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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"

27323 results found.

  1. GRB 260503A: SVOM/GRM observation of a GRB
  2. Konus-Wind detection of GRB 260411C
  3. GRB 260504B: REM optical/NIR observations
  4. GRB 260504B: LCO z-band upper limit
  5. SVOM GRB 260504B: MASTER-OAFA optical observations
  6. GRB 260504B: SVOM detection of a short burst
  7. Fermi GRB 260504A: Global MASTER-Net observations report
  8. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  9. GRB 260429B / EP260429a: EP-FXT follow-up observation
  10. EP260502a: Einstein Probe detection of an X-ray transient
  11. GRB 260429A: SVOM/GRM observation of a short burst
  12. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  13. EP260429a: Global MASTER-Net observations report
  14. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  15. GRB 260424B: AstroSat CZTI detection
  16. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  17. EP260429a: LCO optical upper limits
  18. EP260430a: LCO optical upper limits
  19. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  20. GRB 260429A: Fermi GBM Detection
  21. Fermi GRB 260429A: Global MASTER-Net observations report
  22. EP260430a: Global MASTER-Net observations report
  23. EP260430a: Einstein Probe detection of an X-ray transient
  24. EP260429a: EP-WXT detection of a fast X-ray transient
  25. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  26. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  27. Fermi GRB 260428A: Global MASTER-Net observations report
  28. EP260416a: Mondy and Terskol optical upper limits
  29. GRB 260424B: Glowbug gamma-ray detection of a short burst
  30. GRB 260424B: COLIBRÍ optical upper limit
  31. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  32. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  33. IceCube Alert 260425A: Global MASTER-Net observations report
  34. Fermi trigger No 798737427: Global MASTER-Net observations report
  35. GRB 260401A: cubesat Avion detection
  36. EP260321a: Upper limits from ATCA radio observations
  37. GRB 260421B: Kilonova-Catcher optical afterglow detection
  38. The EP-WXT trigger 01709258652: Mondy optical observations
  39. EP260416a: Mondy optical observations
  40. GRB 260421B: 3.6m DOT optical observation
  41. EP260416a: ZTSh R band observations
  42. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  43. GRB 260421B: SVOM/GRM observation
  44. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  45. GRB 260421B: EP-FXT follow-up observation
  46. GOTO26djh/AT2026jpw: ATCA radio detection
  47. GRB 260421B: J-band upper limit with WINTER
  48. GRB 260421B: LCO optical counterpart detection
  49. GRB 260421B: Fermi GBM Observation
  50. GOTO26djh/AT2026jpw: radio detection at 15GHz
  51. GRB 260421B: SVOM/VT optical observations
  52. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  53. GRB 260310A: Late-time Chandra X-ray Detection
  54. EP260416a: 1.3m DFOT optical observation
  55. Fermi GRB 260421C: Global MASTER-Net observations report
  56. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  57. Fermi GRB 260421B: Global MASTER-Net observations report
  58. GRB 260421B: LCO optical afterglow confirmation
  59. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  60. GRB 260421B: TRT optical counterpart detection
  61. GRB 260421B: SVOM detection of a long burst
  62. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  63. Fermi GRB 260421A: Global MASTER-Net observations report
  64. EP260321a: VLA radio follow-up
  65. GRB 260412A: LCOGT Optical Upper Limits
  66. EP260416a: Optical follow-up observations with Kinder
  67. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  68. GRB 260417A: SVOM/GRM observation
  69. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  70. Fermi trigger No 798275385: Global MASTER-Net observations report
  71. EP260417a: GROWTH-India Telescope optical upper limit
  72. Fermi GRB 260417B: Global MASTER-Net observations report
  73. EP260417b: GROWTH-India Telescope optical upper limit
  74. EP260416a: Ondrejov D50 optical detection
  75. EP260417a: Global MASTER-Net observations report
  76. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  77. EP260416a: GMG Optical Observation
  78. Fermi GRB 260417A: Global MASTER-Net observations report
  79. EP260416a: LCO observations confirm end of flaring phase
  80. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  81. EP260417a: TRT optical counterpart detection
  82. EP260417a: Einstein Probe detection of an X-ray transient
  83. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  84. EP260417b: Einstein Probe detection of a fast X-ray transient
  85. EP260416a: KAIT optical upper limit
  86. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  87. EP260416a: WFST optical observations and rebrightening
  88. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  89. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  90. GRB 260415B: Glowbug gamma-ray detection
  91. GRB 260411B: Glowbug gamma-ray detection
  92. EP260416a: COLIBRÍ optical counterpart candidate
  93. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  94. EP260416a: Global MASTER-Net observations report
  95. EP260416a: Einstein Probe detection of an X-ray transient
  96. GOTO26djh/AT2026jpw : MASTER OT observation
  97. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  98. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  99. GRB 260415B: NuSTAR detection of long prompt emission
  100. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow

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