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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"
  1. GRB 250108A: Swift-XRT afterglow detection
  2. GRB 250108A:SVOM/VT optical candidate
  3. LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate
  4. GRB 250108B: Swift/UVOT Upper Limits
  5. GRB 250103A: Swift-XRT afterglow detection
  6. GRB 250108B: Enhanced Swift-XRT position
  7. GRB 250108B: Swift detection of a burst
  8. GRB 250108A: Swift ToO observations
  9. GRB 250108A: SVOM detection of a soft long burst
  10. GRB 250107A: Fermi GBM Observation
  11. GRB 241228B: Fermi-LAT detection
  12. Fermi GRB 250107B: Global MASTER-Net observations report
  13. GRB 250107A: Swift ToO observations
  14. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  15. GRB 250107B: Fermi GBM Final Real-time Localization
  16. GRB 250106A: SVOM/VT 2nd optical deep observation
  17. GRB 250101A: J band upper limit by SYSU 80cm telescope
  18. GRB 250107A: Fermi GBM Final Real-time Localization
  19. EPWXT01709129925: Xinglong optical observations
  20. GRB 250106A: NOT optical observations
  21. LIGO/Virgo/KAGRA S250104v: Updated Sky localization
  22. GRB 250103B: REM optical/NIR upper limits
  23. GRB 250101A: REM optical/NIR counterpart detection
  24. GRB 250106A: Swift-XRT observations
  25. GRB 250106A: SVOM/VT optical candidate
  26. GRB 250106A: Swift ToO observations
  27. The EP-WXT trigger 01709129925 is likely a flaring star
  28. GRB 250106A: SVOM detection of a long burst
  29. Fermi trigger No 757753930: Global MASTER-Net observations report
  30. GRB 241229A: SVOM/VT optical upperlimit
  31. GRB 250103B: Swift-XRT refined Analysis
  32. GRB 250103B: LCO/1m optical afterglow candidate detection
  33. GRB 250103A: Bassano Bresciano Observatory upper limit
  34. GRB 250103B: VLT/X-shooter spectroscopic redshift z = 1.416
  35. GRB 250103A: Swift-XRT observations
  36. GRB 250101A: 1.3m DFOT optical afterglow detection
  37. GRB 241229A: 1.3m DFOT upper limit
  38. GRB 241228B: 1.3m DFOT Optical observations
  39. GRB 241228A: 1.3m DFOT upper limit
  40. GRB 250103A: NOT spectroscopic redshift
  41. GRB 250103B：SVOM/VT optical counterpart
  42. LIGO/Virgo/KAGRA S250104v: Identification of a GW compact binary merger candidate
  43. GRB 250103A: Montarrenti Observatory optical detection
  44. GRB 250101A: further LCOGT optical afterglow observations
  45. GRB 250103A: Redshift 4.01 from OSIRIS+/GTC
  46. GRB 250103A: NOT optical observations
  47. GRB 250103A: TSHAO optical upper limit
  48. GRB 250103A: Fermi GBM Observation
  49. GRB 250103B: LCOGT Optical Upper Limit
  50. IceCube-250102A: Upper limits from a search for additional neutrino events in IceCube
  51. Swift GRB 250103B: Global MASTER-Net observations report
  52. GRB 250103A: SVOM/VT optical counterpart confirmation
  53. EP250101a: Liverpool Telescope optical upper limit
  54. GRB 250103A: Swift ToO observations
  55. IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
  56. GRB 250101a: Liverpool Telescope optical follow-up
  57. GRB 250103B: SVOM detection of a long burst
  58. GRB 250103B: Swift detection of a burst
  59. GRB 250103A: Xinglong 2.16m Optical Candidate
  60. Fermi GRB 250102A: Global MASTER-Net observations report
  61. GRB 250101B: SVOM/GRM observation
  62. GRB 250103A: GOTO optical upper limit
  63. GRB 250103A: SVOM/C-GFT optical upper limit
  64. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  65. IceCube Alert 250102.58: Global MASTER-Net observations report
  66. EP241231b: optical upper limit with the Liverpool Telescope
  67. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  68. GRB 250103A: SVOM detection of a long burst
  69. EP250101a: Xinglong optical upper limit
  70. GRB 250102A: Fermi GBM Final Real-time Localization
  71. LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
  72. GRB 250101A: Swift-BAT refined analysis
  73. IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event
  74. GRB 250101A: further SAO RAS optical observations
  75. GRB 250101A: LCO optical counterpart detection
  76. EP241231b and EP250101a: EP-WXT detection of two X-ray transients
  77. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  78. GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
  79. GRB 250101A: Swift/UVOT Detection
  80. GRB 250101A: 1.6m Mephisto multi-band optical followup
  81. GRB 250101A: Swift-XRT refined Analysis
  82. Fermi Gamma-ray Burst Monitor trigger 757464861/250101954 is not a GRB
  83. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  84. IceCube-250101A - IceCube observation of a high-energy neutrino candidate track-like event
  85. GRB 250101A: LCOGT optical afterglow detection
  86. GRB 250101A: OASDG optical observations
  87. Fermi GRB 250101B: Global MASTER-Net observations report
  88. GRB 250101B: Fermi GBM Final Real-time Localization
  89. GRB 250101A: SAO RAS observations of optical brightening
  90. GRB 250101A: BOOTES-4/MET optical afterglow detection
  91. GRB 250101A: AKO Optical Afterglow Detection
  92. GRB 250101A: SAO RAS optical observations
  93. GRB 250101A: Enhanced Swift-XRT position
  94. LIGO/Virgo/KAGRA S250101k: Updated Sky localization and Source Classification
  95. GRB 250101A: Xinglong-2.16m spectroscopic redshift
  96. GRB 250101A: SVOM/C-GFT early optical observations
  97. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
  98. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  99. GRB 250101A: Nanshan/HMT optical observations
  100. GRB 250101A : GIT optical detection

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