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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"

37704 results found.

  1. GRB250312A: Swift/UVOT Upper Limits
  2. GRB 250317B: REM optical/NIR observations
  3. GRB 250317B: Swift-XRT observations
  4. GRB 250316A: Swift/UVOT Upper Limits
  5. GRB 250314A: REM optical/NIR upper limits
  6. GRB 250316A: AbAO AS-32 Optical Upper Limit
  7. EP 250317B: Fading optical counterpart detection by LCO
  8. GRB 250316A: Swift-XRT afterglow detection
  9. GRB 250317B: LCO detection of the fading optical afterglow
  10. GRB 250317B: refined SVOM/MXT analysis
  11. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  12. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  13. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  14. GRB 250317B: SVOM detection of a burst
  15. GRB 250316A: Fermi GBM Observation
  16. GRB 250316A: Swift-XRT observations
  17. Fermi trigger No 763862734: Global MASTER-Net observations report
  18. GRB 250317A: Fermi GBM Final Real-time Localization
  19. Fermi GRB 250316A: Global MASTER-Net observations report
  20. GRB 250314A: SVOM/GRM analysis
  21. GRB 250316A: Swift ToO observations
  22. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  23. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  24. GRB 250316A: Fermi GBM Final Real-time Localization
  25. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  26. GRB 250314A: EP-FXT afterglow detection
  27. GRB 250314A: Swift/UVOT Upper Limits
  28. GRB 250312B: GRBAlpha detection
  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. SVOM/MXT upper limit on GRB 250314A
  34. GRB 250314A: SVOM/VT upper limit
  35. GRB 250314A: NOT near-infrared candidate counterpart
  36. GRB 250313A: Fermi GBM Detection
  37. GRB 250313A: CALET Gamma-Ray Burst Monitor detection
  38. GRB 250312B: Fermi GBM Observation
  39. GRB 250313A: Swift-XRT observations
  40. Konus-Wind detection of GRB 250313A
  41. Konus-Wind detection of GRB 250308A
  42. GRB 250314A: SVOM detection of a burst
  43. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  44. GRB 250313B: SVOM/GRM observation of a soft bright short burst
  45. GRB 250313A: SVOM/GRM observation of a bright long burst
  46. GRB 250313A: AstroSat CZTI detection of a bright long burst
  47. Fermi trigger No 763581136: Global MASTER-Net observations report
  48. GRB 250313A: Fermi-LAT detection
  49. GRB 250313A: Swift ToO observations
  50. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  51. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  52. Fermi GRB 250313A: Global MASTER-Net observations report
  53. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  54. GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)
  55. GRB 250313A: Fermi GBM Final Real-time Localization
  56. EP250311a/GRB 250311A: EP-FXT follow-up observation
  57. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  58. GRB 250312A: Swift-XRT refined Analysis
  59. Fermi Gamma-ray Burst Monitor trigger 763509110/250312911 is not a GRB
  60. Fermi trigger No 763509110: Global MASTER-Net observations report
  61. Fermi GRB 250312B: Global MASTER-Net observations report
  62. GRB 250312A: Enhanced Swift-XRT position
  63. GRB 250312B: Fermi GBM Final Localization
  64. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  65. GRB 250226B: Fermi GBM Observation
  66. Swift GRB 250312A: Global MASTER-Net observations report
  67. GRB 250302A: Fermi GBM Observation
  68. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  69. GRB 250312A: Swift detection of a burst
  70. GRB 241213A: VIRT Optical Upper Limit
  71. GRB 241228A: VIRT Optical Upper Limit
  72. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  73. GRB 250223B: Fermi GBM Observation
  74. GRB 250311A: Swift-XRT observations
  75. GRB 250228A: Fermi GBM Observation
  76. GRB 250309B: 1.3m DFOT Optical observations
  77. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  78. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  79. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  80. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  81. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  82. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  83. GRB 250309B: PRIME near-infrared detection
  84. GRB 250225B: Swift-BAT refined analysis
  85. GRB 250311A/EP250311a: TRT optical upper limit
  86. GRB 250311A: Tiled Swift observations
  87. EP250311a/GRB 250311A: EP-WXT detection
  88. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  89. GRB 250311B: SVOM detection of a burst
  90. GRB 250309B: SVOM/VT optical observation
  91. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  92. GRB 250309B / AT2025dws: further SAO RAS optical observations
  93. IceCube-250309A: Upper limits from Fermi-GBM Observations
  94. Konus-Wind detection of GRB 250309B
  95. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  96. IPN triangulation of GRB 250308A (short)
  97. IPN triangulation of GRB 250309B
  98. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  99. GRB 250309B: Swift-XRT refined Analysis
  100. GRB 250309B / IceCube-250309A: GECAM-B observations

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