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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').
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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"

3757 results found.

  1. Fermi-LAT Gamma-ray Observations of IceCube-250926A
  2. LIGO/Virgo/KAGRA S250927cy: Identification of a GW compact binary merger candidate
  3. IceCube-250926A: Upper limits from a search for additional neutrino events in IceCube
  4. IceCube-250926A - IceCube observation of a high-energy neutrino candidate track-like event
  5. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  6. GRB 250924A: J-band detection with WINTER
  7. GRB 250920B: CrAO ZTSH optical observations
  8. Fermi trigger No 780156732: Global MASTER-Net observations report
  9. IPN triangulation of GRB 250920A (long/bright)
  10. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  11. GRB 250919A: Glowbug gamma-ray detection
  12. GRB 250919A: Fermi GBM Observation
  13. GRB 250919A: Fermi-LAT detection
  14. GRB 250919A: BALROG localization (Fermi Trigger 779934537 / GRB 250919020)
  15. EP250919a: Global MASTER-Net observations report
  16. GRB 250919A: Fermi GBM Final Real-time Localization
  17. EP250827b: VLA Observations
  18. Fermi GRB 250912A: Global MASTER-Net observations report
  19. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  20. Fermi GRB 250910B: Global MASTER-Net observations report
  21. EP250911a: Einstein Probe detection of an X-ray transient
  22. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  23. Fermi GRB 250909A: Global MASTER-Net observations report
  24. GRB 250909A: Fermi GBM Final Real-time Localization
  25. EP250905b: Global MASTER-Net observations report
  26. EP250905b: EP-WXT detection of a fast X-ray transient
  27. EP250905a: FTW one optical and multiple NIR counterpart candidates
  28. EP250905a: JinShan likely optical counterpart detection
  29. IceCube Alert 250905.84: Global MASTER-Net observations report
  30. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  31. Fermi GRB 250902B: Global MASTER-Net observations report
  32. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  33. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  34. GRB 250831A: Swift-XRT counterpart detection
  35. GRB 250831A: SVOM detection of a soft burst
  36. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  37. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  38. EP250828a: KAIT optical upper limit
  39. EP250828a: Seimei/TriCCS optical counterpart detection
  40. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  41. EP250827a: LCO observations show fading optical counterpart
  42. GRB 250828A: Fermi GBM Final Localization
  43. EP250827a: Global MASTER-Net observations report
  44. Fermi GRB 250824B: Global MASTER-Net observations report
  45. GRB 250823A: SVOM/VT optical observation
  46. GRB 250823A: BOOTES6/DPRT early optical detection
  47. GRB 250821A: Prompt enhanced Swift-XRT position
  48. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  49. Fermi trigger No 776849714: Global MASTER-Net observations report
  50. GRB 250812A: NTT spectroscopic redshift z = 2.57
  51. IceCube Alert 250813.14: Global MASTER-Net observations report
  52. GRB 250702B: Chandra X-ray Detection
  53. Fermi GRB 250808A: Global MASTER-Net observations report
  54. Konus-Wind detection of GRB 250807A
  55. GRB 250805A: Kilonova-Catcher optical upper limits
  56. GRB 250804B: Swift-XRT observations
  57. GRB 250804B: SVOM/GRM observation of a short burst
  58. EP250711a: CrAO and Assy optical observations
  59. EP250730a: Global MASTER-Net observations report
  60. LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
  61. GRB 250725A: AstroSat CZTI detection
  62. GRB 250728A: Fermi GBM Observation
  63. Fermi trigger No 775387550: Global MASTER-Net observations report
  64. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT detection of a new source, AT 2025smm
  65. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  66. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  67. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  68. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  69. GRB 250721A: MAXI/GSC detection
  70. Fermi trigger No 774730635: Global MASTER-Net observations report
  71. Swift GRB250718.01: Global MASTER-Net observations report
  72. GRB 250711A: DDOTI Optical Upper Limit
  73. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  74. EP250711a: NOT optical counterpart candidate
  75. Fermi GRB 250711A: Global MASTER-Net observations report
  76. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  77. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  78. EP250704a / GRB 250704B - REM observations
  79. Fermi GRB 250702E: Global MASTER-Net observations report
  80. Fermi GRB 250702B: Global MASTER-Net observations report
  81. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  82. Fermi GRB 250702F: Global MASTER-Net observations report
  83. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  84. GRB 250628A: REM optical/NIR upper limits
  85. GRB 250628C: Fermi GBM Final Real-time Localization
  86. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  87. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  88. GRB 250628A: VLT/X-shooter upper limits
  89. Fermi GRB 250626A: Global MASTER-Net observations report
  90. Swift GRB 250628A: Global MASTER-Net observations report
  91. GRB 250625A: SVOM/C-GFT upper limit in early phase
  92. GRB 250625A: OHP/T193 optical detection
  93. Swift GRB 250625A: Global MASTER-Net observations report
  94. Fermi GRB 250623A: Global MASTER-Net observations report
  95. Fermi trigger No 772190032: Global MASTER-Net observations report
  96. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  97. Fermi trigger No 772058337: Global MASTER-Net observations report
  98. GRB 250617B: SAO RAS optical observations
  99. Fermi trigger No 771752663: Global MASTER-Net observations report
  100. Fermi trigger No 771424081: Global MASTER-Net observations report

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