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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"

17412 results found.

  1. SVOM alert sb26021801: LAST optical upper limit
  2. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  3. The EP-WXT trigger 01709258455 is likely a flaring star
  4. EP-WXT 01709258455: NOT optical upper limits
  5. EP260214b: Mondy optical observations
  6. EP260214b: 1.3m DFOT optical upper limit
  7. EP260210a: Mondy optical upper limits
  8. Konus-Wind detection of GRB 260212A
  9. GRB 260208A: AbAO and Terskol optical upper limits
  10. GRB 260208A: continued Mondy optical observations
  11. IPN triangulation of GRB 260212A
  12. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  13. EP260214b: Liverpool Telescope optical observations
  14. EP260214b: Optical upper limit with Kinder observations
  15. EP260214a: Optical upper limits with Kinder observations
  16. EP260214b: EP-FXT follow-up observation
  17. EP260214b: DDOTI Optical Detection
  18. EP260214b: GROWTH-India Telescope optical upper limit
  19. EP260214a: VLT near-infrared observation
  20. EP260214a: NOT optical upper limits
  21. EP260214a: COLIBRÍ optical upper limits
  22. EP260214b: OHP/T120 optical observations
  23. EP260214a: refined analysis of the EP-FXT observation
  24. EP260214b: LCO optical counterpart detection
  25. EP260214b: COLIBRÍ optical observations
  26. EP260214b: NOT optical counterpart detection
  27. EP260214b: Einstein Probe detection of a fast X-ray transient
  28. EP260214a: Einstein Probe detection of an X-ray transient
  29. EP260213a: Liverpool Telescope optical upper limits
  30. EP260213a: COLIBRÍ optical upper limits
  31. EP260213a: Optical upper limits with Kinder observations
  32. EP260213a: Mondy R-band optical upper limit
  33. EP260213a: SVOM/C-GFT upper limit
  34. EP260213a: refined analysis of the EP-FXT observation
  35. EP260213a: Einstein Probe detection of a fast X-ray transient
  36. EP/WXT 01709258378: NOT optical upper limits
  37. GRB 260212A: SVOM/GRM observation of a long burst
  38. GRB 260211A: EP-FXT follow-up observation
  39. GRB 260211A: LAST optical upper limit
  40. GRB 260210A: SVOM/GRM observation
  41. Konus-Wind detection of GRB 260207B
  42. GRB 260211A: LCO optical upper limits
  43. GRB260131A/B: 3.6m DOT Optical Observations
  44. GRB 260211A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  45. EP260209a: COLIBRÍ optical upper limit
  46. EP260209a: LCO optical upper limits
  47. EP260210a: refined analysis of the EP-FXT observation
  48. GRB 260208A: LCO detection of the optical counterpart
  49. EP260209a: Einstein Probe detection of a fast X-ray transient
  50. EP260210a: Optical upper limits with Kinder observations
  51. GRB 260210A: AstroSat CZTI detection
  52. EP260210a: COLIBRÍ optical upper limit
  53. EP260210a: SVOM/C-GFT upper limit
  54. GRB 260208B: refined analysis of the EP-FXT observation
  55. EP260210a: Einstein Probe detection of an X-ray transient
  56. GRB 260208C: SVOM/GRM observation
  57. GRB 260204A: Swift-XRT afterglow detection
  58. GRB260208A: Liverpool Telescope optical follow-up observations
  59. GRB 260131A/B: continued Mondy optical observations
  60. GRB 260204A: Swift/UVOT Upper Limits
  61. GRB 260208B: COLIBRÍ optical observations
  62. GRB 260208A: Mondy optical observations
  63. GRB 260208A: 1.3m DFOT optical detection
  64. GRB 260208A: COLIBRÍ optical observations
  65. GRB 260208B: EP-FXT observation
  66. GRB 260208A: NOT spectroscopic redshift z = 2.36
  67. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  68. GRB 260209A: Fermi GBM Final Real-time Localization
  69. GRB 260208A: SVOM/VT optical observation
  70. GRB 260208B: SVOM/GRM observation of a bright burst
  71. LAT GRB 260208B: Global MASTER-Net observations report
  72. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  73. GRB 260131A/B: Mondy and Terskol optical observations
  74. GRB 260204A: SVOM/VT optical candidate
  75. GRB 260204A: LCO optical upper limits
  76. EP260110a: Late GTC/EMIR near-infrared observations
  77. GRB 260131A: KAIT optical observations
  78. GRB 251230A: MeerLICHT afterglow detection
  79. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  80. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  81. EP260131a: Liverpool Telescope optical upper limits
  82. EP260131a: COLIBRÍ further observations
  83. EP260131a: SVOM/VT optical observation
  84. EP260131a: Xinglong optical upper limit
  85. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  86. EP260131a: COLIBRÍ observations of slow optical fading
  87. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  88. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  89. EP260131a: COLIBRÍ optical observations of the counterpart
  90. GRB 260127B: AstroSat CZTI detection
  91. EP260131a: Einstein Probe detection of an X-ray transient
  92. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  93. GRB 260128B: LCO optical upper limits
  94. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  95. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  96. GRB 260127B: Swift-XRT observations
  97. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  98. EP260128a: NOT optical counterpart candidate
  99. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  100. EP260128a: Liverpool Telescope optical observations and possible counterpart

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