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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"

31672 results found.

  1. GRB 250101A: Terskol Zeiss-2000 optical observations
  2. EP250108a / AT 2025kg: SAO RAS optical observations
  3. EP241021a: SMA radio observation
  4. GRB 250107A: VZLUSAT-2 detection
  5. GRB 250109A / EP250109a: GRBAlpha detection
  6. GRB 250107D: GRBAlpha detection
  7. EP250111a: KAIT optical observations
  8. GRB 250109A / EP250109a: Mephisto optical upper limits
  9. EP250108a: Mephisto detection
  10. EP250111a: Mondy optical observation
  11. EP250108a / AT 2025kg: LCO optical observations
  12. EP250111a: Global MASTER-Net observations report
  13. EP250111a: Swift/XRT detection and fading
  14. EP250108a / AT 2025kg: Swift UVOT detections
  15. EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
  16. EP250108a: optical follow-up observations with the Liverpool Telescope
  17. EP250111a: NOT likely optical counterpart
  18. EP250109a/GRB 250109A:SVOM/VT optical counterpart
  19. GRB 250101B: Fermi GBM Observation
  20. EP250108a: further NOT optical observations
  21. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  22. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  23. GRB 250109A / EP250109a: Swift detection of the X-ray afterglow
  24. GRB 250108A: Swift/XRT afterglow fading
  25. GRB 250107D: CALET Gamma-Ray Burst Monitor detection
  26. GRB 250107C: CALET Gamma-Ray Burst Monitor detection
  27. Konus-Wind detection of GRB 250107C
  28. LIGO/Virgo/KAGRA S250109bi: Updated Sky localization
  29. LIGO/Virgo/KAGRA S250109f: Updated Sky localization
  30. LIGO/Virgo/KAGRA S250108eo: Updated Sky localization
  31. GRB 250101A: CMO RC-500 optical observations
  32. EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
  33. EP250108a: EP-FXT follow-up observation
  34. GRB 250109A: Fermi GBM Observation
  35. EP250108a: NOT optical observations
  36. GRB 250109a: GMG Optical Upper Limit
  37. EP250109a: Swift/UVOT non-detection
  38. Konus-Wind detection of GRB 250107D (short/hard)
  39. IPN triangulation of GRB 250107D (short/hard)
  40. IPN triangulation of GRB 250107C
  41. EP250108a: Liverpool Telescope likely optical counterpart
  42. GRB 250108B: Gemini-North likely redshift z = 2.197
  43. GRB 250108B: Swift-BAT refined analysis
  44. GRB 250108B: 1.3m DFOT upper limit
  45. GRB 250108B: REM optical/NIR upper limits
  46. GRB 250109A /EP250109a: Fermi GBM Final Localization
  47. EP250109a: SVOM/VT optical candidate
  48. EP250109a: Global MASTER-Net observations report
  49. GRB 250101A: Terskol K-800 optical observations
  50. EP250109a: GOTO optical upper limits
  51. EP250109a: Swift/XRT non-detection
  52. GRB 250108A: Swift/UVOT Upper Limits
  53. EP250108a: Global MASTER-Net observations report
  54. LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
  55. GRB 250108A: NOT optical upper limit
  56. LIGO/Virgo/KAGRA S250109f: Identification of a GW compact binary merger candidate
  57. Swift GRB 250108B: Global MASTER-Net observations report
  58. Fermi Gamma-ray Burst Monitor trigger 758061038/250108855 is not a GRB
  59. GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
  60. GRB 250103A: 1.6m Mephisto optical observations
  61. GRB 250108A:SVOM/VT optical candidate
  62. LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate
  63. GRB 250108B: Swift/UVOT Upper Limits
  64. GRB 250108A: Swift ToO observations
  65. GRB 250107A: Fermi GBM Observation
  66. GRB 241228B: Fermi-LAT detection
  67. Fermi GRB 250107B: Global MASTER-Net observations report
  68. GRB 250107A: Swift ToO observations
  69. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  70. GRB 250106A: SVOM/VT 2nd optical deep observation
  71. GRB 250101A: J band upper limit by SYSU 80cm telescope
  72. GRB 250106A: NOT optical observations
  73. LIGO/Virgo/KAGRA S250104v: Updated Sky localization
  74. GRB 250103B: REM optical/NIR upper limits
  75. GRB 250101A: REM optical/NIR counterpart detection
  76. GRB 250106A: Swift-XRT observations
  77. GRB 250106A: SVOM/VT optical candidate
  78. GRB 250106A: Swift ToO observations
  79. GRB 241229A: SVOM/VT optical upperlimit
  80. GRB 250103B: LCO/1m optical afterglow candidate detection
  81. GRB 250103B: VLT/X-shooter spectroscopic redshift z = 1.416
  82. GRB 250103A: Swift-XRT observations
  83. GRB 250101A: 1.3m DFOT optical afterglow detection
  84. GRB 241229A: 1.3m DFOT upper limit
  85. GRB 241228B: 1.3m DFOT Optical observations
  86. GRB 241228A: 1.3m DFOT upper limit
  87. GRB 250103A: NOT spectroscopic redshift
  88. GRB 250103B：SVOM/VT optical counterpart
  89. LIGO/Virgo/KAGRA S250104v: Identification of a GW compact binary merger candidate
  90. GRB 250103A: Montarrenti Observatory optical detection
  91. GRB 250101A: further LCOGT optical afterglow observations
  92. GRB 250103A: Redshift 4.01 from OSIRIS+/GTC
  93. GRB 250103A: NOT optical observations
  94. GRB 250103A: TSHAO optical upper limit
  95. GRB 250103A: Fermi GBM Observation
  96. GRB 250103B: LCOGT Optical Upper Limit
  97. IceCube-250102A: Upper limits from a search for additional neutrino events in IceCube
  98. Swift GRB 250103B: Global MASTER-Net observations report
  99. GRB 250103A: SVOM/VT optical counterpart confirmation
  100. EP250101a: Liverpool Telescope optical upper limit

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