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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"

20958 results found.

  1. EP 260329b: COLIBRÍ optical observations
  2. EP260329a: Optical upper limit with Kinder observations
  3. EP260329b: LCO optical observations of the counterpart
  4. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  5. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  6. EP260327a: SVOM/VT optical upper limits
  7. SMA Detection of GRB 260310A / AT 2026fgk
  8. GRB 260307B: ATCA Radio Upper Limits
  9. EP260327a: WINTER J-band upper limit
  10. EP260327a: COLIBRÍ optical upper limits
  11. EP260327a: Gemini-North optical upper limits
  12. EP260324a: GROWTH-India Telescope optical observation
  13. EP260327a: Global MASTER-Net observations report
  14. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  15. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  16. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  17. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  18. EP260321a: JinShan near-infrared observations
  19. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  20. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  21. EP260321a: Gemini-South confirmation of a supernova
  22. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  23. GRB 260310A: LBT optical observations
  24. EP260321A: Mondy optical observations
  25. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  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. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  29. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  30. EP260321a: COLIBRÍ further optical observations and brightening
  31. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  32. EP260214b: ATCA 6 GHz detection
  33. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  34. EP260321a: GOTO detection of blue variable source
  35. EP260321a: further Kinder optical observations
  36. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  37. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  38. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  39. EP260321a: SVOM/VT optical upper limit
  40. GRB 260310A: continued optical observation at Mondy
  41. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  42. EP260321a: Global MASTER-Net observations report
  43. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  44. GRB 260310A / AT 2026fgk: KAIT optical observations
  45. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  46. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  47. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  48. GRB 260310A/AT2026fgk: LBT near-infrared observations
  49. NOEMA Detection of GRB 260310A / AT 2026fgk
  50. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  51. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  52. Fermi GRB 260318A: Global MASTER-Net observations report
  53. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  54. GRB 260310A / AT 2026fgk: radio detection with the VLA
  55. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  56. GRB 260310A / AT2026fgk: LCO optical observations
  57. EP260316a: COLIBRÍ faint optical counterpart candidate
  58. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  59. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  60. EP260316a: optical upper limit with Kinder observations
  61. IceCube-260315A: COLIBRÍ optical observations
  62. EP260314a: optical upper limit with Kinder observations
  63. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  64. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  65. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  66. GRB 260310A / AT 2026fgk: iTelescope optical observations
  67. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  68. EP260314a: Global MASTER-Net observations report
  69. Fermi trigger No 795185313: Global MASTER-Net observations report
  70. IceCube Alert 260315A: Global MASTER-Net observations report
  71. GRB 260310A / AT2026fgk: SAO RAS optical observations
  72. GRB 260310A/AT2026fgk: radio detection at 15GHz
  73. GRB 260310A / AT2026fgk: OASDG optical observations
  74. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  75. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  76. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  77. Fermi GRB 260314A: Global MASTER-Net observations report
  78. Fermi GRB 260313A: Global MASTER-Net observations report
  79. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  80. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  81. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  82. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  83. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  84. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  85. GRB260310A / AT2026fgk: P200 Spectroscopy
  86. GRB 260310A: potential optical counterpart
  87. Fermi GRB 260312B: Global MASTER-Net observations report
  88. Fermi GRB 260311B: Global MASTER-Net observations report
  89. GRB 260131A/B: radio detection with the VLA
  90. EP260302a: MeerKAT radio counterpart
  91. Fermi GRB 260310B: Global MASTER-Net observations report
  92. Fermi GRB 260310A: Global MASTER-Net observations report
  93. GRB 260307B: SVOM/ECLAIRs refined analysis
  94. GRB 260208A: radio detection with the VLA
  95. GRB 260307B: possible NOT optical counterpart
  96. GRB 260307B: SVOM/VT upper limit with X band data analysis
  97. Fermi GRB 260307A: Global MASTER-Net observations report
  98. GRB260307B: GROWTH-India Telescope optical upper limit
  99. GRB 260307B: SVOM/C-GFT upper limit
  100. GRB 260211A: late-time NOT i-band observations consistent with archival flux

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