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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"

11756 results found.

  1. LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
  2. Swift GRB 250920B: Global MASTER-Net observations report
  3. GRB 250920A: AstroSat CZTI detection
  4. GRB 250920B: Fermi GBM Final Real-time Localization
  5. GRB 250920A: BALROG localization (Fermi Trigger 780029651 / GRB 250920121)
  6. GRB 250920A: Fermi GBM Final Localization
  7. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  8. GRB 250919A: Swift-XRT afterglow detection
  9. GRB 250919A: Fermi-LAT detection
  10. EP250919a: Einstein Probe detection of an X-ray transient
  11. GRB 250912A: SVOM/ECLAIRs refined analysis
  12. GRB 250916A: MAO/AZT-22 optical observations
  13. GRB 250916A: SAO RAS optical observations
  14. GRB 250917B: Fermi GBM Observation
  15. GRB 250916A: AstroSat CZTI detection of a bright long burst
  16. GRB 250910A: SVOM/ECLAIRs refined analysis
  17. Fermi GRB 250916A: Global MASTER-Net observations report
  18. SVOM/sb25091517: SVOM detection of an X-ray transient
  19. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  20. GRB 250912A: Swift-XRT observations
  21. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  22. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  23. EP250911a: Swift-XRT observations
  24. EP250910a: Global MASTER-Net observations report
  25. EP250911a: Einstein Probe detection of an X-ray transient
  26. GRB 250911A: Swift detection of a burst
  27. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  28. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  29. GRB 250909B: AstroSat CZTI detection of a long burst
  30. GRB 250909A: AstroSat CZTI detection
  31. GRB 250910A: SVOM detection of a faint burst
  32. EP#01709240653: Swift-XRT observations
  33. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  34. EP250908c: Global MASTER-Net observations report
  35. Fermi GRB 250909A: Global MASTER-Net observations report
  36. EP250908c: Einstein Probe detection of an X-ray transient
  37. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  38. GRB 250903A: Swift-XRT afterglow detection
  39. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  40. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  41. EP250905b: EP-FXT follow-up observation
  42. EP250905a: Liverpool Telescope observations
  43. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  44. EP250905b: Global MASTER-Net observations report
  45. EP250905b: EP-WXT detection of a fast X-ray transient
  46. EP250905a: FTW one optical and multiple NIR counterpart candidates
  47. GRB 250905A: Swift-XRT refined Analysis
  48. EP250905a: JinShan likely optical counterpart detection
  49. IceCube-250905A - IceCube observation of a high-energy neutrino candidate track-like event
  50. IceCube Alert 250905.84: Global MASTER-Net observations report
  51. EP250905a: Einstein Probe detection of an X-ray transient
  52. GRB 250903A: Swift/UVOT detection
  53. EP detected a brightening of LMXB 1ES 1735-26.9
  54. GRB 250905A: Swift detection of a burst
  55. Swift GRB250905.09: Global MASTER-Net observations report
  56. GRB 250903A: Swift-XRT observations
  57. EP250903a: Swift-XRT observations
  58. EP#01709201209: Swift-XRT observations
  59. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  60. GRB 250903A: EP-FXT counterpart detection
  61. EP250901a: Mondy, Assy and SAO RAS optical limits
  62. GRB 250902B: AstroSat CZTI detection
  63. GRB 250903A: SVOM detection of a burst
  64. EP250903a: Einstein Probe detection of an X-ray transient
  65. GRB 250902B: SVOM/GRM observation
  66. Fermi GRB 250902B: Global MASTER-Net observations report
  67. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  68. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  69. GRB 250901A: EP-FXT follow-up observation
  70. GRB 250901A: SVOM/VT optical afterglow with VHF data
  71. GRB 250901A: Swift-XRT afterglow detection
  72. EP250901a: Swift-XRT observations
  73. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  74. GRB 250901A: SVOM detection of a burst
  75. GRB 250830C: AstroSat CZTI detection of a long burst
  76. EP250901a: Einstein Probe detection of an X-ray transient
  77. EP250831a: EP-FXT follow-up observation
  78. EP250831a: Swift-XRT observations
  79. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  80. EP250831a: Global MASTER-Net observations report
  81. EP250831a: EP-WXT detection of a fast X-ray transient
  82. GRB 250831A: Swift-XRT counterpart detection
  83. GRB 250831A: SVOM detection of a soft burst
  84. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  85. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  86. GRB 250830B: MAXI/GSC detection
  87. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  88. The EP-WXT trigger 01709200994 is likely a flaring star
  89. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  90. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  91. GRB 250808B: SVOM detection of a burst through offline search
  92. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  93. EP250828a: Global MASTER-Net observations report
  94. EP250828a: SVOM/VT optical candidate
  95. EP250828a: Seimei/TriCCS optical counterpart detection
  96. EP250828a: Optical upper limit with Kinder observations
  97. EP250828a: Einstein Probe detection of an X-ray transient
  98. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  99. Fermi GRB 250827A: Global MASTER-Net observations report
  100. EP250827a: Swift-XRT counterpart detection

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