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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"

36003 results found.

  1. GRB 260428A: Fermi GBM Final Real-time Localization
  2. GRB 260424C: Fermi GBM Final Localization
  3. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  4. IPN triangulation of GRB 260424B (short)
  5. GRB 260424B: SVOM/GRM detection of a short burst
  6. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  7. GRB 260401A: cubesat Avion detection
  8. GRB 260424A: AstroSat CZTI detection of a long burst
  9. GRB 260421B: Kilonova-Catcher optical afterglow detection
  10. GRB 260421B: Insight-HXMT/HE detection
  11. The EP-WXT trigger 01709258652: Mondy optical observations
  12. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  13. EP260416a: Mondy optical observations
  14. GRB 260421B: SVOM/ECLAIRs refined analysis
  15. GRB 260421B: 3.6m DOT optical observation
  16. EP260416a: ZTSh R band observations
  17. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  18. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  19. GRB 260419A: AstroSat CZTI detection
  20. GRB 260421B: SVOM/GRM observation
  21. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  22. GRB 260421B: EP-FXT follow-up observation
  23. GRB 260421B: J-band upper limit with WINTER
  24. GRB 260421B: LCO optical counterpart detection
  25. GRB 260421B: Fermi GBM Observation
  26. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  27. GRB 260421A: AstroSat CZTI detection
  28. GRB 260412A: SVOM/ECLAIRs refined analysis
  29. GRB 260421B: SVOM/VT optical observations
  30. GRB 260310A: Late-time Chandra X-ray Detection
  31. GRB 260418A: Insight-HXMT/HE detection
  32. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  33. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  34. Fermi GRB 260421C: Global MASTER-Net observations report
  35. GRB 260421C: Fermi GBM Final Real-time Localization
  36. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  37. Fermi GRB 260421B: Global MASTER-Net observations report
  38. GRB 260421B: BOOTES-7 early optical afterglow detection
  39. GRB 260421B: LCO optical afterglow confirmation
  40. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  41. GRB 260421B: TRT optical counterpart detection
  42. GRB 260421B: SVOM detection of a long burst
  43. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  44. GRB 260421B: Fermi GBM Final Real-time Localization
  45. Fermi GRB 260421A: Global MASTER-Net observations report
  46. GRB 260421A: Fermi GBM Final Real-time Localization
  47. GRB 260412A: LCOGT Optical Upper Limits
  48. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  49. EP-WXT trigger 01709260303: KAIT optical observations
  50. GRB 260417A: SVOM/GRM observation
  51. GRB 260419B: Fermi GBM Final Real-time Localization
  52. GRB 260419A: Fermi GBM Final Real-time Localization
  53. Fermi GRB 260417B: Global MASTER-Net observations report
  54. GRB 260418B: Fermi GBM Final Real-time Localization
  55. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  56. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  57. GRB 260418A: Fermi GBM Final Real-time Localization
  58. Fermi GRB 260417A: Global MASTER-Net observations report
  59. Konus-Wind detection of GRB 260411B
  60. GRB 260417B: Fermi GBM Final Real-time Localization
  61. GRB 260417A: AstroSat CZTI detection
  62. IPN triangulation of GRB 260411B
  63. EP-WXT trigger 01709259586: KAIT optical observations
  64. EP260416a: KAIT optical upper limit
  65. GRB 260414A: Insight-HXMT/HE detection
  66. GRB 260417A: Fermi GBM Final Real-time Localization
  67. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  68. GRB 260415B: Glowbug gamma-ray detection
  69. GRB 260411B: Glowbug gamma-ray detection
  70. GRB 260415A: Insight-HXMT/HE detection
  71. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  72. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  73. GRB 260415B: NuSTAR detection of long prompt emission
  74. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  75. GRB 260415B: Fermi GBM Final Localization
  76. GRB 260415A: Fermi GBM Final Real-time Localization
  77. GRB 260414A: Glowbug gamma-ray detection
  78. EP260321a: CMO SAI J,K observations
  79. GRB 260412A: Insight-HXMT/HE detection
  80. GRB 260414A: Fermi GBM Final Real-time Localization
  81. Fermi GRB 260413A: Global MASTER-Net observations report
  82. GRB 260410A: Glowbug gamma-ray detection of a short burst
  83. GRB 260413A: Fermi GBM Final Real-time Localization
  84. GRB 260410B: Insight-HXMT/HE detection
  85. GRB 260410A: Insight-HXMT/HE detection
  86. Konus-Wind detection of GRB 260410A (short/hard)
  87. GRB 260411B: GECAM-B observation of a long burst
  88. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  89. GRB 260412A: GECAM-B observation of a long burst
  90. Fermi GRB 260412A: Global MASTER-Net observations report
  91. GRB 260412A: Fermi GBM Observation
  92. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  93. GRB 260411B: Fermi-LAT detection
  94. GRB 260412A: SVOM detection of a long burst
  95. GRB 260412A: Fermi GBM Final Real-time Localization
  96. GRB 260411B: COLIBRÍ optical observations
  97. GRB 260410B: Fermi GBM Observation
  98. GRB 260411B: Ondrejov D50 optical afterglow detection
  99. GRB 260411A: SVOM/GRM observation
  100. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst

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