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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"

36180 results found.

  1. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  2. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  3. GRB 260429A: Fermi GBM Detection
  4. Fermi GRB 260429A: Global MASTER-Net observations report
  5. GRB 260429A: Fermi GBM Final Real-time Localization
  6. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  7. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  8. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  9. GRB 260428A: AstroSat CZTI detection
  10. Fermi GRB 260428A: Global MASTER-Net observations report
  11. EP260416a: Mondy and Terskol optical upper limits
  12. GRB 260424B: Glowbug gamma-ray detection of a short burst
  13. GRB 260424B: COLIBRÍ optical upper limit
  14. Konus-Wind detection of GRB 260424B
  15. GRB 260428A: Fermi GBM Final Real-time Localization
  16. GRB 260424C: Fermi GBM Final Localization
  17. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  18. IPN triangulation of GRB 260424B (short)
  19. GRB 260424B: SVOM/GRM detection of a short burst
  20. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  21. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  22. GRB 260401A: cubesat Avion detection
  23. GRB 260424A: AstroSat CZTI detection of a long burst
  24. GRB 260421B: Kilonova-Catcher optical afterglow detection
  25. GRB 260421B: Insight-HXMT/HE detection
  26. The EP-WXT trigger 01709258652: Mondy optical observations
  27. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  28. EP260416a: Mondy optical observations
  29. GRB 260421B: SVOM/ECLAIRs refined analysis
  30. GRB 260421B: 3.6m DOT optical observation
  31. EP260416a: ZTSh R band observations
  32. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  33. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  34. GRB 260419A: AstroSat CZTI detection
  35. GRB 260421B: SVOM/GRM observation
  36. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  37. GRB 260421B: EP-FXT follow-up observation
  38. GRB 260421B: J-band upper limit with WINTER
  39. GRB 260421B: LCO optical counterpart detection
  40. GRB 260421B: Fermi GBM Observation
  41. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  42. GRB 260421A: AstroSat CZTI detection
  43. GRB 260412A: SVOM/ECLAIRs refined analysis
  44. GRB 260421B: SVOM/VT optical observations
  45. GRB 260310A: Late-time Chandra X-ray Detection
  46. GRB 260418A: Insight-HXMT/HE detection
  47. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  48. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  49. Fermi GRB 260421C: Global MASTER-Net observations report
  50. GRB 260421C: Fermi GBM Final Real-time Localization
  51. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  52. Fermi GRB 260421B: Global MASTER-Net observations report
  53. GRB 260421B: BOOTES-7 early optical afterglow detection
  54. GRB 260421B: LCO optical afterglow confirmation
  55. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  56. GRB 260421B: TRT optical counterpart detection
  57. GRB 260421B: SVOM detection of a long burst
  58. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  59. GRB 260421B: Fermi GBM Final Real-time Localization
  60. Fermi GRB 260421A: Global MASTER-Net observations report
  61. GRB 260421A: Fermi GBM Final Real-time Localization
  62. GRB 260412A: LCOGT Optical Upper Limits
  63. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  64. EP-WXT trigger 01709260303: KAIT optical observations
  65. GRB 260417A: SVOM/GRM observation
  66. GRB 260419B: Fermi GBM Final Real-time Localization
  67. GRB 260419A: Fermi GBM Final Real-time Localization
  68. Fermi GRB 260417B: Global MASTER-Net observations report
  69. GRB 260418B: Fermi GBM Final Real-time Localization
  70. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  71. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  72. GRB 260418A: Fermi GBM Final Real-time Localization
  73. Fermi GRB 260417A: Global MASTER-Net observations report
  74. Konus-Wind detection of GRB 260411B
  75. GRB 260417B: Fermi GBM Final Real-time Localization
  76. GRB 260417A: AstroSat CZTI detection
  77. IPN triangulation of GRB 260411B
  78. EP-WXT trigger 01709259586: KAIT optical observations
  79. EP260416a: KAIT optical upper limit
  80. GRB 260414A: Insight-HXMT/HE detection
  81. GRB 260417A: Fermi GBM Final Real-time Localization
  82. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  83. GRB 260415B: Glowbug gamma-ray detection
  84. GRB 260411B: Glowbug gamma-ray detection
  85. GRB 260415A: Insight-HXMT/HE detection
  86. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  87. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  88. GRB 260415B: NuSTAR detection of long prompt emission
  89. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  90. GRB 260415B: Fermi GBM Final Localization
  91. GRB 260415A: Fermi GBM Final Real-time Localization
  92. GRB 260414A: Glowbug gamma-ray detection
  93. EP260321a: CMO SAI J,K observations
  94. GRB 260412A: Insight-HXMT/HE detection
  95. GRB 260414A: Fermi GBM Final Real-time Localization
  96. Fermi GRB 260413A: Global MASTER-Net observations report
  97. GRB 260410A: Glowbug gamma-ray detection of a short burst
  98. GRB 260413A: Fermi GBM Final Real-time Localization
  99. GRB 260410B: Insight-HXMT/HE detection
  100. GRB 260410A: Insight-HXMT/HE detection

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