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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"

15984 results found.

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

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