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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: J-band upper limit with WINTER
  2. EP Alert 260903.47: Global MASTER-Net observations report
  3. GRB 260903A: SVOM/ECLAIRs refined analysis
  4. GRB260903A: Liverpool Telescope optical observations
  5. GRB 260903A: SAO RAS optical observations
  6. GRB 260830A: GECAM-B detection of a burst
  7. EP260903a: EP-WXT detection of a fast X-ray transient
  8. EP Alert 260903.62: Global MASTER-Net observations report
  9. GRB 260830A: Insight-HXMT/HE detection
  10. GRB 260903A: EP-FXT follow-up observation
  11. GRB 260903A: OHP/T193 optical afterglow detection
  12. GRB 260903A: NOT optical observations and afterglow fading
  13. NuSTAR Transient 260828: SOAR Optical Upper Limits
  14. SVOM GRB260903A: Global MASTER-Net observations report
  15. GRB 260903A: LCO optical observations
  16. GRB 260903A: SVOM/VT optical candidate
  17. GRB 260903A: Retraction of optical counterpart of GCN 45501
  18. GRB 260831A: GECAM-B observation
  19. GRB 260903A: LCO optical counterpart detection
  20. GRB 260827A: Insight-HXMT/HE detection
  21. GRB 260903A: SVOM detection of a soft faint burst
  22. EP260901a: SVOM/VT optical upper limits
  23. EP260901a: EP-FXT follow-up observation
  24. Konus-Wind detection of GRB 260829A
  25. GRB 260829A: SVOM/GRM observation
  26. GRB 260818A: ATCA detection of a candidate radio counterpart
  27. EP260830a: EP-FXT follow-up observation
  28. EP260901a: Global MASTER-Net observations report
  29. IceCube-260827A: No transient candidates from the Zwicky Transient Facility
  30. GRB 260831B / sb26083106: SVOM/GWAC-F60A/B confirmation of optical variation of nova V* GK Per
  31. GRB 260831B / sb26083106: SVOM/VT optical variability of V* GK Per
  32. NuSTAR Transient 260828: LCO Optical Upper Limits
  33. EP260901a: EP-WXT detection of a fast X-ray transient
  34. SVOM trigger sb26083106 is not a GRB
  35. GRB 260829A: AstroSat CZTI detection
  36. GRB 260831B: EP-FXT follow-up observation
  37. GRB 260830A: NuSTAR detection of prompt emission
  38. GRB 260831B: LCO optical upper limits
  39. EP260830a: Global MASTER-Net observations report
  40. EP260830a: EP-WXT detection of a fast X-ray transient
  41. GRB 260827A: SVOM/GRM observation
  42. NuSTAR 260828: a 1100s hard X-ray transient
  43. GRB 260831B: SVOM detection of a possible burst
  44. IPN triangulation of GRB 260829A
  45. GRB 260827A: Glowbug gamma-ray detection
  46. EP260727a: ATCA 10 GHz detection
  47. GRB 260831A: Fermi GBM Final Real-time Localization
  48. Fermi-LAT Gamma-ray Observations of IceCube-260827A
  49. Fermi-LAT Gamma-ray Observations of IceCube-260825A
  50. GRB 260829A: GECAM-B observation of a long burst
  51. GRB 260825A: SVOM/GRM observation of a long burst
  52. GRB 260825A: GECAM-B observation
  53. GRB 260829A: Fermi GBM Detection
  54. GRB 260825A: AstroSat CZTI detection
  55. GRB 260829A: BALROG localization (Fermi Trigger 809676494 / GRB 260829256)
  56. GRB 260829A: Fermi GBM Final Real-time Localization
  57. IceCube-260827A: Upper limits from a search for additional neutrino events in IceCube
  58. IceCube-260825A: Upper limits from a search for additional neutrino events in IceCube
  59. IceCube-260825A: Upper limits from a search for additional neutrino events in IceCube
  60. Fermi GBM trigger 809666623/260829141 is not a GRB
  61. GRB 260818B: Further EP-FXT observation
  62. GRB 260818B: VLT optical and nIR observations
  63. GRB 260818B: TNG NIR observations
  64. MAXI GRB260827.40: Global MASTER-Net observations report
  65. IceCube-260827A - IceCube observation of a high-energy neutrino candidate track-like event
  66. The EP-WXT trigger 01709291839 is likely the known LMXB 4U 1745-203
  67. GRB 260827A: Fermi GBM Final Real-time Localization
  68. GRB 260818B: 6 GHz VLA observations
  69. GRB 260818B: SVOM/VT optical upper limit and continuous observations
  70. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  71. GRB 260808B: SAO RAS observations of the optical rebrightening
  72. EP260822a: Global MASTER-Net observations report
  73. EP Alert 260820.31: Global MASTER-Net observations report
  74. IceCube-260825A: No transient candidates from the Zwicky Transient Facility
  75. GRB 260807A: EP-FXT follow-up observations
  76. GRB 260822A: SVOM/ECLAIRs refined analysis
  77. GRB 260809A: SVOM/ECLAIRs refined analysis
  78. GRB 260822A: SVOM/VT optical upper limits
  79. IceCube Alert 260825A: Global MASTER-Net observations report
  80. IceCube-Cascade 260824A: Upper limits from a search for additional neutrino events in IceCube
  81. GRB 260825A: Fermi GBM Final Real-time Localization
  82. IceCube-260825A - IceCube observation of a high-energy neutrino candidate track-like event
  83. GRB 260822A: PRIME near-infrared upper limits from multiple epochs
  84. GRB 260822A: EP/FXT follow-up observations
  85. GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
  86. GRB 260818A: further EP-FXT observations and X-ray afterglow confirmation
  87. EP260822a: EP-FXT non-detection and upper limit
  88. GRB 260822A: Retraction of GOTO optical counterpart detection GCN 45431
  89. GRB 260822A: GOTO optical counterpart detection
  90. GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
  91. GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  92. EP260822a: Einstein Probe detection of a fast X-ray transient
  93. GRB 260822A: LCO optical upper limits
  94. The EP-WXT trigger 01709287395 is likely a flaring star
  95. GRB260822B: Fermi GBM Final Localization
  96. GRB 260822A: GROWTH-India Telescope Upper Limits
  97. GRB 260822A: GOTO optical upper limit
  98. GRB 260822A: SVOM detection of a short burst
  99. Fermi-LAT Gamma-ray Observations of IceCube-260821A
  100. Fermi-LAT Gamma-ray Observations of IceCube-260807A

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