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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"

35953 results found.

  1. GRB 250313A: Fermi GBM Final Real-time Localization
  2. EP250311a/GRB 250311A: EP-FXT follow-up observation
  3. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  4. GRB 250312A: Swift-XRT refined Analysis
  5. Fermi Gamma-ray Burst Monitor trigger 763509110/250312911 is not a GRB
  6. Fermi GRB 250312B: Global MASTER-Net observations report
  7. GRB 250312A: Enhanced Swift-XRT position
  8. GRB 250312B: Fermi GBM Final Localization
  9. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  10. GRB 250226B: Fermi GBM Observation
  11. Swift GRB 250312A: Global MASTER-Net observations report
  12. GRB 250302A: Fermi GBM Observation
  13. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  14. GRB 250312A: Swift detection of a burst
  15. GRB 241213A: VIRT Optical Upper Limit
  16. GRB 241228A: VIRT Optical Upper Limit
  17. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  18. GRB 250223B: Fermi GBM Observation
  19. GRB 250311A: Swift-XRT observations
  20. GRB 250228A: Fermi GBM Observation
  21. GRB 250309B: 1.3m DFOT Optical observations
  22. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  23. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  24. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  25. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  26. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  27. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  28. GRB 250309B: PRIME near-infrared detection
  29. GRB 250225B: Swift-BAT refined analysis
  30. GRB 250311A/EP250311a: TRT optical upper limit
  31. GRB 250311A: Tiled Swift observations
  32. EP250311a/GRB 250311A: EP-WXT detection
  33. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  34. GRB 250311B: SVOM detection of a burst
  35. GRB 250309B: SVOM/VT optical observation
  36. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  37. GRB 250309B / AT2025dws: further SAO RAS optical observations
  38. IceCube-250309A: Upper limits from Fermi-GBM Observations
  39. Konus-Wind detection of GRB 250309B
  40. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  41. IPN triangulation of GRB 250308A (short)
  42. IPN triangulation of GRB 250309B
  43. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  44. GRB 250309B: Swift-XRT refined Analysis
  45. GRB 250309B / IceCube-250309A: GECAM-B observations
  46. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  47. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  48. GRB 250309B / AT2025dws: SAO RAS optical observations
  49. GRB 250309B / AT2025dws: Swift-UVOT detection
  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. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  55. Fermi-LAT gamma-ray observations of IceCube-250309A
  56. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  57. GRB 250309B: Fermi GBM Final Localization
  58. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  59. GRB 230509B: Tiled Swift observations
  60. GRB 250308A: SVOM/GRM observation of a bright short burst
  61. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  62. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  63. GRB 250309A: Fermi GBM Final Real-time Localization
  64. GRB 250306A: EIRSAT-1 GMOD detection
  65. Fermi GRB 250307A: Global MASTER-Net observations report
  66. Konus-Wind detection of GRB 250306A
  67. GRB 250307A: Fermi GBM Final Real-time Localization
  68. GRB 250306A: Swift-BAT refined analysis
  69. GRB 250306A: NuSTAR detection of the prompt emission
  70. GRB 250305A: AstroSat CZTI detection
  71. GRB 250306A: AstroSat CZTI detection
  72. Fermi Gamma-ray Burst Monitor trigger 762963055/250306591 is not a GRB
  73. Swift GRB 250306A: Global MASTER-Net observations report
  74. GRB 250306A: Swift detection of a burst
  75. GRB 250305A: SVOM/GRM observation of a burst
  76. EP250304A: Upper limits from Fermi-GBM Observations
  77. Fermi GRB 250305A: Global MASTER-Net observations report
  78. GRB 250305A: Fermi GBM Final Real-time Localization
  79. EP250302a: Optical Observations at CrAO and SAO RAS
  80. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  81. EP 250304A: Optical counterpart detection by LCO
  82. Konus-Wind detection of GRB 250222A
  83. IPN triangulation of GRB 250222A
  84. EP250302a: Mondy Continued Optical Observations
  85. EP250304a: VLT/X-shooter redshift z = 0.200
  86. EP250302a: Mondy Observations and Optical Light Curve
  87. EP250302a: OHP/T193 optical and spectroscopic observations
  88. GRB 250226A: GRANDMA Optical Observations
  89. EP250302a: Montarrenti Observatory optical detection
  90. Fermi GRB 250302A: Global MASTER-Net observations report
  91. GRB 250302A: Fermi GBM Final Real-time Localization
  92. GRB 250228A: Fermi GBM Final Localization
  93. GRB 250225B: VLT near-infrared afterglow confirmation
  94. Konus-Wind detection of GRB 250226A
  95. GRB 250225B: EIRSAT-1 GMOD Detection
  96. GRB 250226A: KAO Optical Upper Limit
  97. GRB 250226A: AbAO AS-32 Optical Upper Limit
  98. EP250223A: Upper limits from Fermi-GBM Observations
  99. GRB 250225B: VLT/HAWKI near-infrared observations
  100. GRB 250226A: Fermi GBM Observation

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