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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"

44281 results found.

  1. GRB 260424C: Fermi GBM Final Localization
  2. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  3. IPN triangulation of GRB 260424B (short)
  4. GRB 260424B: SVOM/GRM detection of a short burst
  5. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  6. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  7. IceCube Alert 260425A: Global MASTER-Net observations report
  8. Fermi trigger No 798737427: Global MASTER-Net observations report
  9. GRB 260401A: cubesat Avion detection
  10. GRB 260424A: AstroSat CZTI detection of a long burst
  11. EP260321a: Upper limits from ATCA radio observations
  12. GRB 260421B: Kilonova-Catcher optical afterglow detection
  13. GRB 260421B: Insight-HXMT/HE detection
  14. The EP-WXT trigger 01709258652: Mondy optical observations
  15. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  16. EP260416a: Mondy optical observations
  17. GRB 260421B: SVOM/ECLAIRs refined analysis
  18. GRB 260421B: 3.6m DOT optical observation
  19. EP260416a: ZTSh R band observations
  20. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  21. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  22. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  23. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  24. GRB 260419A: AstroSat CZTI detection
  25. GRB 260421B: SVOM/GRM observation
  26. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  27. GRB 260421B: EP-FXT follow-up observation
  28. The EP-WXT trigger 01709260362 is likely a flaring star
  29. GOTO26djh/AT2026jpw: ATCA radio detection
  30. GRB 260421B: J-band upper limit with WINTER
  31. GRB 260421B: LCO optical counterpart detection
  32. GRB 260421B: Fermi GBM Observation
  33. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  34. GRB 260421A: AstroSat CZTI detection
  35. GOTO26djh/AT2026jpw: radio detection at 15GHz
  36. GRB 260412A: SVOM/ECLAIRs refined analysis
  37. GRB 260421B: SVOM/VT optical observations
  38. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  39. GRB 260310A: Late-time Chandra X-ray Detection
  40. GRB 260418A: Insight-HXMT/HE detection
  41. EP260416a: 1.3m DFOT optical observation
  42. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  43. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  44. Fermi GRB 260421C: Global MASTER-Net observations report
  45. GRB 260421C: Fermi GBM Final Real-time Localization
  46. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  47. Fermi GRB 260421B: Global MASTER-Net observations report
  48. GRB 260421B: BOOTES-7 early optical afterglow detection
  49. GRB 260421B: LCO optical afterglow confirmation
  50. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  51. GRB 260421B: TRT optical counterpart detection
  52. GRB 260421B: SVOM detection of a long burst
  53. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  54. GRB 260421B: Fermi GBM Final Real-time Localization
  55. Fermi GRB 260421A: Global MASTER-Net observations report
  56. GRB 260421A: Fermi GBM Final Real-time Localization
  57. EP260321a: VLA radio follow-up
  58. GRB 260412A: LCOGT Optical Upper Limits
  59. The EP-WXT trigger 01709260314 is likely a flaring star
  60. EP260416a: Optical follow-up observations with Kinder
  61. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  62. EP-WXT trigger 01709260303: KAIT optical observations
  63. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  64. The EP-WXT trigger 01709260303 is likely a flaring star
  65. GRB 260417A: SVOM/GRM observation
  66. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  67. GRB 260419B: Fermi GBM Final Real-time Localization
  68. GRB 260419A: Fermi GBM Final Real-time Localization
  69. Fermi trigger No 798275385: Global MASTER-Net observations report
  70. EP260417a: GROWTH-India Telescope optical upper limit
  71. Fermi GRB 260417B: Global MASTER-Net observations report
  72. EP260417b: GROWTH-India Telescope optical upper limit
  73. EP260416a: Ondrejov D50 optical detection
  74. GRB 260418B: Fermi GBM Final Real-time Localization
  75. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  76. EP260417a: Global MASTER-Net observations report
  77. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  78. EP260416a: NOT tentative spectroscopic redshift of z =1.909
  79. GRB 260418A: Fermi GBM Final Real-time Localization
  80. EP260416a: GMG Optical Observation
  81. Fermi GRB 260417A: Global MASTER-Net observations report
  82. Konus-Wind detection of GRB 260411B
  83. GRB 260417B: Fermi GBM Final Real-time Localization
  84. GRB 260417A: AstroSat CZTI detection
  85. IPN triangulation of GRB 260411B
  86. EP260416a: LCO observations confirm end of flaring phase
  87. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  88. EP260417a: TRT optical counterpart detection
  89. EP260417a: Einstein Probe detection of an X-ray transient
  90. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  91. EP260417b: Einstein Probe detection of a fast X-ray transient
  92. EP-WXT trigger 01709259586: KAIT optical observations
  93. EP260416a: KAIT optical upper limit
  94. GRB 260414A: Insight-HXMT/HE detection
  95. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  96. EP260416a: WFST optical observations and rebrightening
  97. GRB 260417A: Fermi GBM Final Real-time Localization
  98. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  99. EP260416a: SVOM/VT optical observation
  100. GOTO26djh/AT2026jpw: SVOM/VT optical observation

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