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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"
  1. GRB 260421B: J-band upper limit with WINTER
  2. GRB 260421B: LCO optical counterpart detection
  3. GRB 260421B: Fermi GBM Observation
  4. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  5. GRB 260421A: AstroSat CZTI detection
  6. GOTO26djh/AT2026jpw: radio detection at 15GHz
  7. GRB 260412A: SVOM/ECLAIRs refined analysis
  8. GRB 260421B: SVOM/VT optical observations
  9. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  10. GRB 260310A: Late-time Chandra X-ray Detection
  11. GRB 260418A: Insight-HXMT/HE detection
  12. EP260416a: 1.3m DFOT optical observation
  13. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  14. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  15. Fermi GRB 260421C: Global MASTER-Net observations report
  16. GRB 260421C: Fermi GBM Final Real-time Localization
  17. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  18. Fermi GRB 260421B: Global MASTER-Net observations report
  19. GRB 260421B: BOOTES-7 early optical afterglow detection
  20. GRB 260421B: LCO optical afterglow confirmation
  21. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  22. GRB 260421B: TRT optical counterpart detection
  23. GRB 260421B: SVOM detection of a long burst
  24. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  25. GRB 260421B: Fermi GBM Final Real-time Localization
  26. Fermi GRB 260421A: Global MASTER-Net observations report
  27. GRB 260421A: Fermi GBM Final Real-time Localization
  28. EP260321a: VLA radio follow-up
  29. GRB 260412A: LCOGT Optical Upper Limits
  30. The EP-WXT trigger 01709260314 is likely a flaring star
  31. EP260416a: Optical follow-up observations with Kinder
  32. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  33. EP-WXT trigger 01709260303: KAIT optical observations
  34. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  35. The EP-WXT trigger 01709260303 is likely a flaring star
  36. GRB 260417A: SVOM/GRM observation
  37. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  38. GRB 260419B: Fermi GBM Final Real-time Localization
  39. GRB 260419A: Fermi GBM Final Real-time Localization
  40. Fermi trigger No 798275385: Global MASTER-Net observations report
  41. EP260417a: GROWTH-India Telescope optical upper limit
  42. Fermi GRB 260417B: Global MASTER-Net observations report
  43. EP260417b: GROWTH-India Telescope optical upper limit
  44. EP260416a: Ondrejov D50 optical detection
  45. GRB 260418B: Fermi GBM Final Real-time Localization
  46. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  47. EP260417a: Global MASTER-Net observations report
  48. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  49. EP260416a: NOT tentative spectroscopic redshift of z =1.909
  50. GRB 260418A: Fermi GBM Final Real-time Localization
  51. EP260416a: GMG Optical Observation
  52. Fermi GRB 260417A: Global MASTER-Net observations report
  53. Konus-Wind detection of GRB 260411B
  54. GRB 260417B: Fermi GBM Final Real-time Localization
  55. GRB 260417A: AstroSat CZTI detection
  56. IPN triangulation of GRB 260411B
  57. EP260416a: LCO observations confirm end of flaring phase
  58. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  59. EP260417a: TRT optical counterpart detection
  60. EP260417a: Einstein Probe detection of an X-ray transient
  61. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  62. EP260417b: Einstein Probe detection of a fast X-ray transient
  63. EP-WXT trigger 01709259586: KAIT optical observations
  64. EP260416a: KAIT optical upper limit
  65. GRB 260414A: Insight-HXMT/HE detection
  66. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  67. EP260416a: WFST optical observations and rebrightening
  68. GRB 260417A: Fermi GBM Final Real-time Localization
  69. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  70. EP260416a: SVOM/VT optical observation
  71. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  72. GRB 260415B: Glowbug gamma-ray detection
  73. GRB 260411B: Glowbug gamma-ray detection
  74. GRB 260415A: Insight-HXMT/HE detection
  75. EP260416a: COLIBRÍ optical counterpart candidate
  76. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  77. EP260416a: Global MASTER-Net observations report
  78. EP260416a: Einstein Probe detection of an X-ray transient
  79. GOTO26djh/AT2026jpw : MASTER OT observation
  80. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  81. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  82. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  83. GRB 260415B: NuSTAR detection of long prompt emission
  84. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  85. GRB 260415B: Fermi GBM Final Localization
  86. GRB 260415A: Fermi GBM Final Real-time Localization
  87. Fermi trigger No 797912738: Global MASTER-Net observations report
  88. GRB 260414A: Glowbug gamma-ray detection
  89. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  90. EP260321a: CMO SAI J,K observations
  91. GRB 260412A: Insight-HXMT/HE detection
  92. GRB 260414A: Fermi GBM Final Real-time Localization
  93. The EP-WXT trigger 01709260122 is likely a flaring star
  94. Fermi GRB 260413A: Global MASTER-Net observations report
  95. GRB 260410A: Glowbug gamma-ray detection of a short burst
  96. GRB 260413A: Fermi GBM Final Real-time Localization
  97. GRB 260410B: Insight-HXMT/HE detection
  98. GRB 260410A: Insight-HXMT/HE detection
  99. Konus-Wind detection of GRB 260410A (short/hard)
  100. GRB 260411B: GECAM-B observation of a long burst

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