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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"

5512 results found.

  1. Fermi trigger No 802141998: Global MASTER-Net observations report
  2. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  3. EP260602a: COLIBRÍ optical observations
  4. GRB260601B/EP260601a: NOT near-infrared observations
  5. SVOM GRB260603.23: Global MASTER-Net observations report
  6. Fermi GRB 260602B: Global MASTER-Net observations report
  7. Fermi GRB 260602B: Global MASTER-Net observations report
  8. EP260602a: SVOM/VT optical candidate
  9. Fermi trigger No 801900520: Global MASTER-Net observations report
  10. GRB 260531A: MAXI/GSC detection
  11. IPN triangulation of GRB 260527A / EP260527a
  12. GRB 260529A: GOTO tentative optical afterglow candidate
  13. Fermi GRB 260529A: Global MASTER-Net observations report
  14. Fermi trigger No 801580882: Global MASTER-Net observations report
  15. Fermi GRB 260526A: Global MASTER-Net observations report
  16. GRB 260522A: GOTO optical upper limit
  17. GRB 260307A: TERI Gamma-ray detection
  18. GRB 260519B: Fermi GBM Final Localization
  19. GRB 260516D: GOTO optical counterpart detection
  20. GRB 260516D: GTC/OSIRIS+ spectroscopic redshift z = 1.801
  21. Fermi GRB 260516C: Global MASTER-Net observations report
  22. EP260514a: SVOM/VT optical candidate
  23. Fermi GRB 260516B: Global MASTER-Net observations report
  24. EP260514a: COLIBRÍ optical upper limits
  25. SVOM GRB 260515A: Global MASTER-Net observations report
  26. SVOM GRB 260515A: MASTER OT J151044.43+243321.7 optical counterpart detection
  27. Fermi GRB 260512A: Global MASTER-Net observations report
  28. GRB 260511B: further SAO RAS optical observations
  29. GRB 260511B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  30. GRB 260511B: LCO optical counterpart detection
  31. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) further optical observations
  32. GRB 260511B: SVOM/COLIBRÍ (FM-GFT) optical observations
  33. GRB 260511B: SVOM detection of a burst
  34. GRB 260510C: EP-FXT follow-up observation
  35. Fermi GRB 260511A: Global MASTER-Net observations report
  36. GRB 260510C: MAXI/GSC detection
  37. SVOM GRB 260509A: MASTER-OAFA optical observation
  38. Fermi GRB 260510A: Global MASTER-Net observations report
  39. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  40. GRB 260509A: SVOM detection of a burst
  41. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  42. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  43. IPN triangulation of GRB 260428A
  44. SVOM GRB 260504B: MASTER-OAFA optical observations
  45. Fermi GRB 260504A: Global MASTER-Net observations report
  46. EP260430a: LCO optical upper limits
  47. EP260430a: Global MASTER-Net observations report
  48. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  49. Fermi trigger No 798737427: Global MASTER-Net observations report
  50. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  51. Fermi GRB 260421C: Global MASTER-Net observations report
  52. Fermi GRB 260421B: Global MASTER-Net observations report
  53. Fermi GRB 260421A: Global MASTER-Net observations report
  54. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  55. EP260417a: Global MASTER-Net observations report
  56. Fermi GRB 260417A: Global MASTER-Net observations report
  57. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  58. EP260416a: COLIBRÍ optical counterpart candidate
  59. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  60. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  61. Fermi trigger No 797912738: Global MASTER-Net observations report
  62. GRB 260410A: Glowbug gamma-ray detection of a short burst
  63. GRB 260410A: Insight-HXMT/HE detection
  64. Konus-Wind detection of GRB 260410A (short/hard)
  65. EP260321a: SVOM/VT optical observations and color changes around peak
  66. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  67. GRB 260410A: COLIBRÍ optical upper limit
  68. GRB 260410A: Fermi GBM Observation
  69. GRB 260410A: Fermi-LAT detection
  70. GRB 260410A: Fermi GBM Final Real-time Localization
  71. EP260409a: COLIBRÍ optical upper limits
  72. EP260403a: Mephisto optical upper limits
  73. EP260321a: Upper limits from VLA radio observations
  74. EP260405a: Global MASTER-Net observations report
  75. Fermi trigger No 797039833: Global MASTER-Net observations report
  76. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  77. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  78. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  79. GRB 260330B: SVOM/ECLAIRs refined analysis
  80. EP260403a: LCO optical observations of the counterpart
  81. EP260403a: LCO optical counterpart detection
  82. GRB 260330B: SVOM/VT optical candidate
  83. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  84. GRB 260403A: AstroSat CZTI detection
  85. EP260324A / AT 2026hir: COLIBRÍ optical observations
  86. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  87. EP260329b: Mondy and Assy-Turgen optical upper limits
  88. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  89. EP260321a :Xinglong optical observations
  90. EP260327a: Xinglong optical upper limit
  91. EP260329b: GOTO detection of optical counterpart
  92. GRB 260330B: SVOM/VT optical upper limits
  93. GRB 260321A: SVOM/ECLAIRs refined analysis
  94. EP260329b: J-band upper limits with WINTER
  95. EP260329a: J-band upper limit with WINTER
  96. GRB 260330A: Glowbug gamma-ray detection
  97. GRB 260310A: VLA Multi-frequency Radio Observations
  98. Fermi GBM Sub-Threshold Detection of GRB 260330B
  99. GRB 260330B: LCO optical upper limits
  100. GRB 260330B: SVOM detection of a burst

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