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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 240824A: Swift-XRT observations
  2. LIGO/Virgo/KAGRA S240825ar: Identification of a GW compact binary merger candidate
  3. GRB 240824B: Swift/BAT arcminute localization of a burst
  4. GRB 240824B: Swift ToO observations
  5. Fermi GRB 240824C: Global MASTER-Net observations report
  6. GRB 240824C: Fermi GBM Final Localization
  7. GRB 240824A: Swift/UVOT Upper Limits
  8. GRB 240821A: Swift/UVOT observations of the XRT sources.
  9. GRB 240824B: MAXI/GSC detection
  10. GRB 240824B: Fermi GBM Final Real-time Localization
  11. GRB 240824A: Retraction of GCN 37255
  12. GRB240824A: GRANDMA/TAROT-TCA Upper Limit
  13. SGR 1E 1841-045 / Kes 73: Leavitt Observatory optical upper limit
  14. GRB 240824A: KAIT optical upper limit
  15. GRB 240824A: Skynet Optical Afterglow Discovery
  16. GRB 240824A: Swift detection of a burst
  17. Swift GRB240824.04: Global MASTER-Net observations report
  18. SGR 1E 1841-045 / Kes 73: Montarrenti Observatory optical upper limits
  19. GRB 240821A: Colibri Optical Upper Limit
  20. EP240820a: PRIME J-band Observations
  21. GRB 240821A: Swift-XRT observations
  22. GRB 240822A: AstroSat CZTI detection of a short burst
  23. GRB 240821A: REM optical/NIR upper limits
  24. GRB 240821A: LCO optical observations
  25. GRB 240821A: JinShan optical upper limits
  26. GRB 240809A: Mondy and AbAO Optical Observations
  27. GRB 240821A: SVOM/VT follow-up and optical upper limit
  28. GRB 240821A: GMG Optical Upper Limit
  29. Fermi GRB 240821A: Global MASTER-Net observations report
  30. GECAM-B observation of a short burst from SGR 1E 1841-045 / Kes 73
  31. GRB 240821A: Fermi GBM Observation
  32. Fermi trigger No 745964969: Global MASTER-Net observations report
  33. Fermi trigger No 745925274: Global MASTER-Net observations report
  34. GRB 240821A: Swift ToO observations
  35. Fermi trigger No 746019401: Global MASTER-Net observations report
  36. Fermi-GBM Observations of the reactivation of SGR 1E 1841-045 / Kes 73
  37. Fermi trigger No 745935375: Global MASTER-Net observations report
  38. GRB240821A: EIRSAT-1 GMOD Detection
  39. GRB240821B: First GRB Detected by EIRSAT-1 GMOD
  40. GRB 240821A: EP-FXT follow-up observation and afterglow candidates
  41. Fermi GRB 240821B: Global MASTER-Net observations report
  42. EP240801a: Keck/LRIS spectroscopic redshift confirmation
  43. GRB 240821A: SVOM/GRM observation
  44. GRB 240821A: SVOM/GRM observation
  45. GRB 240821A: GRANDMA/LesMakes-T60 Upper Limit
  46. GRB 240821B: Fermi GBM Final Localization
  47. Fermi trigger No 745866488: Global MASTER-Net observations report
  48. Trigger 1249878: Swift detection of another burst from SGR 1E 1841-045 / Kes 73
  49. GRB 240821A: BALROG localization (Fermi Trigger 745958167 / GRB 240821775)
  50. GRB 240821A : a likely short GRB detected by SVOM/ECLAIRs
  51. GRB 240821A: Fermi GBM Final Real-time Localization
  52. GRB 240819A: Swift-XRT observations
  53. GRB 240819A: JinShan optical upper limits on one Swift/XRT source
  54. GRB 240820B: SVOM/GRM observation
  55. EP240820a: TRT optical upper limit
  56. EP240820a: EP detection of a fast X-ray transient
  57. GRB 240819A: KAIT optical upper limit
  58. EP240816a: PRIME upper limits
  59. Trigger 1249653: Swift detection of SGR 1E 1841-045 / Kes 73
  60. Fermi trigger No 745873283: Global MASTER-Net observations report
  61. Fermi trigger No 745871958: Global MASTER-Net observations report
  62. GRB 240819A : an X-ray transient detected by SVOM/ECLAIRs
  63. GRB 240819A: TRT optical upper limits on the Swift/XRT and EP/FXT sources
  64. GRB 240819A: X-ray follow-up observation with EP-FXT
  65. Fermi Gamma-ray Burst Monitor trigger 745811685 / 240820080 is not a GRB
  66. GRB 240820A: Fermi GBM Final Real-time Localization
  67. GRB 240819A: Swift ToO observations
  68. GRB 240814A: SVOM/GRM observation
  69. EP240816b: Liverpool Telescope optical follow-up observations
  70. GRB 240814C: SVOM/GRM observation
  71. EP240816a: BOOTES-6/DPRT optical upper limit
  72. GRB 240815A: SVOM/GRM observation
  73. GRB 240817A: Fermi GBM Final Real-time Localization
  74. Integral GRB240816.79: Global MASTER-Net observations report
  75. IceCube-240721A: AT2023qqp and AT2024pge likely unrelated
  76. GRB GRB 240809A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  77. IBAS Alert n.10856: not a GRB
  78. GRB 240805B: Osservatorio Astronomico Nastro Verde upper limit
  79. EP240816b: KAIT optical upper limit
  80. GRB 240814B: GRBAlpha detection
  81. Fermi trigger No 745501396: Global MASTER-Net observations report
  82. EP240816a: EP detection of a fast X-ray transient and follow-up observation
  83. EP EP240816b: Global MASTER-Net observations report
  84. EP240816b: TRT optical upper limit
  85. EP240816b: EP-WXT detection and EP-FXT follow-up observation of a fast X-ray transient
  86. Fermi GRB 240814A: Global MASTER-Net observations report
  87. Fermi GRB 240814C: Global MASTER-Net observations report
  88. Fermi trigger No 745306088: Global MASTER-Net observations report
  89. GRB 240814C: Fermi GBM Final Real-time Localization
  90. Fermi GRB 240814B: Global MASTER-Net observations report
  91. GRB 240812B: SVOM/GRM observation
  92. EP240802a: Kinder optical, SWIFT-UVOT, and SWIFT-XRT upper limits 6 days after the WXT detection
  93. GRB 240814B: Fermi GBM Final Real-time Localization
  94. GRB 240814A: Fermi GBM Final Real-time Localization
  95. LIGO/Virgo/KAGRA S240813d: Updated Sky localization
  96. Fermi trigger No 745220784: Global MASTER-Net observations report
  97. Konus-Wind detection of GRB 240811A
  98. Konus-Wind detection of GRB 240810A
  99. Fermi Gamma-ray Burst Monitor trigger 745220784/240813240 is not a GRB
  100. LIGO/Virgo/KAGRA S240813d: Identification of a GW compact binary merger candidate

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