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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. EP260713a: Einstein Probe detection of an X-ray transient
  2. GRB 260619A: SVOM/VT continuous optical observations
  3. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  4. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  5. EP260623a: KAIT optical observations
  6. EP260711a: EP-FXT follow-up observation
  7. GRB 260708A: GRANDMA Optical Observations
  8. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  9. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  10. GRB 260710A: Insight-HXMT/HE detection
  11. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  12. IceCube-260708A: Upper limits from a search for additional neutrino events in IceCube
  13. IceCube-260712A - IceCube observation of a high-energy neutrino candidate track-like event
  14. GRB 260708A: LCO optical observations
  15. EP260711a: Einstein Probe detection of an X-ray transient
  16. GRB 260710A: Fermi GBM Detection
  17. GRB 260709A: SVOM/GRM detection
  18. GRB 260709A: GECAM-B observation
  19. The EP-WXT trigger 01709274666 is likely a new outburst of the CV SS Cyg
  20. IceCube-260708A: Observations with the Vera C. Rubin Observatory
  21. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  22. GRB 260705C: AstroSat CZTI detection
  23. GRB 260710A: Fermi GBM Final Real-time Localization
  24. GRB 260708A: Glowbug gamma-ray detection
  25. GRB 260704A: SVOM/ECLAIRs refined analysis
  26. GRB 260706A : GRANDMA Upper limits
  27. GRB 260708A: Kilonova-Catcher optical afterglow detection
  28. GRB 260708A: GECAM-B observation of a burst
  29. IceCube-260708A: One candidate from the Zwicky Transient Facility
  30. GRB 260708A: Fermi-GBM observation
  31. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
  32. IceCube Alert 260709A: Global MASTER-Net observations report
  33. GRB 260709A: Fermi GBM Final Real-time Localization
  34. IceCube-260708A - IceCube observation of a high-energy neutrino candidate track-like event
  35. LAT GRB260708.42: Global MASTER-Net observations report
  36. GRB260708B: MAXI/GSC detection
  37. GRB 260708A: Fermi-LAT detection
  38. GRB 260705B: SVOM/GRM observation
  39. GRB 260708A: Fermi-GBM detection
  40. GRB 260706A: Further EP-FXT follow-up observation
  41. GRB 260706A: SVOM/VT optical upper limits
  42. EP260707a (by EP-FXT): NOT optical upper limit
  43. EP260707a is not a real source
  44. EP260707a: LCOGT Optical Upper Limit
  45. EP260707a: TRT optical upper limit
  46. Fermi GBM trigger 805087514/260707142 (GRB 260707A) is not a GRB
  47. EP260707a: Einstein Probe detection of an X-ray transient
  48. Nova AT2026oyp (ASASSN-26dt): Pre-outburst Swift UVOT observation
  49. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  50. GRB 260705C: Glowbug gamma-ray detection of a short burst
  51. GRB 260706A: SVOM/ECLAIRs refined analysis
  52. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  53. GRB 260706A: SVOM/GRM observation
  54. GRB 260706A: REM optical/NIR observations
  55. IceCube-260704A: No candidates from the Zwicky Transient Facility
  56. GRB 260706A: LCO optical upper limit
  57. GRB 260706A: EP-FXT follow-up observation
  58. GRB 260707A: Fermi GBM Final Real-time Localization
  59. The EP-WXT trigger 01709274151 is likely a flaring star
  60. The EP-WXT trigger 01709274141 is likely a flaring star
  61. GRB 260706A: Fermi GBM Observation
  62. IceCube-260704A: Upper limits from a search for additional neutrino events in IceCube
  63. IPN triangulation of GRB 260627A
  64. GRB 260705A: SVOM/ECLAIRs refined analysis
  65. GRB 260706A: SVOM detection of a burst
  66. GRB 260706A: Fermi GBM Final Real-time Localization
  67. The EP-WXT trigger 01709274014: KAIT confirmation of a stellar flare
  68. The EP-WXT trigger 01709274014 is likely a flaring star
  69. IceCube260704A: OHP/T193 optical observations
  70. GRB 260705A: LCO optical upper limits
  71. GRB 260704A: NOT optical upper limits
  72. GRB 260705C: Fermi GBM Final Localization
  73. GRB 260705B: Fermi GBM Final Real-time Localization
  74. Fermi GBM Sub-Threshold Detection of GRB 260705A
  75. GRB 260705A: SVOM detection of a burst
  76. GRB 260704A: EP-FXT follow-up observation
  77. GRB 260629A: SVOM/GRM observation of a short burst
  78. GRB 260629A: GECAM-A observation of a short burst
  79. IceCube-260704A - IceCube observation of a high-energy neutrino candidate track-like event
  80. GRB 260629A: AstroSat CZTI detection
  81. EP260703a: EP-FXT follow-up observation
  82. GRB 260704A: SVOM detection of a possible GRB
  83. GRB 260703B: Fermi GBM Final Localization
  84. EP260703a: EP-WXT detection of a fast X-ray transient
  85. EP260628b: EP-WXT detection of an X-ray transient and EP-FXT follow-up observation
  86. Fermi trigger No 804738310: Global MASTER-Net observations report
  87. Fermi GRB 260703A: Global MASTER-Net observations report
  88. GRB 260703A: Fermi GBM Final Localization
  89. GRB 260610B: VLA detection
  90. GRB 260623A: Glowbug gamma-ray detection
  91. GRB 260614B: ATCA Radio Upper Limits
  92. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  93. Fermi trigger No 804552016: Global MASTER-Net observations report
  94. GRB 260701A: Fermi GBM Final Real-time Localization
  95. Fermi GBM trigger 804552016/260630945 is not a GRB
  96. Fermi-LAT Gamma-ray Observations of IceCube-260622A
  97. EP260628a: EP-FXT follow-up observation
  98. GRB 260629A: Fermi GBM Final Real-time Localization
  99. Fermi GRB 260628A: Global MASTER-Net observations report
  100. EP260628a: EP-WXT detection of a fast X-ray transient

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