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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. GRB 250314A: NOT near-infrared candidate counterpart
  2. GRB 250313A: Fermi GBM Detection
  3. GRB 250313A: CALET Gamma-Ray Burst Monitor detection
  4. GRB 250312B: Fermi GBM Observation
  5. GRB 250313A: Swift-XRT observations
  6. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  7. Konus-Wind detection of GRB 250313A
  8. Konus-Wind detection of GRB 250308A
  9. GRB 250314A: SVOM detection of a burst
  10. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  11. GRB 250313B: SVOM/GRM observation of a soft bright short burst
  12. GRB 250313A: SVOM/GRM observation of a bright long burst
  13. FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
  14. GRB 250313A: AstroSat CZTI detection of a bright long burst
  15. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  16. Fermi trigger No 763581136: Global MASTER-Net observations report
  17. GRB 250313A: Fermi-LAT detection
  18. GRB 250313A: Swift ToO observations
  19. EP250304a: Pan-STARRS r and i-band imaging and photometry
  20. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  21. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  22. Fermi GRB 250313A: Global MASTER-Net observations report
  23. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  24. GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)
  25. GRB 250313A: Fermi GBM Final Real-time Localization
  26. The EP-WXT trigger 01709132551 is not a real source
  27. EP250304a: SVOM/VT optical observation
  28. EP250311a/GRB 250311A: EP-FXT follow-up observation
  29. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  30. EP250302a: Chandra X-ray Detection
  31. GRB 250312A: Swift-XRT refined Analysis
  32. Fermi Gamma-ray Burst Monitor trigger 763509110/250312911 is not a GRB
  33. Fermi trigger No 763509110: Global MASTER-Net observations report
  34. Fermi GRB 250312B: Global MASTER-Net observations report
  35. GRB 250312A: Enhanced Swift-XRT position
  36. GRB 250312B: Fermi GBM Final Localization
  37. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  38. GRB 250226B: Fermi GBM Observation
  39. Swift GRB 250312A: Global MASTER-Net observations report
  40. GRB 250302A: Fermi GBM Observation
  41. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  42. GRB 250312A: Swift detection of a burst
  43. GRB 241213A: VIRT Optical Upper Limit
  44. GRB 241228A: VIRT Optical Upper Limit
  45. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  46. GRB 250223B: Fermi GBM Observation
  47. GRB 250311A: Swift-XRT observations
  48. GRB 250228A: Fermi GBM Observation
  49. GRB 250309B: 1.3m DFOT Optical observations
  50. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  51. EP250311a: Global MASTER-Net observations report
  52. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  53. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  54. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  55. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  56. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  57. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  58. GRB 250309B: PRIME near-infrared detection
  59. EP250304a: Chandra detection
  60. GRB 250225B: Swift-BAT refined analysis
  61. GRB 250311A/EP250311a: TRT optical upper limit
  62. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  63. GRB 250311A: Tiled Swift observations
  64. EP250311a/GRB 250311A: EP-WXT detection
  65. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  66. GRB 250311B: SVOM detection of a burst
  67. GRB 250309B: SVOM/VT optical observation
  68. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  69. The EP-WXT trigger 01709132425 is not a real source
  70. GRB 250309B / AT2025dws: further SAO RAS optical observations
  71. IceCube-250309A: Upper limits from Fermi-GBM Observations
  72. EP250308a: 1.6m Mephisto optical upper limits
  73. Konus-Wind detection of GRB 250309B
  74. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  75. IPN triangulation of GRB 250308A (short)
  76. IPN triangulation of GRB 250309B
  77. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  78. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  79. GRB 250309B: Swift-XRT refined Analysis
  80. GRB 250309B / IceCube-250309A: GECAM-B observations
  81. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  82. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  83. GRB 250309B / AT2025dws: SAO RAS optical observations
  84. GRB 250309B / AT2025dws: Swift-UVOT detection
  85. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  86. GRB 250309B: Fermi GBM Observation
  87. Fermi GRB 250309B: Global MASTER-Net observations report
  88. Fermi GRB 250309A: Global MASTER-Net observations report
  89. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  90. IceCube-250309A: No candidates from the Zwicky Transient Facility
  91. Fermi-LAT gamma-ray observations of IceCube-250309A
  92. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  93. GRB 250309B: Fermi GBM Final Localization
  94. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  95. GRB 230509B: Tiled Swift observations
  96. GRB 250308A: SVOM/GRM observation of a bright short burst
  97. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  98. IceCube Alert 250309.32: Global MASTER-Net observations report
  99. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  100. EP250308a: Global MASTER-Net observations report

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