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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"

5515 results found.

  1. Fermi GRB 250321A: Global MASTER-Net observations report
  2. EP250321a: Einstein Probe detection of an X-ray transient
  3. GRB 250321A: GOTO optical upper limits
  4. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  5. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  6. Fermi GRB 250319B: Global MASTER-Net observations report
  7. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  8. GRB 250313A: GRBAlpha detection
  9. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  10. GRB 250317D: EIRSAT-1 GMOD Detection
  11. EP250302a: VLA observations
  12. GRB 250317B: OHP/T193 continued follow-up
  13. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  14. GRB 250317C: SVOM/GRM observation of a long burst
  15. GRB 250317B: Leavitt Observatory optical upper limit
  16. GRB 250309B/AT2025dws: further ATCA observations
  17. GRB 250317B: Mondy AZT-33IK Optical Observations
  18. GRB 250317C: AstroSat CZTI detection
  19. GRB 250317B: NOT optical observations suggest an optical plateau phase
  20. GRB 250317B: GTC/OSIRIS+ spectroscopic redshift z=3.44
  21. GRB 250317C: GECAM-B detection
  22. GRB 250317B: OHP/T193 optical observations
  23. Fermi trigger No 763933627: Global MASTER-Net observations report
  24. GRB 250317B: REM optical/NIR observations
  25. GRB 250316A: AbAO AS-32 Optical Upper Limit
  26. EP 250317B: Fading optical counterpart detection by LCO
  27. GRB 250317B: LCO detection of the fading optical afterglow
  28. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  29. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  30. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  31. GRB 250317B: SVOM detection of a burst
  32. Fermi trigger No 763862734: Global MASTER-Net observations report
  33. Fermi GRB 250316A: Global MASTER-Net observations report
  34. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  35. The EP-WXT trigger 01709132801 is likely a flaring star
  36. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  37. GRB 250314A: EP-FXT afterglow detection
  38. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  39. GRB 250312B: GRBAlpha detection
  40. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  41. EP250315a: Einstein Probe detection of an X-ray transient
  42. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  43. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  44. GRB 250314A: SVOM detection of a burst
  45. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  46. GRB 250313B: SVOM/GRM observation of a soft bright short burst
  47. GRB 250313A: SVOM/GRM observation of a bright long burst
  48. GRB 250313A: AstroSat CZTI detection of a bright long burst
  49. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  50. Fermi trigger No 763581136: Global MASTER-Net observations report
  51. EP250304a: Pan-STARRS r and i-band imaging and photometry
  52. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  53. Fermi GRB 250313A: Global MASTER-Net observations report
  54. The EP-WXT trigger 01709132551 is not a real source
  55. EP250304a: SVOM/VT optical observation
  56. EP250311a/GRB 250311A: EP-FXT follow-up observation
  57. EP250302a: Chandra X-ray Detection
  58. Fermi trigger No 763509110: Global MASTER-Net observations report
  59. Fermi GRB 250312B: Global MASTER-Net observations report
  60. Swift GRB 250312A: Global MASTER-Net observations report
  61. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  62. GRB 241228A: VIRT Optical Upper Limit
  63. GRB 250309B: 1.3m DFOT Optical observations
  64. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  65. EP250311a: Global MASTER-Net observations report
  66. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  67. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  68. EP250304a: Chandra detection
  69. GRB 250311A/EP250311a: TRT optical upper limit
  70. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  71. EP250311a/GRB 250311A: EP-WXT detection
  72. GRB 250311B: SVOM detection of a burst
  73. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  74. The EP-WXT trigger 01709132425 is not a real source
  75. EP250308a: 1.6m Mephisto optical upper limits
  76. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  77. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  78. GRB 250309B: Swift-XRT refined Analysis
  79. GRB 250309B / IceCube-250309A: GECAM-B observations
  80. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  81. GRB 250309B / AT2025dws: SAO RAS optical observations
  82. GRB 250309B / AT2025dws: Swift-UVOT detection
  83. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  84. Fermi GRB 250309B: Global MASTER-Net observations report
  85. Fermi GRB 250309A: Global MASTER-Net observations report
  86. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  87. IceCube-250309A: No candidates from the Zwicky Transient Facility
  88. Fermi-LAT gamma-ray observations of IceCube-250309A
  89. GRB 250308A: SVOM/GRM observation of a bright short burst
  90. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  91. IceCube Alert 250309.32: Global MASTER-Net observations report
  92. EP250308a: Global MASTER-Net observations report
  93. EP250308a: FTW optical and NIR upper limits
  94. EP250308a: Einstein Probe detection of an X-ray transient
  95. GRB 250309A: Fermi GBM Final Real-time Localization
  96. GRB 250306A: EIRSAT-1 GMOD detection
  97. The EP-WXT trigger 01709132387 is likely a flaring star
  98. Fermi GRB 250307A: Global MASTER-Net observations report
  99. GRB 250306A: NuSTAR detection of the prompt emission
  100. GRB 250305A: AstroSat CZTI detection

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