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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"

32486 results found.

  1. Konus-Wind detection of GRB 250313A
  2. Konus-Wind detection of GRB 250308A
  3. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  4. GRB 250313A: SVOM/GRM observation of a bright long burst
  5. FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
  6. GRB 250313A: AstroSat CZTI detection of a bright long burst
  7. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  8. GRB 250313A: Fermi-LAT detection
  9. GRB 250313A: Swift ToO observations
  10. EP250304a: Pan-STARRS r and i-band imaging and photometry
  11. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  12. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  13. Fermi GRB 250313A: Global MASTER-Net observations report
  14. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  15. EP250304a: SVOM/VT optical observation
  16. EP250311a/GRB 250311A: EP-FXT follow-up observation
  17. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  18. EP250302a: Chandra X-ray Detection
  19. Fermi GRB 250312B: Global MASTER-Net observations report
  20. GRB 250226B: Fermi GBM Observation
  21. Swift GRB 250312A: Global MASTER-Net observations report
  22. GRB 250302A: Fermi GBM Observation
  23. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  24. GRB 241213A: VIRT Optical Upper Limit
  25. GRB 241228A: VIRT Optical Upper Limit
  26. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  27. GRB 250223B: Fermi GBM Observation
  28. GRB 250311A: Swift-XRT observations
  29. GRB 250228A: Fermi GBM Observation
  30. GRB 250309B: 1.3m DFOT Optical observations
  31. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  32. EP250311a: Global MASTER-Net observations report
  33. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  34. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  35. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  36. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  37. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  38. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  39. GRB 250309B: PRIME near-infrared detection
  40. EP250304a: Chandra detection
  41. GRB 250225B: Swift-BAT refined analysis
  42. GRB 250311A/EP250311a: TRT optical upper limit
  43. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  44. GRB 250311A: Tiled Swift observations
  45. EP250311a/GRB 250311A: EP-WXT detection
  46. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  47. GRB 250309B: SVOM/VT optical observation
  48. GRB 250309B / AT2025dws: further SAO RAS optical observations
  49. IceCube-250309A: Upper limits from Fermi-GBM Observations
  50. EP250308a: 1.6m Mephisto optical upper limits
  51. Konus-Wind detection of GRB 250309B
  52. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  53. IPN triangulation of GRB 250308A (short)
  54. IPN triangulation of GRB 250309B
  55. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  56. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  57. GRB 250309B: Swift-XRT refined Analysis
  58. GRB 250309B / IceCube-250309A: GECAM-B observations
  59. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  60. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  61. GRB 250309B / AT2025dws: SAO RAS optical observations
  62. GRB 250309B / AT2025dws: Swift-UVOT detection
  63. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  64. GRB 250309B: Fermi GBM Observation
  65. Fermi GRB 250309B: Global MASTER-Net observations report
  66. Fermi GRB 250309A: Global MASTER-Net observations report
  67. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  68. IceCube-250309A: No candidates from the Zwicky Transient Facility
  69. Fermi-LAT gamma-ray observations of IceCube-250309A
  70. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  71. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  72. GRB 230509B: Tiled Swift observations
  73. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  74. EP250308a: Global MASTER-Net observations report
  75. EP250308a: GSP optical upper limit
  76. GRB 250306A: EIRSAT-1 GMOD detection
  77. Fermi GRB 250307A: Global MASTER-Net observations report
  78. Konus-Wind detection of GRB 250306A
  79. GRB 250306A: Swift-BAT refined analysis
  80. GRB 250306A: NuSTAR detection of the prompt emission
  81. EP250304a: MeerKAT detection of a possible radio counterpart
  82. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  83. GRB 250305A: AstroSat CZTI detection
  84. EP250302a:Xinglong optical observations
  85. GRB 250306A: AstroSat CZTI detection
  86. Swift GRB 250306A: Global MASTER-Net observations report
  87. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  88. GRB250101A: Radio upper limits from VLA observations
  89. GRB 250305A: SVOM/GRM observation of a burst
  90. EP250304A: Upper limits from Fermi-GBM Observations
  91. Fermi GRB 250305A: Global MASTER-Net observations report
  92. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  93. EP250302a: Optical Observations at CrAO and SAO RAS
  94. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  95. EP 250304A: Optical counterpart detection by LCO
  96. EP250302A: 1.3m DFOT optical afterglow detection
  97. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  98. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  99. Konus-Wind detection of GRB 250222A
  100. EP250304a: REM NIR upper limits

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