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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"

24279 results found.

  1. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  2. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  3. The EP-WXT trigger 01709259586 is likely a flaring star
  4. GRB 260330B: SVOM/VT further optical observation
  5. GRB 260330B: SVOM/ECLAIRs refined analysis
  6. GRB 260330B: SVOM/VT optical candidate
  7. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  8. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  9. GRB 260402C: NuSTAR detection of prompt emission
  10. EP260324A / AT 2026hir: COLIBRÍ optical observations
  11. GRB 260403A: Fermi GBM Final Real-time Localization
  12. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  13. GRB 260402B: Fermi GBM Final Real-time Localization
  14. GRB260402A: GROWTH-India Telescope optical upper limit
  15. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  16. GRB 260401A: SVOM/GRM observation
  17. GRB 260401A: GECAM-B observation
  18. GRB 260402A: MASTER optical observations
  19. GRB 260402A: SVOM detection of a burst
  20. Fermi GRB 260401A: Global MASTER-Net observations report
  21. GRB 260401A: Fermi GBM Observation
  22. GRB 260401A: NuSTAR detection of prompt emission
  23. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  24. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  25. GRB 260401A: Fermi GBM Final Real-time Localization
  26. EP260321a :Xinglong optical observations
  27. EP260327a: Xinglong optical upper limit
  28. EP260329b: GOTO detection of optical counterpart
  29. GRB 260330B: SVOM/VT optical upper limits
  30. Konus-Wind detection of GRB 260320A
  31. Konus-Wind detection of GRB 260316B
  32. GRB 260321A: SVOM/ECLAIRs refined analysis
  33. Fermi GBM Sub-Threshold Detection of GRB 260330B
  34. GRB 260330B: LCO optical upper limits
  35. GRB 260330B: SVOM detection of a burst
  36. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  37. EP260329a: EP-FXT follow up observation
  38. EP260329a: NOT optical counterpart candidate
  39. GRB 260330A: Fermi GBM Final Real-time Localization
  40. EP260329b: Global MASTER-Net observations report
  41. Fermi trigger No 796485221: Global MASTER-Net observations report
  42. EP260329a: Optical upper limit with Kinder observations
  43. EP-WXT trigger 01709259209: TRT optical counterpart detection
  44. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  45. EP260327a: SVOM/VT optical upper limits
  46. GRB 260307B: ATCA Radio Upper Limits
  47. EP260327a: WINTER J-band upper limit
  48. EP260327a: Gemini-North optical upper limits
  49. EP260324a: GROWTH-India Telescope optical observation
  50. EP260327a: Global MASTER-Net observations report
  51. The EP-WXT trigger 01709259173 is likely a flaring star
  52. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  53. IPN triangulation of GRB 260320A
  54. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  55. GRB 260326A: Fermi GBM Detection
  56. EP260321a: JinShan near-infrared observations
  57. GRB 260325A: Fermi GBM Final Localization
  58. GRB 260326A: Fermi GBM Final Real-time Localization
  59. EP260321a: Upper limits from a neutrino search with IceCube
  60. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  61. IPN triangulation of GRB 260316B
  62. EP260321a: Gemini-South confirmation of a supernova
  63. GRB 260310A: LBT optical observations
  64. EP260321A: Mondy optical observations
  65. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  66. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  67. The EP-WXT trigger 01709259112 is likely a flaring star
  68. Fermi GRB 260323A: Global MASTER-Net observations report
  69. GRB 260323A: Fermi GBM Final Real-time Localization
  70. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  71. GRB 260322A: Fermi GBM Final Localization
  72. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  73. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  74. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  75. GRB 260321A: EP-FXT follow-up observation
  76. The EP-WXT trigger 01709259045 is likely a flaring star
  77. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  78. GRB 260321A: SVOM/VT optical upper limits
  79. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  80. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  81. EP260321a: SVOM/VT optical upper limit
  82. Fermi GBM Sub-Threshold Detection of GRB 260321A
  83. GRB 260321A: SVOM detection of a burst
  84. EP260321a: Global MASTER-Net observations report
  85. GRB 260320A: NuSTAR detection of prompt emission
  86. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  87. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  88. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  89. GRB 260318A: SVOM/GRM observation
  90. The EP-WXT trigger 01709258989 is likely a flaring star
  91. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  92. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  93. Fermi GRB 260318A: Global MASTER-Net observations report
  94. GRB 260318A: Fermi GBM Final Real-time Localization
  95. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  96. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  97. GRB 260310A / AT2026fgk: LCO optical observations
  98. GRB 260317A: Fermi GBM Final Localization
  99. GRB 260316B: SVOM/GRM observation
  100. EP260316a / GRB 260316A: SVOM/VT optical upper limits

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