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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"

24609 results found.

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

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