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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 240411B: Enhanced Swift-XRT position
  2. GRB 240411B: LCO optical afterglow detection
  3. GRB 240411B: Swift detection of a burst
  4. GRB 240408B: GRBAlpha detection
  5. GRB 240411A: Fermi GBM Final Real-time Localization
  6. EP240408A: MASTER optical observations
  7. EP240408a: GROND detection of a candidate counterpart
  8. EP240408a: Upper limits from GECAM-B Observation
  9. EP240408a: Swift follow-up observation
  10. EP240408a: BOOTES-6/DPRT optical upper limit
  11. X-ray transient EP240315a: second epoch e-MERLIN radio observations
  12. GRB 240405A: GRBAlpha detection
  13. EP240408a: EP-WXT detection of a fast X-ray transient
  14. Swift Trigger 1220736: detection of 4U 1543-62.
  15. GRB 240408B: AstroSat CZTI detection
  16. IceCube-240327B: GRANDMA/Kilonova-Catcher observations of 4FGL J0555.9+0030 and optical upper limits
  17. Fermi GRB 240408A: Global MASTER-Net observations report
  18. GRB 240408A: Fermi GBM Final Real-time Localization
  19. GRB 240407A: BALROG localization (Fermi Trigger 734144396 / GRB 240407042)
  20. GRB 240402C: CALET Gamma-Ray Burst Monitor detection
  21. Fermi GRB 240407A: Global MASTER-Net observations report
  22. GRB 240407A: Fermi GBM Final Real-time Localization
  23. Fermi-LAT gamma-ray observations of IceCube-240327B
  24. Fermi-LAT gamma-ray observations of IceCube-240327A
  25. LXT 240402A/GRB 240402B: rest-frame energetics from Konus-Wind observation
  26. Fermi GRB 240405B: Global MASTER-Net observations report
  27. GRB 240405B: Fermi GBM Final Real-time Localization
  28. GRB 240402C: Glowbug gamma-ray detection
  29. GRB 240405A: Fermi GBM Final Real-time Localization
  30. GRB 240402C: GRBAlpha detection
  31. GRB 240331A: GRBAlpha detection
  32. LXT 240402A/GRB 240402B: GECAM-C refined analysis
  33. Swift satellite resumes pointed science observations
  34. GRB 240403B: Glowbug gamma-ray detection
  35. GRB 240403A: Glowbug gamma-ray detection
  36. LXT 240402A/GRB 240402B: Glowbug gamma-ray detection
  37. X-ray transient LXT 240402A: WFST optical upper limits​
  38. Konus-Wind detection of LXT 240402A/GRB 240402B
  39. GRB/FXT 240402B: Kinder optical counterpart candidate
  40. IceCube-240327B: GRANDMA observations of 4FGL J0555.9+0030
  41. GRB/FXT 240402B: VLT/FORS2 optical afterglow candidate
  42. GRB 240403A: Fermi GBM Detection
  43. X-ray transient LXT240402A: AST3-3 optical upper limits
  44. LXT 240402A: EP-FXT detection of the X-ray afterglow
  45. Fermi GRB 240404A: Global MASTER-Net observations report
  46. GRB 240404A: Fermi GBM Final Real-time Localization
  47. LXT 240402A: MASTER optical observations with AGN in error-box
  48. GRB 240402B: GWAC-F50A optical upper limit
  49. GRB 240402B: GECAM-C detection
  50. X-ray transient LXT 240402A: LEIA detection
  51. GRB 240403A: BALROG localization (Fermi Trigger 733838255 / GRB 240403498)
  52. Fermi trigger No 733808041: Global MASTER-Net observations report
  53. Fermi GRB 240402A: Global MASTER-Net observations report
  54. GRB 240402A: Fermi GBM Final Real-time Localization
  55. X-ray transient EP240331a: Kinder optical upper limits
  56. X-ray transient EP240331A: GRANDMA-Kilonova catcher optical upper limit
  57. EP240331A: MASTER optical observations
  58. Transient EP240315a: J-band observations of AT2024eju with WIRC
  59. X-ray transient EP20240331a: MeerLICHT optical upper limits
  60. IBAS Alert n.10651 not a GRB
  61. IceCube-240327B: Upper limits from a search for additional neutrino events in IceCube
  62. IceCube-240327A: Upper limits from a search for additional neutrino events in IceCube
  63. Integral GRB240401.69: Global MASTER-Net observations report
  64. GRB 240329A: Glowbug gamma-ray detection
  65. GRB 240324A: AstroSat CZTI detection of a short burst
  66. GRB 240331A: AstroSat CZTI detection
  67. GRB 240329A: AstroSat CZTI detection
  68. GRB 240331A: Fermi GBM Final Real-time Localization
  69. GRB 240329A: GRBAlpha detection
  70. Fermi trigger No 733366352: Global MASTER-Net observations report
  71. Fermi GRB 240329A: Global MASTER-Net observations report
  72. GRB 240329A: BALROG localization (Fermi Trigger 733441392 / GRB 240329905)
  73. GRB 240329A: Fermi GBM Final Real-time Localization
  74. Fermi GRB 240328B: Global MASTER-Net observations report
  75. Fermi GRB 240328A: Global MASTER-Net observations report
  76. X-ray transient EP240315a: continued ATCA monitoring
  77. IceCube-240327B: No candidates from the Zwicky Transient Facility
  78. GRB 240328C: Glowbug gamma-ray detection
  79. GRB 240328B: Fermi GBM Final Real-time Localization
  80. GRB 240328A: Fermi GBM Final Real-time Localization
  81. IceCube Alert 240327.68: Global MASTER-Net observations report
  82. IceCube-240327B - IceCube observation of a high-energy neutrino candidate track-like event
  83. IceCube-240327A - IceCube observation of a high-energy neutrino candidate track-like event
  84. X-ray transient EP 240315a: Second epoch Chandra observations
  85. Fermi trigger No 733097506: Global MASTER-Net observations report
  86. X-ray transient EP240315a: e-MERLIN radio observations
  87. X-ray transient EP240315a: Ondrejov D50 optical limit
  88. Transient EPW20240219aa: REM optical/NIR further observations
  89. Fermi trigger No 733092476: Global MASTER-Net observations report
  90. GRB 240320A: Glowbug gamma-ray detection
  91. Fermi trigger No 732937833: Global MASTER-Net observations report
  92. GRB 240318A: Fermi GBM Observation
  93. Fermi GRB 240320A: Global MASTER-Net observations report
  94. Konus-Wind detection of GRB 240315C (possible counterpart of EP240315a)
  95. GRB 240315C / X-ray transient EP240315a: Swift/BAT detection
  96. Fermi trigger No 732657380: Global MASTER-Net observations report
  97. GRB 240318A: Swift/BAT-GUANO detection of a burst outside the coded FOV
  98. X-ray transient EP240315a: ATCA detection of radio counterpart
  99. GRB 240320A: Fermi GBM Final Real-time Localization
  100. IPN triangulation of GRB 240315C (consistent with a fast X-ray transient EP240315a)

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