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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').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
  1. GRB 260903A: LCO optical observations
  2. GRB 260903A: SVOM/VT optical candidate
  3. GRB 260903A: Retraction of optical counterpart of GCN 45501
  4. GRB 260831A: GECAM-B observation
  5. GRB 260903A: LCO optical counterpart detection
  6. GRB 260827A: Insight-HXMT/HE detection
  7. GRB 260903A: SVOM detection of a soft faint burst
  8. EP260901a: SVOM/VT optical upper limits
  9. EP260901a: EP-FXT follow-up observation
  10. Konus-Wind detection of GRB 260829A
  11. GRB 260829A: SVOM/GRM observation
  12. GRB 260818A: ATCA detection of a candidate radio counterpart
  13. EP260830a: EP-FXT follow-up observation
  14. EP260901a: Global MASTER-Net observations report
  15. IceCube-260827A: No transient candidates from the Zwicky Transient Facility
  16. GRB 260831B / sb26083106: SVOM/GWAC-F60A/B confirmation of optical variation of nova V* GK Per
  17. GRB 260831B / sb26083106: SVOM/VT optical variability of V* GK Per
  18. NuSTAR Transient 260828: LCO Optical Upper Limits
  19. EP260901a: EP-WXT detection of a fast X-ray transient
  20. SVOM trigger sb26083106 is not a GRB
  21. GRB 260829A: AstroSat CZTI detection
  22. GRB 260831B: EP-FXT follow-up observation
  23. GRB 260830A: NuSTAR detection of prompt emission
  24. GRB 260831B: LCO optical upper limits
  25. EP260830a: Global MASTER-Net observations report
  26. EP260830a: EP-WXT detection of a fast X-ray transient
  27. GRB 260827A: SVOM/GRM observation
  28. NuSTAR 260828: a 1100s hard X-ray transient
  29. GRB 260831B: SVOM detection of a possible burst
  30. IPN triangulation of GRB 260829A
  31. GRB 260827A: Glowbug gamma-ray detection
  32. EP260727a: ATCA 10 GHz detection
  33. GRB 260831A: Fermi GBM Final Real-time Localization
  34. Fermi-LAT Gamma-ray Observations of IceCube-260827A
  35. Fermi-LAT Gamma-ray Observations of IceCube-260825A
  36. GRB 260829A: GECAM-B observation of a long burst
  37. GRB 260825A: SVOM/GRM observation of a long burst
  38. GRB 260825A: GECAM-B observation
  39. GRB 260829A: Fermi GBM Detection
  40. GRB 260825A: AstroSat CZTI detection
  41. GRB 260829A: BALROG localization (Fermi Trigger 809676494 / GRB 260829256)
  42. GRB 260829A: Fermi GBM Final Real-time Localization
  43. IceCube-260827A: Upper limits from a search for additional neutrino events in IceCube
  44. IceCube-260825A: Upper limits from a search for additional neutrino events in IceCube
  45. IceCube-260825A: Upper limits from a search for additional neutrino events in IceCube
  46. Fermi GBM trigger 809666623/260829141 is not a GRB
  47. GRB 260818B: Further EP-FXT observation
  48. GRB 260818B: VLT optical and nIR observations
  49. GRB 260818B: TNG NIR observations
  50. MAXI GRB260827.40: Global MASTER-Net observations report
  51. IceCube-260827A - IceCube observation of a high-energy neutrino candidate track-like event
  52. The EP-WXT trigger 01709291839 is likely the known LMXB 4U 1745-203
  53. GRB 260827A: Fermi GBM Final Real-time Localization
  54. GRB 260818B: 6 GHz VLA observations
  55. GRB 260818B: SVOM/VT optical upper limit and continuous observations
  56. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  57. GRB 260808B: SAO RAS observations of the optical rebrightening
  58. EP260822a: Global MASTER-Net observations report
  59. EP Alert 260820.31: Global MASTER-Net observations report
  60. IceCube-260825A: No transient candidates from the Zwicky Transient Facility
  61. GRB 260807A: EP-FXT follow-up observations
  62. GRB 260822A: SVOM/ECLAIRs refined analysis
  63. GRB 260809A: SVOM/ECLAIRs refined analysis
  64. GRB 260822A: SVOM/VT optical upper limits
  65. IceCube Alert 260825A: Global MASTER-Net observations report
  66. IceCube-Cascade 260824A: Upper limits from a search for additional neutrino events in IceCube
  67. GRB 260825A: Fermi GBM Final Real-time Localization
  68. IceCube-260825A - IceCube observation of a high-energy neutrino candidate track-like event
  69. GRB 260822A: PRIME near-infrared upper limits from multiple epochs
  70. GRB 260822A: EP/FXT follow-up observations
  71. GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
  72. GRB 260818A: further EP-FXT observations and X-ray afterglow confirmation
  73. EP260822a: EP-FXT non-detection and upper limit
  74. GRB 260822A: Retraction of GOTO optical counterpart detection GCN 45431
  75. GRB 260822A: GOTO optical counterpart detection
  76. GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
  77. GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  78. EP260822a: Einstein Probe detection of a fast X-ray transient
  79. GRB 260822A: LCO optical upper limits
  80. The EP-WXT trigger 01709287395 is likely a flaring star
  81. GRB260822B: Fermi GBM Final Localization
  82. GRB 260822A: GROWTH-India Telescope Upper Limits
  83. GRB 260822A: GOTO optical upper limit
  84. GRB 260822A: SVOM detection of a short burst
  85. Fermi-LAT Gamma-ray Observations of IceCube-260821A
  86. Fermi-LAT Gamma-ray Observations of IceCube-260807A
  87. IceCube-260821A: Upper limits from a search for additional neutrino events in IceCube
  88. GRB 260818B: VLA radio observations
  89. GRB 260818B: SVOM/C-GFT optical upper limit
  90. EP260731a: SVOM/ECLAIRs detection through offline targeted search
  91. IceCube Alert 260821A: Global MASTER-Net observations report
  92. The EP-WXT trigger 01709286204 is likely a flaring star
  93. GRB 260820A: Insight-HXMT/HE detection
  94. IceCube-260821A - IceCube observation of a high-energy neutrino candidate track-like event
  95. GRB 260818B: SVOM/GRM observation
  96. EP detected a brightening of LMXB 1ES 1735-26.9
  97. GRB260820A: Fermi GBM Final Real-Time Localization
  98. GRB 260818B: Insight-HXMT detection
  99. GRB 260818B: EP-FXT follow-up observation
  100. GRB 260818A: J-band observations with WINTER

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