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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"

24385 results found.

  1. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  2. GRB 250313A: GRBAlpha detection
  3. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  4. GRB 250319B: Fermi GBM Final Localization
  5. GRB 250319A: Fermi GBM Final Localization
  6. GRB 250317D: EIRSAT-1 GMOD Detection
  7. LIGO/Virgo/KAGRA S250319bu: Updated Sky localization
  8. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  9. GRB 250317B: Leavitt Observatory optical upper limit
  10. GRB 250317C: GECAM-B detection
  11. Fermi trigger No 763933627: Global MASTER-Net observations report
  12. GRB 250317B: REM optical/NIR observations
  13. GRB 250314A: REM optical/NIR upper limits
  14. GRB 250316A: Swift-XRT afterglow detection
  15. GRB 250317B: LCO detection of the fading optical afterglow
  16. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  17. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  18. GRB 250317B: SVOM detection of a burst
  19. GRB 250316A: Fermi GBM Observation
  20. GRB 250316A: Swift-XRT observations
  21. Fermi trigger No 763862734: Global MASTER-Net observations report
  22. GRB 250317A: Fermi GBM Final Real-time Localization
  23. Fermi GRB 250316A: Global MASTER-Net observations report
  24. GRB 250314A: SVOM/GRM analysis
  25. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  26. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  27. GRB 250316A: Fermi GBM Final Real-time Localization
  28. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  29. GRB 250312B: GRBAlpha detection
  30. EP250315a: optical counterpart candidate detected by Gemini North
  31. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  32. GRB 250314A: NOT near-infrared candidate counterpart
  33. GRB 250313A: Fermi GBM Detection
  34. GRB 250312B: Fermi GBM Observation
  35. GRB 250313A: Swift-XRT observations
  36. Konus-Wind detection of GRB 250313A
  37. Konus-Wind detection of GRB 250308A
  38. GRB 250314A: SVOM detection of a burst
  39. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  40. GRB 250313B: SVOM/GRM observation of a soft bright short burst
  41. GRB 250313A: SVOM/GRM observation of a bright long burst
  42. FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
  43. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  44. Fermi trigger No 763581136: Global MASTER-Net observations report
  45. GRB 250313A: Fermi-LAT detection
  46. EP250304a: Pan-STARRS r and i-band imaging and photometry
  47. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  48. Fermi GRB 250313A: Global MASTER-Net observations report
  49. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  50. GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)
  51. GRB 250313A: Fermi GBM Final Real-time Localization
  52. The EP-WXT trigger 01709132551 is not a real source
  53. EP250304a: SVOM/VT optical observation
  54. EP250311a/GRB 250311A: EP-FXT follow-up observation
  55. EP250302a: Chandra X-ray Detection
  56. Fermi trigger No 763509110: Global MASTER-Net observations report
  57. Fermi GRB 250312B: Global MASTER-Net observations report
  58. GRB 250312B: Fermi GBM Final Localization
  59. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  60. GRB 250226B: Fermi GBM Observation
  61. Swift GRB 250312A: Global MASTER-Net observations report
  62. GRB 250302A: Fermi GBM Observation
  63. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  64. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  65. GRB 250223B: Fermi GBM Observation
  66. GRB 250311A: Swift-XRT observations
  67. GRB 250228A: Fermi GBM Observation
  68. GRB 250309B: 1.3m DFOT Optical observations
  69. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  70. EP250311a: Global MASTER-Net observations report
  71. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  72. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  73. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  74. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  75. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  76. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  77. EP250304a: Chandra detection
  78. GRB 250225B: Swift-BAT refined analysis
  79. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  80. GRB 250311B: SVOM detection of a burst
  81. GRB 250309B: SVOM/VT optical observation
  82. The EP-WXT trigger 01709132425 is not a real source
  83. IceCube-250309A: Upper limits from Fermi-GBM Observations
  84. EP250308a: 1.6m Mephisto optical upper limits
  85. Konus-Wind detection of GRB 250309B
  86. IPN triangulation of GRB 250308A (short)
  87. IPN triangulation of GRB 250309B
  88. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  89. GRB 250309B / IceCube-250309A: GECAM-B observations
  90. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  91. GRB 250309B / AT2025dws: SAO RAS optical observations
  92. GRB 250309B / AT2025dws: Swift-UVOT detection
  93. GRB 250309B: Fermi GBM Observation
  94. Fermi GRB 250309B: Global MASTER-Net observations report
  95. Fermi GRB 250309A: Global MASTER-Net observations report
  96. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  97. IceCube-250309A: No candidates from the Zwicky Transient Facility
  98. Fermi-LAT gamma-ray observations of IceCube-250309A
  99. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  100. GRB 250309B: Fermi GBM Final Localization

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