-time Localization
  92. LIGO/Virgo/KAGRA S240813d: Updated Sky localization
  93. Fermi trigger No 745220784: Global MASTER-Net observations report
  94. Konus-Wind detection of GRB 240811A
  95. Konus-Wind detection of GRB 240810A
  96. Fermi Gamma-ray Burst Monitor trigger 745220784/240813240 is not a GRB
  97. LIGO/Virgo/KAGRA S240813d: Identification of a GW compact binary merger candidate
  98. LIGO/Virgo/KAGRA S240813c: Updated Sky localization
  99. LIGO/Virgo/KAGRA S240813c: Identification of a GW compact binary merger candidate
  100. GRB 240809A: Correction to the VLA source position in GCN 37158

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