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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"

32485 results found.

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

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