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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"

5621 results found.

  1. The EP-WXT trigger 01709291839 is likely the known LMXB 4U 1745-203
  2. EP260822a: Global MASTER-Net observations report
  3. IceCube Alert 260825A: Global MASTER-Net observations report
  4. GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
  5. GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
  6. GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  7. GRB 260818B: SVOM/C-GFT optical upper limit
  8. IceCube Alert 260821A: Global MASTER-Net observations report
  9. GRB 260810A: SVOM/GRM observation
  10. GRB 260810A: Insight-HXMT/HE detection
  11. EP260812a: NOT and Liverpool Telescope upper limits:
  12. EP trigger #01709278129 (EP260812b?): NOT optical counterpart
  13. Fermi GBM Sub-Threshold Detection of GRB 260809A
  14. GRB 260810A: Glowbug gamma-ray detection
  15. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  16. GRB 260810A: AstroSat CZTI detection of a long burst
  17. GRB 260809A: SAO RAS optical observations
  18. GRB 260808B: SAO RAS optical observations
  19. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  20. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  21. GRB260809A: MAO/AZT-22 optical observations
  22. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  23. GRB 260808B: Liverpool Telescope optical observations
  24. EP260809a: COLIBRÍ optical observations
  25. Fermi GRB 260808A: Global MASTER-Net observations report
  26. GRB 260709A: cubesat Avion detection
  27. Fermi GRB 260805A: Global MASTER-Net observations report
  28. GRB 260805A: Fermi GBM Final Localization
  29. GRB 260804A: Fermi GBM Final Real-time Localization
  30. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  31. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  32. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  33. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  34. GRB 260705A: Retraction of optical counterpart
  35. GRB 260718A: EP-FXT follow-up observation
  36. Fermi trigger No 806104130: Global MASTER-Net observations report
  37. Fermi GRB 260718A: Global MASTER-Net observations report
  38. GRB 260709A: AstroSat CZTI detection
  39. GRB 260706A: ATCA detection of possible radio counterpart
  40. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  41. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  42. IceCube-260708A: Upper limits from a search for additional neutrino events in IceCube
  43. IceCube-260708A: One candidate from the Zwicky Transient Facility
  44. IceCube Alert 260709A: Global MASTER-Net observations report
  45. EP260707a (by EP-FXT): NOT optical upper limit
  46. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  47. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  48. GRB 260707A: Fermi GBM Final Real-time Localization
  49. The EP-WXT trigger 01709274014: KAIT confirmation of a stellar flare
  50. Fermi trigger No 804738310: Global MASTER-Net observations report
  51. Fermi GRB 260703A: Global MASTER-Net observations report
  52. Fermi trigger No 804552016: Global MASTER-Net observations report
  53. EP260626a: COLIBRÍ optical upper limit
  54. MASS-Cube (GRID 2.0) detection of GRB 260616B
  55. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  56. EP260618a: EP-FXT follow-up observation
  57. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
  58. GRB260616C: MAXI/GSC detection
  59. EP260610b: MAO/AZT-22 optical observations
  60. EP260610a: COLIBRÍ optical upper limits
  61. EP260610a: Einstein Probe detection of a fast X-ray transient
  62. GRB 260609A: Fermi GBM Final Localization
  63. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  64. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  65. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  66. EP260603a: COLIBRÍ optical upper limit
  67. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  68. Fermi GRB 260604C: Global MASTER-Net observations report
  69. Fermi GRB 260604C: Global MASTER-Net observations report
  70. Fermi trigger No 802141998: Global MASTER-Net observations report
  71. SVOM GRB260603.23: Global MASTER-Net observations report
  72. Fermi GRB 260602B: Global MASTER-Net observations report
  73. Fermi GRB 260602B: Global MASTER-Net observations report
  74. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  75. Fermi GRB 260601A: Global MASTER-Net observations report
  76. Fermi trigger No 801900520: Global MASTER-Net observations report
  77. GRB 260531A: MAXI/GSC detection
  78. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  79. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  80. GRB 260522B: Fermi GBM Final Real-time Localization
  81. Fermi trigger No 801135305: Global MASTER-Net observations report
  82. Fermi GRB 260522A: Global MASTER-Net observations report
  83. GRB 260520B: Fermi GBM Final Localization
  84. GRB 260509A: SVOM/ECLAIRs refined analysis
  85. GRB 260509A: CrAO ZTSh optical upper limit
  86. GRB 260515A: CrAO ZTSh BVRI optical observations
  87. Fermi GRB 260516C: Global MASTER-Net observations report
  88. GRB 260515A: SVOM/COLIBRÍ (FM-GFT) optical observations
  89. GRID detection of GRB 260507A
  90. SVOM GRB 260515A: Global MASTER-Net observations report
  91. EP260507a: Xinglong Schmidt optical counterpart detection
  92. Fermi GRB 260512A: Global MASTER-Net observations report
  93. EP260512a: COLIBRÍ optical upper limits
  94. MASS-Cube (GRID 2.0) detection of GRB 260507A
  95. GRB 260511B: SAO RAS optical observations
  96. GRB 260511B: GOTO optical counterpart detection
  97. GRB 260511B: SVOM/VT optical observations
  98. Fermi GRB 260511A: Global MASTER-Net observations report
  99. GRB 260509A: Liverpool Telescope optical observations
  100. GRB 260509A: SVOM/VT optical candidate with VHF data

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