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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. EP Alert 260903.62: Global MASTER-Net observations report
  2. GRB 260830A: Insight-HXMT/HE detection
  3. GRB 260903A: EP-FXT follow-up observation
  4. GRB 260903A: OHP/T193 optical afterglow detection
  5. GRB 260903A: NOT optical observations and afterglow fading
  6. NuSTAR Transient 260828: SOAR Optical Upper Limits
  7. SVOM GRB260903.53: Global MASTER-Net observations report
  8. GRB 260903A: LCO optical observations
  9. GRB 260903A: SVOM/VT optical candidate
  10. GRB 260903A: Retraction of optical counterpart of GCN 45501
  11. GRB 260831A: GECAM-B observation
  12. GRB 260903A: LCO optical counterpart detection
  13. GRB 260827A: Insight-HXMT/HE detection
  14. GRB 260903A: SVOM detection of a soft faint burst
  15. EP260901a: SVOM/VT optical upper limits
  16. EP260901a: EP-FXT follow-up observation
  17. Konus-Wind detection of GRB 260829A
  18. GRB 260829A: SVOM/GRM observation
  19. GRB 260818A: ATCA detection of a candidate radio counterpart
  20. EP260830a: EP-FXT follow-up observation
  21. EP260901a: Global MASTER-Net observations report
  22. IceCube-260827A: No transient candidates from the Zwicky Transient Facility
  23. GRB 260831B / sb26083106: SVOM/GWAC-F60A/B confirmation of optical variation of nova V* GK Per
  24. GRB 260831B / sb26083106: SVOM/VT optical variability of V* GK Per
  25. NuSTAR Transient 260828: LCO Optical Upper Limits
  26. EP260901a: EP-WXT detection of a fast X-ray transient
  27. SVOM trigger sb26083106 is not a GRB
  28. GRB 260829A: AstroSat CZTI detection
  29. GRB 260831B: EP-FXT follow-up observation
  30. GRB 260830A: NuSTAR detection of prompt emission
  31. GRB 260831B: LCO optical upper limits
  32. EP260830a: Global MASTER-Net observations report
  33. EP260830a: EP-WXT detection of a fast X-ray transient
  34. GRB 260827A: SVOM/GRM observation
  35. NuSTAR 260828: a 1100s hard X-ray transient
  36. GRB 260831B: SVOM detection of a possible burst
  37. IPN triangulation of GRB 260829A
  38. GRB 260827A: Glowbug gamma-ray detection
  39. EP260727a: ATCA 10 GHz detection
  40. GRB 260831A: Fermi GBM Final Real-time Localization
  41. Fermi-LAT Gamma-ray Observations of IceCube-260827A
  42. Fermi-LAT Gamma-ray Observations of IceCube-260825A
  43. GRB 260829A: GECAM-B observation of a long burst
  44. GRB 260825A: SVOM/GRM observation of a long burst
  45. GRB 260825A: GECAM-B observation
  46. GRB 260829A: Fermi GBM Detection
  47. GRB 260825A: AstroSat CZTI detection
  48. GRB 260829A: BALROG localization (Fermi Trigger 809676494 / GRB 260829256)
  49. GRB 260829A: Fermi GBM Final Real-time Localization
  50. IceCube-260827A: Upper limits from a search for additional neutrino events in IceCube
  51. IceCube-260825A: Upper limits from a search for additional neutrino events in IceCube
  52. IceCube-260825A: Upper limits from a search for additional neutrino events in IceCube
  53. Fermi GBM trigger 809666623/260829141 is not a GRB
  54. GRB 260818B: Further EP-FXT observation
  55. GRB 260818B: VLT optical and nIR observations
  56. GRB 260818B: TNG NIR observations
  57. MAXI GRB260827.40: Global MASTER-Net observations report
  58. IceCube-260827A - IceCube observation of a high-energy neutrino candidate track-like event
  59. The EP-WXT trigger 01709291839 is likely the known LMXB 4U 1745-203
  60. GRB 260827A: Fermi GBM Final Real-time Localization
  61. GRB 260818B: 6 GHz VLA observations
  62. GRB 260818B: SVOM/VT optical upper limit and continuous observations
  63. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  64. GRB 260808B: SAO RAS observations of the optical rebrightening
  65. EP260822a: Global MASTER-Net observations report
  66. EP Alert 260820.31: Global MASTER-Net observations report
  67. IceCube-260825A: No transient candidates from the Zwicky Transient Facility
  68. GRB 260807A: EP-FXT follow-up observations
  69. GRB 260822A: SVOM/ECLAIRs refined analysis
  70. GRB 260809A: SVOM/ECLAIRs refined analysis
  71. GRB 260822A: SVOM/VT optical upper limits
  72. IceCube Alert 260825A: Global MASTER-Net observations report
  73. IceCube-Cascade 260824A: Upper limits from a search for additional neutrino events in IceCube
  74. GRB 260825A: Fermi GBM Final Real-time Localization
  75. IceCube-260825A - IceCube observation of a high-energy neutrino candidate track-like event
  76. GRB 260822A: PRIME near-infrared upper limits from multiple epochs
  77. GRB 260822A: EP/FXT follow-up observations
  78. GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
  79. GRB 260818A: further EP-FXT observations and X-ray afterglow confirmation
  80. EP260822a: EP-FXT non-detection and upper limit
  81. GRB 260822A: Retraction of GOTO optical counterpart detection GCN 45431
  82. GRB 260822A: GOTO optical counterpart detection
  83. GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
  84. GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  85. EP260822a: Einstein Probe detection of a fast X-ray transient
  86. GRB 260822A: LCO optical upper limits
  87. The EP-WXT trigger 01709287395 is likely a flaring star
  88. GRB260822B: Fermi GBM Final Localization
  89. GRB 260822A: GROWTH-India Telescope Upper Limits
  90. GRB 260822A: GOTO optical upper limit
  91. GRB 260822A: SVOM detection of a short burst
  92. Fermi-LAT Gamma-ray Observations of IceCube-260821A
  93. Fermi-LAT Gamma-ray Observations of IceCube-260807A
  94. IceCube-260821A: Upper limits from a search for additional neutrino events in IceCube
  95. GRB 260818B: VLA radio observations
  96. GRB 260818B: SVOM/C-GFT optical upper limit
  97. EP260731a: SVOM/ECLAIRs detection through offline targeted search
  98. IceCube Alert 260821A: Global MASTER-Net observations report
  99. The EP-WXT trigger 01709286204 is likely a flaring star
  100. GRB 260820A: Insight-HXMT/HE detection

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