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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"

32508 results found.

  1. GRB 250316A: Fermi GBM Observation
  2. GRB 250316A: Swift-XRT observations
  3. Fermi GRB 250316A: Global MASTER-Net observations report
  4. GRB 250314A: SVOM/GRM analysis
  5. GRB 250316A: Swift ToO observations
  6. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  7. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  8. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  9. GRB 250314A: EP-FXT afterglow detection
  10. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  11. GRB 250314A: Swift/UVOT Upper Limits
  12. GRB 250312B: GRBAlpha detection
  13. GRB 250314A: Swift XRT Detection
  14. EP250315a: optical counterpart candidate detected by Gemini North
  15. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  16. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  17. SVOM/MXT upper limit on GRB 250314A
  18. GRB 250314A: SVOM/VT upper limit
  19. GRB 250314A: NOT near-infrared candidate counterpart
  20. GRB 250313A: Fermi GBM Detection
  21. GRB 250313A: CALET Gamma-Ray Burst Monitor detection
  22. GRB 250312B: Fermi GBM Observation
  23. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  24. Konus-Wind detection of GRB 250313A
  25. Konus-Wind detection of GRB 250308A
  26. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  27. GRB 250313A: SVOM/GRM observation of a bright long burst
  28. FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
  29. GRB 250313A: AstroSat CZTI detection of a bright long burst
  30. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  31. GRB 250313A: Fermi-LAT detection
  32. GRB 250313A: Swift ToO observations
  33. EP250304a: Pan-STARRS r and i-band imaging and photometry
  34. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  35. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  36. Fermi GRB 250313A: Global MASTER-Net observations report
  37. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  38. EP250304a: SVOM/VT optical observation
  39. EP250311a/GRB 250311A: EP-FXT follow-up observation
  40. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  41. EP250302a: Chandra X-ray Detection
  42. Fermi GRB 250312B: Global MASTER-Net observations report
  43. GRB 250226B: Fermi GBM Observation
  44. Swift GRB 250312A: Global MASTER-Net observations report
  45. GRB 250302A: Fermi GBM Observation
  46. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  47. GRB 241213A: VIRT Optical Upper Limit
  48. GRB 241228A: VIRT Optical Upper Limit
  49. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  50. GRB 250223B: Fermi GBM Observation
  51. GRB 250311A: Swift-XRT observations
  52. GRB 250228A: Fermi GBM Observation
  53. GRB 250309B: 1.3m DFOT Optical observations
  54. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  55. EP250311a: Global MASTER-Net observations report
  56. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  57. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  58. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  59. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  60. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  61. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  62. GRB 250309B: PRIME near-infrared detection
  63. EP250304a: Chandra detection
  64. GRB 250225B: Swift-BAT refined analysis
  65. GRB 250311A/EP250311a: TRT optical upper limit
  66. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  67. GRB 250311A: Tiled Swift observations
  68. EP250311a/GRB 250311A: EP-WXT detection
  69. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  70. GRB 250309B: SVOM/VT optical observation
  71. GRB 250309B / AT2025dws: further SAO RAS optical observations
  72. IceCube-250309A: Upper limits from Fermi-GBM Observations
  73. EP250308a: 1.6m Mephisto optical upper limits
  74. Konus-Wind detection of GRB 250309B
  75. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  76. IPN triangulation of GRB 250308A (short)
  77. IPN triangulation of GRB 250309B
  78. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  79. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  80. GRB 250309B: Swift-XRT refined Analysis
  81. GRB 250309B / IceCube-250309A: GECAM-B observations
  82. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  83. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  84. GRB 250309B / AT2025dws: SAO RAS optical observations
  85. GRB 250309B / AT2025dws: Swift-UVOT detection
  86. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  87. GRB 250309B: Fermi GBM Observation
  88. Fermi GRB 250309B: Global MASTER-Net observations report
  89. Fermi GRB 250309A: Global MASTER-Net observations report
  90. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  91. IceCube-250309A: No candidates from the Zwicky Transient Facility
  92. Fermi-LAT gamma-ray observations of IceCube-250309A
  93. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  94. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  95. GRB 230509B: Tiled Swift observations
  96. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  97. EP250308a: Global MASTER-Net observations report
  98. EP250308a: GSP optical upper limit
  99. GRB 250306A: EIRSAT-1 GMOD detection
  100. Fermi GRB 250307A: Global MASTER-Net observations report

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