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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"

16214 results found.

  1. EP250108a: EP-FXT follow-up observation
  2. The EP-WXT trigger 01709130111 is likely a flaring star
  3. EP250108a: NOT optical observations
  4. EP-WXT trigger EP250109a：Xinglong optical follow-up observations
  5. GRB 250109a: GMG Optical Upper Limit
  6. EP250109a: Swift/UVOT non-detection
  7. IPN triangulation of GRB 250107D (short/hard)
  8. EP250108a: Liverpool Telescope likely optical counterpart
  9. GRB 250108B: 1.3m DFOT upper limit
  10. GRB 250108B: REM optical/NIR upper limits
  11. GRB 250109A /EP250109a: Fermi GBM Final Localization
  12. GRB 250101A: Terskol K-800 optical observations
  13. EP250109a: Swift/XRT non-detection
  14. GRB 250108A: Swift/UVOT Upper Limits
  15. EP250109a: EP-WXT detection of an X-ray transient
  16. GRB 250108A: NOT optical upper limit
  17. EP250108a: EP-WXT detection of an X-ray transient
  18. GRB 250108B: Swift-XRT refined Analysis
  19. GRB 250103A: 1.6m Mephisto optical observations
  20. GRB 250108A: Swift-XRT afterglow detection
  21. GRB 250108B: Swift/UVOT Upper Limits
  22. GRB 250103A: Swift-XRT afterglow detection
  23. GRB 250108B: Enhanced Swift-XRT position
  24. GRB 250108B: Swift detection of a burst
  25. GRB 250108A: SVOM detection of a soft long burst
  26. GRB 250101A: J band upper limit by SYSU 80cm telescope
  27. EPWXT01709129925: Xinglong optical observations
  28. GRB 250106A: NOT optical observations
  29. GRB 250103B: REM optical/NIR upper limits
  30. GRB 250101A: REM optical/NIR counterpart detection
  31. The EP-WXT trigger 01709129925 is likely a flaring star
  32. GRB 250103B: Swift-XRT refined Analysis
  33. GRB 250103B: LCO/1m optical afterglow candidate detection
  34. GRB 250103A: Bassano Bresciano Observatory upper limit
  35. GRB 250101A: 1.3m DFOT optical afterglow detection
  36. GRB 241229A: 1.3m DFOT upper limit
  37. GRB 241228B: 1.3m DFOT Optical observations
  38. GRB 241228A: 1.3m DFOT upper limit
  39. GRB 250103A: Montarrenti Observatory optical detection
  40. GRB 250101A: further LCOGT optical afterglow observations
  41. GRB 250103A: TSHAO optical upper limit
  42. GRB 250103B: LCOGT Optical Upper Limit
  43. EP250101a: Liverpool Telescope optical upper limit
  44. GRB 250101a: Liverpool Telescope optical follow-up
  45. GRB 250103B: Swift detection of a burst
  46. GRB 250103A: Xinglong 2.16m Optical Candidate
  47. GRB 250101B: SVOM/GRM observation
  48. GRB 250103A: GOTO optical upper limit
  49. GRB 250103A: SVOM/C-GFT optical upper limit
  50. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  51. EP241231b: optical upper limit with the Liverpool Telescope
  52. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  53. GRB 250103A: SVOM detection of a long burst
  54. EP250101a: Xinglong optical upper limit
  55. GRB 250101A: further SAO RAS optical observations
  56. GRB 250101A: LCO optical counterpart detection
  57. EP241231b and EP250101a: EP-WXT detection of two X-ray transients
  58. GRB 250101A: Swift/UVOT Detection
  59. GRB 250101A: 1.6m Mephisto multi-band optical followup
  60. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  61. GRB 250101A: LCOGT optical afterglow detection
  62. GRB 250101A: OASDG optical observations
  63. GRB 250101A: AKO Optical Afterglow Detection
  64. GRB 250101A: SAO RAS optical observations
  65. GRB 250101A: Enhanced Swift-XRT position
  66. GRB 250101A: SVOM/C-GFT early optical observations
  67. GRB 250101A : GIT optical detection
  68. GRB 250101A: GMG Optical Observation
  69. GRB 250101A: Swift detection of a burst with an optical counterpart
  70. GRB 241217a/EP241217b: ATCA Radio Detection
  71. LIGO/Virgo/KAGRA S241231du: Coverage and upper limit from MAXI/GSC observations
  72. GRB 241229B: Continued CrAO ZTSh observations
  73. GRB 241229A: EP-FXT X-ray afterglow confirmation
  74. GRB 241228B: Multiband optical monitoring with 1.6m Mephisto
  75. GRB 241229B: SVOM/GRM observation
  76. LIGO/Virgo/KAGRA S241231bg: Identification of a GW compact binary merger candidate
  77. EP241217A: J band upper limit by SYSU 80cm telescope
  78. GRB 241229B: SAO RAS optical upper limit
  79. GRB 241228B: SAO RAS optical observations
  80. GRB 241229A: SAO RAS optical observations
  81. GRB 241229A: EP-FXT afterglow candidates
  82. EP240702a: 7DT Optical upper limits
  83. GRB 240606B: 7DT Optical upper limits
  84. GRB241229B: UVOT upper limits
  85. GRB 241228B: Swift-XRT afterglow detection
  86. GRB 241228A: Mondy optical afterglow observations
  87. GRB 241229A: GOTO optical upper limits
  88. GRB 241228B: VLT/X-shooter redshift of z = 2.674
  89. GRB 241228A: NOT optical upper limits
  90. GRB 241228B: LCO optical observation
  91. GRB 241228B: Swift/BAT-GUANO localization skymap of a burst
  92. GRB241228B: GROWTH-India Telescope optical observations
  93. GRB 241226A: Swift/BAT-GUANO localization skymap of a burst
  94. GRB 241228A: GROWTH-India telescope optical upper limit
  95. GRB 241228B: TRT optical counterpart confirmation
  96. GRB 241228A: Swift/UVOT Upper Limits
  97. GRB 241228A: Enhanced Swift-XRT position
  98. GRB 241228A: Swift detection of a burst
  99. EP241223a: Mondy AZT-33IK optical observations
  100. GRB 241029A: LCO optical observation

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