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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"

16157 results found.

  1. GRB 260511A: REM near-infrared detection
  2. GRB 260511B: GROWTH-India Telescope optical observations
  3. GRB 260511B: J-band observations by the SYSU 80 cm infrared telescope
  4. GRB 260511B: NuSTAR detection of prompt emission
  5. GRB 260511A: NuSTAR detection of prompt emission
  6. GRB 260511B: Fermi GBM Detection
  7. GRB 260511B: SVOM/VT optical observation with VHF data
  8. GRB 260511B: TRT optical observation
  9. GRB 260511B : MITSuME Akeno optical afterglow candidate detection
  10. GRB 260511A: Fermi GBM Detection
  11. GRB 260511B SVOM/C-GFT optical counterpart detection
  12. EP260509a: LCO optical upper limits
  13. GRB 260511A: UTGO H50 optical afterglow observation
  14. GRB 260510C: EP-FXT follow-up observation
  15. GRB 260510C: SVOM/VT optical counterpart confirmation
  16. GRB 260511A: SVOM/VT optical observation with VHF data
  17. GRB 260511A: KAIT optical afterglow observations
  18. GRB 260511A: LCO optical afterglow detection
  19. GRB 260511A: SVOM/COLIBRÍ (FM-GFT) optical counterpart
  20. GRB 260511A: TRT optical counterpart detection
  21. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  22. GRB 260510B: SVOM/VT optical upper limits
  23. GRB 260510C: SVOM/VT optical upper limits
  24. GRB 260510B: GOTO early upper limit
  25. GRB 260510B: LCO optical upper limits
  26. GRB 260509A: Liverpool Telescope optical observations
  27. GRB 260509A: NOT spectroscopic redshift upper limit z < 1.95
  28. GRB 260509A: LCO optical observations
  29. SVOM GRB 260509A: MASTER-OAFA optical observation
  30. GRB 260509A: KAIT optical observations
  31. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  32. GRB 260509A: SVOM/VT optical candidate with VHF data
  33. GRB 260509A: LCO optical counterpart detection
  34. GRB 260509A: GOTO optical counterpart candidate
  35. EP260507a: REM optical/NIR observations
  36. EP260507a: COLIBRÍ optical observations
  37. EP260507a: SVOM/VT optical observations
  38. EP260507a: NOT optical observations
  39. EP260507a: further Liverpool Telescope observations
  40. EP260507a: Liverpool Telescope optical upper limits
  41. EP260507a: GOTO optical counterpart detection
  42. EP260507a: TRT optical counterpart detection
  43. EP260507a: Kinder optical counterpart candidate
  44. EP260507a: LCO optical counterpart
  45. EP260502a is likely a flaring star
  46. GRB 260504B: SVOM/VT optical upper limits
  47. GRB 260502A: SVOM/GRM observation of a short GRB
  48. GRB 260503A: SVOM/GRM observation of a GRB
  49. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  50. GRB 260504B: REM optical/NIR observations
  51. GRB 260504B: AST3-2 i-band upper limit
  52. SVOM GRB 260504B: MASTER-OAFA optical observations
  53. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  54. GRB 260429B / EP260429a: EP-FXT follow-up observation
  55. EP260502a: BOOTES-7: early optical upper limit
  56. EP260502a: Las Cumbres upper limit
  57. GRB 260429A: SVOM/GRM observation of a short burst
  58. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  59. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  60. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  61. EP260429a: LCO optical upper limits
  62. EP260430a: LCO optical upper limits
  63. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  64. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  65. EP260416a: Mondy and Terskol optical upper limits
  66. GRB 260424B: COLIBRÍ optical upper limit
  67. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  68. EP260321a: Upper limits from ATCA radio observations
  69. GRB 260421B: Kilonova-Catcher optical afterglow detection
  70. The EP-WXT trigger 01709258652: Mondy optical observations
  71. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  72. EP260416a: Mondy optical observations
  73. GRB 260421B: 3.6m DOT optical observation
  74. EP260416a: ZTSh R band observations
  75. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  76. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  77. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  78. GRB 260421B: SVOM/GRM observation
  79. GRB 260421B: EP-FXT follow-up observation
  80. GRB 260421B: J-band upper limit with WINTER
  81. GRB 260421B: LCO optical counterpart detection
  82. GRB 260421B: SVOM/VT optical observations
  83. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  84. GRB 260310A: Late-time Chandra X-ray Detection
  85. EP260416a: 1.3m DFOT optical observation
  86. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  87. GRB 260421B: BOOTES-7 early optical afterglow detection
  88. GRB 260421B: LCO optical afterglow confirmation
  89. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  90. GRB 260421B: TRT optical counterpart detection
  91. GRB 260412A: LCOGT Optical Upper Limits
  92. EP260416a: Optical follow-up observations with Kinder
  93. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  94. EP-WXT trigger 01709260303: KAIT optical observations
  95. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  96. GRB 260417A: SVOM/GRM observation
  97. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  98. EP260417a: GROWTH-India Telescope optical upper limit
  99. EP260417b: GROWTH-India Telescope optical upper limit
  100. EP260416a: Ondrejov D50 optical detection

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