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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.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

15984 results found.

  1. EP 260623a: COLIBRÍ optical observations
  2. EP260623a: OSIRIS+/GTC redshift z = 0.703
  3. EP260623a: Las Cumbres discovery of the optical counterpart
  4. GRB 260614B: EP-FXT follow-up observation
  5. EP260618a: Liverpool Telescope optical observations
  6. GRB 260619A: NOT optical observations
  7. GRB 260618B: LCO optical observations
  8. EP260618a: JinShan optical observations
  9. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  10. GRB 260619A: TRT optical counterpart confirmation
  11. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  12. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  13. GRB 260619A: SVOM/VT optical counterpart confirmation
  14. GRB 260618B: SVOM/VT optical candidate
  15. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  16. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  17. GRB 260616A: SVOM/GRM observation
  18. EP260618a: OHP/T193 optical observations
  19. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  20. GRB 260619A: Kilonova-Catcher optical upper limit
  21. EP260618a: EP-FXT follow-up observation
  22. EP260618a: LCO optical counterpart confirmation
  23. EP260618a: COLIBRÍ optical counterpart candidate
  24. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  25. GRB 260610B: AbAO optical observations
  26. EP260616a/GRB 260616B: EP-FXT follow-up observation
  27. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  28. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  29. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  30. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  31. GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
  32. GRB 260610B: Terskol optical observations
  33. GRB 260610B: SVOM/GRM observation
  34. GRB 260614B: SVOM/VT optical afterglow confirmation
  35. GRB 260610B: ALMA detection
  36. GRB 260614B: SVOM/VT optical candidate from VHF data
  37. GRB 260611B: SVOM/GRM detection
  38. GRB 260610B: further Liverpool Telescope optical observations
  39. GRB 260610B: Fermi GBM Observation
  40. GRB 260610B / AT2026owq: GRANDMA optical observations
  41. GRB 260610B / AT2026owq: further SAO RAS optical observations
  42. EP260605a: COLIBRÍ optical upper limits
  43. GRB 260610b: Liverpool Telescope optical observations
  44. EP260610b: Liverpool Telescope optical upper limits
  45. GRB 260610B / AT2026owq: SVOM/VT optical observations
  46. GRB 260610B / AT2026owq: OASDG optical observations
  47. GRB 260610B: IAC-80 Optical observations
  48. GRB 260610B / AT2026owq: SAO RAS optical observations
  49. EP260601a: VLT/X-shooter spectroscopic host galaxy redshift z = 1.068
  50. EP260610b: GTC likely spectroscopic redshift z = 1.10
  51. GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
  52. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  53. GRB 260610B / AT2026owq: Early ATLAS observations
  54. GRB 260610B: TRT optical observation
  55. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  56. EP260610b: COLIBRÍ optical observations
  57. GRB 260610B: DDOTI optical observations
  58. EP260610b: MAO/AZT-22 optical observations
  59. GRB 260610B: GOTO optical counterpart candidate
  60. EP260610b: NOT optical observation
  61. EP260610b: SVOM/VT optical confirmation with blue color
  62. GRB 260515A: SOAR optical observations
  63. EP260610b: Gemini North optical counterpart candidate
  64. EP260610a: SVOM/VT optical upper limits
  65. EP260610a: COLIBRÍ optical upper limits
  66. GRB 260604C: further SAO RAS optical observations
  67. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  68. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  69. GRB 260604C: SVOM/C-GFT upper limit
  70. GRB 260608A: SVOM detection of a burst
  71. GRB 260607A: TRT optical observations
  72. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  73. GRB 260604A: SVOM/GRM detection
  74. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  75. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  76. GRB 260604C: 6 GHz VLA observations
  77. GRB 260604C: SAO RAS optical observations
  78. GRB 260604C: GRANDMA observations
  79. GRB 260604B: SVOM/GRM detection
  80. EP260603a: COLIBRÍ optical upper limit
  81. GRB 260604C: LCO optical upper limit
  82. GRB 260604C: Liverpool Telescope optical detection
  83. EP260602d: EP-FXT follow-up observation
  84. GRB 260604C: GOTO detections of the optical afterglow
  85. GRB 260604C: Correction to GCN 44828
  86. GRB 260604C: Kilonova-Catcher optical afterglow detection
  87. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  88. GRB 260604C: Jinshan optical observations
  89. EP260602b: J-band upper limit with WINTER
  90. GRB 260604C: LAST detection of optical counterpart candidate
  91. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  92. GRB 260604C: SVOM detection of a long burst
  93. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  94. GRB 260603A: NOT optical observations
  95. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  96. EP260602a: EP-FXT follow-up observation
  97. EP260602d: Optical Upper limits with kinder observations
  98. EP260602b: Liverpool Telescope observations
  99. EP260602a: Liverpool Telescope optical upper limits
  100. EP260602b: Liverpool Telescope and LCO observations

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