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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"

12319 results found.

  1. Fermi GRB 260401A: Global MASTER-Net observations report
  2. GRB 260401A: MAXI/GSC detection
  3. EP260329b: Mondy and Assy-Turgen optical upper limits
  4. EP260327a: Xinglong optical upper limit
  5. GRB 260330B: SVOM/VT optical upper limits
  6. Konus-Wind detection of GRB 260320A
  7. GRB 260321A: SVOM/ECLAIRs refined analysis
  8. EP260329b: J-band upper limits with WINTER
  9. EP260329a: J-band upper limit with WINTER
  10. GRB 260330B: LCO optical upper limits
  11. EP260329a: COLIBRÍ optical upper limit
  12. EP260329a: EP-FXT follow up observation
  13. EP260329b: Global MASTER-Net observations report
  14. Fermi trigger No 796485221: Global MASTER-Net observations report
  15. EP260329b: Optical follow-up with Kinder observations
  16. EP260329a: Optical upper limit with Kinder observations
  17. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  18. EP260327a: SVOM/VT optical upper limits
  19. GRB 260307B: ATCA Radio Upper Limits
  20. EP260327a: WINTER J-band upper limit
  21. EP260327a: COLIBRÍ optical upper limits
  22. EP260327a: Gemini-North optical upper limits
  23. EP260327a: Global MASTER-Net observations report
  24. EP260321a: Upper limits from a neutrino search with IceCube
  25. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  26. Fermi GRB 260323A: Global MASTER-Net observations report
  27. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  28. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  29. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  30. EP260321a: further Kinder optical observations
  31. GRB 260321A: SVOM/VT optical upper limits
  32. EP260321a: Las Cumbres upper limit
  33. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  34. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  35. EP260321a: SVOM/VT optical upper limit
  36. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  37. EP260321a: Global MASTER-Net observations report
  38. Fermi GRB 260318A: Global MASTER-Net observations report
  39. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  40. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  41. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  42. EP260316a: Xinglong optical upper limit
  43. EP260316a: optical upper limit with Kinder observations
  44. EP260314a: Xinglong optical upper limit
  45. EP260314a: optical upper limit with Kinder observations
  46. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  47. EP260314a: COLIBRÍ optical upper limit
  48. EP260314a: BOOTES-6/DPR optical upper limits at early times
  49. EP260314a: Global MASTER-Net observations report
  50. Fermi trigger No 795185313: Global MASTER-Net observations report
  51. IceCube Alert 260315A: Global MASTER-Net observations report
  52. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  53. GRB 260310A/AT2026fgk: radio detection at 15GHz
  54. Fermi GRB 260314A: Global MASTER-Net observations report
  55. Fermi GRB 260313A: Global MASTER-Net observations report
  56. GRB 260310A: NOT optical polarimetry
  57. Fermi GRB 260312B: Global MASTER-Net observations report
  58. Fermi GRB 260311B: Global MASTER-Net observations report
  59. EP260306a: Mondy optical upper limit
  60. Fermi GRB 260310B: Global MASTER-Net observations report
  61. Fermi GRB 260310A: Global MASTER-Net observations report
  62. GRB 260307B: Mephisto optical upper limits
  63. GRB 260307B: SVOM/VT upper limit with X band data analysis
  64. Fermi GRB 260307A: Global MASTER-Net observations report
  65. GRB260307B: GROWTH-India Telescope optical upper limit
  66. GRB 260307B: SVOM/C-GFT upper limit
  67. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  68. EP260302a: Gemini-South redshift z = 1.535
  69. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  70. GRB 260303A: 1.3m DFOT optical upper limit
  71. EP260214b: ATCA 6 GHz observations
  72. Fermi GRB 260305A: Global MASTER-Net observations report
  73. GRB 260303A: J-band observations with WINTER
  74. EP260302a: Global MASTER-Net observations report
  75. Fermi GRB 260303B: Global MASTER-Net observations report
  76. GRB 260228A: CAHA 2.2m telescope optical upper limit
  77. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  78. GRB 260228A: SVOM/VT optical upper limits
  79. GRB 260226A: Asiago r-band upper limit
  80. GRB 260225A: SVOM/VT optical continued observations and upper limit
  81. EP260227a: Global MASTER-Net observations report
  82. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  83. GRB 260225A: WINTER J-band upper limit
  84. GRB 260226A: COLIBRÍ optical upper limits
  85. GRB 260226A: LCOGT Optical Upper Limit
  86. GRB 260226A : GROWTH-India Telescope optical observations
  87. GRB 260226A: LAST optical upper limit
  88. LAT GRB260226.44: Global MASTER-Net observations report
  89. Fermi GRB 260226A: Global MASTER-Net observations report
  90. EP260224a: LCO optical upper limits
  91. GRB 260225A: SVOM/VT optical upper limits
  92. EP260223a: Liverpool Telescope upper limits
  93. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  94. EP260223a: Xinglong optical upper limit
  95. EP260213a: Mephisto optical upper limits
  96. EP260223a: EP-FXT follow-up observation
  97. sb26021801: SVOM/VT optical upper limits
  98. sb26021801: SVOM/C-GFT upper limit
  99. EP260223a: COLIBRÍ optical upper limits
  100. EP260221a: Optical upper limit with Kinder observations

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