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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.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

3676 results found.

  1. EP251021b: Einstein Probe detection of a fast X-ray transient
  2. IceCube-251018A: Global MASTER-Net observations report
  3. GRB 251017A: VLT/MUSE spectroscopic redshift z = 4.327
  4. Fermi GRB 251016B: Global MASTER-Net observations report
  5. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
  6. sb25101602: Swift-XRT counterpart detection
  7. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) further multi-band optical observations
  8. GRB 251014A: Glowbug gamma-ray detection of a likely short burst
  9. GRB 251013C: OHP/T193 optical afterglow photometry and spectroscopy
  10. GRB 251014A: Fermi GBM Observation
  11. GRB 251014A: Swift detection of a possibly-short burst
  12. GRB 251014A: Fermi GBM Final Real-time Localization
  13. Fermi GRB 251013C: Global MASTER-Net observations report
  14. Fermi GRB 251013B: Global MASTER-Net observations report
  15. Fermi GRB 251011A: Global MASTER-Net observations report
  16. GRB 250919A: TERI gamma-ray detection
  17. Fermi GRB 251006B: Global MASTER-Net observations report
  18. GRB 251005C: AstroSat CZTI detection
  19. GRB 251003A: Swift-BAT refined analysis
  20. Fermi-LAT Gamma-ray Observations of IceCube-250926A
  21. LIGO/Virgo/KAGRA S250927cy: Identification of a GW compact binary merger candidate
  22. IceCube-250926A: Upper limits from a search for additional neutrino events in IceCube
  23. IceCube-250926A - IceCube observation of a high-energy neutrino candidate track-like event
  24. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  25. GRB 250924A: J-band detection with WINTER
  26. GRB 250920B: CrAO ZTSH optical observations
  27. Fermi trigger No 780156732: Global MASTER-Net observations report
  28. IPN triangulation of GRB 250920A (long/bright)
  29. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  30. GRB 250919A: Glowbug gamma-ray detection
  31. GRB 250919A: Fermi GBM Observation
  32. GRB 250919A: Fermi-LAT detection
  33. GRB 250919A: BALROG localization (Fermi Trigger 779934537 / GRB 250919020)
  34. EP250919a: Global MASTER-Net observations report
  35. GRB 250919A: Fermi GBM Final Real-time Localization
  36. EP250827b: VLA Observations
  37. Fermi GRB 250912A: Global MASTER-Net observations report
  38. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  39. Fermi GRB 250910B: Global MASTER-Net observations report
  40. EP250911a: Einstein Probe detection of an X-ray transient
  41. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  42. Fermi GRB 250909A: Global MASTER-Net observations report
  43. GRB 250909A: Fermi GBM Final Real-time Localization
  44. EP250905b: Global MASTER-Net observations report
  45. EP250905b: EP-WXT detection of a fast X-ray transient
  46. EP250905a: FTW one optical and multiple NIR counterpart candidates
  47. EP250905a: JinShan likely optical counterpart detection
  48. IceCube Alert 250905.84: Global MASTER-Net observations report
  49. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  50. Fermi GRB 250902B: Global MASTER-Net observations report
  51. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  52. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  53. GRB 250831A: Swift-XRT counterpart detection
  54. GRB 250831A: SVOM detection of a soft burst
  55. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  56. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  57. EP250828a: KAIT optical upper limit
  58. EP250828a: Seimei/TriCCS optical counterpart detection
  59. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  60. EP250827a: LCO observations show fading optical counterpart
  61. GRB 250828A: Fermi GBM Final Localization
  62. EP250827a: Global MASTER-Net observations report
  63. Fermi GRB 250824B: Global MASTER-Net observations report
  64. GRB 250823A: SVOM/VT optical observation
  65. GRB 250823A: BOOTES6/DPRT early optical detection
  66. GRB 250821A: Prompt enhanced Swift-XRT position
  67. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  68. Fermi trigger No 776849714: Global MASTER-Net observations report
  69. GRB 250812A: NTT spectroscopic redshift z = 2.57
  70. IceCube Alert 250813.14: Global MASTER-Net observations report
  71. GRB 250702B: Chandra X-ray Detection
  72. Fermi GRB 250808A: Global MASTER-Net observations report
  73. Konus-Wind detection of GRB 250807A
  74. GRB 250805A: Kilonova-Catcher optical upper limits
  75. GRB 250804B: Swift-XRT observations
  76. GRB 250804B: SVOM/GRM observation of a short burst
  77. EP250711a: CrAO and Assy optical observations
  78. EP250730a: Global MASTER-Net observations report
  79. LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
  80. GRB 250725A: AstroSat CZTI detection
  81. GRB 250728A: Fermi GBM Observation
  82. Fermi trigger No 775387550: Global MASTER-Net observations report
  83. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT detection of a new source, AT 2025smm
  84. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  85. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  86. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  87. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  88. GRB 250721A: MAXI/GSC detection
  89. Fermi trigger No 774730635: Global MASTER-Net observations report
  90. Swift GRB250718.01: Global MASTER-Net observations report
  91. GRB 250711A: DDOTI Optical Upper Limit
  92. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  93. EP250711a: NOT optical counterpart candidate
  94. Fermi GRB 250711A: Global MASTER-Net observations report
  95. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  96. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  97. EP250704a / GRB 250704B - REM observations
  98. Fermi GRB 250702E: Global MASTER-Net observations report
  99. Fermi GRB 250702B: Global MASTER-Net observations report
  100. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient

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