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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. GRB 250312A: Swift detection of a burst
  2. GRB 241213A: VIRT Optical Upper Limit
  3. GRB 241228A: VIRT Optical Upper Limit
  4. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  5. GRB 250223B: Fermi GBM Observation
  6. GRB 250311A: Swift-XRT observations
  7. GRB 250228A: Fermi GBM Observation
  8. GRB 230509B: 1.3m DFOT Optical observations
  9. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  10. EP250311a: Global MASTER-Net observations report
  11. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  12. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  13. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  14. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  15. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  16. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  17. GRB 250309B: PRIME near-infrared detection
  18. EP250304a: Chandra detection
  19. GRB 250225B: Swift-BAT refined analysis
  20. GRB 250311A/EP250311a: TRT optical upper limit
  21. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  22. GRB 250311A: Tiled Swift observations
  23. EP250311a/GRB 250311A: EP-WXT detection
  24. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  25. GRB 250311B: SVOM detection of a burst
  26. GRB 250309B: SVOM/VT optical observation
  27. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  28. The EP-WXT trigger 01709132425 is not a real source
  29. GRB 250309B / AT2025dws: further SAO RAS optical observations
  30. IceCube-250309A: Upper limits from Fermi-GBM Observations
  31. EP250308a: 1.6m Mephisto optical upper limits
  32. Konus-Wind detection of GRB 250309B
  33. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  34. IPN triangulation of GRB 250308A (short)
  35. IPN triangulation of GRB 250309B
  36. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  37. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  38. GRB 250309B: Swift-XRT refined Analysis
  39. GRB 250309B / IceCube-250309A: GECAM-B observations
  40. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  41. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  42. GRB 250309B / AT2025dws: SAO RAS optical observations
  43. GRB 250309B / AT2025dws: Swift-UVOT detection
  44. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  45. GRB 250309B: Fermi GBM Observation
  46. Fermi GRB 250309B: Global MASTER-Net observations report
  47. Fermi GRB 250309A: Global MASTER-Net observations report
  48. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  49. IceCube-250309A: No candidates from the Zwicky Transient Facility
  50. Fermi-LAT gamma-ray observations of IceCube-250309A
  51. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  52. GRB 250309B: Fermi GBM Final Localization
  53. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  54. GRB 230509B: Tiled Swift observations
  55. GRB 250308A: SVOM/GRM observation of a bright short burst
  56. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  57. IceCube Alert 250309.32: Global MASTER-Net observations report
  58. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  59. EP250308a: Global MASTER-Net observations report
  60. EP250308a: GSP optical upper limit
  61. EP250308a: FTW optical and NIR upper limits
  62. EP250308a: Einstein Probe detection of an X-ray transient
  63. EP250308a: NOT optical upper limit
  64. GRB 250309A: Fermi GBM Final Real-time Localization
  65. GRB 250306A: EIRSAT-1 GMOD detection
  66. The EP-WXT trigger 01709132387 is likely a flaring star
  67. Fermi GRB 250307A: Global MASTER-Net observations report
  68. Konus-Wind detection of GRB 250306A
  69. GRB 250307A: Fermi GBM Final Real-time Localization
  70. GRB 250306A: Swift-BAT refined analysis
  71. GRB 250306A: NuSTAR detection of the prompt emission
  72. EP250304a: MeerKAT detection of a possible radio counterpart
  73. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  74. GRB 250305A: AstroSat CZTI detection
  75. EP250302a:Xinglong optical observations
  76. GRB 250306A: AstroSat CZTI detection
  77. Fermi trigger No 762963055: Global MASTER-Net observations report
  78. Fermi Gamma-ray Burst Monitor trigger 762963055/250306591 is not a GRB
  79. Swift GRB 250306A: Global MASTER-Net observations report
  80. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  81. GRB 250306A: Swift detection of a burst
  82. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  83. GRB250101A: Radio upper limits from VLA observations
  84. LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate
  85. GRB 250305A: SVOM/GRM observation of a burst
  86. The EP-WXT trigger 01709132323 is likely a flaring star
  87. EP250304A: Upper limits from Fermi-GBM Observations
  88. Fermi GRB 250305A: Global MASTER-Net observations report
  89. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  90. GRB 250305A: Fermi GBM Final Real-time Localization
  91. EP250302a: Optical Observations at CrAO and SAO RAS
  92. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  93. EP 250304A: Optical counterpart detection by LCO
  94. EP250302A: 1.3m DFOT optical afterglow detection
  95. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  96. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  97. Konus-Wind detection of GRB 250222A
  98. EP250304a: REM NIR upper limits
  99. IPN triangulation of GRB 250222A
  100. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve

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