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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"

24602 results found.

  1. GRB 250114A: Enhanced Swift-XRT position
  2. GRB 250114A: REM detection of the optical and NIR counterpart
  3. LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
  4. Swift GRB250114A: Global MASTER-Net OT detection
  5. GRB 250114A: LCO optical observations
  6. GRB 250114A: TRT optical observations
  7. GRB 250114A: Swift detection of a burst with an optical counterpart
  8. GRB 250101A: Terskol Zeiss-2000 optical observations
  9. EP250108a / AT 2025kg: SAO RAS optical observations
  10. EP241021a: SMA radio observation
  11. GRB 250113A: SVOM/GRM observation of a long burst
  12. GRB 250107A: VZLUSAT-2 detection
  13. EP250109b: optical upper limits with the Liverpool Telescope
  14. GRB 250106A: Swift-XRT afterglow detection
  15. EP250111a: KAIT optical observations
  16. GRB 250109A / EP250109a: Mephisto optical upper limits
  17. EP250108a: Mephisto detection
  18. EP250111a: Mondy optical observation
  19. EP250108a / AT 2025kg: LCO optical observations
  20. EP250108a / AT 2025kg: Swift UVOT detections
  21. EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
  22. EP250111a: NOT likely optical counterpart
  23. GRB 250101B: Fermi GBM Observation
  24. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  25. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  26. GRB 250108A: Swift/XRT afterglow fading
  27. LIGO/Virgo/KAGRA S250109bi: Updated Sky localization
  28. LIGO/Virgo/KAGRA S250109f: Updated Sky localization
  29. LIGO/Virgo/KAGRA S250108eo: Updated Sky localization
  30. EP-WXT trigger EP250108a:Xinglong optical follow-up observations
  31. GRB 250101A: CMO RC-500 optical observations
  32. GRB 250109A: Fermi GBM Observation
  33. EP250108a: NOT optical observations
  34. EP-WXT trigger EP250109a:Xinglong optical follow-up observations
  35. GRB 250109a: GMG Optical Upper Limit
  36. EP250109a: Swift/UVOT non-detection
  37. IPN triangulation of GRB 250107D (short/hard)
  38. EP250108a: Liverpool Telescope likely optical counterpart
  39. GRB 250108B: Swift-BAT refined analysis
  40. GRB 250108B: 1.3m DFOT upper limit
  41. GRB 250108B: REM optical/NIR upper limits
  42. GRB 250101A: Terskol K-800 optical observations
  43. EP250109a: Swift/XRT non-detection
  44. GRB 250108A: Swift/UVOT Upper Limits
  45. LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
  46. GRB 250108A: NOT optical upper limit
  47. EP250108a: EP-WXT detection of an X-ray transient
  48. LIGO/Virgo/KAGRA S250109f: Identification of a GW compact binary merger candidate
  49. GRB 250108B: Swift-XRT refined Analysis
  50. GRB 250103A: 1.6m Mephisto optical observations
  51. GRB 250108A: Swift-XRT afterglow detection
  52. GRB 250108A:SVOM/VT optical candidate
  53. LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate
  54. GRB 250108B: Swift/UVOT Upper Limits
  55. GRB 250103A: Swift-XRT afterglow detection
  56. GRB 250108B: Enhanced Swift-XRT position
  57. GRB 250108B: Swift detection of a burst
  58. GRB 250107A: Fermi GBM Observation
  59. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  60. GRB 250106A: SVOM/VT 2nd optical deep observation
  61. GRB 250101A: J band upper limit by SYSU 80cm telescope
  62. EPWXT01709129925: Xinglong optical observations
  63. GRB 250106A: NOT optical observations
  64. LIGO/Virgo/KAGRA S250104v: Updated Sky localization
  65. GRB 250103B: REM optical/NIR upper limits
  66. GRB 250101A: REM optical/NIR counterpart detection
  67. GRB 250106A: Swift-XRT observations
  68. GRB 250106A: SVOM/VT optical candidate
  69. The EP-WXT trigger 01709129925 is likely a flaring star
  70. GRB 250103B: Swift-XRT refined Analysis
  71. GRB 250103B: LCO/1m optical afterglow candidate detection
  72. GRB 250103A: Bassano Bresciano Observatory upper limit
  73. GRB 250103A: Swift-XRT observations
  74. GRB 250101A: 1.3m DFOT optical afterglow detection
  75. GRB 241229A: 1.3m DFOT upper limit
  76. GRB 241228B: 1.3m DFOT Optical observations
  77. GRB 241228A: 1.3m DFOT upper limit
  78. LIGO/Virgo/KAGRA S250104v: Identification of a GW compact binary merger candidate
  79. GRB 250103A: Montarrenti Observatory optical detection
  80. GRB 250101A: further LCOGT optical afterglow observations
  81. GRB 250103A: TSHAO optical upper limit
  82. GRB 250103A: Fermi GBM Observation
  83. GRB 250103B: LCOGT Optical Upper Limit
  84. IceCube-250102A: Upper limits from a search for additional neutrino events in IceCube
  85. EP250101a: Liverpool Telescope optical upper limit
  86. IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
  87. GRB 250101a: Liverpool Telescope optical follow-up
  88. GRB 250103B: Swift detection of a burst
  89. GRB 250103A: Xinglong 2.16m Optical Candidate
  90. GRB 250101B: SVOM/GRM observation
  91. GRB 250103A: GOTO optical upper limit
  92. GRB 250103A: SVOM/C-GFT optical upper limit
  93. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  94. EP241231b: optical upper limit with the Liverpool Telescope
  95. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  96. GRB 250103A: SVOM detection of a long burst
  97. EP250101a: Xinglong optical upper limit
  98. LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
  99. GRB 250101A: Swift-BAT refined analysis
  100. GRB 250101A: further SAO RAS optical observations

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