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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').
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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"

20958 results found.

  1. GRB 260511B: NOT optical observations
  2. EP260514a: Global MASTER-Net observations report
  3. GRB 260511B: Mephisto multi-band optical followup
  4. Fermi GRB 260514A: Global MASTER-Net observations report
  5. EP260512a: EP-FXT follow-up observation
  6. EP260507a: Xinglong Schmidt optical counterpart detection
  7. EP260512a: Global MASTER-Net observations report
  8. Fermi GRB 260513A: Global MASTER-Net observations report
  9. Fermi GRB 260512A: Global MASTER-Net observations report
  10. GRB 260511B: further SAO RAS optical observations
  11. GRB 260509A: SVOM/VT optical observations
  12. GRB 260511B: further J-band observations by the SYSU 80 cm infrared telescope
  13. GRB 260511B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  14. GRB 260509A: Infrared J and Hs observations with MDM/MIRAGE
  15. GRB 260510C: Infrared J and Hs detections with MDM/MIRAGE
  16. EP260507a: Infrared J and Hs upper limits with MDM/MIRAGE
  17. GRB 260511B: SAO RAS optical observations
  18. GRB 260511B: FRAM-ORM optical detection
  19. GRB 260511B: LCO optical counterpart detection
  20. GRB260511B: MAO/AZT-22 optical observations
  21. GRB 260511A: SVOM/VT optical observations
  22. GRB 260511B: LCO optical observations
  23. GRB 260511B: OHP/T193 spectroscopic observations
  24. GRB 260511B: GOTO optical counterpart detection
  25. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) further optical observations
  26. GRB 260511B: SVOM/VT optical observations
  27. GRB 260511B: SVOM/COLIBRÍ (FM-GFT) optical observations
  28. GRB 260509A: SAO RAS optical observations
  29. GRB 260511A: REM near-infrared detection
  30. GRB 260511B: GROWTH-India Telescope optical observations
  31. GRB 260511B: J-band observations by the SYSU 80 cm infrared telescope
  32. GRB 260510B: SVOM/ECLAIRs refined analysis
  33. GRB 260511B SVOM/C-GFT optical counterpart detection
  34. GRB 260511A: UTGO H50 optical afterglow observation
  35. GRB 260510C: SVOM/VT optical counterpart confirmation
  36. EP260509a: EP-FXT non-detection and upper limit
  37. GRB 260511A: SVOM/VT optical observation with VHF data
  38. Fermi GRB 260511A: Global MASTER-Net observations report
  39. GRB 260511A: KAIT optical afterglow observations
  40. GRB 260510B: SVOM/VT optical upper limits
  41. GRB 260510C: SVOM/VT optical upper limits
  42. EP260509a: Global MASTER-Net observations report
  43. GRB 260510B: GOTO early upper limit
  44. GRB 260509A: Liverpool Telescope optical observations
  45. GRB 260509A: LCO optical observations
  46. SVOM GRB 260509A: MASTER-OAFA optical observation
  47. Fermi GRB 260510A: Global MASTER-Net observations report
  48. GRB 260509A: KAIT optical observations
  49. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  50. GRB 260509A: SVOM/VT optical candidate with VHF data
  51. GRB 260509A: GOTO optical counterpart candidate
  52. EP260507a: REM optical/NIR observations
  53. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  54. EP260507a: COLIBRÍ optical observations
  55. EP260507a: SVOM/VT optical observations
  56. EP260507a: NOT optical observations
  57. EP260507a: further Liverpool Telescope observations
  58. EP260507a: Liverpool Telescope optical upper limits
  59. EP260507a: GOTO optical counterpart detection
  60. EP260507a: Kinder optical counterpart candidate
  61. GRB 260504B: SVOM/ECLAIRs refined analysis
  62. EP260502a is likely a flaring star
  63. Fermi GRB 260506A: Global MASTER-Net observations report
  64. IceCube Alert 260505A: Global MASTER-Net observations report
  65. GRB 260504B: SVOM/VT optical upper limits
  66. GRB 260421B: radio observation with the VLA
  67. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  68. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  69. GRB 260504B: REM optical/NIR observations
  70. GRB 260504B: AST3-2 i-band upper limit
  71. SVOM GRB 260504B: MASTER-OAFA optical observations
  72. Fermi GRB 260504A: Global MASTER-Net observations report
  73. GRB 260429B / EP260429a: EP-FXT follow-up observation
  74. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  75. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  76. EP260429a: Global MASTER-Net observations report
  77. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  78. Fermi GRB 260429A: Global MASTER-Net observations report
  79. EP260430a: Global MASTER-Net observations report
  80. Fermi GRB 260428A: Global MASTER-Net observations report
  81. GRB 260424B: COLIBRÍ optical upper limit
  82. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  83. IceCube Alert 260425A: Global MASTER-Net observations report
  84. Fermi trigger No 798737427: Global MASTER-Net observations report
  85. EP260321a: Upper limits from ATCA radio observations
  86. GRB 260421B: Kilonova-Catcher optical afterglow detection
  87. The EP-WXT trigger 01709258652: Mondy optical observations
  88. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  89. EP260416a: Mondy optical observations
  90. GRB 260421B: SVOM/ECLAIRs refined analysis
  91. GRB 260421B: 3.6m DOT optical observation
  92. EP260416a: ZTSh R band observations
  93. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  94. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  95. GOTO26djh/AT2026jpw: ATCA radio detection
  96. GRB 260421B: J-band upper limit with WINTER
  97. GRB 260421B: LCO optical counterpart detection
  98. GOTO26djh/AT2026jpw: radio detection at 15GHz
  99. GRB 260412A: SVOM/ECLAIRs refined analysis
  100. GRB 260421B: SVOM/VT optical observations

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