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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').
  1. GRB 240523A: Enhanced Swift-XRT position
  2. GRB 240523A: Swift detection of a burst
  3. GRB 240521B: Fermi GBM Observation
  4. Fermi GBM Sub-Threshold Detection of GRB 240516B
  5. GRB 240513A: Swift-XRT afterglow detection
  6. GRB 240521B: Swift/BAT-GUANO arcminute localization of a long burst
  7. Fermi trigger No 737996942: Global MASTER-Net observations report
  8. LIGO/Virgo/KAGRA S240520cv: Updated Sky localization and EM Bright Classification
  9. EP240518a: GSP optical upper limit
  10. GRB 240521A: GECAM-B detection of a long burst
  11. GRB 240516B: AstroSat CZTI detection
  12. LIGO/Virgo/KAGRA S240515m: Upper limits from Swift/BAT-GUANO
  13. LIGO/Virgo/KAGRA S240514x: Upper limits from Swift/BAT-GUANO
  14. LIGO/Virgo/KAGRA S240513ei: Upper limits from Swift/BAT-GUANO
  15. LIGO/Virgo/KAGRA S240520cv: Identification of a GW compact binary merger candidate
  16. IceCube-Cascade 240518A: Upper limits from a search for additional neutrino events in IceCube
  17. GRB 240514B: VZLUSAT-2 detection
  18. GRB 240504A: VZLUSAT-2 detection
  19. GRB 240502A: VZLUSAT-2 detection
  20. GRB 240519A: GRBAlpha detection
  21. GRB 240516A: Swift/UVOT Upper Limits
  22. GRB 240519A: AstroSat CZTI detection
  23. Fermi trigger No 737788024: Global MASTER-Net observations report
  24. EP240518a: possibly identified with a flare star by EP-FXT
  25. GRB 240519A: BALROG localization (Fermi Trigger 737788024 / GRB 240519213)
  26. EP240518a: EP-WXT detection of a new X-ray transient
  27. LIGO/Virgo/KAGRA S240514c: Updated Sky localization
  28. GRB 240516A: Swift-BAT refined analysis
  29. Fermi GRB 240517A: Global MASTER-Net observations report
  30. GRB 240516A ATCA radio observations
  31. IPN triangulation of GRB 240514B (short)
  32. GRB 240513A: Swift ToO observations
  33. GRB 240517A: Fermi GBM Final Real-time Localization
  34. Konus-Wind detection of GRB 240513A
  35. GRB 240516A: AstroSat CZTI detection
  36. GRB 240516A: Swift-XRT refined Analysis
  37. GRB 240514E: A possible candidate BD-21 1074
  38. Fermi trigger No 737559855: Global MASTER-Net observations report
  39. GRB 240516A: Fermi GBM Observation
  40. GRB 240511A: Observations from GTC/OSIRIS+
  41. GRB 240502C: Zeiss-1000 at Koshka observations of GOTO24bao optical counterpart candidate
  42. GRB 240516A: GOTO optical upper limit
  43. LIGO/Virgo/KAGRA S240422ed: GRID non-detection and upper limits
  44. Fermi trigger No 737523389: Global MASTER-Net observations report
  45. GRB 240516A: Swift detection of a burst
  46. Swift GRB240516.15: Global MASTER-Net observations report
  47. GRB 240514B: AT2024ixa/GOTO24bph is not consistent with the Fermi localisation
  48. Fermi trigger No 737476171: Global MASTER-Net observations report
  49. GRB 240511A: radio detection of afterglow candidate
  50. GRB 240514B: GOTO candidate optical counterpart
  51. MAXI GRB240514.78: Global MASTER-Net observations report
  52. Fermi Gamma-ray Burst Monitor list of triggers that are not a GRB
  53. GRB 240514E: MAXI/GSC detection of a probable afterglow
  54. GRB 240514B: GRBAlpha detection
  55. LIGO/Virgo/KAGRA S240514x: Updated Sky localization
  56. LIGO/Virgo/KAGRA S240515m: Identification of a GW compact binary merger candidate
  57. GRB 240514B: Fermi GBM Detection
  58. LIGO/Virgo/KAGRA S240422ed: Las Cumbres Observatory Follow-up Observations of the Localization Region
  59. GRB 240513A: Fermi GBM observation
  60. GRB 240513A: Swift-XRT observations
  61. LIGO/Virgo/KAGRA S240513ei: Updated Sky localization
  62. LIGO/Virgo/KAGRA S240514x: Identification of a GW compact binary merger candidate
  63. GRB 240514D: AstroSat CZTI detection
  64. GRB 240514C: Fermi GBM Final Real-time Localization
  65. LIGO/Virgo/KAGRA S240514c: Identification of a GW compact binary merger candidate
  66. Fermi GRB 240514B: Global MASTER-Net observations report
  67. transient: Xinglong Nearby Galaxy Supernova Survey detection of AT2024iss
  68. Fermi Gamma-ray Burst Monitor triggers 737345659/240514093 and GRB240514A are not GRBs
  69. GRB 240514B: Fermi GBM Final Real-time Localization
  70. LIGO/Virgo/KAGRA S240507p: Upper limits from Swift/BAT-GUANO
  71. LIGO/Virgo/KAGRA S240505av: Upper limits from Swift/BAT-GUANO
  72. LIGO/Virgo/KAGRA S240505av: Upper limits from Swift/BAT-GUANO
  73. GRB 240514A: Fermi GBM Final Real-time Localization
  74. GRB 240513A: Tiled Swift observations
  75. LAT GRB240513.31: Global MASTER-Net observations report
  76. GRB 240513A: Fermi-LAT detection
  77. LIGO/Virgo/KAGRA S240513ei: Identification of a GW compact binary merger candidate
  78. GRB 240511A: Fermi GBM Observation
  79. GRB 240511A: Swift-BAT refined analysis
  80. Fermi GRB 240513B: Global MASTER-Net observations report
  81. Fermi trigger No 737277727: Global MASTER-Net observations report
  82. GRB 240513B: Fermi GBM Final Real-time Localization
  83. GRB 240513A: AstroSat CZTI detection
  84. LIGO/Virgo/KAGRA S240513cx: Coverage and upper limits from MAXI/GSC observations
  85. Fermi trigger No 737258655: Global MASTER-Net observations report
  86. GRB 240511A: J-band observations with WINTER
  87. Fermi trigger No 737247400: Global MASTER-Net observations report
  88. Fermi trigger No 737244199: Global MASTER-Net observations report
  89. Fermi trigger No 737218721: Global MASTER-Net observations report
  90. Fermi trigger No 737196587: Global MASTER-Net observations report
  91. Fermi trigger No 737168073: Global MASTER-Net observations report
  92. GRB 240511A: Enhanced Swift-XRT position
  93. GRB 240511A : MITSuME Akeno optical upper limits
  94. LIGO/Virgo/KAGRA S240512r: Updated Sky localization and EM Bright Classification
  95. GRB 240511A: Swift-XRT refined Analysis
  96. GRB 240511A: optical afterglow detection from the NOT
  97. Fermi Gamma-ray Burst Monitor trigger 737102480/240511279 is not a GRB
  98. Fermi Gamma-ray Burst Monitor trigger 737111207/240511380 is not a GRB
  99. Fermi GBM trigger 737105243/240511311 is not a GRB
  100. Fermi trigger No 737173236: Global MASTER-Net observations report

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