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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"

28105 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: GOTO optical upper limits
  10. GRB 250321A: Swift-XRT localisation
  11. GRB 250314A: Keck/NIRC2 J-band upper limit
  12. EP250226a/GRB 250226A: KAIT optical observations
  13. GRB 250321A: Swift detection of a burst
  14. GRB 250321A: Fermi GBM Final Real-time Localization
  15. GRB 250320B: Fermi GBM Final Real-time Localization
  16. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  17. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  18. GRB 250320A: Fermi GBM Final Real-time Localization
  19. GRB 250313A: GRBAlpha detection
  20. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  21. GRB 250319B: Fermi GBM Final Localization
  22. GRB 250319A: Fermi GBM Final Localization
  23. GRB 250317D: EIRSAT-1 GMOD Detection
  24. EP250302a: VLA observations
  25. GRB 250317B: OHP/T193 continued follow-up
  26. GRB 250309B/AT2025dws: further ATCA observations
  27. GRB 250317B: Mondy AZT-33IK Optical Observations
  28. GRB 250317C: AstroSat CZTI detection
  29. GRB 250317B: NOT optical observations suggest an optical plateau phase
  30. GRB 250317B: GTC/OSIRIS+ spectroscopic redshift z=3.44
  31. GRB 250317C: GECAM-B detection
  32. GRB250312A: Swift/UVOT Upper Limits
  33. GRB 250317B: REM optical/NIR observations
  34. GRB 250317B: Swift-XRT observations
  35. GRB 250316A: Swift/UVOT Upper Limits
  36. GRB 250314A: REM optical/NIR upper limits
  37. GRB 250316A: AbAO AS-32 Optical Upper Limit
  38. EP 250317B: Fading optical counterpart detection by LCO
  39. GRB 250316A: Swift-XRT afterglow detection
  40. GRB 250317B: LCO detection of the fading optical afterglow
  41. GRB 250317B: refined SVOM/MXT analysis
  42. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  43. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  44. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  45. GRB 250317B: SVOM detection of a burst
  46. GRB 250316A: Swift-XRT observations
  47. GRB 250317A: Fermi GBM Final Real-time Localization
  48. GRB 250316A: Swift ToO observations
  49. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  50. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  51. GRB 250316A: Fermi GBM Final Real-time Localization
  52. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  53. GRB 250314A: EP-FXT afterglow detection
  54. GRB 250314A: Swift/UVOT Upper Limits
  55. GRB 250312B: GRBAlpha detection
  56. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  57. GRB 250314A: Swift XRT Detection
  58. EP250315a: Einstein Probe detection of an X-ray transient
  59. SVOM/MXT upper limit on GRB 250314A
  60. GRB 250314A: SVOM/VT upper limit
  61. GRB 250314A: NOT near-infrared candidate counterpart
  62. GRB 250313A: Fermi GBM Detection
  63. GRB 250313A: CALET Gamma-Ray Burst Monitor detection
  64. GRB 250313A: Swift-XRT observations
  65. Konus-Wind detection of GRB 250313A
  66. Konus-Wind detection of GRB 250308A
  67. GRB 250314A: SVOM detection of a burst
  68. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  69. FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
  70. GRB 250313A: AstroSat CZTI detection of a bright long burst
  71. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  72. GRB 250313A: Fermi-LAT detection
  73. GRB 250313A: Swift ToO observations
  74. EP250304a: Pan-STARRS r and i-band imaging and photometry
  75. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  76. GRB 250313A: Fermi GBM Final Real-time Localization
  77. EP250304a: SVOM/VT optical observation
  78. EP250311a/GRB 250311A: EP-FXT follow-up observation
  79. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  80. EP250302a: Chandra X-ray Detection
  81. GRB 250312A: Swift-XRT refined Analysis
  82. GRB 250312A: Enhanced Swift-XRT position
  83. GRB 250312B: Fermi GBM Final Localization
  84. GRB 250312A: Swift detection of a burst
  85. GRB 241213A: VIRT Optical Upper Limit
  86. GRB 241228A: VIRT Optical Upper Limit
  87. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  88. GRB 250311A: Swift-XRT observations
  89. GRB 250309B: 1.3m DFOT Optical observations
  90. GRB 250309B: PRIME near-infrared detection
  91. EP250304a: Chandra detection
  92. GRB 250311A: Tiled Swift observations
  93. EP250311a/GRB 250311A: EP-WXT detection
  94. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  95. GRB 250311B: SVOM detection of a burst
  96. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  97. IceCube-250309A: Upper limits from Fermi-GBM Observations
  98. Konus-Wind detection of GRB 250309B
  99. IPN triangulation of GRB 250308A (short)
  100. IPN triangulation of GRB 250309B

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