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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"

27397 results found.

  1. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  2. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  3. IceCube Alert 260425A: Global MASTER-Net observations report
  4. Fermi trigger No 798737427: Global MASTER-Net observations report
  5. GRB 260401A: cubesat Avion detection
  6. EP260321a: Upper limits from ATCA radio observations
  7. GRB 260421B: Kilonova-Catcher optical afterglow detection
  8. The EP-WXT trigger 01709258652: Mondy optical observations
  9. EP260416a: Mondy optical observations
  10. GRB 260421B: 3.6m DOT optical observation
  11. EP260416a: ZTSh R band observations
  12. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  13. GRB 260421B: SVOM/GRM observation
  14. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  15. GRB 260421B: EP-FXT follow-up observation
  16. GOTO26djh/AT2026jpw: ATCA radio detection
  17. GRB 260421B: J-band upper limit with WINTER
  18. GRB 260421B: LCO optical counterpart detection
  19. GRB 260421B: Fermi GBM Observation
  20. GOTO26djh/AT2026jpw: radio detection at 15GHz
  21. GRB 260421B: SVOM/VT optical observations
  22. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  23. GRB 260310A: Late-time Chandra X-ray Detection
  24. EP260416a: 1.3m DFOT optical observation
  25. Fermi GRB 260421C: Global MASTER-Net observations report
  26. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  27. Fermi GRB 260421B: Global MASTER-Net observations report
  28. GRB 260421B: LCO optical afterglow confirmation
  29. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  30. GRB 260421B: TRT optical counterpart detection
  31. GRB 260421B: SVOM detection of a long burst
  32. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  33. Fermi GRB 260421A: Global MASTER-Net observations report
  34. EP260321a: VLA radio follow-up
  35. GRB 260412A: LCOGT Optical Upper Limits
  36. EP260416a: Optical follow-up observations with Kinder
  37. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  38. GRB 260417A: SVOM/GRM observation
  39. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  40. Fermi trigger No 798275385: Global MASTER-Net observations report
  41. EP260417a: GROWTH-India Telescope optical upper limit
  42. Fermi GRB 260417B: Global MASTER-Net observations report
  43. EP260417b: GROWTH-India Telescope optical upper limit
  44. EP260416a: Ondrejov D50 optical detection
  45. EP260417a: Global MASTER-Net observations report
  46. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  47. EP260416a: GMG Optical Observation
  48. Fermi GRB 260417A: Global MASTER-Net observations report
  49. EP260416a: LCO observations confirm end of flaring phase
  50. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  51. EP260417a: TRT optical counterpart detection
  52. EP260417a: Einstein Probe detection of an X-ray transient
  53. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  54. EP260417b: Einstein Probe detection of a fast X-ray transient
  55. EP260416a: KAIT optical upper limit
  56. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  57. EP260416a: WFST optical observations and rebrightening
  58. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  59. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  60. GRB 260415B: Glowbug gamma-ray detection
  61. GRB 260411B: Glowbug gamma-ray detection
  62. EP260416a: COLIBRÍ optical counterpart candidate
  63. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  64. EP260416a: Global MASTER-Net observations report
  65. EP260416a: Einstein Probe detection of an X-ray transient
  66. GOTO26djh/AT2026jpw : MASTER OT observation
  67. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  68. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  69. GRB 260415B: NuSTAR detection of long prompt emission
  70. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  71. Fermi trigger No 797912738: Global MASTER-Net observations report
  72. GRB 260414A: Glowbug gamma-ray detection
  73. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  74. EP260321a: CMO SAI J,K observations
  75. Fermi GRB 260413A: Global MASTER-Net observations report
  76. GRB 260410A: Glowbug gamma-ray detection of a short burst
  77. Fermi GRB 260412A: Global MASTER-Net observations report
  78. GRB 260412A: Fermi GBM Observation
  79. GRB 260411B: Fermi-LAT detection
  80. GRB 260411B: COLIBRÍ optical observations
  81. GRB 260410B: Fermi GBM Observation
  82. GRB260411B: 3.6m DOT optical observation
  83. GRB 260411A: SVOM/GRM observation
  84. GRB 260411B: SVOM/GRM observation of a long burst
  85. GRB 260409A: Insight-HXMT/HE detection
  86. GRB 260411B: Fermi GBM Detection
  87. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  88. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  89. GRB 260410A: COLIBRÍ optical upper limit
  90. EP-WXT01709259790: Optical Upper limits with kinder observations
  91. GRB 260410A: Fermi GBM Observation
  92. GRB 260410B: SVOM/GRM detection of a short faint burst
  93. EP-WXT01709259790: Xinglong optical upper limit
  94. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  95. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  96. EP260409a: COLIBRÍ optical upper limits
  97. EP260409a: Global MASTER-Net observations report
  98. EP260409a: Einstein Probe detection of an X-ray transient
  99. EP260321a: VLA radio detection
  100. GRB 260407A: Glowbug gamma-ray detection

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