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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. NuSTAR 260828: a 1100s hard X-ray transient
  2. GRB 260831B: SVOM detection of a possible burst
  3. IPN triangulation of GRB 260829A
  4. GRB 260827A: Glowbug gamma-ray detection
  5. EP260727a: ATCA 10 GHz detection
  6. GRB 260831A: Fermi GBM Final Real-time Localization
  7. Fermi-LAT Gamma-ray Observations of IceCube-260827A
  8. Fermi-LAT Gamma-ray Observations of IceCube-260825A
  9. GRB 260829A: GECAM-B observation of a long burst
  10. GRB 260825A: SVOM/GRM observation of a long burst
  11. GRB 260825A: GECAM-B observation
  12. GRB 260829A: Fermi GBM Detection
  13. GRB 260825A: AstroSat CZTI detection
  14. GRB 260829A: BALROG localization (Fermi Trigger 809676494 / GRB 260829256)
  15. GRB 260829A: Fermi GBM Final Real-time Localization
  16. IceCube-260827A: Upper limits from a search for additional neutrino events in IceCube
  17. IceCube-260825A: Upper limits from a search for additional neutrino events in IceCube
  18. IceCube-260825A: Upper limits from a search for additional neutrino events in IceCube
  19. Fermi GBM trigger 809666623/260829141 is not a GRB
  20. GRB 260818B: Further EP-FXT observation
  21. GRB 260818B: VLT optical and nIR observations
  22. GRB 260818B: TNG NIR observations
  23. MAXI GRB260827.40: Global MASTER-Net observations report
  24. IceCube-260827A - IceCube observation of a high-energy neutrino candidate track-like event
  25. The EP-WXT trigger 01709291839 is likely the known LMXB 4U 1745-203
  26. GRB 260827A: Fermi GBM Final Real-time Localization
  27. GRB 260818B: 6 GHz VLA observations
  28. GRB 260818B: SVOM/VT optical upper limit and continuous observations
  29. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  30. GRB 260808B: SAO RAS observations of the optical rebrightening
  31. EP260822a: Global MASTER-Net observations report
  32. EP Alert 260820.31: Global MASTER-Net observations report
  33. IceCube-260825A: No transient candidates from the Zwicky Transient Facility
  34. GRB 260807A: EP-FXT follow-up observations
  35. GRB 260822A: SVOM/ECLAIRs refined analysis
  36. GRB 260809A: SVOM/ECLAIRs refined analysis
  37. GRB 260822A: SVOM/VT optical upper limits
  38. IceCube Alert 260825A: Global MASTER-Net observations report
  39. IceCube-Cascade 260824A: Upper limits from a search for additional neutrino events in IceCube
  40. GRB 260825A: Fermi GBM Final Real-time Localization
  41. IceCube-260825A - IceCube observation of a high-energy neutrino candidate track-like event
  42. GRB 260822A: PRIME near-infrared upper limits from multiple epochs
  43. GRB 260822A: EP/FXT follow-up observations
  44. GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
  45. GRB 260818A: further EP-FXT observations and X-ray afterglow confirmation
  46. EP260822a: EP-FXT non-detection and upper limit
  47. GRB 260822A: Retraction of GOTO optical counterpart detection GCN 45431
  48. GRB 260822A: GOTO optical counterpart detection
  49. GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
  50. GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  51. EP260822a: Einstein Probe detection of a fast X-ray transient
  52. GRB 260822A: LCO optical upper limits
  53. The EP-WXT trigger 01709287395 is likely a flaring star
  54. GRB260822B: Fermi GBM Final Localization
  55. GRB 260822A: GROWTH-India Telescope Upper Limits
  56. GRB 260822A: GOTO optical upper limit
  57. GRB 260822A: SVOM detection of a short burst
  58. Fermi-LAT Gamma-ray Observations of IceCube-260821A
  59. Fermi-LAT Gamma-ray Observations of IceCube-260807A
  60. IceCube-260821A: Upper limits from a search for additional neutrino events in IceCube
  61. GRB 260818B: VLA radio observations
  62. GRB 260818B: SVOM/C-GFT optical upper limit
  63. EP260731a: SVOM/ECLAIRs detection through offline targeted search
  64. IceCube Alert 260821A: Global MASTER-Net observations report
  65. The EP-WXT trigger 01709286204 is likely a flaring star
  66. GRB 260820A: Insight-HXMT/HE detection
  67. IceCube-260821A - IceCube observation of a high-energy neutrino candidate track-like event
  68. GRB 260818B: SVOM/GRM observation
  69. EP detected a brightening of LMXB 1ES 1735-26.9
  70. GRB260820A: Fermi GBM Final Real-Time Localization
  71. GRB 260818B: Insight-HXMT detection
  72. GRB 260818B: EP-FXT follow-up observation
  73. GRB 260818A: J-band observations with WINTER
  74. GRB 260818B: SVOM/ECLAIRs refined analysis
  75. GRB 260818A: SVOM/ECLAIRs refined analysis
  76. GRB 260818B: NOT optical upper limits
  77. GRB 260810A: SVOM/GRM observation
  78. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  79. GRB260818A: EP-FXT follow-up observation
  80. GRB 260818B: LCO optical upper limits
  81. GRB 260818B: SVOM detection of a short burst
  82. SVOM trigger sb26081806 is not a GRB
  83. EP260806a: SAO RAS multicolor optical observations
  84. GRB 260818A: LCO optical upper limits
  85. EP260812a: AbAO optical upper limit
  86. GRB 260818A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  87. GRB 260810A: Insight-HXMT/HE detection
  88. GRB 260818A: SVOM possible detection of a long and faint GRB
  89. EP260806a: SVOM/ECLAIRs detection through targeted search
  90. EP260806a: NUTTELA-TAO optical observations
  91. The EP-WXT trigger 01709281429 is likely a flaring star
  92. EP260812a: AZT-22 optical upper limit
  93. EP260812b: GTC/OSIRIS+ tentative spectroscopic redshift z = 2.034
  94. EP260806a: WFST optical observations
  95. The EP-WXT trigger 01709280562 is likely a flaring star
  96. EP260812b: Optical upper limit with Kinder
  97. The EP-WXT trigger 01709279838 is likely a flaring star
  98. GRB 260805D: SVOM/GRM detection of a possible magnetar burst
  99. GRB 260808B: Liverpool Telescope further optical observations
  100. GRB 260808B: GTC/OSIRIS+ spectroscopic redshift z = 1.295

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