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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"

43953 results found.

  1. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  2. EP250315a: Einstein Probe detection of an X-ray transient
  3. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  4. SVOM/MXT upper limit on GRB 250314A
  5. GRB 250314A: SVOM/VT upper limit
  6. GRB 250314A: NOT near-infrared candidate counterpart
  7. GRB 250313A: Fermi GBM Detection
  8. GRB 250313A: CALET Gamma-Ray Burst Monitor detection
  9. GRB 250312B: Fermi GBM Observation
  10. GRB 250313A: Swift-XRT observations
  11. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  12. Konus-Wind detection of GRB 250313A
  13. Konus-Wind detection of GRB 250308A
  14. GRB 250314A: SVOM detection of a burst
  15. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  16. GRB 250313B: SVOM/GRM observation of a soft bright short burst
  17. GRB 250313A: SVOM/GRM observation of a bright long burst
  18. FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
  19. GRB 250313A: AstroSat CZTI detection of a bright long burst
  20. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  21. Fermi trigger No 763581136: Global MASTER-Net observations report
  22. GRB 250313A: Fermi-LAT detection
  23. GRB 250313A: Swift ToO observations
  24. EP250304a: Pan-STARRS r and i-band imaging and photometry
  25. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  26. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  27. Fermi GRB 250313A: Global MASTER-Net observations report
  28. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  29. GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)
  30. GRB 250313A: Fermi GBM Final Real-time Localization
  31. The EP-WXT trigger 01709132551 is not a real source
  32. EP250304a: SVOM/VT optical observation
  33. EP250311a/GRB 250311A: EP-FXT follow-up observation
  34. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  35. EP250302a: Chandra X-ray Detection
  36. GRB 250312A: Swift-XRT refined Analysis
  37. Fermi Gamma-ray Burst Monitor trigger 763509110/250312911 is not a GRB
  38. Fermi trigger No 763509110: Global MASTER-Net observations report
  39. Fermi GRB 250312B: Global MASTER-Net observations report
  40. GRB 250312A: Enhanced Swift-XRT position
  41. GRB 250312B: Fermi GBM Final Localization
  42. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  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 250312A: Swift detection of a burst
  48. GRB 241213A: VIRT Optical Upper Limit
  49. GRB 241228A: VIRT Optical Upper Limit
  50. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  51. GRB 250223B: Fermi GBM Observation
  52. GRB 250311A: Swift-XRT observations
  53. GRB 250228A: Fermi GBM Observation
  54. GRB 250309B: 1.3m DFOT Optical observations
  55. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  56. EP250311a: Global MASTER-Net observations report
  57. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  58. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  59. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  60. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  61. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  62. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  63. GRB 250309B: PRIME near-infrared detection
  64. EP250304a: Chandra detection
  65. GRB 250225B: Swift-BAT refined analysis
  66. GRB 250311A/EP250311a: TRT optical upper limit
  67. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  68. GRB 250311A: Tiled Swift observations
  69. EP250311a/GRB 250311A: EP-WXT detection
  70. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  71. GRB 250311B: SVOM detection of a burst
  72. GRB 250309B: SVOM/VT optical observation
  73. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  74. The EP-WXT trigger 01709132425 is not a real source
  75. GRB 250309B / AT2025dws: further SAO RAS optical observations
  76. IceCube-250309A: Upper limits from Fermi-GBM Observations
  77. EP250308a: 1.6m Mephisto optical upper limits
  78. Konus-Wind detection of GRB 250309B
  79. IPN triangulation of GRB 250308A (short)
  80. IPN triangulation of GRB 250309B
  81. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  82. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  83. GRB 250309B: Swift-XRT refined Analysis
  84. GRB 250309B / IceCube-250309A: GECAM-B observations
  85. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  86. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  87. GRB 250309B / AT2025dws: SAO RAS optical observations
  88. GRB 250309B / AT2025dws: Swift-UVOT detection
  89. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  90. GRB 250309B: Fermi GBM Observation
  91. Fermi GRB 250309B: Global MASTER-Net observations report
  92. Fermi GRB 250309A: Global MASTER-Net observations report
  93. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  94. IceCube-250309A: No candidates from the Zwicky Transient Facility
  95. Fermi-LAT gamma-ray observations of IceCube-250309A
  96. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  97. GRB 250309B: Fermi GBM Final Localization
  98. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  99. GRB 230509B: Tiled Swift observations
  100. GRB 250308A: SVOM/GRM observation of a bright short burst

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