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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 241229A: 1.3m DFOT upper limit
  2. GRB 241228B: 1.3m DFOT Optical observations
  3. GRB 241228A: 1.3m DFOT upper limit
  4. GRB 250103A: NOT spectroscopic redshift
  5. GRB 250103B：SVOM/VT optical counterpart
  6. LIGO/Virgo/KAGRA S250104v: Identification of a GW compact binary merger candidate
  7. GRB 250103A: Montarrenti Observatory optical detection
  8. GRB 250101A: further LCOGT optical afterglow observations
  9. GRB 250103A: Redshift 4.01 from OSIRIS+/GTC
  10. GRB 250103A: NOT optical observations
  11. GRB 250103A: TSHAO optical upper limit
  12. GRB 250103A: Fermi GBM Observation
  13. GRB 250103B: LCOGT Optical Upper Limit
  14. IceCube-250102A: Upper limits from a search for additional neutrino events in IceCube
  15. Swift GRB 250103B: Global MASTER-Net observations report
  16. GRB 250103A: SVOM/VT optical counterpart confirmation
  17. EP250101a: Liverpool Telescope optical upper limit
  18. GRB 250103A: Swift ToO observations
  19. IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
  20. GRB 250101a: Liverpool Telescope optical follow-up
  21. GRB 250103B: SVOM detection of a long burst
  22. GRB 250103B: Swift detection of a burst
  23. GRB 250103A: Xinglong 2.16m Optical Candidate
  24. Fermi GRB 250102A: Global MASTER-Net observations report
  25. GRB 250101B: SVOM/GRM observation
  26. GRB 250103A: GOTO optical upper limit
  27. GRB 250103A: SVOM/C-GFT optical upper limit
  28. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  29. IceCube Alert 250102.58: Global MASTER-Net observations report
  30. EP241231b: optical upper limit with the Liverpool Telescope
  31. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  32. GRB 250103A: SVOM detection of a long burst
  33. EP250101a: Xinglong optical upper limit
  34. GRB 250102A: Fermi GBM Final Real-time Localization
  35. LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
  36. GRB 250101A: Swift-BAT refined analysis
  37. IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event
  38. GRB 250101A: further SAO RAS optical observations
  39. GRB 250101A: LCO optical counterpart detection
  40. EP241231b and EP250101a: EP-WXT detection of two X-ray transients
  41. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  42. GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
  43. GRB 250101A: Swift/UVOT Detection
  44. GRB 250101A: 1.6m Mephisto multi-band optical followup
  45. GRB 250101A: Swift-XRT refined Analysis
  46. Fermi Gamma-ray Burst Monitor trigger 757464861/250101954 is not a GRB
  47. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  48. IceCube-250101A - IceCube observation of a high-energy neutrino candidate track-like event
  49. GRB 250101A: LCOGT optical afterglow detection
  50. GRB 250101A: OASDG optical observations
  51. Fermi GRB 250101B: Global MASTER-Net observations report
  52. GRB 250101B: Fermi GBM Final Real-time Localization
  53. GRB 250101A: SAO RAS observations of optical brightening
  54. GRB 250101A: BOOTES-4/MET optical afterglow detection
  55. GRB 250101A: AKO Optical Afterglow Detection
  56. GRB 250101A: SAO RAS optical observations
  57. GRB 250101A: Enhanced Swift-XRT position
  58. LIGO/Virgo/KAGRA S250101k: Updated Sky localization and Source Classification
  59. GRB 250101A: Xinglong-2.16m spectroscopic redshift
  60. GRB 250101A: SVOM/C-GFT early optical observations
  61. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
  62. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  63. GRB 250101A: Nanshan/HMT optical observations
  64. GRB 250101A : GIT optical detection
  65. GRB 250101A: GMG Optical Observation
  66. GRB 250101A: Swift detection of a burst with an optical counterpart
  67. Swift GRB250101.56: Global MASTER-Net observations report
  68. GRB 241217a/EP241217b: ATCA Radio Detection
  69. EP241217a: VLA Radio Detection

  70. LIGO/Virgo/KAGRA S241231du: Coverage and upper limit from MAXI/GSC observations
  71. LIGO/Virgo/KAGRA S250101k: Identification of a GW compact binary merger candidate
  72. GRB 241229B: Continued CrAO ZTSh observations
  73. LIGO/Virgo/KAGRA S241231bg: Updated NED Galaxies in the Localization Volume
  74. LIGO/Virgo/KAGRA S241231bg: Updated Sky localization and EM Bright Classification
  75. LIGO/Virgo/KAGRA S241230ev: Updated Sky localization
  76. LIGO/Virgo/KAGRA S241231bg: NED Galaxies in the Localization Volume
  77. LIGO/Virgo/KAGRA S241230bd: Updated Sky localization
  78. GRB 241229A: EP-FXT X-ray afterglow confirmation
  79. GRB 241228B: Multiband optical monitoring with 1.6m Mephisto
  80. GRB 241229B: SVOM/GRM observation
  81. LIGO/Virgo/KAGRA S241231bg: Identification of a GW compact binary merger candidate
  82. EP241217A: J band upper limit by SYSU 80cm telescope
  83. LIGO/Virgo/KAGRA S241230ev: Identification of a GW compact binary merger candidate
  84. GRB 241229B: SAO RAS optical upper limit
  85. GRB 241228B: SAO RAS optical observations
  86. GRB 241229B: CrAO ZTSh possible optical counterpart of SVOM/VT confirmation
  87. GRB 241229A: SAO RAS optical observations
  88. IceCube-Cascade 241228A: Upper limits from a search for additional neutrino events in IceCube
  89. GRB 241229B: SVOM/VT optical candidate
  90. GRB 241229A: Swift-XRT observations
  91. Konus-Wind detection of GRB 241228A
  92. GRB 241229A: EP-FXT afterglow candidates
  93. EP240702a: 7DT Optical upper limits
  94. GRB 240606B: 7DT Optical upper limits
  95. Fermi trigger No 757231333: Global MASTER-Net observations report
  96. LIGO/Virgo/KAGRA S241230bd: Identification of a GW compact binary merger candidate
  97. GRB 241229B: Swift-BAT refined analysis
  98. LIGO/Virgo/KAGRA S241225v: Updated Sky localization
  99. LIGO/Virgo/KAGRA S241225c: Updated Sky localization and EM Bright Classification
  100. Fermi Gamma-ray Burst Monitor trigger 757207662/241229978 (GRB 241229C) is not a GRB

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