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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. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  2. EP250311a: Global MASTER-Net observations report
  3. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  4. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  5. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  6. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  7. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  8. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  9. GRB 250309B: PRIME near-infrared detection
  10. EP250304a: Chandra detection
  11. GRB 250225B: Swift-BAT refined analysis
  12. GRB 250311A/EP250311a: TRT optical upper limit
  13. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  14. GRB 250311A: Tiled Swift observations
  15. EP250311a/GRB 250311A: EP-WXT detection
  16. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  17. GRB 250311B: SVOM detection of a burst
  18. GRB 250309B: SVOM/VT optical observation
  19. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  20. The EP-WXT trigger 01709132425 is not a real source
  21. GRB 250309B / AT2025dws: further SAO RAS optical observations
  22. IceCube-250309A: Upper limits from Fermi-GBM Observations
  23. EP250308a: 1.6m Mephisto optical upper limits
  24. Konus-Wind detection of GRB 250309B
  25. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  26. IPN triangulation of GRB 250308A (short)
  27. IPN triangulation of GRB 250309B
  28. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  29. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  30. GRB 250309B: Swift-XRT refined Analysis
  31. GRB 250309B / IceCube-250309A: GECAM-B observations
  32. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  33. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  34. GRB 250309B / AT2025dws: SAO RAS optical observations
  35. GRB 250309B / AT2025dws: Swift-UVOT detection
  36. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  37. GRB 250309B: Fermi GBM Observation
  38. Fermi GRB 250309B: Global MASTER-Net observations report
  39. Fermi GRB 250309A: Global MASTER-Net observations report
  40. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  41. IceCube-250309A: No candidates from the Zwicky Transient Facility
  42. Fermi-LAT gamma-ray observations of IceCube-250309A
  43. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  44. GRB 250309B: Fermi GBM Final Localization
  45. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  46. GRB 230509B: Tiled Swift observations
  47. GRB 250308A: SVOM/GRM observation of a bright short burst
  48. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  49. IceCube Alert 250309.32: Global MASTER-Net observations report
  50. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  51. EP250308a: Global MASTER-Net observations report
  52. EP250308a: GSP optical upper limit
  53. EP250308a: FTW optical and NIR upper limits
  54. EP250308a: Einstein Probe detection of an X-ray transient
  55. EP250308a: NOT optical upper limit
  56. GRB 250309A: Fermi GBM Final Real-time Localization
  57. GRB 250306A: EIRSAT-1 GMOD detection
  58. The EP-WXT trigger 01709132387 is likely a flaring star
  59. Fermi GRB 250307A: Global MASTER-Net observations report
  60. Konus-Wind detection of GRB 250306A
  61. GRB 250307A: Fermi GBM Final Real-time Localization
  62. GRB 250306A: Swift-BAT refined analysis
  63. GRB 250306A: NuSTAR detection of the prompt emission
  64. EP250304a: MeerKAT detection of a possible radio counterpart
  65. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  66. GRB 250305A: AstroSat CZTI detection
  67. EP250302a:Xinglong optical observations
  68. GRB 250306A: AstroSat CZTI detection
  69. Fermi trigger No 762963055: Global MASTER-Net observations report
  70. Fermi Gamma-ray Burst Monitor trigger 762963055/250306591 is not a GRB
  71. Swift GRB 250306A: Global MASTER-Net observations report
  72. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  73. GRB 250306A: Swift detection of a burst
  74. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  75. GRB250101A: Radio upper limits from VLA observations
  76. LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate
  77. GRB 250305A: SVOM/GRM observation of a burst
  78. The EP-WXT trigger 01709132323 is likely a flaring star
  79. EP250304A: Upper limits from Fermi-GBM Observations
  80. Fermi GRB 250305A: Global MASTER-Net observations report
  81. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  82. GRB 250305A: Fermi GBM Final Real-time Localization
  83. EP250302a: Optical Observations at CrAO and SAO RAS
  84. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  85. EP 250304A: Optical counterpart detection by LCO
  86. EP250302A: 1.3m DFOT optical afterglow detection
  87. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  88. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  89. Konus-Wind detection of GRB 250222A
  90. EP250304a: REM NIR upper limits
  91. IPN triangulation of GRB 250222A
  92. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  93. EP250302a: Mondy Continued Optical Observations
  94. EP250304a: VLT/X-shooter redshift z = 0.200
  95. EP250304a: Swift-XRT detection of a fading X-ray source
  96. EP250304a: TRT optical counterpart detection
  97. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  98. EP250304a: Global MASTER-Net observations report
  99. EP250304a: Einstein Probe detection of an X-ray transient
  100. The EP-WXT trigger 01709132212 is not a real source

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