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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. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  2. GRB 250226B: Fermi GBM Observation
  3. Swift GRB 250312A: Global MASTER-Net observations report
  4. GRB 250302A: Fermi GBM Observation
  5. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  6. GRB 250312A: Swift detection of a burst
  7. GRB 241213A: VIRT Optical Upper Limit
  8. GRB 241228A: VIRT Optical Upper Limit
  9. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  10. GRB 250223B: Fermi GBM Observation
  11. GRB 250311A: Swift-XRT observations
  12. GRB 250228A: Fermi GBM Observation
  13. GRB 230509B: 1.3m DFOT Optical observations
  14. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  15. EP250311a: Global MASTER-Net observations report
  16. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  17. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  18. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  19. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  20. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  21. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  22. GRB 250309B: PRIME near-infrared detection
  23. EP250304a: Chandra detection
  24. GRB 250225B: Swift-BAT refined analysis
  25. GRB 250311A/EP250311a: TRT optical upper limit
  26. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  27. GRB 250311A: Tiled Swift observations
  28. EP250311a/GRB 250311A: EP-WXT detection
  29. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  30. GRB 250311B: SVOM detection of a burst
  31. GRB 250309B: SVOM/VT optical observation
  32. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  33. The EP-WXT trigger 01709132425 is not a real source
  34. GRB 250309B / AT2025dws: further SAO RAS optical observations
  35. IceCube-250309A: Upper limits from Fermi-GBM Observations
  36. EP250308a: 1.6m Mephisto optical upper limits
  37. Konus-Wind detection of GRB 250309B
  38. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  39. IPN triangulation of GRB 250308A (short)
  40. IPN triangulation of GRB 250309B
  41. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  42. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  43. GRB 250309B: Swift-XRT refined Analysis
  44. GRB 250309B / IceCube-250309A: GECAM-B observations
  45. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  46. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  47. GRB 250309B / AT2025dws: SAO RAS optical observations
  48. GRB 250309B / AT2025dws: Swift-UVOT detection
  49. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  50. GRB 250309B: Fermi GBM Observation
  51. Fermi GRB 250309B: Global MASTER-Net observations report
  52. Fermi GRB 250309A: Global MASTER-Net observations report
  53. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  54. IceCube-250309A: No candidates from the Zwicky Transient Facility
  55. Fermi-LAT gamma-ray observations of IceCube-250309A
  56. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  57. GRB 250309B: Fermi GBM Final Localization
  58. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  59. GRB 230509B: Tiled Swift observations
  60. GRB 250308A: SVOM/GRM observation of a bright short burst
  61. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  62. IceCube Alert 250309.32: Global MASTER-Net observations report
  63. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  64. EP250308a: Global MASTER-Net observations report
  65. EP250308a: GSP optical upper limit
  66. EP250308a: FTW optical and NIR upper limits
  67. EP250308a: Einstein Probe detection of an X-ray transient
  68. EP250308a: NOT optical upper limit
  69. GRB 250309A: Fermi GBM Final Real-time Localization
  70. GRB 250306A: EIRSAT-1 GMOD detection
  71. The EP-WXT trigger 01709132387 is likely a flaring star
  72. Fermi GRB 250307A: Global MASTER-Net observations report
  73. Konus-Wind detection of GRB 250306A
  74. GRB 250307A: Fermi GBM Final Real-time Localization
  75. GRB 250306A: Swift-BAT refined analysis
  76. GRB 250306A: NuSTAR detection of the prompt emission
  77. EP250304a: MeerKAT detection of a possible radio counterpart
  78. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  79. GRB 250305A: AstroSat CZTI detection
  80. EP250302a:Xinglong optical observations
  81. GRB 250306A: AstroSat CZTI detection
  82. Fermi trigger No 762963055: Global MASTER-Net observations report
  83. Fermi Gamma-ray Burst Monitor trigger 762963055/250306591 is not a GRB
  84. Swift GRB 250306A: Global MASTER-Net observations report
  85. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  86. GRB 250306A: Swift detection of a burst
  87. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  88. GRB250101A: Radio upper limits from VLA observations
  89. LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate
  90. GRB 250305A: SVOM/GRM observation of a burst
  91. The EP-WXT trigger 01709132323 is likely a flaring star
  92. EP250304A: Upper limits from Fermi-GBM Observations
  93. Fermi GRB 250305A: Global MASTER-Net observations report
  94. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  95. GRB 250305A: Fermi GBM Final Real-time Localization
  96. EP250302a: Optical Observations at CrAO and SAO RAS
  97. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  98. EP 250304A: Optical counterpart detection by LCO
  99. EP250302A: 1.3m DFOT optical afterglow detection
  100. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube

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