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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"

39164 results found.

  1. GRB 250106A: SVOM detection of a long burst
  2. Fermi trigger No 757753930: Global MASTER-Net observations report
  3. GRB 241229A: SVOM/VT optical upperlimit
  4. GRB 250103B: Swift-XRT refined Analysis
  5. GRB 250103B: LCO/1m optical afterglow candidate detection
  6. GRB 250103A: Bassano Bresciano Observatory upper limit
  7. GRB 250103B: VLT/X-shooter spectroscopic redshift z = 1.416
  8. GRB 250103A: Swift-XRT observations
  9. GRB 250101A: 1.3m DFOT optical afterglow detection
  10. GRB 241229A: 1.3m DFOT upper limit
  11. GRB 241228B: 1.3m DFOT Optical observations
  12. GRB 241228A: 1.3m DFOT upper limit
  13. GRB 250103A: NOT spectroscopic redshift
  14. GRB 250103B:SVOM/VT optical counterpart
  15. GRB 250103A: Montarrenti Observatory optical detection
  16. GRB 250101A: further LCOGT optical afterglow observations
  17. GRB 250103A: Redshift 4.01 from OSIRIS+/GTC
  18. GRB 250103A: NOT optical observations
  19. GRB 250103A: TSHAO optical upper limit
  20. GRB 250103A: Fermi GBM Observation
  21. GRB 250103B: LCOGT Optical Upper Limit
  22. Swift GRB 250103B: Global MASTER-Net observations report
  23. GRB 250103A: SVOM/VT optical counterpart confirmation
  24. GRB 250103A: Swift ToO observations
  25. GRB 250101a: Liverpool Telescope optical follow-up
  26. GRB 250103B: SVOM detection of a long burst
  27. GRB 250103B: Swift detection of a burst
  28. GRB 250103A: Xinglong 2.16m Optical Candidate
  29. Fermi GRB 250102A: Global MASTER-Net observations report
  30. GRB 250101B: SVOM/GRM observation
  31. GRB 250103A: GOTO optical upper limit
  32. GRB 250103A: SVOM/C-GFT optical upper limit
  33. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  34. IceCube Alert 250102.58: Global MASTER-Net observations report
  35. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  36. GRB 250103A: SVOM detection of a long burst
  37. GRB 250102A: Fermi GBM Final Real-time Localization
  38. LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
  39. GRB 250101A: Swift-BAT refined analysis
  40. GRB 250101A: further SAO RAS optical observations
  41. GRB 250101A: LCO optical counterpart detection
  42. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  43. GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
  44. GRB 250101A: Swift/UVOT Detection
  45. GRB 250101A: 1.6m Mephisto multi-band optical followup
  46. GRB 250101A: Swift-XRT refined Analysis
  47. Fermi Gamma-ray Burst Monitor trigger 757464861/250101954 is not a GRB
  48. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  49. GRB 250101A: LCOGT optical afterglow detection
  50. GRB 250101A: OASDG optical observations
  51. Fermi GRB 250101B: Global MASTER-Net observations report
  52. GRB 250101B: Fermi GBM Final Real-time Localization
  53. GRB 250101A: SAO RAS observations of optical brightening
  54. GRB 250101A: BOOTES-4/MET optical afterglow detection
  55. GRB 250101A: AKO Optical Afterglow Detection
  56. GRB 250101A: SAO RAS optical observations
  57. GRB 250101A: Enhanced Swift-XRT position
  58. GRB 250101A: Xinglong-2.16m spectroscopic redshift
  59. GRB 250101A: SVOM/C-GFT early optical observations
  60. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
  61. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  62. GRB 250101A: Nanshan/HMT optical observations
  63. GRB 250101A : GIT optical detection
  64. GRB 250101A: GMG Optical Observation
  65. GRB 250101A: Swift detection of a burst with an optical counterpart
  66. Swift GRB250101.56: Global MASTER-Net observations report
  67. GRB 241217a/EP241217b: ATCA Radio Detection
  68. GRB 241229B: Continued CrAO ZTSh observations
  69. GRB 241229A: EP-FXT X-ray afterglow confirmation
  70. GRB 241228B: Multiband optical monitoring with 1.6m Mephisto
  71. GRB 241229B: SVOM/GRM observation
  72. GRB 241229B: SAO RAS optical upper limit
  73. GRB 241228B: SAO RAS optical observations
  74. GRB 241229B: CrAO ZTSh possible optical counterpart of SVOM/VT confirmation
  75. GRB 241229A: SAO RAS optical observations
  76. GRB 241229B: SVOM/VT optical candidate
  77. GRB 241229A: Swift-XRT observations
  78. Konus-Wind detection of GRB 241228A
  79. GRB 241229A: EP-FXT afterglow candidates
  80. EP240702a: 7DT Optical upper limits
  81. GRB 240606B: 7DT Optical upper limits
  82. Fermi trigger No 757231333: Global MASTER-Net observations report
  83. GRB 241229B: Swift-BAT refined analysis
  84. Fermi Gamma-ray Burst Monitor trigger 757207662/241229978 (GRB 241229C) is not a GRB
  85. GRB241229B: UVOT upper limits
  86. GRB 241229C: Fermi GBM Final Real-time Localization
  87. GRB 241228B: D50 optical detection
  88. GRB 241228B: Fermi GBM Observation
  89. GRB 241228B: Swift-XRT afterglow detection
  90. GRB 241229B: Fermi GBM Observation
  91. GRB 241229A: Swift ToO observations
  92. GRB 241229B: NUTTelA-TAO / BSTI Optical Limits
  93. GRB 241228A: Mondy optical afterglow observations
  94. GRB 241229B: Swift-XRT refined Analysis
  95. IceCube-241224A: No transient candidates from the Zwicky Transient Facility
  96. Swift GRB 241229B: Global MASTER-Net observations report
  97. GRB 241229A: GOTO optical upper limits
  98. GRB 241228B: VLT/X-shooter redshift of z = 2.674
  99. GRB 241228A: NOT optical upper limits
  100. GRB 241228B: LCO optical observation

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