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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"

43612 results found.

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

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