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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. Fermi GBM trigger 809666623/260829141 is not a GRB
  2. GRB 260818B: Further EP-FXT observation
  3. GRB 260818B: VLT optical and nIR observations
  4. GRB 260818B: TNG NIR observations
  5. MAXI GRB260827.40: Global MASTER-Net observations report
  6. IceCube-260827A - IceCube observation of a high-energy neutrino candidate track-like event
  7. The EP-WXT trigger 01709291839 is likely the known LMXB 4U 1745-203
  8. GRB 260827A: Fermi GBM Final Real-time Localization
  9. GRB 260818B: 6 GHz VLA observations
  10. GRB 260818B: SVOM/VT optical upper limit and continuous observations
  11. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  12. GRB 260808B: SAO RAS observations of the optical rebrightening
  13. EP260822a: Global MASTER-Net observations report
  14. EP Alert 260820.31: Global MASTER-Net observations report
  15. IceCube-260825A: No transient candidates from the Zwicky Transient Facility
  16. GRB 260807A: EP-FXT follow-up observations
  17. GRB 260822A: SVOM/ECLAIRs refined analysis
  18. GRB 260809A: SVOM/ECLAIRs refined analysis
  19. GRB 260822A: SVOM/VT optical upper limits
  20. IceCube Alert 260825A: Global MASTER-Net observations report
  21. IceCube-Cascade 260824A: Upper limits from a search for additional neutrino events in IceCube
  22. GRB 260825A: Fermi GBM Final Real-time Localization
  23. IceCube-260825A - IceCube observation of a high-energy neutrino candidate track-like event
  24. GRB 260822A: PRIME near-infrared upper limits from multiple epochs
  25. GRB 260822A: EP/FXT follow-up observations
  26. GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
  27. GRB 260818A: further EP-FXT observations and X-ray afterglow confirmation
  28. EP260822a: EP-FXT non-detection and upper limit
  29. GRB 260822A: Retraction of GOTO optical counterpart detection GCN 45431
  30. GRB 260822A: GOTO optical counterpart detection
  31. GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
  32. GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  33. EP260822a: Einstein Probe detection of a fast X-ray transient
  34. GRB 260822A: LCO optical upper limits
  35. The EP-WXT trigger 01709287395 is likely a flaring star
  36. GRB260822B: Fermi GBM Final Localization
  37. GRB 260822A: GROWTH-India Telescope Upper Limits
  38. GRB 260822A: GOTO optical upper limit
  39. GRB 260822A: SVOM detection of a short burst
  40. Fermi-LAT Gamma-ray Observations of IceCube-260821A
  41. Fermi-LAT Gamma-ray Observations of IceCube-260807A
  42. IceCube-260821A: Upper limits from a search for additional neutrino events in IceCube
  43. GRB 260818B: VLA radio observations
  44. GRB 260818B: SVOM/C-GFT optical upper limit
  45. EP260731a: SVOM/ECLAIRs detection through offline targeted search
  46. IceCube Alert 260821A: Global MASTER-Net observations report
  47. The EP-WXT trigger 01709286204 is likely a flaring star
  48. GRB 260820A: Insight-HXMT/HE detection
  49. IceCube-260821A - IceCube observation of a high-energy neutrino candidate track-like event
  50. GRB 260818B: SVOM/GRM observation
  51. EP detected a brightening of LMXB 1ES 1735-26.9
  52. GRB260820A: Fermi GBM Final Real-Time Localization
  53. GRB 260818B: Insight-HXMT detection
  54. GRB 260818B: EP-FXT follow-up observation
  55. GRB 260818A: J-band observations with WINTER
  56. GRB 260818B: SVOM/ECLAIRs refined analysis
  57. GRB 260818A: SVOM/ECLAIRs refined analysis
  58. GRB 260818B: NOT optical upper limits
  59. GRB 260810A: SVOM/GRM observation
  60. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  61. GRB260818A: EP-FXT follow-up observation
  62. GRB 260818B: LCO optical upper limits
  63. GRB 260818B: SVOM detection of a short burst
  64. SVOM trigger sb26081806 is not a GRB
  65. EP260806a: SAO RAS multicolor optical observations
  66. GRB 260818A: LCO optical upper limits
  67. EP260812a: AbAO optical upper limit
  68. GRB 260818A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  69. GRB 260810A: Insight-HXMT/HE detection
  70. GRB 260818A: SVOM possible detection of a long and faint GRB
  71. EP260806a: SVOM/ECLAIRs detection through targeted search
  72. EP260806a: NUTTELA-TAO optical observations
  73. The EP-WXT trigger 01709281429 is likely a flaring star
  74. EP260812a: AZT-22 optical upper limit
  75. EP260812b: GTC/OSIRIS+ tentative spectroscopic redshift z = 2.034
  76. EP260806a: WFST optical observations
  77. The EP-WXT trigger 01709280562 is likely a flaring star
  78. EP260812b: Optical upper limit with Kinder
  79. The EP-WXT trigger 01709279838 is likely a flaring star
  80. GRB 260805D: SVOM/GRM detection of a possible magnetar burst
  81. GRB 260808B: Liverpool Telescope further optical observations
  82. GRB 260808B: GTC/OSIRIS+ spectroscopic redshift z = 1.295
  83. GRB 260813A: BALROG localization (Fermi Trigger 808341387 / GRB 260813803)
  84. GRB 260813A: Fermi GBM Final Real-time Localization
  85. EP260812a: NOT and Liverpool Telescope upper limits:
  86. EP260812b: Liverpool Telescope observations
  87. EP260812b: GOTO detection of the optical counterpart
  88. EP260812a: refined analysis of the EP-WXT and autonomous EP-FXT observation
  89. EP260812a: SVOM/C-GFT optical upper limit
  90. EP260812b: COLIBRÍ optical observations
  91. EP260812b: SVOM/VT optical observation
  92. GRB 260808A: SVOM/GRM observation
  93. EP260812b: Einstein Probe detection of an X-ray transient
  94. EP trigger #01709278129 (EP260812b?): NOT optical counterpart
  95. Fermi GBM Sub-Threshold Detection of GRB 260809A
  96. GRB 260810A: Glowbug gamma-ray detection
  97. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  98. GRB 260810A: AstroSat CZTI detection of a long burst
  99. EP260812a: Einstein Probe detection of an X-ray transient
  100. GRB 260809A: SAO RAS optical observations

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