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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 260714B: Fermi GBM Final Real-time Localization
  2. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  3. GRB 260706A: ATCA detection of possible radio counterpart
  4. GRB 260705A: ATCA radio observations
  5. GRB 260714A: Fermi GBM Final Real-time Localization
  6. EP260713a: Einstein Probe detection of an X-ray transient
  7. GRB 260619A: SVOM/VT continuous optical observations
  8. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  9. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  10. EP260623a: KAIT optical observations
  11. EP260711a: EP-FXT follow-up observation
  12. GRB 260708A: GRANDMA Optical Observations
  13. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  14. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  15. GRB 260710A: Insight-HXMT/HE detection
  16. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  17. IceCube-260708A: Upper limits from a search for additional neutrino events in IceCube
  18. IceCube-260712A - IceCube observation of a high-energy neutrino candidate track-like event
  19. GRB 260708A: LCO optical observations
  20. EP260711a: Einstein Probe detection of an X-ray transient
  21. GRB 260710A: Fermi GBM Detection
  22. GRB 260709A: SVOM/GRM detection
  23. GRB 260709A: GECAM-B observation
  24. The EP-WXT trigger 01709274666 is likely a new outburst of the CV SS Cyg
  25. IceCube-260708A: Observations with the Vera C. Rubin Observatory
  26. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  27. GRB 260705C: AstroSat CZTI detection
  28. GRB 260710A: Fermi GBM Final Real-time Localization
  29. GRB 260708A: Glowbug gamma-ray detection
  30. GRB 260704A: SVOM/ECLAIRs refined analysis
  31. GRB 260706A : GRANDMA Upper limits
  32. GRB 260708A: Kilonova-Catcher optical afterglow detection
  33. GRB 260708A: GECAM-B observation of a burst
  34. IceCube-260708A: One candidate from the Zwicky Transient Facility
  35. GRB 260708A: Fermi-GBM observation
  36. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
  37. IceCube Alert 260709A: Global MASTER-Net observations report
  38. GRB 260709A: Fermi GBM Final Real-time Localization
  39. IceCube-260708A - IceCube observation of a high-energy neutrino candidate track-like event
  40. LAT GRB260708.42: Global MASTER-Net observations report
  41. GRB260708B: MAXI/GSC detection
  42. GRB 260708A: Fermi-LAT detection
  43. GRB 260705B: SVOM/GRM observation
  44. GRB 260708A: Fermi-GBM detection
  45. GRB 260706A: Further EP-FXT follow-up observation
  46. GRB 260706A: SVOM/VT optical upper limits
  47. EP260707a (by EP-FXT): NOT optical upper limit
  48. EP260707a is not a real source
  49. EP260707a: LCOGT Optical Upper Limit
  50. EP260707a: TRT optical upper limit
  51. Fermi GBM trigger 805087514/260707142 (GRB 260707A) is not a GRB
  52. EP260707a: Einstein Probe detection of an X-ray transient
  53. Nova AT2026oyp (ASASSN-26dt): Pre-outburst Swift UVOT observation
  54. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  55. GRB 260705C: Glowbug gamma-ray detection of a short burst
  56. GRB 260706A: SVOM/ECLAIRs refined analysis
  57. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  58. GRB 260706A: SVOM/GRM observation
  59. GRB 260706A: REM optical/NIR observations
  60. IceCube-260704A: No candidates from the Zwicky Transient Facility
  61. GRB 260706A: LCO optical upper limit
  62. GRB 260706A: EP-FXT follow-up observation
  63. GRB 260707A: Fermi GBM Final Real-time Localization
  64. The EP-WXT trigger 01709274151 is likely a flaring star
  65. The EP-WXT trigger 01709274141 is likely a flaring star
  66. GRB 260706A: Fermi GBM Observation
  67. IceCube-260704A: Upper limits from a search for additional neutrino events in IceCube
  68. IPN triangulation of GRB 260627A
  69. GRB 260705A: SVOM/ECLAIRs refined analysis
  70. GRB 260706A: SVOM detection of a burst
  71. GRB 260706A: Fermi GBM Final Real-time Localization
  72. The EP-WXT trigger 01709274014: KAIT confirmation of a stellar flare
  73. The EP-WXT trigger 01709274014 is likely a flaring star
  74. IceCube260704A: OHP/T193 optical observations
  75. GRB 260705A: LCO optical upper limits
  76. GRB 260704A: NOT optical upper limits
  77. GRB 260705C: Fermi GBM Final Localization
  78. GRB 260705B: Fermi GBM Final Real-time Localization
  79. Fermi GBM Sub-Threshold Detection of GRB 260705A
  80. GRB 260705A: SVOM detection of a burst
  81. GRB 260704A: EP-FXT follow-up observation
  82. GRB 260629A: SVOM/GRM observation of a short burst
  83. GRB 260629A: GECAM-A observation of a short burst
  84. IceCube-260704A - IceCube observation of a high-energy neutrino candidate track-like event
  85. GRB 260629A: AstroSat CZTI detection
  86. EP260703a: EP-FXT follow-up observation
  87. GRB 260704A: SVOM detection of a possible GRB
  88. GRB 260703B: Fermi GBM Final Localization
  89. EP260703a: EP-WXT detection of a fast X-ray transient
  90. EP260628b: EP-WXT detection of an X-ray transient and EP-FXT follow-up observation
  91. Fermi trigger No 804738310: Global MASTER-Net observations report
  92. Fermi GRB 260703A: Global MASTER-Net observations report
  93. GRB 260703A: Fermi GBM Final Localization
  94. GRB 260610B: VLA detection
  95. GRB 260623A: Glowbug gamma-ray detection
  96. GRB 260614B: ATCA Radio Upper Limits
  97. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  98. Fermi trigger No 804552016: Global MASTER-Net observations report
  99. GRB 260701A: Fermi GBM Final Real-time Localization
  100. Fermi GBM trigger 804552016/260630945 is not a GRB

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