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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 250103B: REM optical/NIR upper limits
  2. GRB 250101A: REM optical/NIR counterpart detection
  3. GRB 250106A: Swift-XRT observations
  4. GRB 250106A: SVOM/VT optical candidate
  5. GRB 250106A: Swift ToO observations
  6. The EP-WXT trigger 01709129925 is likely a flaring star
  7. GRB 250106A: SVOM detection of a long burst
  8. Fermi trigger No 757753930: Global MASTER-Net observations report
  9. GRB 241229A: SVOM/VT optical upperlimit
  10. GRB 250103B: Swift-XRT refined Analysis
  11. GRB 250103B: LCO/1m optical afterglow candidate detection
  12. GRB 250103A: Bassano Bresciano Observatory upper limit
  13. GRB 250103B: VLT/X-shooter spectroscopic redshift z = 1.416
  14. GRB 250103A: Swift-XRT observations
  15. GRB 250101A: 1.3m DFOT optical afterglow detection
  16. GRB 241229A: 1.3m DFOT upper limit
  17. GRB 241228B: 1.3m DFOT Optical observations
  18. GRB 241228A: 1.3m DFOT upper limit
  19. GRB 250103A: NOT spectroscopic redshift
  20. GRB 250103B：SVOM/VT optical counterpart
  21. LIGO/Virgo/KAGRA S250104v: Identification of a GW compact binary merger candidate
  22. GRB 250103A: Montarrenti Observatory optical detection
  23. GRB 250101A: further LCOGT optical afterglow observations
  24. GRB 250103A: Redshift 4.01 from OSIRIS+/GTC
  25. GRB 250103A: NOT optical observations
  26. GRB 250103A: TSHAO optical upper limit
  27. GRB 250103A: Fermi GBM Observation
  28. GRB 250103B: LCOGT Optical Upper Limit
  29. IceCube-250102A: Upper limits from a search for additional neutrino events in IceCube
  30. Swift GRB 250103B: Global MASTER-Net observations report
  31. GRB 250103A: SVOM/VT optical counterpart confirmation
  32. EP250101a: Liverpool Telescope optical upper limit
  33. GRB 250103A: Swift ToO observations
  34. IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
  35. GRB 250101a: Liverpool Telescope optical follow-up
  36. GRB 250103B: SVOM detection of a long burst
  37. GRB 250103B: Swift detection of a burst
  38. GRB 250103A: Xinglong 2.16m Optical Candidate
  39. Fermi GRB 250102A: Global MASTER-Net observations report
  40. GRB 250101B: SVOM/GRM observation
  41. GRB 250103A: GOTO optical upper limit
  42. GRB 250103A: SVOM/C-GFT optical upper limit
  43. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  44. IceCube Alert 250102.58: Global MASTER-Net observations report
  45. EP241231b: optical upper limit with the Liverpool Telescope
  46. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  47. GRB 250103A: SVOM detection of a long burst
  48. EP250101a: Xinglong optical upper limit
  49. GRB 250102A: Fermi GBM Final Real-time Localization
  50. LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
  51. GRB 250101A: Swift-BAT refined analysis
  52. IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event
  53. GRB 250101A: further SAO RAS optical observations
  54. GRB 250101A: LCO optical counterpart detection
  55. EP241231b and EP250101a: EP-WXT detection of two X-ray transients
  56. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  57. GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
  58. GRB 250101A: Swift/UVOT Detection
  59. GRB 250101A: 1.6m Mephisto multi-band optical followup
  60. GRB 250101A: Swift-XRT refined Analysis
  61. Fermi Gamma-ray Burst Monitor trigger 757464861/250101954 is not a GRB
  62. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  63. IceCube-250101A - IceCube observation of a high-energy neutrino candidate track-like event
  64. GRB 250101A: LCOGT optical afterglow detection
  65. GRB 250101A: OASDG optical observations
  66. Fermi GRB 250101B: Global MASTER-Net observations report
  67. GRB 250101B: Fermi GBM Final Real-time Localization
  68. GRB 250101A: SAO RAS observations of optical brightening
  69. GRB 250101A: BOOTES-4/MET optical afterglow detection
  70. GRB 250101A: AKO Optical Afterglow Detection
  71. GRB 250101A: SAO RAS optical observations
  72. GRB 250101A: Enhanced Swift-XRT position
  73. LIGO/Virgo/KAGRA S250101k: Updated Sky localization and Source Classification
  74. GRB 250101A: Xinglong-2.16m spectroscopic redshift
  75. GRB 250101A: SVOM/C-GFT early optical observations
  76. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
  77. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  78. GRB 250101A: Nanshan/HMT optical observations
  79. GRB 250101A : GIT optical detection
  80. GRB 250101A: GMG Optical Observation
  81. GRB 250101A: Swift detection of a burst with an optical counterpart
  82. Swift GRB250101.56: Global MASTER-Net observations report
  83. GRB 241217a/EP241217b: ATCA Radio Detection
  84. EP241217a: VLA Radio Detection

  85. LIGO/Virgo/KAGRA S241231du: Coverage and upper limit from MAXI/GSC observations
  86. LIGO/Virgo/KAGRA S250101k: Identification of a GW compact binary merger candidate
  87. GRB 241229B: Continued CrAO ZTSh observations
  88. LIGO/Virgo/KAGRA S241231bg: Updated NED Galaxies in the Localization Volume
  89. LIGO/Virgo/KAGRA S241231bg: Updated Sky localization and EM Bright Classification
  90. LIGO/Virgo/KAGRA S241230ev: Updated Sky localization
  91. LIGO/Virgo/KAGRA S241231bg: NED Galaxies in the Localization Volume
  92. LIGO/Virgo/KAGRA S241230bd: Updated Sky localization
  93. GRB 241229A: EP-FXT X-ray afterglow confirmation
  94. GRB 241228B: Multiband optical monitoring with 1.6m Mephisto
  95. GRB 241229B: SVOM/GRM observation
  96. LIGO/Virgo/KAGRA S241231bg: Identification of a GW compact binary merger candidate
  97. EP241217A: J band upper limit by SYSU 80cm telescope
  98. LIGO/Virgo/KAGRA S241230ev: Identification of a GW compact binary merger candidate
  99. GRB 241229B: SAO RAS optical upper limit
  100. GRB 241228B: SAO RAS optical observations

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