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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"

17396 results found.

  1. EP260214b: DDOTI Optical Detection
  2. EP260214b: GROWTH-India Telescope optical upper limit
  3. EP250214a: VLT near-infrared observation
  4. EP260214a: NOT optical upper limits
  5. EP260214a: COLIBRÍ optical upper limits
  6. EP260214b: OHP/T120 optical observations
  7. EP260214a: refined analysis of the EP-FXT observation
  8. EP260214b: LCO optical counterpart detection
  9. EP260214b: COLIBRÍ optical observations
  10. EP260214b: NOT optical counterpart detection
  11. EP260214b: Einstein Probe detection of a fast X-ray transient
  12. EP260214a: Einstein Probe detection of an X-ray transient
  13. EP260213a: Liverpool Telescope optical upper limits
  14. EP260213a: COLIBRÍ optical upper limits
  15. EP260213a: Optical upper limits with Kinder observations
  16. EP260213a: Mondy R-band optical upper limit
  17. EP260213a: SVOM/C-GFT upper limit
  18. EP260213a: refined analysis of the EP-FXT observation
  19. EP260213a: Einstein Probe detection of a fast X-ray transient
  20. EP/WXT 01709258378: NOT optical upper limits
  21. GRB 260212A: SVOM/GRM observation of a long burst
  22. GRB 260211A: EP-FXT follow-up observation
  23. GRB 260211A: LAST optical upper limit
  24. GRB 260210A: SVOM/GRM observation
  25. Konus-Wind detection of GRB 260207B
  26. GRB 260211A: LCO optical upper limits
  27. GRB260131A/B: 3.6m DOT Optical Observations
  28. GRB 260211A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  29. EP260209a: COLIBRÍ optical upper limit
  30. EP260209a: LCO optical upper limits
  31. EP260210a: refined analysis of the EP-FXT observation
  32. GRB 260208A: LCO detection of the optical counterpart
  33. EP260209a: Einstein Probe detection of a fast X-ray transient
  34. EP260210a: Optical upper limits with Kinder observations
  35. GRB 260210A: AstroSat CZTI detection
  36. EP260210a: COLIBRÍ optical upper limit
  37. EP260210a: SVOM/C-GFT upper limit
  38. GRB 260208B: refined analysis of the EP-FXT observation
  39. EP260210a: Einstein Probe detection of an X-ray transient
  40. GRB 260208C: SVOM/GRM observation
  41. GRB 260204A: Swift-XRT afterglow detection
  42. GRB260208A: Liverpool Telescope optical follow-up observations
  43. GRB 260131A/B: continued Mondy optical observations
  44. GRB 260204A: Swift/UVOT Upper Limits
  45. GRB 260208B: COLIBRÍ optical observations
  46. GRB 260208A: Mondy optical observations
  47. GRB 260208A: 1.3m DFOT optical detection
  48. GRB 260208A: COLIBRÍ optical observations
  49. GRB 260208B: EP-FXT observation
  50. GRB 260208A: NOT spectroscopic redshift z = 2.36
  51. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  52. GRB 260209A: Fermi GBM Final Real-time Localization
  53. GRB 260208A: SVOM/VT optical observation
  54. GRB 260208B: SVOM/GRM observation of a bright burst
  55. LAT GRB 260208B: Global MASTER-Net observations report
  56. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  57. GRB 260131A/B: Mondy and Terskol optical observations
  58. GRB 260204A: SVOM/VT optical candidate
  59. GRB 260204A: LCO optical upper limits
  60. EP260110a: Late GTC/EMIR near-infrared observations
  61. GRB 260131A: KAIT optical observations
  62. GRB 251230A: MeerLICHT afterglow detection
  63. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  64. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  65. EP260131a: Liverpool Telescope optical upper limits
  66. EP260131a: COLIBRÍ further observations
  67. EP260131a: SVOM/VT optical observation
  68. EP260131a: Xinglong optical upper limit
  69. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  70. EP260131a: COLIBRÍ observations of slow optical fading
  71. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  72. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  73. EP260131a: COLIBRÍ optical observations of the counterpart
  74. GRB 260127B: AstroSat CZTI detection
  75. EP260131a: Einstein Probe detection of an X-ray transient
  76. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  77. GRB 260128B: LCO optical upper limits
  78. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  79. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  80. GRB 260127B: Swift-XRT observations
  81. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  82. EP260128a: NOT optical counterpart candidate
  83. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  84. EP260128a: Liverpool Telescope optical observations and possible counterpart
  85. EP260128a: LCO optical upper limits
  86. EP260128a: Einstein Probe detection of an X-ray transient
  87. GRB 260127A: COLIBRÍ optical observations
  88. EP260126a: Seimei/TriCCS optical upper limit
  89. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  90. GRB 260127A: Swift-XRT refined Analysis
  91. GRB 260127B: GOTO candidate optical counterpart
  92. GRB 260127A: SVOM/C-GFT optical observations
  93. The EP-WXT trigger 01709253145 is likely a flaring star
  94. GRB 260127A: Enhanced Swift-XRT position
  95. GRB 260127A: LCO optical afterglow discovery
  96. GRB 260127A: Swift detection of a burst
  97. GRB 260125A: Swift-XRT observations
  98. EP260126a: EP-FXT follow-up observation
  99. EP260126a: Optical upper limit with Kinder observations
  100. EP260126a: Liverpool Telescope optical upper limits

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