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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"

18656 results found.

  1. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  2. Swift-BAT trigger 1334535 is not a GRB
  3. GRB 250721A: Swift-XRT observations
  4. GRB 250717B: SVOM/GRM observation
  5. GRB 250721A: Tiled Swift observations
  6. GRB 250717B: COLIBRÍ optical upper limit
  7. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  8. GRB 250717B: Swift-XRT observations
  9. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  10. Swift Trigger 1334535: a possible GRB 250718A
  11. Swift GRB250718.01: Global MASTER-Net observations report
  12. GRB 250717B: Swift ToO observations
  13. GRB 270713A: Kitab and AbAO Optical Observations
  14. GRB 250717B: Fermi GBM Observation
  15. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  16. GRB 250716A: Swift-XRT afterglow detection
  17. GRB 250716A: Swift ToO observations
  18. GRB 250713A: SVOM/C-GFT upper limit
  19. GRB 250713A: Swift-XRT observations
  20. GRB 250706A: Swift-BAT refined analysis
  21. GRB 250702F: Swift-BAT refined analysis
  22. GRB 250628A: Swift-BAT refined analysis
  23. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  24. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  25. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  26. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  27. GRB 250706B/C: Fermi-LAT detection
  28. GRB 250706B: Swift/UVOT Detection
  29. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  30. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  31. GRB 250702F: GRANDMA observations
  32. GRB 250706A: Swift-XRT refined Analysis
  33. GRB 250706A: Swift/UVOT Upper Limits
  34. GRB 250706A: REM optical/NIR observations
  35. Swift GRB 250706A: Global MASTER-Net observations report
  36. GRB 250706A: JinShan optical upper limits
  37. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  38. GRB250706B: Swift-XRT counterpart detection
  39. GRB 250706A: GROWTH-India Telescope optical upper limit
  40. GRB 250706A: Swift detection of a burst
  41. GRB 250704B: Swift-XRT refined Analysis
  42. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  43. GRB 250704B: Swift/UVOT Upper Limits
  44. GRB 250704A: Swift/UVOT Detection
  45. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  46. GRB 250702F: Kilonova-Catcher optical afterglow detection
  47. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  48. GRB 250704A: SVOM/VT optical observation
  49. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  50. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  51. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  52. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  53. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  54. EP250704a / GRB250704B: Swift-XRT counterpart detection
  55. GRB 250704A: Swift-XRT afterglow detection
  56. GRB 250702B / EP2050702a: FTW optical and NIR observations
  57. Konus-Wind detection of GRB 250702F
  58. GRB 250702F: GROWTH-India Telescope optical observations
  59. EP250702a: WFST optical observations
  60. GRB 250702F: SVOM/VT optical observation
  61. GRB 250702F: Swift/UVOT Detection
  62. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  63. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  64. GRB 250702F: Swift-XRT refined Analysis
  65. GRB 250702F: Fermi GBM Observation
  66. GRB 250702F: Leavitt Observatory optical observations
  67. GRB 250702F: AKO Optical Afterglow Detection
  68. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  69. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  70. GRB 250702F: Skynet Optical Observations
  71. GRB 250424A: VIRT Optical Upper Limit
  72. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  73. GRB 250702F: TRT Optical Observation
  74. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  75. GRB 250702F: REM optical afterglow detection
  76. GRB 250702F: DDOTI Optical Observation
  77. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  78. GRB 250702F: COLIBRÍ Observations of the Afterglow
  79. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  80. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  81. GRB 250702F: Enhanced Swift-XRT position
  82. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  83. GRB 250702F: NOT observations of the optical afterglow
  84. GRB 250702F: MASTER optical afterglow observation
  85. GRB 250702F: GOTO optical counterpart detection
  86. GRB 250702F: Ondrejov D50 optical afterglow detection
  87. GRB 250702F: Swift detection of a burst with an optical counterpart
  88. Swift GRB 250702F: Global MASTER-Net observations report
  89. GRB 250628B: Swift-XRT observations
  90. GRB 250628B: SVOM/VT optical upper limit
  91. GRB 250628A: REM optical/NIR upper limits
  92. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  93. GRB 250628A: VLT/X-shooter upper limits
  94. GRB 250628A: Swift/UVOT Upper Limits
  95. GRB 250628A: Swift-XRT refined Analysis
  96. Swift GRB 250628A: Global MASTER-Net observations report
  97. GRB 250628A: Enhanced Swift-XRT position
  98. GRB 250628A: Swift detection of a burst
  99. GRB 250625A: Swift-BAT refined analysis
  100. GRB 250625A: Leavitt Observatory afterglow detection

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