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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"

11529 results found.

  1. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  2. GRB 250312B: GRBAlpha detection
  3. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  4. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  5. GRB 250313A: Fermi GBM Detection
  6. GRB 250313A: CALET Gamma-Ray Burst Monitor detection
  7. GRB 250312B: Fermi GBM Observation
  8. GRB 250313A: Swift-XRT observations
  9. Konus-Wind detection of GRB 250313A
  10. Konus-Wind detection of GRB 250308A
  11. GRB 250313A: SVOM/GRM observation of a bright long burst
  12. GRB 250313A: AstroSat CZTI detection of a bright long burst
  13. Fermi trigger No 763581136: Global MASTER-Net observations report
  14. GRB 250313A: Fermi-LAT detection
  15. GRB 250313A: Swift ToO observations
  16. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  17. Fermi GRB 250313A: Global MASTER-Net observations report
  18. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  19. GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)
  20. GRB 250313A: Fermi GBM Final Real-time Localization
  21. Fermi Gamma-ray Burst Monitor trigger 763509110/250312911 is not a GRB
  22. Fermi trigger No 763509110: Global MASTER-Net observations report
  23. Fermi GRB 250312B: Global MASTER-Net observations report
  24. GRB 250312B: Fermi GBM Final Localization
  25. GRB 250226B: Fermi GBM Observation
  26. GRB 250302A: Fermi GBM Observation
  27. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  28. GRB 250223B: Fermi GBM Observation
  29. GRB 250228A: Fermi GBM Observation
  30. GRB 250309B: 1.3m DFOT Optical observations
  31. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  32. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  33. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  34. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  35. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  36. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  37. GRB 250309B: PRIME near-infrared detection
  38. GRB 250309B: SVOM/VT optical observation
  39. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  40. GRB 250309B / AT2025dws: further SAO RAS optical observations
  41. IceCube-250309A: Upper limits from Fermi-GBM Observations
  42. Konus-Wind detection of GRB 250309B
  43. IPN triangulation of GRB 250308A (short)
  44. IPN triangulation of GRB 250309B
  45. GRB 250309B: Swift-XRT refined Analysis
  46. GRB 250309B / IceCube-250309A: GECAM-B observations
  47. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  48. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  49. GRB 250309B / AT2025dws: SAO RAS optical observations
  50. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  51. GRB 250309B: Fermi GBM Observation
  52. Fermi GRB 250309B: Global MASTER-Net observations report
  53. Fermi GRB 250309A: Global MASTER-Net observations report
  54. Fermi-LAT gamma-ray observations of IceCube-250309A
  55. GRB 250309B: Fermi GBM Final Localization
  56. GRB 230509B: Tiled Swift observations
  57. GRB 250308A: SVOM/GRM observation of a bright short burst
  58. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  59. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  60. GRB 250309A: Fermi GBM Final Real-time Localization
  61. Fermi GRB 250307A: Global MASTER-Net observations report
  62. GRB 250307A: Fermi GBM Final Real-time Localization
  63. GRB 250305A: AstroSat CZTI detection
  64. Fermi trigger No 762963055: Global MASTER-Net observations report
  65. Fermi Gamma-ray Burst Monitor trigger 762963055/250306591 is not a GRB
  66. GRB 250305A: SVOM/GRM observation of a burst
  67. EP250304A: Upper limits from Fermi-GBM Observations
  68. Fermi GRB 250305A: Global MASTER-Net observations report
  69. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  70. GRB 250305A: Fermi GBM Final Real-time Localization
  71. IPN triangulation of GRB 250222A
  72. GRB 250226A: GRANDMA Optical Observations
  73. Fermi GRB 250302A: Global MASTER-Net observations report
  74. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  75. GRB 250302A: Fermi GBM Final Real-time Localization
  76. GRB 250228A: Fermi GBM Final Localization
  77. Konus-Wind detection of GRB 250226A
  78. GRB 250225B: EIRSAT-1 GMOD Detection
  79. GRB 250226A: KAO Optical Upper Limit
  80. GRB 250226A: AbAO AS-32 Optical Upper Limit
  81. EP250223A: Upper limits from Fermi-GBM Observations
  82. GRB 250226A: Fermi GBM Observation
  83. GRB 250226A / EP250226a: LCO detection of the afterglow
  84. GRB 250205A / EP250205A: further radio observations with the VLA
  85. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  86. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  87. GRB 250225B: INTEGRAL SPI-ACS detection
  88. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  89. EP250226a / GRB 250226A: SVOM/VT optical observations
  90. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  91. EP250226a/GRB 250226A: 1.6m Mephisto observations
  92. EP250226a/GRB 250226A: Kinder optical follow-up observations
  93. Fermi GRB 250226B: Global MASTER-Net observations report
  94. GRB 250226B: Fermi GBM Final Real-time Localization
  95. GRB 250225B: Fermi GBM Observation
  96. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  97. GRB 250225B: SVOM/GRM observation of a long burst
  98. GRB 250226A: GECAM-B detection
  99. GRB 250214A: SVOM/GRM observation
  100. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart

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