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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 240521A: GECAM-B detection of a long burst
  2. GRB 240516B: AstroSat CZTI detection
  3. LIGO/Virgo/KAGRA S240515m: Upper limits from Swift/BAT-GUANO
  4. LIGO/Virgo/KAGRA S240514x: Upper limits from Swift/BAT-GUANO
  5. LIGO/Virgo/KAGRA S240513ei: Upper limits from Swift/BAT-GUANO
  6. LIGO/Virgo/KAGRA S240520cv: Identification of a GW compact binary merger candidate
  7. IceCube-Cascade 240518A: Upper limits from a search for additional neutrino events in IceCube
  8. GRB 240514B: VZLUSAT-2 detection
  9. GRB 240504A: VZLUSAT-2 detection
  10. GRB 240502A: VZLUSAT-2 detection
  11. GRB 240519A: GRBAlpha detection
  12. GRB 240516A: Swift/UVOT Upper Limits
  13. GRB 240519A: AstroSat CZTI detection
  14. Fermi trigger No 737788024: Global MASTER-Net observations report
  15. EP240518a: possibly identified with a flare star by EP-FXT
  16. GRB 240519A: BALROG localization (Fermi Trigger 737788024 / GRB 240519213)
  17. EP240518a: EP-WXT detection of a new X-ray transient
  18. LIGO/Virgo/KAGRA S240514c: Updated Sky localization
  19. GRB 240516A: Swift-BAT refined analysis
  20. Fermi GRB 240517A: Global MASTER-Net observations report
  21. GRB 240516A ATCA radio observations
  22. IPN triangulation of GRB 240514B (short)
  23. GRB 240513A: Swift ToO observations
  24. GRB 240517A: Fermi GBM Final Real-time Localization
  25. Konus-Wind detection of GRB 240513A
  26. GRB 240516A: AstroSat CZTI detection
  27. GRB 240516A: Swift-XRT refined Analysis
  28. GRB 240514E: A possible candidate BD-21 1074
  29. Fermi trigger No 737559855: Global MASTER-Net observations report
  30. GRB 240516A: Fermi GBM Observation
  31. GRB 240511A: Observations from GTC/OSIRIS+
  32. GRB 240502C: Zeiss-1000 at Koshka observations of GOTO24bao optical counterpart candidate
  33. GRB 240516A: GOTO optical upper limit
  34. LIGO/Virgo/KAGRA S240422ed: GRID non-detection and upper limits
  35. Fermi trigger No 737523389: Global MASTER-Net observations report
  36. GRB 240516A: Swift detection of a burst
  37. Swift GRB240516.15: Global MASTER-Net observations report
  38. GRB 240514B: AT2024ixa/GOTO24bph is not consistent with the Fermi localisation
  39. Fermi trigger No 737476171: Global MASTER-Net observations report
  40. GRB 240511A: radio detection of afterglow candidate
  41. GRB 240514B: GOTO candidate optical counterpart
  42. MAXI GRB240514.78: Global MASTER-Net observations report
  43. Fermi Gamma-ray Burst Monitor list of triggers that are not a GRB
  44. GRB 240514E: MAXI/GSC detection of a probable afterglow
  45. GRB 240514B: GRBAlpha detection
  46. LIGO/Virgo/KAGRA S240514x: Updated Sky localization
  47. LIGO/Virgo/KAGRA S240515m: Identification of a GW compact binary merger candidate
  48. GRB 240514B: Fermi GBM Detection
  49. LIGO/Virgo/KAGRA S240422ed: Las Cumbres Observatory Follow-up Observations of the Localization Region
  50. GRB 240513A: Fermi GBM observation
  51. GRB 240513A: Swift-XRT observations
  52. LIGO/Virgo/KAGRA S240513ei: Updated Sky localization
  53. LIGO/Virgo/KAGRA S240514x: Identification of a GW compact binary merger candidate
  54. GRB 240514D: AstroSat CZTI detection
  55. GRB 240514C: Fermi GBM Final Real-time Localization
  56. LIGO/Virgo/KAGRA S240514c: Identification of a GW compact binary merger candidate
  57. Fermi GRB 240514B: Global MASTER-Net observations report
  58. transient: Xinglong Nearby Galaxy Supernova Survey detection of AT2024iss
  59. Fermi Gamma-ray Burst Monitor triggers 737345659/240514093 and GRB240514A are not GRBs
  60. GRB 240514B: Fermi GBM Final Real-time Localization
  61. LIGO/Virgo/KAGRA S240507p: Upper limits from Swift/BAT-GUANO
  62. LIGO/Virgo/KAGRA S240505av: Upper limits from Swift/BAT-GUANO
  63. LIGO/Virgo/KAGRA S240505av: Upper limits from Swift/BAT-GUANO
  64. GRB 240514A: Fermi GBM Final Real-time Localization
  65. GRB 240513A: Tiled Swift observations
  66. LAT GRB240513.31: Global MASTER-Net observations report
  67. GRB 240513A: Fermi-LAT detection
  68. LIGO/Virgo/KAGRA S240513ei: Identification of a GW compact binary merger candidate
  69. GRB 240511A: Fermi GBM Observation
  70. GRB 240511A: Swift-BAT refined analysis
  71. Fermi GRB 240513B: Global MASTER-Net observations report
  72. Fermi trigger No 737277727: Global MASTER-Net observations report
  73. GRB 240513B: Fermi GBM Final Real-time Localization
  74. GRB 240513A: AstroSat CZTI detection
  75. LIGO/Virgo/KAGRA S240513cx: Coverage and upper limits from MAXI/GSC observations
  76. Fermi trigger No 737258655: Global MASTER-Net observations report
  77. GRB 240511A: J-band observations with WINTER
  78. Fermi trigger No 737247400: Global MASTER-Net observations report
  79. Fermi trigger No 737244199: Global MASTER-Net observations report
  80. Fermi trigger No 737218721: Global MASTER-Net observations report
  81. Fermi trigger No 737196587: Global MASTER-Net observations report
  82. Fermi trigger No 737168073: Global MASTER-Net observations report
  83. GRB 240511A: Enhanced Swift-XRT position
  84. GRB 240511A : MITSuME Akeno optical upper limits
  85. LIGO/Virgo/KAGRA S240512r: Updated Sky localization and EM Bright Classification
  86. GRB 240511A: Swift-XRT refined Analysis
  87. GRB 240511A: optical afterglow detection from the NOT
  88. Fermi Gamma-ray Burst Monitor trigger 737102480/240511279 is not a GRB
  89. Fermi Gamma-ray Burst Monitor trigger 737111207/240511380 is not a GRB
  90. Fermi GBM trigger 737105243/240511311 is not a GRB
  91. Fermi trigger No 737173236: Global MASTER-Net observations report
  92. LIGO/Virgo/KAGRA S240512r: Identification of a GW compact binary merger candidate
  93. Fermi GRB 240511A: Global MASTER-Net observations report
  94. Swift GRB 240511A: Global MASTER-Net observations report
  95. Fermi trigger No 737105243: Global MASTER-Net observations report
  96. Fermi Gamma-ray Burst Monitor trigger 737133200/240511634 is not a GRB
  97. Fermi trigger No 737152719: Global MASTER-Net observations report
  98. GRB 240511A: Prompt enhanced Swift-XRT position
  99. GRB 240511A: Swift detection of a burst
  100. LIGO/Virgo/KAGRA S240511i: Updated Sky localization

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