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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. LXT 240402A/GRB 240402B: rest-frame energetics from Konus-Wind observation
  2. Fermi GRB 240405B: Global MASTER-Net observations report
  3. GRB 240405B: Fermi GBM Final Real-time Localization
  4. GRB 240402C: Glowbug gamma-ray detection
  5. GRB 240405A: Fermi GBM Final Real-time Localization
  6. GRB 240402C: GRBAlpha detection
  7. GRB 240331A: GRBAlpha detection
  8. LXT 240402A/GRB 240402B: GECAM-C refined analysis
  9. Swift satellite resumes pointed science observations
  10. GRB 240403B: Glowbug gamma-ray detection
  11. GRB 240403A: Glowbug gamma-ray detection
  12. LXT 240402A/GRB 240402B: Glowbug gamma-ray detection
  13. X-ray transient LXT 240402A: WFST optical upper limits​
  14. Konus-Wind detection of LXT 240402A/GRB 240402B
  15. GRB/FXT 240402B: Kinder optical counterpart candidate
  16. IceCube-240327B: GRANDMA observations of 4FGL J0555.9+0030
  17. GRB/FXT 240402B: VLT/FORS2 optical afterglow candidate
  18. GRB 240403A: Fermi GBM Detection
  19. X-ray transient LXT240402A: AST3-3 optical upper limits
  20. LXT 240402A: EP-FXT detection of the X-ray afterglow
  21. Fermi GRB 240404A: Global MASTER-Net observations report
  22. GRB 240404A: Fermi GBM Final Real-time Localization
  23. LXT 240402A: MASTER optical observations with AGN in error-box
  24. GRB 240402B: GWAC-F50A optical upper limit
  25. GRB 240402B: GECAM-C detection
  26. X-ray transient LXT 240402A: LEIA detection
  27. GRB 240403A: BALROG localization (Fermi Trigger 733838255 / GRB 240403498)
  28. Fermi trigger No 733808041: Global MASTER-Net observations report
  29. Fermi GRB 240402A: Global MASTER-Net observations report
  30. GRB 240402A: Fermi GBM Final Real-time Localization
  31. X-ray transient EP240331a: Kinder optical upper limits
  32. X-ray transient EP240331A: GRANDMA-Kilonova catcher optical upper limit
  33. EP240331A: MASTER optical observations
  34. Transient EP240315a: J-band observations of AT2024eju with WIRC
  35. X-ray transient EP20240331a: MeerLICHT optical upper limits
  36. IBAS Alert n.10651 not a GRB
  37. IceCube-240327B: Upper limits from a search for additional neutrino events in IceCube
  38. IceCube-240327A: Upper limits from a search for additional neutrino events in IceCube
  39. Integral GRB240401.69: Global MASTER-Net observations report
  40. GRB 240329A: Glowbug gamma-ray detection
  41. GRB 240324A: AstroSat CZTI detection of a short burst
  42. GRB 240331A: AstroSat CZTI detection
  43. GRB 240329A: AstroSat CZTI detection
  44. GRB 240331A: Fermi GBM Final Real-time Localization
  45. GRB 240329A: GRBAlpha detection
  46. Fermi trigger No 733366352: Global MASTER-Net observations report
  47. Fermi GRB 240329A: Global MASTER-Net observations report
  48. GRB 240329A: BALROG localization (Fermi Trigger 733441392 / GRB 240329905)
  49. GRB 240329A: Fermi GBM Final Real-time Localization
  50. Fermi GRB 240328B: Global MASTER-Net observations report
  51. Fermi GRB 240328A: Global MASTER-Net observations report
  52. X-ray transient EP240315a: continued ATCA monitoring
  53. IceCube-240327B: No candidates from the Zwicky Transient Facility
  54. GRB 240328C: Glowbug gamma-ray detection
  55. GRB 240328B: Fermi GBM Final Real-time Localization
  56. GRB 240328A: Fermi GBM Final Real-time Localization
  57. IceCube Alert 240327.68: Global MASTER-Net observations report
  58. IceCube-240327B - IceCube observation of a high-energy neutrino candidate track-like event
  59. IceCube-240327A - IceCube observation of a high-energy neutrino candidate track-like event
  60. X-ray transient EP 240315a: Second epoch Chandra observations
  61. Fermi trigger No 733097506: Global MASTER-Net observations report
  62. X-ray transient EP240315a: e-MERLIN radio observations
  63. X-ray transient EP240315a: Ondrejov D50 optical limit
  64. Transient EPW20240219aa: REM optical/NIR further observations
  65. Fermi trigger No 733092476: Global MASTER-Net observations report
  66. GRB 240320A: Glowbug gamma-ray detection
  67. Fermi trigger No 732937833: Global MASTER-Net observations report
  68. GRB 240318A: Fermi GBM Observation
  69. Fermi GRB 240320A: Global MASTER-Net observations report
  70. Konus-Wind detection of GRB 240315C (possible counterpart of EP240315a)
  71. GRB 240315C / X-ray transient EP240315a: Swift/BAT detection
  72. Fermi trigger No 732657380: Global MASTER-Net observations report
  73. GRB 240318A: Swift/BAT-GUANO detection of a burst outside the coded FOV
  74. X-ray transient EP240315a: ATCA detection of radio counterpart
  75. GRB 240320A: Fermi GBM Final Real-time Localization
  76. IPN triangulation of GRB 240315C (consistent with a fast X-ray transient EP240315a)
  77. GRB 240317B: Swift/BAT-GUANO Angular Error Correction
  78. Fermi Gamma-ray Burst Monitor trigger 732299243/240316686 is not a GRB
  79. X-ray transient EP 240315a: Chandra observations
  80. X-ray transient EP240315a: GTC/HiPERCAM photometry
  81. X-ray transient EP240315a: MeerKAT radio detection
  82. X-ray transient EP240315a: GTC/OSIRIS spectroscopic redshift confirmation
  83. GRB 240318A: Glowbug gamma-ray detection
  84. GRB 240317C: Glowbug gamma-ray detection
  85. GRB 240318B: Glowbug gamma-ray detection
  86. X-ray transient EP240315a: PRIME near infrared detection
  87. GRB 240317B: Fermi GBM Observation
  88. X-ray transient EP240315a: 3.6 m TNG NIR detection
  89. Swift satellite in safe mode
  90. X-ray transient EP240315a/AT2024eju: TShAO (Zeiss-1000) observatory optical upper limit
  91. X-ray transient EP240315a: EP-FXT detection of the X-ray afterglow
  92. Fermi GRB 240318A: Global MASTER-Net observations report
  93. GRB 240318A: Fermi GBM Final Real-time Localization
  94. GRB 240317B: Swift/BAT-GUANO arcminute localization of a burst
  95. GRB 240317A: AstroSat CZTI detection
  96. GRB 240315B: AstroSat CZTI detection
  97. X-ray transient EP240315a: Kitab observatory optical upper limitns
  98. X-ray transient EP240315a: Montarrenti Observatory optical upper limit
  99. Fermi GRB 240317B: Global MASTER-Net observations report
  100. Fermi GRB 240317A: Global MASTER-Net observations report

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