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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"

35985 results found.

  1. GRB 260419A: AstroSat CZTI detection
  2. GRB 260421B: SVOM/GRM observation
  3. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  4. GRB 260421B: EP-FXT follow-up observation
  5. GRB 260421B: J-band upper limit with WINTER
  6. GRB 260421B: LCO optical counterpart detection
  7. GRB 260421B: Fermi GBM Observation
  8. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  9. GRB 260421A: AstroSat CZTI detection
  10. GRB 260412A: SVOM/ECLAIRs refined analysis
  11. GRB 260421B: SVOM/VT optical observations
  12. GRB 260310A: Late-time Chandra X-ray Detection
  13. GRB 260418A: Insight-HXMT/HE detection
  14. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  15. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  16. Fermi GRB 260421C: Global MASTER-Net observations report
  17. GRB 260421C: Fermi GBM Final Real-time Localization
  18. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  19. Fermi GRB 260421B: Global MASTER-Net observations report
  20. GRB 260421B: BOOTES-7 early optical afterglow detection
  21. GRB 260421B: LCO optical afterglow confirmation
  22. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  23. GRB 260421B: TRT optical counterpart detection
  24. GRB 260421B: SVOM detection of a long burst
  25. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  26. GRB 260421B: Fermi GBM Final Real-time Localization
  27. Fermi GRB 260421A: Global MASTER-Net observations report
  28. GRB 260421A: Fermi GBM Final Real-time Localization
  29. GRB 260412A: LCOGT Optical Upper Limits
  30. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  31. EP-WXT trigger 01709260303: KAIT optical observations
  32. GRB 260417A: SVOM/GRM observation
  33. GRB 260419B: Fermi GBM Final Real-time Localization
  34. GRB 260419A: Fermi GBM Final Real-time Localization
  35. Fermi GRB 260417B: Global MASTER-Net observations report
  36. GRB 260418B: Fermi GBM Final Real-time Localization
  37. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  38. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  39. GRB 260418A: Fermi GBM Final Real-time Localization
  40. Fermi GRB 260417A: Global MASTER-Net observations report
  41. Konus-Wind detection of GRB 260411B
  42. GRB 260417B: Fermi GBM Final Real-time Localization
  43. GRB 260417A: AstroSat CZTI detection
  44. IPN triangulation of GRB 260411B
  45. EP-WXT trigger 01709259586: KAIT optical observations
  46. EP260416a: KAIT optical upper limit
  47. GRB 260414A: Insight-HXMT/HE detection
  48. GRB 260417A: Fermi GBM Final Real-time Localization
  49. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  50. GRB 260415B: Glowbug gamma-ray detection
  51. GRB 260411B: Glowbug gamma-ray detection
  52. GRB 260415A: Insight-HXMT/HE detection
  53. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  54. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  55. GRB 260415B: NuSTAR detection of long prompt emission
  56. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  57. GRB 260415B: Fermi GBM Final Localization
  58. GRB 260415A: Fermi GBM Final Real-time Localization
  59. GRB 260414A: Glowbug gamma-ray detection
  60. EP260321a: CMO SAI J,K observations
  61. GRB 260412A: Insight-HXMT/HE detection
  62. GRB 260414A: Fermi GBM Final Real-time Localization
  63. Fermi GRB 260413A: Global MASTER-Net observations report
  64. GRB 260410A: Glowbug gamma-ray detection of a short burst
  65. GRB 260413A: Fermi GBM Final Real-time Localization
  66. GRB 260410B: Insight-HXMT/HE detection
  67. GRB 260410A: Insight-HXMT/HE detection
  68. Konus-Wind detection of GRB 260410A (short/hard)
  69. GRB 260411B: GECAM-B observation of a long burst
  70. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  71. GRB 260412A: GECAM-B observation of a long burst
  72. Fermi GRB 260412A: Global MASTER-Net observations report
  73. GRB 260412A: Fermi GBM Observation
  74. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  75. GRB 260411B: Fermi-LAT detection
  76. GRB 260412A: SVOM detection of a long burst
  77. GRB 260412A: Fermi GBM Final Real-time Localization
  78. GRB 260411B: COLIBRÍ optical observations
  79. GRB 260410B: Fermi GBM Observation
  80. GRB 260411B: Ondrejov D50 optical afterglow detection
  81. GRB 260411A: SVOM/GRM observation
  82. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  83. GRB 260411B: SVOM/GRM observation of a long burst
  84. GRB 260409A: Insight-HXMT/HE detection
  85. GRB 260411B: Fermi GBM Detection
  86. GRB 260411B: GOTO optical counterpart candidate
  87. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  88. GRB 260411B: Fermi GBM Final Real-time Localization
  89. GRB 260411A: Fermi GBM Final Real-time Localization
  90. GRB 260410A: COLIBRÍ optical upper limit
  91. GRB 260410A: Fermi GBM Observation
  92. GRB 260410B: SVOM/GRM detection of a short faint burst
  93. GRB 260410B: Fermi GBM Final Real-time Localization
  94. GRB 260410A: Fermi-LAT detection
  95. GRB 260410A: Fermi GBM Final Real-time Localization
  96. EP260321a: Chandra X-ray Non-detection
  97. GRB 260409A: Fermi GBM Final Real-time Localization
  98. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  99. GRB 260407A: GECAM-A detection
  100. GRB 260407A: Insight-HXMT/HE detection

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