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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').

19137 results found.

  1. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  2. GRB 250314A: ATCA radio upper limits
  3. EP250302a: VLA observations
  4. GRB 250317B: OHP/T193 continued follow-up
  5. GRB 250317B: Leavitt Observatory optical upper limit
  6. GRB 250309B/AT2025dws: further ATCA observations
  7. GRB 250317B: Mondy AZT-33IK Optical Observations
  8. GRB 250317B: NOT optical observations suggest an optical plateau phase
  9. GRB 250317B: GTC/OSIRIS+ spectroscopic redshift z=3.44
  10. GRB 250317B: OHP/T193 optical observations
  11. Fermi trigger No 763933627: Global MASTER-Net observations report
  12. GRB250312A: Swift/UVOT Upper Limits
  13. GRB 250317B: REM optical/NIR observations
  14. GRB 250317B: Swift-XRT observations
  15. GRB 250314A: REM optical/NIR upper limits
  16. GRB 250316A: AbAO AS-32 Optical Upper Limit
  17. EP 250317B: Fading optical counterpart detection by LCO
  18. GRB 250316A: Swift-XRT afterglow detection
  19. GRB 250317B: LCO detection of the fading optical afterglow
  20. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  21. GRB 250316A: Swift-XRT observations
  22. Fermi trigger No 763862734: Global MASTER-Net observations report
  23. Fermi GRB 250316A: Global MASTER-Net observations report
  24. GRB 250316A: Swift ToO observations
  25. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  26. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  27. GRB 250314A: EP-FXT afterglow detection
  28. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  29. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  30. GRB 250314A: Swift XRT Detection
  31. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  32. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  33. GRB 250314A: NOT near-infrared candidate counterpart
  34. GRB 250313A: Swift-XRT observations
  35. Fermi trigger No 763581136: Global MASTER-Net observations report
  36. GRB 250313A: Swift ToO observations
  37. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  38. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  39. Fermi GRB 250313A: Global MASTER-Net observations report
  40. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  41. EP250304a: SVOM/VT optical observation
  42. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  43. EP250302a: Chandra X-ray Detection
  44. Fermi trigger No 763509110: Global MASTER-Net observations report
  45. Fermi GRB 250312B: Global MASTER-Net observations report
  46. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  47. Swift GRB 250312A: Global MASTER-Net observations report
  48. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  49. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  50. GRB 250311A: Swift-XRT observations
  51. GRB 230509B: 1.3m DFOT Optical observations
  52. EP250311a: Global MASTER-Net observations report
  53. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  54. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  55. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  56. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  57. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  58. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  59. GRB 250309B: PRIME near-infrared detection
  60. EP250304a: Chandra detection
  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 250311A/MAXI J1457-026: MAXI/GSC detection
  66. GRB 250309B / AT2025dws: further SAO RAS optical observations
  67. IceCube-250309A: Upper limits from Fermi-GBM Observations
  68. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  69. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  70. GRB 250309B / IceCube-250309A: GECAM-B observations
  71. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  72. GRB 250309B / AT2025dws: SAO RAS optical observations
  73. GRB 250309B / AT2025dws: Swift-UVOT detection
  74. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  75. Fermi GRB 250309B: Global MASTER-Net observations report
  76. Fermi GRB 250309A: Global MASTER-Net observations report
  77. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  78. IceCube-250309A: No candidates from the Zwicky Transient Facility
  79. Fermi-LAT gamma-ray observations of IceCube-250309A
  80. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  81. GRB 230509B: Tiled Swift observations
  82. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  83. IceCube Alert 250309.32: Global MASTER-Net observations report
  84. EP250308a: Global MASTER-Net observations report
  85. EP250308a: GSP optical upper limit
  86. EP250308a: FTW optical and NIR upper limits
  87. EP250308a: Einstein Probe detection of an X-ray transient
  88. Fermi GRB 250307A: Global MASTER-Net observations report
  89. EP250304a: MeerKAT detection of a possible radio counterpart
  90. EP250302a:Xinglong optical observations
  91. Fermi trigger No 762963055: Global MASTER-Net observations report
  92. Swift GRB 250306A: Global MASTER-Net observations report
  93. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  94. GRB250101A: Radio upper limits from VLA observations
  95. EP250304A: Upper limits from Fermi-GBM Observations
  96. Fermi GRB 250305A: Global MASTER-Net observations report
  97. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  98. EP250302a: Optical Observations at CrAO and SAO RAS
  99. EP 250304A: Optical counterpart detection by LCO
  100. EP250302A: 1.3m DFOT optical afterglow detection

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