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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. Konus-Wind detection of GRB 250313A
  2. Konus-Wind detection of GRB 250308A
  3. GRB 250314A: SVOM detection of a burst
  4. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  5. GRB 250313B: SVOM/GRM observation of a soft bright short burst
  6. GRB 250313A: SVOM/GRM observation of a bright long burst
  7. FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
  8. GRB 250313A: AstroSat CZTI detection of a bright long burst
  9. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  10. Fermi trigger No 763581136: Global MASTER-Net observations report
  11. GRB 250313A: Fermi-LAT detection
  12. GRB 250313A: Swift ToO observations
  13. EP250304a: Pan-STARRS r and i-band imaging and photometry
  14. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  15. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  16. Fermi GRB 250313A: Global MASTER-Net observations report
  17. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  18. GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)
  19. GRB 250313A: Fermi GBM Final Real-time Localization
  20. The EP-WXT trigger 01709132551 is not a real source
  21. EP250304a: SVOM/VT optical observation
  22. EP250311a/GRB 250311A: EP-FXT follow-up observation
  23. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  24. EP250302a: Chandra X-ray Detection
  25. GRB 250312A: Swift-XRT refined Analysis
  26. Fermi Gamma-ray Burst Monitor trigger 763509110/250312911 is not a GRB
  27. Fermi trigger No 763509110: Global MASTER-Net observations report
  28. Fermi GRB 250312B: Global MASTER-Net observations report
  29. GRB 250312A: Enhanced Swift-XRT position
  30. GRB 250312B: Fermi GBM Final Localization
  31. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  32. GRB 250226B: Fermi GBM Observation
  33. Swift GRB 250312A: Global MASTER-Net observations report
  34. GRB 250302A: Fermi GBM Observation
  35. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  36. GRB 250312A: Swift detection of a burst
  37. GRB 241213A: VIRT Optical Upper Limit
  38. GRB 241228A: VIRT Optical Upper Limit
  39. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  40. GRB 250223B: Fermi GBM Observation
  41. GRB 250311A: Swift-XRT observations
  42. GRB 250228A: Fermi GBM Observation
  43. GRB 250309B: 1.3m DFOT Optical observations
  44. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  45. EP250311a: Global MASTER-Net observations report
  46. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  47. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  48. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  49. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  50. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  51. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  52. GRB 250309B: PRIME near-infrared detection
  53. EP250304a: Chandra detection
  54. GRB 250225B: Swift-BAT refined analysis
  55. GRB 250311A/EP250311a: TRT optical upper limit
  56. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  57. GRB 250311A: Tiled Swift observations
  58. EP250311a/GRB 250311A: EP-WXT detection
  59. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  60. GRB 250311B: SVOM detection of a burst
  61. GRB 250309B: SVOM/VT optical observation
  62. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  63. The EP-WXT trigger 01709132425 is not a real source
  64. GRB 250309B / AT2025dws: further SAO RAS optical observations
  65. IceCube-250309A: Upper limits from Fermi-GBM Observations
  66. EP250308a: 1.6m Mephisto optical upper limits
  67. Konus-Wind detection of GRB 250309B
  68. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  69. IPN triangulation of GRB 250308A (short)
  70. IPN triangulation of GRB 250309B
  71. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  72. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  73. GRB 250309B: Swift-XRT refined Analysis
  74. GRB 250309B / IceCube-250309A: GECAM-B observations
  75. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  76. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  77. GRB 250309B / AT2025dws: SAO RAS optical observations
  78. GRB 250309B / AT2025dws: Swift-UVOT detection
  79. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  80. GRB 250309B: Fermi GBM Observation
  81. Fermi GRB 250309B: Global MASTER-Net observations report
  82. Fermi GRB 250309A: Global MASTER-Net observations report
  83. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  84. IceCube-250309A: No candidates from the Zwicky Transient Facility
  85. Fermi-LAT gamma-ray observations of IceCube-250309A
  86. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  87. GRB 250309B: Fermi GBM Final Localization
  88. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  89. GRB 230509B: Tiled Swift observations
  90. GRB 250308A: SVOM/GRM observation of a bright short burst
  91. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  92. IceCube Alert 250309.32: Global MASTER-Net observations report
  93. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  94. EP250308a: Global MASTER-Net observations report
  95. EP250308a: GSP optical upper limit
  96. EP250308a: FTW optical and NIR upper limits
  97. EP250308a: Einstein Probe detection of an X-ray transient
  98. EP250308a: NOT optical upper limit
  99. GRB 250309A: Fermi GBM Final Real-time Localization
  100. GRB 250306A: EIRSAT-1 GMOD detection

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