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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').
  1. FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
  2. GRB 250313A: AstroSat CZTI detection of a bright long burst
  3. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  4. Fermi trigger No 763581136: Global MASTER-Net observations report
  5. GRB 250313A: Fermi-LAT detection
  6. GRB 250313A: Swift ToO observations
  7. EP250304a: Pan-STARRS r and i-band imaging and photometry
  8. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  9. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  10. Fermi GRB 250313A: Global MASTER-Net observations report
  11. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  12. GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)
  13. GRB 250313A: Fermi GBM Final Real-time Localization
  14. The EP-WXT trigger 01709132551 is not a real source
  15. EP250304a: SVOM/VT optical observation
  16. EP250311a/GRB 250311A: EP-FXT follow-up observation
  17. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  18. EP250302a: Chandra X-ray Detection
  19. GRB 250312A: Swift-XRT refined Analysis
  20. Fermi Gamma-ray Burst Monitor trigger 763509110/250312911 is not a GRB
  21. Fermi trigger No 763509110: Global MASTER-Net observations report
  22. Fermi GRB 250312B: Global MASTER-Net observations report
  23. GRB 250312A: Enhanced Swift-XRT position
  24. GRB 250312B: Fermi GBM Final Localization
  25. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  26. GRB 250226B: Fermi GBM Observation
  27. Swift GRB 250312A: Global MASTER-Net observations report
  28. GRB 250302A: Fermi GBM Observation
  29. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  30. GRB 250312A: Swift detection of a burst
  31. GRB 241213A: VIRT Optical Upper Limit
  32. GRB 241228A: VIRT Optical Upper Limit
  33. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  34. GRB 250223B: Fermi GBM Observation
  35. GRB 250311A: Swift-XRT observations
  36. GRB 250228A: Fermi GBM Observation
  37. GRB 230509B: 1.3m DFOT Optical observations
  38. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  39. EP250311a: Global MASTER-Net observations report
  40. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  41. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  42. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  43. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  44. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  45. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  46. GRB 250309B: PRIME near-infrared detection
  47. EP250304a: Chandra detection
  48. GRB 250225B: Swift-BAT refined analysis
  49. GRB 250311A/EP250311a: TRT optical upper limit
  50. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  51. GRB 250311A: Tiled Swift observations
  52. EP250311a/GRB 250311A: EP-WXT detection
  53. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  54. GRB 250311B: SVOM detection of a burst
  55. GRB 250309B: SVOM/VT optical observation
  56. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  57. The EP-WXT trigger 01709132425 is not a real source
  58. GRB 250309B / AT2025dws: further SAO RAS optical observations
  59. IceCube-250309A: Upper limits from Fermi-GBM Observations
  60. EP250308a: 1.6m Mephisto optical upper limits
  61. Konus-Wind detection of GRB 250309B
  62. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  63. IPN triangulation of GRB 250308A (short)
  64. IPN triangulation of GRB 250309B
  65. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  66. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  67. GRB 250309B: Swift-XRT refined Analysis
  68. GRB 250309B / IceCube-250309A: GECAM-B observations
  69. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  70. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  71. GRB 250309B / AT2025dws: SAO RAS optical observations
  72. GRB 250309B / AT2025dws: Swift-UVOT detection
  73. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  74. GRB 250309B: Fermi GBM Observation
  75. Fermi GRB 250309B: Global MASTER-Net observations report
  76. Fermi GRB 250309A: Global MASTER-Net observations report
  77. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  78. IceCube-250309A: No candidates from the Zwicky Transient Facility
  79. Fermi-LAT gamma-ray observations of IceCube-250309A
  80. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  81. GRB 250309B: Fermi GBM Final Localization
  82. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  83. GRB 230509B: Tiled Swift observations
  84. GRB 250308A: SVOM/GRM observation of a bright short burst
  85. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  86. IceCube Alert 250309.32: Global MASTER-Net observations report
  87. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  88. EP250308a: Global MASTER-Net observations report
  89. EP250308a: GSP optical upper limit
  90. EP250308a: FTW optical and NIR upper limits
  91. EP250308a: Einstein Probe detection of an X-ray transient
  92. EP250308a: NOT optical upper limit
  93. GRB 250309A: Fermi GBM Final Real-time Localization
  94. GRB 250306A: EIRSAT-1 GMOD detection
  95. The EP-WXT trigger 01709132387 is likely a flaring star
  96. Fermi GRB 250307A: Global MASTER-Net observations report
  97. Konus-Wind detection of GRB 250306A
  98. GRB 250307A: Fermi GBM Final Real-time Localization
  99. GRB 250306A: Swift-BAT refined analysis
  100. GRB 250306A: NuSTAR detection of the prompt emission

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