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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"

27831 results found.

  1. GRB 250312A: Swift-XRT refined Analysis
  2. GRB 250312A: Enhanced Swift-XRT position
  3. GRB 250312B: Fermi GBM Final Localization
  4. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  5. GRB 250226B: Fermi GBM Observation
  6. Swift GRB 250312A: Global MASTER-Net observations report
  7. GRB 250302A: Fermi GBM Observation
  8. GRB 250312A: Swift detection of a burst
  9. GRB 241213A: VIRT Optical Upper Limit
  10. GRB 241228A: VIRT Optical Upper Limit
  11. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  12. GRB 250223B: Fermi GBM Observation
  13. GRB 250311A: Swift-XRT observations
  14. GRB 250228A: Fermi GBM Observation
  15. GRB 250309B: 1.3m DFOT Optical observations
  16. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  17. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  18. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  19. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  20. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  21. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  22. GRB 250309B: PRIME near-infrared detection
  23. EP250304a: Chandra detection
  24. GRB 250225B: Swift-BAT refined analysis
  25. GRB 250311A: Tiled Swift observations
  26. EP250311a/GRB 250311A: EP-WXT detection
  27. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  28. GRB 250311B: SVOM detection of a burst
  29. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  30. IceCube-250309A: Upper limits from Fermi-GBM Observations
  31. Konus-Wind detection of GRB 250309B
  32. IPN triangulation of GRB 250308A (short)
  33. IPN triangulation of GRB 250309B
  34. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  35. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  36. GRB 250309B: Swift-XRT refined Analysis
  37. GRB 250309B / AT2025dws: Swift-UVOT detection
  38. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  39. IceCube-250309A: No candidates from the Zwicky Transient Facility
  40. Fermi-LAT gamma-ray observations of IceCube-250309A
  41. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  42. GRB 250309B: Fermi GBM Final Localization
  43. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  44. GRB 230509B: Tiled Swift observations
  45. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  46. EP250308a: GSP optical upper limit
  47. EP250308a: Einstein Probe detection of an X-ray transient
  48. GRB 250309A: Fermi GBM Final Real-time Localization
  49. GRB 250306A: EIRSAT-1 GMOD detection
  50. Konus-Wind detection of GRB 250306A
  51. GRB 250307A: Fermi GBM Final Real-time Localization
  52. GRB 250306A: Swift-BAT refined analysis
  53. GRB 250306A: NuSTAR detection of the prompt emission
  54. EP250304a: MeerKAT detection of a possible radio counterpart
  55. GRB 250305A: AstroSat CZTI detection
  56. GRB 250306A: AstroSat CZTI detection
  57. Swift GRB 250306A: Global MASTER-Net observations report
  58. GRB 250306A: Swift detection of a burst
  59. LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate
  60. GRB 250305A: Fermi GBM Final Real-time Localization
  61. EP 250304A: Optical counterpart detection by LCO
  62. EP250302A: 1.3m DFOT optical afterglow detection
  63. Konus-Wind detection of GRB 250222A
  64. IPN triangulation of GRB 250222A
  65. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  66. EP250304a: Swift-XRT detection of a fading X-ray source
  67. EP250304a: TRT optical counterpart detection
  68. EP250304a: Einstein Probe detection of an X-ray transient
  69. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  70. EP250225a: the candidate optical counterpart is an AGN
  71. EP250302a: Swift/UVOT detection
  72. EP250302a: Swift-XRT observations of a fading X-ray source
  73. EP250302a: Einstein Probe detection of an X-ray transient
  74. EP250302a: Montarrenti Observatory optical detection
  75. EP250302a: FTW optical and NIR detection
  76. EP250302a: Nanshan/HMT optical counterpart detection
  77. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  78. GRB 250302A: Fermi GBM Final Real-time Localization
  79. GRB 250228A: Fermi GBM Final Localization
  80. EP250228a: Optical observations with Kinder and Swift/UVOT
  81. Konus-Wind detection of GRB 250226A
  82. GRB 250225B: EIRSAT-1 GMOD Detection
  83. GRB 250225B: VLT/HAWKI near-infrared observations
  84. EP250227a: Optical upper limits with Kinder observations
  85. EP250227a: Einstein Probe detected of a fast X-ray transient
  86. EP250228a: updates on the EP observations
  87. EP250225a: EP-FXT follow-up observation
  88. EP250228a: Swift/XRT localisation
  89. EP250228a: Einstein Probe detection of an X-ray transient
  90. GRB 250226A / EP250226a: LCO detection of the afterglow
  91. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  92. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  93. GRB 250225B: INTEGRAL SPI-ACS detection
  94. EP250225a: TRT optical upper limits
  95. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  96. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  97. LIGO/Virgo/KAGRA S250227y: Retraction of GW compact binary merger candidate
  98. GRB 250226B: Fermi GBM Final Real-time Localization
  99. GRB 250225B: Fermi GBM Observation
  100. GRB 250221A: ATCA Detections and Upper Limits

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