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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"
  1. GRB 260421B: TRT optical counterpart detection
  2. GRB 260421B: SVOM detection of a long burst
  3. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  4. GRB 260421B: Fermi GBM Final Real-time Localization
  5. Fermi GRB 260421A: Global MASTER-Net observations report
  6. GRB 260421A: Fermi GBM Final Real-time Localization
  7. EP260321a: VLA radio follow-up
  8. GRB 260412A: LCOGT Optical Upper Limits
  9. The EP-WXT trigger 01709260314 is likely a flaring star
  10. EP260416a: Optical follow-up observations with Kinder
  11. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  12. EP-WXT trigger 01709260303: KAIT optical observations
  13. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  14. The EP-WXT trigger 01709260303 is likely a flaring star
  15. GRB 260417A: SVOM/GRM observation
  16. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  17. GRB 260419B: Fermi GBM Final Real-time Localization
  18. GRB 260419A: Fermi GBM Final Real-time Localization
  19. Fermi trigger No 798275385: Global MASTER-Net observations report
  20. EP260417a: GROWTH-India Telescope optical upper limit
  21. Fermi GRB 260417B: Global MASTER-Net observations report
  22. EP260417b: GROWTH-India Telescope optical upper limit
  23. EP260416a: Ondrejov D50 optical detection
  24. GRB 260418B: Fermi GBM Final Real-time Localization
  25. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  26. EP260417a: Global MASTER-Net observations report
  27. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  28. EP260416a: NOT tentative spectroscopic redshift of z =1.909
  29. GRB 260418A: Fermi GBM Final Real-time Localization
  30. EP260416a: GMG Optical Observation
  31. Fermi GRB 260417A: Global MASTER-Net observations report
  32. Konus-Wind detection of GRB 260411B
  33. GRB 260417B: Fermi GBM Final Real-time Localization
  34. GRB 260417A: AstroSat CZTI detection
  35. IPN triangulation of GRB 260411B
  36. EP260416a: LCO observations confirm end of flaring phase
  37. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  38. EP260417a: TRT optical counterpart detection
  39. EP260417a: Einstein Probe detection of an X-ray transient
  40. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  41. EP260417b: Einstein Probe detection of a fast X-ray transient
  42. EP-WXT trigger 01709259586: KAIT optical observations
  43. EP260416a: KAIT optical upper limit
  44. GRB 260414A: Insight-HXMT/HE detection
  45. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  46. EP260416a: WFST optical observations and rebrightening
  47. GRB 260417A: Fermi GBM Final Real-time Localization
  48. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  49. EP260416a: SVOM/VT optical observation
  50. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  51. GRB 260415B: Glowbug gamma-ray detection
  52. GRB 260411B: Glowbug gamma-ray detection
  53. GRB 260415A: Insight-HXMT/HE detection
  54. EP260416a: COLIBRÍ optical counterpart candidate
  55. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  56. EP260416a: Global MASTER-Net observations report
  57. EP260416a: Einstein Probe detection of an X-ray transient
  58. GOTO26djh/AT2026jpw : MASTER OT observation
  59. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  60. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  61. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  62. GRB 260415B: NuSTAR detection of long prompt emission
  63. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  64. GRB 260415B: Fermi GBM Final Localization
  65. GRB 260415A: Fermi GBM Final Real-time Localization
  66. Fermi trigger No 797912738: Global MASTER-Net observations report
  67. GRB 260414A: Glowbug gamma-ray detection
  68. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  69. EP260321a: CMO SAI J,K observations
  70. GRB 260412A: Insight-HXMT/HE detection
  71. GRB 260414A: Fermi GBM Final Real-time Localization
  72. The EP-WXT trigger 01709260122 is likely a flaring star
  73. Fermi GRB 260413A: Global MASTER-Net observations report
  74. GRB 260410A: Glowbug gamma-ray detection of a short burst
  75. GRB 260413A: Fermi GBM Final Real-time Localization
  76. GRB 260410B: Insight-HXMT/HE detection
  77. GRB 260410A: Insight-HXMT/HE detection
  78. Konus-Wind detection of GRB 260410A (short/hard)
  79. GRB 260411B: GECAM-B observation of a long burst
  80. EP260321a: SVOM/VT optical observations and color changes around peak
  81. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  82. The EP-WXT trigger 01709260010 is likely a flaring star
  83. GRB 260412A: GECAM-B observation of a long burst
  84. Fermi GRB 260412A: Global MASTER-Net observations report
  85. GRB 260412A: Fermi GBM Observation
  86. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  87. GRB 260411B: Fermi-LAT detection
  88. GRB 260412A: SVOM detection of a long burst
  89. GRB 260412A: Fermi GBM Final Real-time Localization
  90. GRB 260411B: COLIBRÍ optical observations
  91. GRB 260410B: Fermi GBM Observation
  92. GRB 260411B: Ondrejov D50 optical afterglow detection
  93. GRB260411B: 3.6m DOT optical observation
  94. GRB 260411A: SVOM/GRM observation
  95. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  96. GRB 260411B: SVOM/GRM observation of a long burst
  97. GRB 260409A: Insight-HXMT/HE detection
  98. GRB 260411B: Fermi GBM Detection
  99. GRB 260411B: GOTO optical counterpart candidate
  100. EP260409a: Gemini/FLAMINGOS2 J-band counterpart

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