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

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