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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').
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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"

32849 results found.

  1. GRB 250321A: Fermi GBM Final Real-time Localization
  2. GRB 250320B: Fermi GBM Final Real-time Localization
  3. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  4. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  5. GRB 250320A: Fermi GBM Final Real-time Localization
  6. Fermi GRB 250319B: Global MASTER-Net observations report
  7. GRB 250313A: GRBAlpha detection
  8. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  9. GRB 250319B: Fermi GBM Final Localization
  10. GRB 250319A: Fermi GBM Final Localization
  11. GRB 250317D: EIRSAT-1 GMOD Detection
  12. GRB 250314A: ATCA radio upper limits
  13. GRB 250317B: OHP/T193 continued follow-up
  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. GRB250312A: Swift/UVOT Upper Limits
  24. GRB 250317B: REM optical/NIR observations
  25. GRB 250317B: Swift-XRT observations
  26. GRB 250316A: Swift/UVOT Upper Limits
  27. GRB 250314A: REM optical/NIR upper limits
  28. GRB 250316A: AbAO AS-32 Optical Upper Limit
  29. EP 250317B: Fading optical counterpart detection by LCO
  30. GRB 250316A: Swift-XRT afterglow detection
  31. GRB 250317B: LCO detection of the fading optical afterglow
  32. GRB 250317B: refined SVOM/MXT analysis
  33. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  34. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  35. GRB 250317B: SVOM detection of a burst
  36. GRB 250316A: Fermi GBM Observation
  37. GRB 250316A: Swift-XRT observations
  38. GRB 250317A: Fermi GBM Final Real-time Localization
  39. Fermi GRB 250316A: Global MASTER-Net observations report
  40. GRB 250314A: SVOM/GRM analysis
  41. GRB 250316A: Swift ToO observations
  42. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  43. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  44. GRB 250316A: Fermi GBM Final Real-time Localization
  45. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  46. GRB 250314A: EP-FXT afterglow detection
  47. GRB 250314A: Swift/UVOT Upper Limits
  48. GRB 250312B: GRBAlpha detection
  49. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  50. GRB 250314A: Swift XRT Detection
  51. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  52. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  53. SVOM/MXT upper limit on GRB 250314A
  54. GRB 250314A: SVOM/VT upper limit
  55. GRB 250314A: NOT near-infrared candidate counterpart
  56. GRB 250313A: Fermi GBM Detection
  57. GRB 250313A: CALET Gamma-Ray Burst Monitor detection
  58. GRB 250312B: Fermi GBM Observation
  59. GRB 250313A: Swift-XRT observations
  60. Konus-Wind detection of GRB 250313A
  61. Konus-Wind detection of GRB 250308A
  62. GRB 250314A: SVOM detection of a burst
  63. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  64. GRB 250313B: SVOM/GRM observation of a soft bright short burst
  65. GRB 250313A: SVOM/GRM observation of a bright long burst
  66. FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
  67. GRB 250313A: AstroSat CZTI detection of a bright long burst
  68. GRB 250313A: Fermi-LAT detection
  69. GRB 250313A: Swift ToO observations
  70. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  71. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  72. Fermi GRB 250313A: Global MASTER-Net observations report
  73. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  74. GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)
  75. GRB 250313A: Fermi GBM Final Real-time Localization
  76. EP250311a/GRB 250311A: EP-FXT follow-up observation
  77. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  78. GRB 250312A: Swift-XRT refined Analysis
  79. Fermi Gamma-ray Burst Monitor trigger 763509110/250312911 is not a GRB
  80. Fermi GRB 250312B: Global MASTER-Net observations report
  81. GRB 250312A: Enhanced Swift-XRT position
  82. GRB 250312B: Fermi GBM Final Localization
  83. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  84. GRB 250226B: Fermi GBM Observation
  85. Swift GRB 250312A: Global MASTER-Net observations report
  86. GRB 250302A: Fermi GBM Observation
  87. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  88. GRB 250312A: Swift detection of a burst
  89. GRB 241213A: VIRT Optical Upper Limit
  90. GRB 241228A: VIRT Optical Upper Limit
  91. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  92. GRB 250223B: Fermi GBM Observation
  93. GRB 250311A: Swift-XRT observations
  94. GRB 250228A: Fermi GBM Observation
  95. GRB 230509B: 1.3m DFOT Optical observations
  96. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  97. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  98. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  99. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  100. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB

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