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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"

14934 results found.

  1. EP250321a: LCO optical counterpart detection
  2. EP250321a: Swift-XRT detection of an X-ray source
  3. EP250321a: VLT/X-shooter redshift z = 4.368
  4. GRB 250320B: AstroSat CZTI detection
  5. EP250321a: REM optical/NIR afterglow detection
  6. EP250321a: BOOTES-5/JGT optical afterglow detection
  7. EP250321a: TRT optical counterpart detection
  8. EP250321a: Einstein Probe detection of an X-ray transient
  9. GRB 250321A: Swift detection of a burst
  10. GRB 250321A: Fermi GBM Final Real-time Localization
  11. GRB 250320B: Fermi GBM Final Real-time Localization
  12. GRB 250320A: Fermi GBM Final Real-time Localization
  13. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  14. GRB 250313A: GRBAlpha detection
  15. GRB 250319B: Fermi GBM Final Localization
  16. GRB 250319A: Fermi GBM Final Localization
  17. GRB 250317D: EIRSAT-1 GMOD Detection
  18. EP250302a: VLA observations
  19. GRB 250309B/AT2025dws: further ATCA observations
  20. GRB 250317C: AstroSat CZTI detection
  21. GRB 250317C: GECAM-B detection
  22. EP 250317B: Fading optical counterpart detection by LCO
  23. GRB 250316A: Swift-XRT afterglow detection
  24. GRB 250317B: LCO detection of the fading optical afterglow
  25. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  26. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  27. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  28. GRB 250317B: SVOM detection of a burst
  29. GRB 250317A: Fermi GBM Final Real-time Localization
  30. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  31. GRB 250316A: Fermi GBM Final Real-time Localization
  32. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  33. GRB 250314A: EP-FXT afterglow detection
  34. GRB 250314A: Swift/UVOT Upper Limits
  35. GRB 250312B: GRBAlpha detection
  36. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  37. GRB 250314A: Swift XRT Detection
  38. EP250315a: Einstein Probe detection of an X-ray transient
  39. GRB 250314A: SVOM/VT upper limit
  40. GRB 250314A: NOT near-infrared candidate counterpart
  41. GRB 250313A: Fermi GBM Detection
  42. GRB 250313A: CALET Gamma-Ray Burst Monitor detection
  43. Konus-Wind detection of GRB 250313A
  44. Konus-Wind detection of GRB 250308A
  45. GRB 250314A: SVOM detection of a burst
  46. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  47. FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
  48. GRB 250313A: AstroSat CZTI detection of a bright long burst
  49. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  50. GRB 250313A: Fermi-LAT detection
  51. EP250304a: Pan-STARRS r and i-band imaging and photometry
  52. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  53. GRB 250313A: Fermi GBM Final Real-time Localization
  54. EP250311a/GRB 250311A: EP-FXT follow-up observation
  55. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  56. EP250302a: Chandra X-ray Detection
  57. GRB 250312B: Fermi GBM Final Localization
  58. GRB 250312A: Swift detection of a burst
  59. GRB 241213A: VIRT Optical Upper Limit
  60. GRB 241228A: VIRT Optical Upper Limit
  61. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  62. GRB 250309B: 1.3m DFOT Optical observations
  63. GRB 250309B: PRIME near-infrared detection
  64. EP250304a: Chandra detection
  65. EP250311a/GRB 250311A: EP-WXT detection
  66. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  67. GRB 250311B: SVOM detection of a burst
  68. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  69. IceCube-250309A: Upper limits from Fermi-GBM Observations
  70. Konus-Wind detection of GRB 250309B
  71. IPN triangulation of GRB 250308A (short)
  72. IPN triangulation of GRB 250309B
  73. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  74. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  75. GRB 250309B / AT2025dws: Swift-UVOT detection
  76. IceCube-250309A: No candidates from the Zwicky Transient Facility
  77. Fermi-LAT gamma-ray observations of IceCube-250309A
  78. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  79. GRB 250309B: Fermi GBM Final Localization
  80. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  81. EP250308a: GSP optical upper limit
  82. EP250308a: Einstein Probe detection of an X-ray transient
  83. GRB 250309A: Fermi GBM Final Real-time Localization
  84. GRB 250306A: EIRSAT-1 GMOD detection
  85. Konus-Wind detection of GRB 250306A
  86. GRB 250307A: Fermi GBM Final Real-time Localization
  87. GRB 250306A: NuSTAR detection of the prompt emission
  88. EP250304a: MeerKAT detection of a possible radio counterpart
  89. GRB 250305A: AstroSat CZTI detection
  90. GRB 250306A: AstroSat CZTI detection
  91. GRB 250306A: Swift detection of a burst
  92. LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate
  93. GRB 250305A: Fermi GBM Final Real-time Localization
  94. EP 250304A: Optical counterpart detection by LCO
  95. EP250302A: 1.3m DFOT optical afterglow detection
  96. Konus-Wind detection of GRB 250222A
  97. IPN triangulation of GRB 250222A
  98. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  99. EP250304a: Swift-XRT detection of a fading X-ray source
  100. EP250304a: TRT optical counterpart detection

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