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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"

21953 results found.

  1. EP250321a: LCO optical counterpart detection
  2. EP250321A: COLIBRÍ Optical Observations
  3. EP250321a: VLT/X-shooter redshift z = 4.368
  4. EP250321a: REM optical/NIR afterglow detection
  5. Fermi GRB 250320B: Global MASTER-Net observations report
  6. EP250321a: Global MASTER-Net observations report
  7. Swift GRB 250321A: Global MASTER-Net observations report
  8. Fermi GRB 250321A: Global MASTER-Net observations report
  9. GRB 250321A: GOTO optical upper limits
  10. GRB 250314A: Keck/NIRC2 J-band upper limit
  11. EP250226a/GRB 250226A: KAIT optical observations
  12. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  13. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  14. Fermi GRB 250319B: Global MASTER-Net observations report
  15. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  16. LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
  17. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  18. GRB 250314A: ATCA radio upper limits
  19. EP250302a: VLA observations
  20. GRB 250317B: OHP/T193 continued follow-up
  21. GRB 250317B: Leavitt Observatory optical upper limit
  22. GRB 250309B/AT2025dws: further ATCA observations
  23. GRB 250317B: Mondy AZT-33IK Optical Observations
  24. GRB 250317B: NOT optical observations suggest an optical plateau phase
  25. GRB 250317B: GTC/OSIRIS+ spectroscopic redshift z=3.44
  26. GRB 250317B: OHP/T193 optical observations
  27. Fermi trigger No 763933627: Global MASTER-Net observations report
  28. GRB250312A: Swift/UVOT Upper Limits
  29. GRB 250317B: REM optical/NIR observations
  30. GRB 250317B: Swift-XRT observations
  31. GRB 250314A: REM optical/NIR upper limits
  32. GRB 250316A: AbAO AS-32 Optical Upper Limit
  33. EP 250317B: Fading optical counterpart detection by LCO
  34. GRB 250316A: Swift-XRT afterglow detection
  35. GRB 250317B: LCO detection of the fading optical afterglow
  36. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  37. GRB 250316A: Swift-XRT observations
  38. Fermi trigger No 763862734: Global MASTER-Net observations report
  39. Fermi GRB 250316A: Global MASTER-Net observations report
  40. GRB 250316A: Swift ToO observations
  41. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  42. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  43. GRB 250314A: EP-FXT afterglow detection
  44. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  45. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  46. GRB 250314A: Swift XRT Detection
  47. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  48. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  49. GRB 250314A: NOT near-infrared candidate counterpart
  50. GRB 250313A: Swift-XRT observations
  51. Fermi trigger No 763581136: Global MASTER-Net observations report
  52. GRB 250313A: Swift ToO observations
  53. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  54. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  55. Fermi GRB 250313A: Global MASTER-Net observations report
  56. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  57. EP250304a: SVOM/VT optical observation
  58. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  59. EP250302a: Chandra X-ray Detection
  60. Fermi trigger No 763509110: Global MASTER-Net observations report
  61. Fermi GRB 250312B: Global MASTER-Net observations report
  62. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  63. Swift GRB 250312A: Global MASTER-Net observations report
  64. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  65. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  66. GRB 250311A: Swift-XRT observations
  67. GRB 250309B: 1.3m DFOT Optical observations
  68. EP250311a: Global MASTER-Net observations report
  69. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  70. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  71. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  72. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  73. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  74. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  75. GRB 250309B: PRIME near-infrared detection
  76. EP250304a: Chandra detection
  77. GRB 250311A/EP250311a: TRT optical upper limit
  78. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  79. GRB 250311A: Tiled Swift observations
  80. EP250311a/GRB 250311A: EP-WXT detection
  81. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  82. GRB 250309B / AT2025dws: further SAO RAS optical observations
  83. IceCube-250309A: Upper limits from Fermi-GBM Observations
  84. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  85. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  86. GRB 250309B / IceCube-250309A: GECAM-B observations
  87. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  88. GRB 250309B / AT2025dws: SAO RAS optical observations
  89. GRB 250309B / AT2025dws: Swift-UVOT detection
  90. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  91. Fermi GRB 250309B: Global MASTER-Net observations report
  92. Fermi GRB 250309A: Global MASTER-Net observations report
  93. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  94. IceCube-250309A: No candidates from the Zwicky Transient Facility
  95. Fermi-LAT gamma-ray observations of IceCube-250309A
  96. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  97. GRB 230509B: Tiled Swift observations
  98. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  99. IceCube Alert 250309.32: Global MASTER-Net observations report
  100. EP250308a: Global MASTER-Net observations report

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