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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: 1.3m DFOT Optical observations
  2. GRB 240411A: GRBAlpha detection
  3. GRB 240411B: OHP/T193 optical observations
  4. GRB 240405A: Glowbug gamma-ray detection
  5. GRB 240411B: Enhanced Swift-XRT position
  6. GRB 240411B: LCO optical afterglow detection
  7. GRB 240411B: Swift detection of a burst
  8. GRB 240408B: GRBAlpha detection
  9. GRB 240411A: Fermi GBM Final Real-time Localization
  10. EP240408A: MASTER optical observations
  11. EP240410a: GROND detection of a candidate counterpart
  12. EP240408a: Upper limits from GECAM-B Observation
  13. EP240408a: Swift follow-up observation
  14. EP240408a: BOOTES-6/DPRT optical upper limit
  15. X-ray transient EP240315a: second epoch e-MERLIN radio observations
  16. GRB 240405A: GRBAlpha detection
  17. EP240408a: EP-WXT detection of a fast X-ray transient
  18. Swift Trigger 1220736: detection of 4U 1543-62.
  19. GRB 240408B: AstroSat CZTI detection
  20. IceCube-240327B: GRANDMA/Kilonova-Catcher observations of 4FGL J0555.9+0030 and optical upper limits
  21. Fermi GRB 240408A: Global MASTER-Net observations report
  22. GRB 240408A: Fermi GBM Final Real-time Localization
  23. GRB 240407A: BALROG localization (Fermi Trigger 734144396 / GRB 240407042)
  24. GRB 240402C: CALET Gamma-Ray Burst Monitor detection
  25. Fermi GRB 240407A: Global MASTER-Net observations report
  26. GRB 240407A: Fermi GBM Final Real-time Localization
  27. Fermi-LAT gamma-ray observations of IceCube-240327B
  28. Fermi-LAT gamma-ray observations of IceCube-240327A
  29. LXT 240402A/GRB 240402B: rest-frame energetics from Konus-Wind observation
  30. Fermi GRB 240405B: Global MASTER-Net observations report
  31. GRB 240405B: Fermi GBM Final Real-time Localization
  32. GRB 240402C: Glowbug gamma-ray detection
  33. GRB 240405A: Fermi GBM Final Real-time Localization
  34. GRB 240402C: GRBAlpha detection
  35. GRB 240331A: GRBAlpha detection
  36. LXT 240402A/GRB 240402B: GECAM-C refined analysis
  37. Swift satellite resumes pointed science observations
  38. GRB 240403B: Glowbug gamma-ray detection
  39. GRB 240403A: Glowbug gamma-ray detection
  40. LXT 240402A/GRB 240402B: Glowbug gamma-ray detection
  41. X-ray transient LXT 240402A: WFST optical upper limits​
  42. Konus-Wind detection of LXT 240402A/GRB 240402B
  43. GRB/FXT 240402B: Kinder optical counterpart candidate
  44. IceCube-240327B: GRANDMA observations of 4FGL J0555.9+0030
  45. GRB/FXT 240402B: VLT/FORS2 optical afterglow candidate
  46. GRB 240403A: Fermi GBM Detection
  47. X-ray transient LXT240402A: AST3-3 optical upper limits
  48. LXT 240402A: EP-FXT detection of the X-ray afterglow
  49. Fermi GRB 240404A: Global MASTER-Net observations report
  50. GRB 240404A: Fermi GBM Final Real-time Localization
  51. LXT 240402A: MASTER optical observations with AGN in error-box
  52. GRB 240402B: GWAC-F50A optical upper limit
  53. GRB 240402B: GECAM-C detection
  54. X-ray transient LXT 240402A: LEIA detection
  55. GRB 240403A: BALROG localization (Fermi Trigger 733838255 / GRB 240403498)
  56. Fermi trigger No 733808041: Global MASTER-Net observations report
  57. Fermi GRB 240402A: Global MASTER-Net observations report
  58. GRB 240402A: Fermi GBM Final Real-time Localization
  59. X-ray transient EP240331a: Kinder optical upper limits
  60. X-ray transient EP240331A: GRANDMA-Kilonova catcher optical upper limit
  61. EP240331A: MASTER optical observations
  62. Transient EP240315a: J-band observations of AT2024eju with WIRC
  63. X-ray transient EP20240331a: MeerLICHT optical upper limits
  64. IBAS Alert n.10651 not a GRB
  65. IceCube-240327B: Upper limits from a search for additional neutrino events in IceCube
  66. IceCube-240327A: Upper limits from a search for additional neutrino events in IceCube
  67. Integral GRB240401.69: Global MASTER-Net observations report
  68. GRB 240329A: Glowbug gamma-ray detection
  69. GRB 240324A: AstroSat CZTI detection of a short burst
  70. GRB 240331A: AstroSat CZTI detection
  71. GRB 240329A: AstroSat CZTI detection
  72. GRB 240331A: Fermi GBM Final Real-time Localization
  73. GRB 240329A: GRBAlpha detection
  74. Fermi trigger No 733366352: Global MASTER-Net observations report
  75. Fermi GRB 240329A: Global MASTER-Net observations report
  76. GRB 240329A: BALROG localization (Fermi Trigger 733441392 / GRB 240329905)
  77. GRB 240329A: Fermi GBM Final Real-time Localization
  78. Fermi GRB 240328B: Global MASTER-Net observations report
  79. Fermi GRB 240328A: Global MASTER-Net observations report
  80. X-ray transient EP240315a: continued ATCA monitoring
  81. IceCube-240327B: No candidates from the Zwicky Transient Facility
  82. GRB 240328C: Glowbug gamma-ray detection
  83. GRB 240328B: Fermi GBM Final Real-time Localization
  84. GRB 240328A: Fermi GBM Final Real-time Localization
  85. IceCube Alert 240327.68: Global MASTER-Net observations report
  86. IceCube-240327B - IceCube observation of a high-energy neutrino candidate track-like event
  87. IceCube-240327A - IceCube observation of a high-energy neutrino candidate track-like event
  88. X-ray transient EP 240315a: Second epoch Chandra observations
  89. Fermi trigger No 733097506: Global MASTER-Net observations report
  90. X-ray transient EP240315a: e-MERLIN radio observations
  91. X-ray transient EP240315a: Ondrejov D50 optical limit
  92. Transient EPW20240219aa: REM optical/NIR further observations
  93. Fermi trigger No 733092476: Global MASTER-Net observations report
  94. GRB 240320A: Glowbug gamma-ray detection
  95. Fermi trigger No 732937833: Global MASTER-Net observations report
  96. GRB 240318A: Fermi GBM Observation
  97. Fermi GRB 240320A: Global MASTER-Net observations report
  98. Konus-Wind detection of GRB 240315C (possible counterpart of EP240315a)
  99. GRB 240315C / X-ray transient EP240315a: Swift/BAT detection
  100. Fermi trigger No 732657380: Global MASTER-Net observations report

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