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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"

17394 results found.

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

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