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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"

24699 results found.

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

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