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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

45675 results found.

  1. Fermi GRB 260428A: Global MASTER-Net observations report
  2. EP260416a: Mondy and Terskol optical upper limits
  3. GRB 260424B: Glowbug gamma-ray detection of a short burst
  4. GRB 260424B: COLIBRÍ optical upper limit
  5. Konus-Wind detection of GRB 260424B
  6. GRB 260428A: Fermi GBM Final Real-time Localization
  7. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  8. GRB 260424C: Fermi GBM Final Localization
  9. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  10. IPN triangulation of GRB 260424B (short)
  11. GRB 260424B: SVOM/GRM detection of a short burst
  12. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  13. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  14. IceCube Alert 260425A: Global MASTER-Net observations report
  15. Fermi trigger No 798737427: Global MASTER-Net observations report
  16. GRB 260401A: cubesat Avion detection
  17. GRB 260424A: AstroSat CZTI detection of a long burst
  18. EP260321a: Upper limits from ATCA radio observations
  19. GRB 260421B: Kilonova-Catcher optical afterglow detection
  20. GRB 260421B: Insight-HXMT/HE detection
  21. The EP-WXT trigger 01709258652: Mondy optical observations
  22. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  23. EP260416a: Mondy optical observations
  24. GRB 260421B: SVOM/ECLAIRs refined analysis
  25. GRB 260421B: 3.6m DOT optical observation
  26. EP260416a: ZTSh R band observations
  27. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  28. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  29. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  30. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  31. GRB 260419A: AstroSat CZTI detection
  32. GRB 260421B: SVOM/GRM observation
  33. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  34. GRB 260421B: EP-FXT follow-up observation
  35. The EP-WXT trigger 01709260362 is likely a flaring star
  36. GOTO26djh/AT2026jpw: ATCA radio detection
  37. GRB 260421B: J-band upper limit with WINTER
  38. GRB 260421B: LCO optical counterpart detection
  39. GRB 260421B: Fermi GBM Observation
  40. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  41. GRB 260421A: AstroSat CZTI detection
  42. GOTO26djh/AT2026jpw: radio detection at 15GHz
  43. GRB 260412A: SVOM/ECLAIRs refined analysis
  44. GRB 260421B: SVOM/VT optical observations
  45. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  46. GRB 260310A: Late-time Chandra X-ray Detection
  47. GRB 260418A: Insight-HXMT/HE detection
  48. EP260416a: 1.3m DFOT optical observation
  49. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  50. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  51. Fermi GRB 260421C: Global MASTER-Net observations report
  52. GRB 260421C: Fermi GBM Final Real-time Localization
  53. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  54. Fermi GRB 260421B: Global MASTER-Net observations report
  55. GRB 260421B: BOOTES-7 early optical afterglow detection
  56. GRB 260421B: LCO optical afterglow confirmation
  57. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  58. GRB 260421B: TRT optical counterpart detection
  59. GRB 260421B: SVOM detection of a long burst
  60. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  61. GRB 260421B: Fermi GBM Final Real-time Localization
  62. Fermi GRB 260421A: Global MASTER-Net observations report
  63. GRB 260421A: Fermi GBM Final Real-time Localization
  64. EP260321a: VLA radio follow-up
  65. GRB 260412A: LCOGT Optical Upper Limits
  66. The EP-WXT trigger 01709260314 is likely a flaring star
  67. EP260416a: Optical follow-up observations with Kinder
  68. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  69. EP-WXT trigger 01709260303: KAIT optical observations
  70. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  71. The EP-WXT trigger 01709260303 is likely a flaring star
  72. GRB 260417A: SVOM/GRM observation
  73. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  74. GRB 260419B: Fermi GBM Final Real-time Localization
  75. GRB 260419A: Fermi GBM Final Real-time Localization
  76. Fermi trigger No 798275385: Global MASTER-Net observations report
  77. EP260417a: GROWTH-India Telescope optical upper limit
  78. Fermi GRB 260417B: Global MASTER-Net observations report
  79. EP260417b: GROWTH-India Telescope optical upper limit
  80. EP260416a: Ondrejov D50 optical detection
  81. GRB 260418B: Fermi GBM Final Real-time Localization
  82. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  83. EP260417a: Global MASTER-Net observations report
  84. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  85. EP260416a: NOT tentative spectroscopic redshift of z =1.909
  86. GRB 260418A: Fermi GBM Final Real-time Localization
  87. EP260416a: GMG Optical Observation
  88. Fermi GRB 260417A: Global MASTER-Net observations report
  89. Konus-Wind detection of GRB 260411B
  90. GRB 260417B: Fermi GBM Final Real-time Localization
  91. GRB 260417A: AstroSat CZTI detection
  92. IPN triangulation of GRB 260411B
  93. EP260416a: LCO observations confirm end of flaring phase
  94. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  95. EP260417a: TRT optical counterpart detection
  96. EP260417a: Einstein Probe detection of an X-ray transient
  97. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  98. EP260417b: Einstein Probe detection of a fast X-ray transient
  99. EP-WXT trigger 01709259586: KAIT optical observations
  100. EP260416a: KAIT optical upper limit

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