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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"

5401 results found.

  1. GRB 250317B: Leavitt Observatory optical upper limit
  2. GRB 250309B/AT2025dws: further ATCA observations
  3. GRB 250317B: Mondy AZT-33IK Optical Observations
  4. GRB 250317C: AstroSat CZTI detection
  5. GRB 250317B: NOT optical observations suggest an optical plateau phase
  6. GRB 250317B: GTC/OSIRIS+ spectroscopic redshift z=3.44
  7. GRB 250317C: GECAM-B detection
  8. GRB 250317B: OHP/T193 optical observations
  9. Fermi trigger No 763933627: Global MASTER-Net observations report
  10. GRB 250317B: REM optical/NIR observations
  11. GRB 250316A: AbAO AS-32 Optical Upper Limit
  12. EP 250317B: Fading optical counterpart detection by LCO
  13. GRB 250317B: LCO detection of the fading optical afterglow
  14. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  15. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  16. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  17. GRB 250317B: SVOM detection of a burst
  18. Fermi trigger No 763862734: Global MASTER-Net observations report
  19. Fermi GRB 250316A: Global MASTER-Net observations report
  20. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  21. The EP-WXT trigger 01709132801 is likely a flaring star
  22. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  23. GRB 250314A: EP-FXT afterglow detection
  24. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  25. GRB 250312B: GRBAlpha detection
  26. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  27. EP250315a: Einstein Probe detection of an X-ray transient
  28. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  29. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  30. GRB 250314A: SVOM detection of a burst
  31. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  32. GRB 250313B: SVOM/GRM observation of a soft bright short burst
  33. GRB 250313A: SVOM/GRM observation of a bright long burst
  34. GRB 250313A: AstroSat CZTI detection of a bright long burst
  35. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  36. Fermi trigger No 763581136: Global MASTER-Net observations report
  37. EP250304a: Pan-STARRS r and i-band imaging and photometry
  38. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  39. Fermi GRB 250313A: Global MASTER-Net observations report
  40. The EP-WXT trigger 01709132551 is not a real source
  41. EP250304a: SVOM/VT optical observation
  42. EP250311a/GRB 250311A: EP-FXT follow-up observation
  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. Swift GRB 250312A: Global MASTER-Net observations report
  47. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  48. GRB 241228A: VIRT Optical Upper Limit
  49. GRB 250309B: 1.3m DFOT Optical observations
  50. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  51. EP250311a: Global MASTER-Net observations report
  52. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  53. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  54. EP250304a: Chandra detection
  55. GRB 250311A/EP250311a: TRT optical upper limit
  56. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  57. EP250311a/GRB 250311A: EP-WXT detection
  58. GRB 250311B: SVOM detection of a burst
  59. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  60. The EP-WXT trigger 01709132425 is not a real source
  61. EP250308a: 1.6m Mephisto optical upper limits
  62. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  63. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  64. GRB 250309B: Swift-XRT refined Analysis
  65. GRB 250309B / IceCube-250309A: GECAM-B observations
  66. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  67. GRB 250309B / AT2025dws: SAO RAS optical observations
  68. GRB 250309B / AT2025dws: Swift-UVOT detection
  69. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  70. Fermi GRB 250309B: Global MASTER-Net observations report
  71. Fermi GRB 250309A: Global MASTER-Net observations report
  72. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  73. IceCube-250309A: No candidates from the Zwicky Transient Facility
  74. Fermi-LAT gamma-ray observations of IceCube-250309A
  75. GRB 250308A: SVOM/GRM observation of a bright short burst
  76. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  77. IceCube Alert 250309.32: Global MASTER-Net observations report
  78. EP250308a: Global MASTER-Net observations report
  79. EP250308a: FTW optical and NIR upper limits
  80. EP250308a: Einstein Probe detection of an X-ray transient
  81. GRB 250309A: Fermi GBM Final Real-time Localization
  82. GRB 250306A: EIRSAT-1 GMOD detection
  83. The EP-WXT trigger 01709132387 is likely a flaring star
  84. Fermi GRB 250307A: Global MASTER-Net observations report
  85. GRB 250306A: NuSTAR detection of the prompt emission
  86. GRB 250305A: AstroSat CZTI detection
  87. EP250302a:Xinglong optical observations
  88. GRB 250306A: AstroSat CZTI detection
  89. Fermi trigger No 762963055: Global MASTER-Net observations report
  90. Swift GRB 250306A: Global MASTER-Net observations report
  91. GRB 250305A: SVOM/GRM observation of a burst
  92. The EP-WXT trigger 01709132323 is likely a flaring star
  93. EP250304A: Upper limits from Fermi-GBM Observations
  94. Fermi GRB 250305A: Global MASTER-Net observations report
  95. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  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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