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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"
  1. EP261015a: VST optical observations
  2. GRB 261024A: BALROG localization (Fermi Trigger 814551785 / GRB 261024683)
  3. GRB 261024A: Fermi GBM Final Real-time Localization
  4. EP261023a: Mondy optical upper limit
  5. EP261015a: MAO/AZT-22 optical observations
  6. EP261015a: VLA non-detection
  7. EP261023a: NOT optical counterpart candidate
  8. EP261023a: Einstein Probe detection of an X-ray transient
  9. GRB 261019A: Insight-HXMT/HE detection
  10. The EP-WXT trigger 01709321472 is likely a flaring star
  11. IceCube-261020A: Upper limits from a search for additional neutrino events in IceCube
  12. NuSTAR 261020, a 830s hard X-ray transient
  13. EP261015a: GSP multiband optical follow-up observations
  14. GRB 261017A: SVOM/GRM observation
  15. GRB 261021A: Fermi GBM Final Real-time Localization
  16. EP261015a: Further optical observations with the 1.3m DFOT
  17. GRB 261020B: AstroSat CZTI detection of a short burst
  18. Fermi-LAT Gamma-ray Observations of IceCube-261020A
  19. EP261015a: AZT-20 Assy-Turgen optical observations
  20. GRB 261020A: Fermi GBM Observation
  21. GRB 261017A: SAO RAS optical upper limit
  22. EP261015a: Wendelstein 43 cm optical observations
  23. GRB 260903A
  24. EP261015a: Follow-up with the 1.3m DFOT
  25. EP261015a: Terskol Zeiss-2000 optical upper limit
  26. EP261007b: Further EP-FXT follow-up observations
  27. GRB 261017A: COLIBRÍ optical upper limit
  28. IceCube-261020A - IceCube observation of a high-energy neutrino candidate track-like event
  29. GRB 261020A: MAXI GSC detection
  30. GRB 261020A: Fermi GBM Final Real-time Localization
  31. EP261015a: COLIBRÍ optical observations of a rebrightening
  32. Konus-Wind detection of GRB 261017A
  33. GRB 261019A: Fermi GBM Final Localization
  34. GRB 261017A: Possible Swift/UVOT Detection
  35. GRB 261017A: Luminance-band upper limit from a 28cm telescope in Chengde
  36. GRB 261017A: R-band upper limit with the 1.3-m DFOT
  37. GRB 261017A: Swift-BAT refined analysis
  38. GRB 261017A: a short minimum variability timescale compatible with a compact object merger origin
  39. EP261015b: NOT Optical Observations
  40. GRB 261017A: J band upper limit by the SYSU 80cm infrared telescope
  41. EP261015c: refined analysis of the EP-FXT observation favors a stellar flare interpretation
  42. GRB 261017A : MITSuME Akeno optical upper limits
  43. GRB 261017A: Swift-XRT refined Analysis
  44. GRB 261017A: Nanshan/NEXT optical upper limit
  45. GRB 261017A: Enhanced Swift-XRT position
  46. GRB 261017A: Fermi GBM Observation
  47. GRB261010A: Retraction of Keck/MOSFIRE near-IR source
  48. GRB 261017A: Swift detection of a burst
  49. GRB 261017A: Fermi GBM Final Real-time Localization
  50. EP261015a: Tentative fading of the candidate optical counterpart from the NOT
  51. EP261015b: Refined analysis of EP-FXT observations
  52. EP261015b: J-band upper limit by the SYSU 80cm infrared telescope
  53. EP261015a: refined analysis of EP-FXT observations
  54. EP261015c: J-band upper limit with WINTER
  55. EP261015a: J-band upper limit with WINTER
  56. EP261006a / AT 2026aetp: Optical follow-up with the 1.3-m DFOT
  57. GRB 261011A: 1.3m DFOT optical upper limit
  58. GRB 261010A: Pan-STARRS z-band imaging and upper limit
  59. EP261015a: SVOM/VT optical observation
  60. EP241111a and EP250125a: Upper limits from SVOM/GRM Observations
  61. GRB 261010A: VLA radio observations
  62. EP261015a: COLIBRÍ optical observations
  63. EP261015c: Einstein Probe detection of a fast X-ray transient
  64. EP261015b: Einstein Probe detection of an X-ray transient
  65. GRB261010A: Keck/MOSFIRE detection of a near-IR source
  66. EP261015a: Einstein Probe detection of a fast X-ray transient
  67. EP261015a (WXT 11900947714): Possible optical counterpart from NOT and LCO
  68. The EP-WXT trigger 01709321333 is likely a flaring star
  69. GRB 261010A: ASKAP non-detection of a radio afterglow
  70. GRB 261010A: LBT tentative near-infrared detection
  71. GRB 261011A: SAO RAS and AbAO optical observations
  72. GRB 261010A: Glowbug gamma-ray detection
  73. GRB 261008A: SVOM/GRM observation
  74. GRB 261009A: GECAM-B detection of a burst
  75. EP261006a : MeerKAT radio observations.
  76. IceCube-261012A: Upper limits from a search for additional neutrino events in IceCube
  77. GRB 261010A: initial pulse rest-frame energetics from Konus-Wind detection
  78. GRB 261010A: a short minimum variability timescale and a distinct pulse evolution compatible with a merger origin
  79. GRB 261013A: Fermi GBM Final Real-time Localization
  80. GRB 261011A: Later-epoch J-band upper limit from the SYSU 80 cm infrared telescope
  81. Fermi-LAT Gamma-ray Observations of IceCube-261012A
  82. GRID detection of GRB 261010A
  83. GRB 261011A: GECAM-B observation
  84. GRB 261011B: GECAM-B observation
  85. GRB 261010A: J-band upper limit by the SYSU 80cm infrared telescope
  86. IceCube-260919A: No transient candidates from the Zwicky Transient Facility
  87. GRB 261010A: Swift-XRT refined Analysis
  88. GRB 261011A: Swift-XRT refined Analysis
  89. GRB 261011A: Enhanced Swift-XRT position
  90. GRB 261010A: a Type I-L (merger-driven) GRB candidate
  91. GRB 261011A: 10.4m GTC spectroscopic redshift (z = 2.407)
  92. GRB 261011A: Swift-BAT refined analysis
  93. IceCube-261012A - IceCube observation of a high-energy neutrino candidate track-like event
  94. GRB 261010A: 10.4m GTC spectroscopy of the galaxy 2" from the afterglow
  95. MAXI GRB261012.23: Global MASTER-Net observations report
  96. GRB 261011A: REM optical/NIR observations
  97. Konus-Wind detection of GRB 261010A
  98. Konus-Wind detection of GRB 261011A
  99. Konus-Wind detection of GRB 261007A/EP261007a
  100. GRB 261011A: SOAR optical afterglow observations at ~17 hours

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