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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 240329A: BALROG localization (Fermi Trigger 733441392 / GRB 240329905)
  2. GRB 240329A: Fermi GBM Final Real-time Localization
  3. Fermi GRB 240328B: Global MASTER-Net observations report
  4. Fermi GRB 240328A: Global MASTER-Net observations report
  5. X-ray transient EP240315a: continued ATCA monitoring
  6. IceCube-240327B: No candidates from the Zwicky Transient Facility
  7. GRB 240328C: Glowbug gamma-ray detection
  8. GRB 240328B: Fermi GBM Final Real-time Localization
  9. GRB 240328A: Fermi GBM Final Real-time Localization
  10. IceCube Alert 240327.68: Global MASTER-Net observations report
  11. IceCube-240327B - IceCube observation of a high-energy neutrino candidate track-like event
  12. IceCube-240327A - IceCube observation of a high-energy neutrino candidate track-like event
  13. X-ray transient EP 240315a: Second epoch Chandra observations
  14. Fermi trigger No 733097506: Global MASTER-Net observations report
  15. X-ray transient EP240315a: e-MERLIN radio observations
  16. X-ray transient EP240315a: Ondrejov D50 optical limit
  17. Transient EPW20240219aa: REM optical/NIR further observations
  18. Fermi trigger No 733092476: Global MASTER-Net observations report
  19. GRB 240320A: Glowbug gamma-ray detection
  20. Fermi trigger No 732937833: Global MASTER-Net observations report
  21. GRB 240318A: Fermi GBM Observation
  22. Fermi GRB 240320A: Global MASTER-Net observations report
  23. Konus-Wind detection of GRB 240315C (possible counterpart of EP240315a)
  24. GRB 240315C / X-ray transient EP240315a: Swift/BAT detection
  25. Fermi trigger No 732657380: Global MASTER-Net observations report
  26. GRB 240318A: Swift/BAT-GUANO detection of a burst outside the coded FOV
  27. X-ray transient EP240315a: ATCA detection of radio counterpart
  28. GRB 240320A: Fermi GBM Final Real-time Localization
  29. IPN triangulation of GRB 240315C (consistent with a fast X-ray transient EP240315a)
  30. GRB 240317B: Swift/BAT-GUANO Angular Error Correction
  31. Fermi Gamma-ray Burst Monitor trigger 732299243/240316686 is not a GRB
  32. X-ray transient EP 240315a: Chandra observations
  33. X-ray transient EP240315a: GTC/HiPERCAM photometry
  34. X-ray transient EP240315a: MeerKAT radio detection
  35. X-ray transient EP240315a: GTC/OSIRIS spectroscopic redshift confirmation
  36. GRB 240318A: Glowbug gamma-ray detection
  37. GRB 240317C: Glowbug gamma-ray detection
  38. GRB 240318B: Glowbug gamma-ray detection
  39. X-ray transient EP240315a: PRIME near infrared detection
  40. GRB 240317B: Fermi GBM Observation
  41. X-ray transient EP240315a: 3.6 m TNG NIR detection
  42. Swift satellite in safe mode
  43. X-ray transient EP240315a/AT2024eju: TShAO (Zeiss-1000) observatory optical upper limit
  44. X-ray transient EP240315a: EP-FXT detection of the X-ray afterglow
  45. Fermi GRB 240318A: Global MASTER-Net observations report
  46. GRB 240318A: Fermi GBM Final Real-time Localization
  47. GRB 240317B: Swift/BAT-GUANO arcminute localization of a burst
  48. GRB 240317A: AstroSat CZTI detection
  49. GRB 240315B: AstroSat CZTI detection
  50. X-ray transient EP240315a: Kitab observatory optical upper limitns
  51. X-ray transient EP240315a: Montarrenti Observatory optical upper limit
  52. Fermi GRB 240317B: Global MASTER-Net observations report
  53. Fermi GRB 240317A: Global MASTER-Net observations report
  54. GRB 240317B: Fermi GBM Final Real-time Localization
  55. X-ray transient EP240315a: orphan FXT?
  56. GRB 240317A: Fermi GBM Final Real-time Localization
  57. X-ray transient EP240315a: Kinder follow-up observations for AT 2024eju with Lulin observatory
  58. X-ray transient EP240315a: GROND J-band detection
  59. X-ray transient EP240315a: VLT/X-shooter spectroscopic redshift of z = 4.859
  60. X-ray transient EP240315a: Nanshan/HMT optical upper limit
  61. Fermi trigger No 732299243: Global MASTER-Net observations report
  62. AT2024eju: followup observations with Liverpool Telescope suggest a fading transient
  63. X-ray transient EP240315a: ATLAS detection of a possible optical counterpart AT2024eju
  64. Einstein Probe detected of a fast X-ray transient EP240315a
  65. GRID detection of GRB 240306A
  66. Changes to the Fermi-GBM Triggering Thresholds
  67. Swift Triggers 1220155, 1220156, 1220157, 1220158, 1220160 and 1220161 were not astrophysical
  68. GRB 240315A: Fermi GBM Final Real-time Localization
  69. Swift Triggers 1220093, 1220094, 1220095 and 1220096 are not astrophysical
  70. Swift Triggers 1220090, 1220091 and 1220092 are not astrophysical
  71. Fermi GRB 240314A: Global MASTER-Net observations report
  72. GRB 240314A: Fermi GBM Final Real-time Localization
  73. GRB240204A: VIRT optical upper limit
  74. GRB 240312A: Glowbug gamma-ray detection
  75. Swift triggers 1219917, 1219917 and 1219922 were not astrophysical
  76. Swift Trigger 1219909 and 1219910 are not a astrophysical
  77. Swift Trigger 1219905 is not a GRB
  78. GRB 240312A: GECAM detection of a long burst
  79. Swift Trigger 1219874 is not astrophysical
  80. GRB 240303C: VZLUSAT-2 detection
  81. GRB 240310A: MASTER OT J200702.72-263928.7 inside 3sigma
  82. Fermi trigger No 731839490: Global MASTER-Net observations report
  83. Fermi-LAT gamma-ray observations of IceCube-240307A
  84. GRB 240310B: Glowbug gamma-ray detection
  85. Fermi GRB 240310A: Global MASTER-Net observations report
  86. Swift GRB240309.61: Global MASTER-Net observations report
  87. GRB 240310A: Fermi GBM Final Real-time Localization
  88. GRB 240309A: MAXI/GSC detection
  89. Swift Trigger 1219325 is not a GRB
  90. IceCube-240307A: Upper limits from a search for additional neutrino events in IceCube
  91. GRID detection of GRB 240229A (Updated Report)
  92. GRID detection of GRB 240229A
  93. GRB 240308A: Fermi GBM Final Localization
  94. Fermi trigger No 731571927: Global MASTER-Net observations report
  95. GRB 231215A: further radio observations with the VLA
  96. GRB 240306A: Fermi GBM observation
  97. IceCube-240307A - IceCube observation of a high-energy neutrino candidate track-like event
  98. GRB 240229A: Glowbug gamma-ray detection
  99. GRB 240227A (short): Glowbug gamma-ray detection
  100. IceCube Alert 240307.32: Global MASTER-Net observations report

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