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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"

15983 results found.

  1. EP260213a: Optical upper limits with Kinder observations
  2. EP260213a: SVOM/VT optical upper limit
  3. EP260213a: Mondy R-band optical upper limit
  4. EP260213a: NUTTelA-TAO Early Optical Limits
  5. EP/WXT 01709258378: NOT optical upper limits
  6. GRB 260212A: SVOM/GRM observation of a long burst
  7. GRB 260211A: SVOM/VT optical observation
  8. GRB 260211A: GOTO optical upper limit
  9. GRB 260211A: LAST optical upper limit
  10. GRB 260210A: SVOM/GRM observation
  11. GRB 260211A: LCO optical upper limits
  12. GRB260131A/B: 3.6m DOT Optical Observations
  13. GRB 260211A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  14. GRB 260211A: SVOM detection of a burst
  15. EP260209a: COLIBRÍ optical upper limit
  16. EP260209a: LCO optical upper limits
  17. GRB 260208A: LCO detection of the optical counterpart
  18. EP260210a: Optical upper limits with Kinder observations
  19. EP260210a: SVOM/VT optical upper limit
  20. EP260210a: COLIBRÍ optical upper limit
  21. GRB 260208C: SVOM/GRM observation
  22. GRB 260204A: Swift-XRT afterglow detection
  23. GRB260208A: Liverpool Telescope optical follow-up observations
  24. GRB 260208A: NuSTAR detection of prompt emission
  25. GRB 260131A/B: continued Mondy optical observations
  26. GRB 260208B: COLIBRÍ optical observations
  27. GRB 260208A: Mondy optical observations (duplicate submission)
  28. GRB 260208A: Mondy optical observations
  29. GRB 260208A: 1.3m DFOT optical detection
  30. GRB 260208A: COLIBRÍ optical observations
  31. GRB 260208B: EP-FXT observation
  32. GRB 260208A: NOT spectroscopic redshift z = 2.36
  33. GRB 260208A: Liverpool Telescope optical detection
  34. GRB 260208B: SVOM/VT optical candidate
  35. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  36. GRB 260208A: SVOM/VT optical observation
  37. GRB 260208A: Swift-XRT observations
  38. GRB 260208B: SVOM/GRM observation of a bright burst
  39. GRB 260208A: Fermi GBM Classification Correction
  40. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  41. GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
  42. GRB 260207A : MASTER optical counterpart discovery
  43. GRB 260131A/B: Mondy and Terskol optical observations
  44. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  45. GRB 260204A: Swift-XRT observations
  46. GRB 260204A: LCO optical afterglow detection
  47. GRB 260204A: SVOM/VT optical candidate
  48. GRB 260204A : MASTER Global robotic net optical observations
  49. GRB 260204A: GOTO optical upper limit
  50. GRB 260204A: LCO optical upper limits
  51. GRB 260131A/B: OHP/T193 optical observations
  52. GRB 260131A: KAIT optical observations
  53. GRB 251230A: MeerLICHT afterglow detection
  54. GRB 260131A: FTW optical and NIR observations
  55. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  56. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  57. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  58. GRB 260131A/B: EP/FXT X-ray afterglow detection
  59. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  60. GRB 260131A: NOT spectroscopic redshift z = 1.434
  61. EP260131a: Liverpool Telescope optical upper limits
  62. EP260131a: COLIBRÍ further observations
  63. EP260131a: SVOM/VT optical observation
  64. EP260131a: Xinglong optical upper limit
  65. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  66. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  67. EP260131a: COLIBRÍ observations of slow optical fading
  68. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  69. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  70. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  71. EP260131a: COLIBRÍ optical observations of the counterpart
  72. EP260131a: Las Cumbres detection of an optical counterpart
  73. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  74. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  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. IPN triangulation of GRB 260127B (short)
  79. GRB 260127B: Swift-XRT observations
  80. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  81. EP260128a: NOT optical counterpart candidate
  82. EP260128a: Liverpool Telescope optical observations and possible counterpart
  83. EP260128a: LCO optical upper limits
  84. EP260126a: SVOM/VT optical upperlimit
  85. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  86. GRB 260127A: COLIBRÍ optical observations
  87. GRB 260127A: NOT optical observations
  88. EP260126a: Seimei/TriCCS optical upper limit
  89. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  90. GRB 260127B: GOTO candidate optical counterpart
  91. GRB 260127A: SVOM/C-GFT optical observations
  92. GRB 260127A: LCO optical afterglow discovery
  93. EP260126a: Optical upper limit with Kinder observations
  94. EP260126a: Liverpool Telescope optical upper limits
  95. EP260126a: Further NOT optical upper limits
  96. EP260126a: COLIBRÍ optical upper limits
  97. EP260126a: NOT optical observations
  98. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  99. GRB 260125A: GOTO candidate optical counterpart
  100. GRB 260114A: SVOM/VT optical upper limits

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