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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"

5172 results found.

  1. Fermi GBM Sub-Threshold Detection of GRB 260307B
  2. GRB 260307B: Mephisto optical upper limits
  3. GRB 260307B: SVOM/VT upper limit with X band data analysis
  4. Fermi GRB 260307A: Global MASTER-Net observations report
  5. GRB260307B: GROWTH-India Telescope optical upper limit
  6. GRB 260307B: SVOM/VT optical candidate
  7. GRB 260307B: SVOM/C-GFT upper limit
  8. GRB 260307B: SVOM detection of a burst
  9. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  10. EP260302a: SVOM/VT optical observation
  11. EP260306a: SVOM/VT optical observation
  12. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  13. EP260306a: Einstein Probe detection of an X-ray transient
  14. EP260302a: Optical afterglow rebrightening
  15. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  16. GRB 260303A: 1.3m DFOT optical upper limit
  17. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  18. GRB 260303A: SVOM/ECLAIRs refined analysis
  19. Fermi GRB 260305A: Global MASTER-Net observations report
  20. GRB 260303B: AstroSat CZTI detection
  21. GRB 260304A: AstroSat CZTI detection of a long burst
  22. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  23. GRB 260303A: SVOM/VT optical observations
  24. GRB 260303A: J-band observations with WINTER
  25. GRB 260303B: NuSTAR detection of prompt emission
  26. EP260302a: Global MASTER-Net observations report
  27. Fermi GRB 260303B: Global MASTER-Net observations report
  28. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  29. EP260302a: analysis of the follow-up EP-FXT observation
  30. EP260227a: Gemini-South optical observations
  31. EP260302a: LCO observations
  32. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  33. GRB 260303A: SVOM detection of a burst
  34. EP260302a: Einstein Probe detection of an X-ray transient
  35. GRB 260228A: CAHA 2.2m telescope optical upper limit
  36. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  37. EP260227a: further LCO observations
  38. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  39. EP260227a: Liverpool Telescope observations
  40. EP260227a: Global MASTER-Net observations report
  41. GRB 260226A: COLIBRÍ optical upper limits
  42. LAT GRB260226.44: Global MASTER-Net observations report
  43. Fermi GRB 260226A: Global MASTER-Net observations report
  44. EP260224a: LCO optical upper limits
  45. EP260224a: Einstein Probe detection of an X-ray transient
  46. Fermi GRB 260223A: Global MASTER-Net observations report
  47. Fermi GRB 260221B: Global MASTER-Net observations report
  48. Fermi GRB 260221A: Global MASTER-Net observations report
  49. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  50. IceCube Alert 260217A: Global MASTER-Net observations report
  51. GRB 260214B/EP260214b: SVOM/ECLAIRs detection through targeted search
  52. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  53. EP260214b: GROWTH-India Telescope optical upper limit
  54. EP260214a: NOT optical upper limits
  55. EP260214b: Einstein Probe detection of a fast X-ray transient
  56. EP260213a: SVOM/VT optical upper limit
  57. EP260213a: refined analysis of the EP-FXT observation
  58. Fermi GRB 260212A: Global MASTER-Net observations report
  59. Fermi GRB 260210C: Global MASTER-Net observations report
  60. Fermi GRB 260209A: Global MASTER-Net observations report
  61. GRB 260131A/B: continued Mondy optical observations
  62. GRB 260208A: Mondy optical observations
  63. GRB 260208A: Liverpool Telescope optical detection
  64. Fermi GRB 260208C: Global MASTER-Net observations report
  65. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  66. GRB 260206A: Swift-XRT observations
  67. GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
  68. GRB 260204A: Swift-XRT observations
  69. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  70. EP260131a: SVOM/VT optical observation
  71. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  72. GRB 260131B: MAXI/GSC detection
  73. Fermi GRB 260129A: Global MASTER-Net observations report
  74. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  75. GRB 260129B: Fermi GBM Final Localization
  76. Fermi GRB 260127A: Global MASTER-Net observations report
  77. GRB 260127B: GOTO candidate optical counterpart
  78. EP260119a: Mondy and SAO RAS optical upper limits
  79. Fermi GRB 260120C: Global MASTER-Net observations report
  80. EP260116a: COLIBRÍ further observations
  81. SVOM GRB260121.06: Global MASTER-Net observations report
  82. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  83. EP260119a: Global MASTER-Net observations report
  84. Fermi GRB 260115A: Global MASTER-Net observations report
  85. GRB260114A: STEP/T80S optical limits
  86. GRB 251222A: radio detection with the VLA
  87. GRB 260114A: COLIBRÍ optical upper limits
  88. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  89. GRB 260111A: GOTO optical upper limits
  90. Swift trigger 1436759 is not an astrophysical event
  91. GRB 260109A: Fermi GBM Final Real-time Localization
  92. Fermi GRB 260107A: Global MASTER-Net observations report
  93. GRB 260102A: AbAO optical observations
  94. Fermi GRB 260105A: Global MASTER-Net observations report
  95. Fermi GRB 260105B: Global MASTER-Net observations report
  96. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  97. GRB 260101A: COLIBRÍ optical upper limits
  98. EP260105a: Global MASTER-Net observations report
  99. Fermi GRB 260104B: Global MASTER-Net observations report
  100. GRB 260101A: COLIBRÍ optical observations

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