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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.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

40633 results found.

  1. Fermi GRB 260429A: Global MASTER-Net observations report
  2. EP260430a: Global MASTER-Net observations report
  3. EP260430a: Einstein Probe detection of an X-ray transient
  4. EP260429a: EP-WXT detection of a fast X-ray transient
  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. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  17. GRB 260424C: Fermi GBM Final Localization
  18. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  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. IceCube Alert 260425A: Global MASTER-Net observations report
  23. Fermi trigger No 798737427: Global MASTER-Net observations report
  24. GRB 260401A: cubesat Avion detection
  25. GRB 260424A: AstroSat CZTI detection of a long burst
  26. EP260321a: Upper limits from ATCA radio observations
  27. GRB 260421B: Kilonova-Catcher optical afterglow detection
  28. GRB 260421B: Insight-HXMT/HE detection
  29. The EP-WXT trigger 01709258652: Mondy optical observations
  30. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  31. EP260416a: Mondy optical observations
  32. GRB 260421B: SVOM/ECLAIRs refined analysis
  33. GRB 260421B: 3.6m DOT optical observation
  34. EP260416a: ZTSh R band observations
  35. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  36. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  37. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  38. GRB 260419A: AstroSat CZTI detection
  39. GRB 260421B: SVOM/GRM observation
  40. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  41. GRB 260421B: EP-FXT follow-up observation
  42. The EP-WXT trigger 01709260362 is likely a flaring star
  43. GOTO26djh/AT2026jpw: ATCA radio detection
  44. GRB 260421B: J-band upper limit with WINTER
  45. GRB 260421B: LCO optical counterpart detection
  46. GRB 260421B: Fermi GBM Observation
  47. GRB 260421A: AstroSat CZTI detection
  48. GOTO26djh/AT2026jpw: radio detection at 15GHz
  49. GRB 260412A: SVOM/ECLAIRs refined analysis
  50. GRB 260421B: SVOM/VT optical observations
  51. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  52. GRB 260310A: Late-time Chandra X-ray Detection
  53. GRB 260418A: Insight-HXMT/HE detection
  54. EP260416a: 1.3m DFOT optical observation
  55. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  56. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  57. Fermi GRB 260421C: Global MASTER-Net observations report
  58. GRB 260421C: Fermi GBM Final Real-time Localization
  59. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  60. Fermi GRB 260421B: Global MASTER-Net observations report
  61. GRB 260421B: LCO optical afterglow confirmation
  62. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  63. GRB 260421B: TRT optical counterpart detection
  64. GRB 260421B: SVOM detection of a long burst
  65. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  66. GRB 260421B: Fermi GBM Final Real-time Localization
  67. Fermi GRB 260421A: Global MASTER-Net observations report
  68. GRB 260421A: Fermi GBM Final Real-time Localization
  69. EP260321a: VLA radio follow-up
  70. GRB 260412A: LCOGT Optical Upper Limits
  71. The EP-WXT trigger 01709260314 is likely a flaring star
  72. EP260416a: Optical follow-up observations with Kinder
  73. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  74. EP-WXT trigger 01709260303: KAIT optical observations
  75. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  76. The EP-WXT trigger 01709260303 is likely a flaring star
  77. GRB 260417A: SVOM/GRM observation
  78. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  79. GRB 260419B: Fermi GBM Final Real-time Localization
  80. GRB 260419A: Fermi GBM Final Real-time Localization
  81. Fermi trigger No 798275385: Global MASTER-Net observations report
  82. EP260417a: GROWTH-India Telescope optical upper limit
  83. Fermi GRB 260417B: Global MASTER-Net observations report
  84. EP260417b: GROWTH-India Telescope optical upper limit
  85. EP260416a: Ondrejov D50 optical detection
  86. GRB 260418B: Fermi GBM Final Real-time Localization
  87. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  88. EP260417a: Global MASTER-Net observations report
  89. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  90. EP260416a: NOT tentative spectroscopic redshift of z =1.909
  91. GRB 260418A: Fermi GBM Final Real-time Localization
  92. Fermi GRB 260417A: Global MASTER-Net observations report
  93. Konus-Wind detection of GRB 260411B
  94. GRB 260417B: Fermi GBM Final Real-time Localization
  95. GRB 260417A: AstroSat CZTI detection
  96. EP260416a: LCO observations confirm end of flaring phase
  97. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  98. EP260417a: TRT optical counterpart detection
  99. EP260417a: Einstein Probe detection of an X-ray transient
  100. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations

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