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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"

45461 results found.

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

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