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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"

5624 results found.

  1. GRB 260825A: AstroSat CZTI detection
  2. GRB 260829A: BALROG localization (Fermi Trigger 809676494 / GRB 260829256)
  3. GRB 260829A: Fermi GBM Final Real-time Localization
  4. The EP-WXT trigger 01709291839 is likely the known LMXB 4U 1745-203
  5. EP260822a: Global MASTER-Net observations report
  6. IceCube Alert 260825A: Global MASTER-Net observations report
  7. GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
  8. GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
  9. GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  10. GRB 260818B: SVOM/C-GFT optical upper limit
  11. IceCube Alert 260821A: Global MASTER-Net observations report
  12. GRB 260810A: SVOM/GRM observation
  13. GRB 260810A: Insight-HXMT/HE detection
  14. EP260812a: NOT and Liverpool Telescope upper limits:
  15. EP trigger #01709278129 (EP260812b?): NOT optical counterpart
  16. Fermi GBM Sub-Threshold Detection of GRB 260809A
  17. GRB 260810A: Glowbug gamma-ray detection
  18. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  19. GRB 260810A: AstroSat CZTI detection of a long burst
  20. GRB 260809A: SAO RAS optical observations
  21. GRB 260808B: SAO RAS optical observations
  22. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  23. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  24. GRB260809A: MAO/AZT-22 optical observations
  25. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  26. GRB 260808B: Liverpool Telescope optical observations
  27. EP260809a: COLIBRÍ optical observations
  28. Fermi GRB 260808A: Global MASTER-Net observations report
  29. GRB 260709A: cubesat Avion detection
  30. Fermi GRB 260805A: Global MASTER-Net observations report
  31. GRB 260805A: Fermi GBM Final Localization
  32. GRB 260804A: Fermi GBM Final Real-time Localization
  33. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  34. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  35. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  36. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  37. GRB 260705A: Retraction of optical counterpart
  38. GRB 260718A: EP-FXT follow-up observation
  39. Fermi trigger No 806104130: Global MASTER-Net observations report
  40. Fermi GRB 260718A: Global MASTER-Net observations report
  41. GRB 260709A: AstroSat CZTI detection
  42. GRB 260706A: ATCA detection of possible radio counterpart
  43. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  44. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  45. IceCube-260708A: Upper limits from a search for additional neutrino events in IceCube
  46. IceCube-260708A: One candidate from the Zwicky Transient Facility
  47. IceCube Alert 260709A: Global MASTER-Net observations report
  48. EP260707a (by EP-FXT): NOT optical upper limit
  49. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  50. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  51. GRB 260707A: Fermi GBM Final Real-time Localization
  52. The EP-WXT trigger 01709274014: KAIT confirmation of a stellar flare
  53. Fermi trigger No 804738310: Global MASTER-Net observations report
  54. Fermi GRB 260703A: Global MASTER-Net observations report
  55. Fermi trigger No 804552016: Global MASTER-Net observations report
  56. EP260626a: COLIBRÍ optical upper limit
  57. MASS-Cube (GRID 2.0) detection of GRB 260616B
  58. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  59. EP260618a: EP-FXT follow-up observation
  60. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
  61. GRB260616C: MAXI/GSC detection
  62. EP260610b: MAO/AZT-22 optical observations
  63. EP260610a: COLIBRÍ optical upper limits
  64. EP260610a: Einstein Probe detection of a fast X-ray transient
  65. GRB 260609A: Fermi GBM Final Localization
  66. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  67. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  68. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  69. EP260603a: COLIBRÍ optical upper limit
  70. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  71. Fermi GRB 260604C: Global MASTER-Net observations report
  72. Fermi GRB 260604C: Global MASTER-Net observations report
  73. Fermi trigger No 802141998: Global MASTER-Net observations report
  74. SVOM GRB260603.23: Global MASTER-Net observations report
  75. Fermi GRB 260602B: Global MASTER-Net observations report
  76. Fermi GRB 260602B: Global MASTER-Net observations report
  77. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  78. Fermi GRB 260601A: Global MASTER-Net observations report
  79. Fermi trigger No 801900520: Global MASTER-Net observations report
  80. GRB 260531A: MAXI/GSC detection
  81. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  82. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  83. GRB 260522B: Fermi GBM Final Real-time Localization
  84. Fermi trigger No 801135305: Global MASTER-Net observations report
  85. Fermi GRB 260522A: Global MASTER-Net observations report
  86. GRB 260520B: Fermi GBM Final Localization
  87. GRB 260509A: SVOM/ECLAIRs refined analysis
  88. GRB 260509A: CrAO ZTSh optical upper limit
  89. GRB 260515A: CrAO ZTSh BVRI optical observations
  90. Fermi GRB 260516C: Global MASTER-Net observations report
  91. GRB 260515A: SVOM/COLIBRÍ (FM-GFT) optical observations
  92. GRID detection of GRB 260507A
  93. SVOM GRB 260515A: Global MASTER-Net observations report
  94. EP260507a: Xinglong Schmidt optical counterpart detection
  95. Fermi GRB 260512A: Global MASTER-Net observations report
  96. EP260512a: COLIBRÍ optical upper limits
  97. MASS-Cube (GRID 2.0) detection of GRB 260507A
  98. GRB 260511B: SAO RAS optical observations
  99. GRB 260511B: GOTO optical counterpart detection
  100. GRB 260511B: SVOM/VT optical observations

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