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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 250101A NUTTelA-TAO / BSTI Early Measurements
  2. GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
  3. GRB 250101A: Swift/UVOT Detection
  4. GRB 250101A: 1.6m Mephisto multi-band optical followup
  5. GRB 250101A: Swift-XRT refined Analysis
  6. Fermi Gamma-ray Burst Monitor trigger 757464861/250101954 is not a GRB
  7. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  8. IceCube-250101A - IceCube observation of a high-energy neutrino candidate track-like event
  9. GRB 250101A: LCOGT optical afterglow detection
  10. GRB 250101A: OASDG optical observations
  11. Fermi GRB 250101B: Global MASTER-Net observations report
  12. GRB 250101B: Fermi GBM Final Real-time Localization
  13. GRB 250101A: SAO RAS observations of optical brightening
  14. GRB 250101A: BOOTES-4/MET optical afterglow detection
  15. GRB 250101A: AKO Optical Afterglow Detection
  16. GRB 250101A: SAO RAS optical observations
  17. GRB 250101A: Enhanced Swift-XRT position
  18. LIGO/Virgo/KAGRA S250101k: Updated Sky localization and Source Classification
  19. GRB 250101A: Xinglong-2.16m spectroscopic redshift
  20. GRB 250101A: SVOM/C-GFT early optical observations
  21. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
  22. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  23. GRB 250101A: Nanshan/HMT optical observations
  24. GRB 250101A : GIT optical detection
  25. GRB 250101A: GMG Optical Observation
  26. GRB 250101A: Swift detection of a burst with an optical counterpart
  27. Swift GRB250101.56: Global MASTER-Net observations report
  28. GRB 241217a/EP241217b: ATCA Radio Detection
  29. EP241217a: VLA Radio Detection

  30. LIGO/Virgo/KAGRA S241231du: Coverage and upper limit from MAXI/GSC observations
  31. LIGO/Virgo/KAGRA S250101k: Identification of a GW compact binary merger candidate
  32. GRB 241229B: Continued CrAO ZTSh observations
  33. LIGO/Virgo/KAGRA S241231bg: Updated NED Galaxies in the Localization Volume
  34. LIGO/Virgo/KAGRA S241231bg: Updated Sky localization and EM Bright Classification
  35. LIGO/Virgo/KAGRA S241230ev: Updated Sky localization
  36. LIGO/Virgo/KAGRA S241231bg: NED Galaxies in the Localization Volume
  37. LIGO/Virgo/KAGRA S241230bd: Updated Sky localization
  38. GRB 241229A: EP-FXT X-ray afterglow confirmation
  39. GRB 241228B: Multiband optical monitoring with 1.6m Mephisto
  40. GRB 241229B: SVOM/GRM observation
  41. LIGO/Virgo/KAGRA S241231bg: Identification of a GW compact binary merger candidate
  42. EP241217A: J band upper limit by SYSU 80cm telescope
  43. LIGO/Virgo/KAGRA S241230ev: Identification of a GW compact binary merger candidate
  44. GRB 241229B: SAO RAS optical upper limit
  45. GRB 241228B: SAO RAS optical observations
  46. GRB 241229B: CrAO ZTSh possible optical counterpart of SVOM/VT confirmation
  47. GRB 241229A: SAO RAS optical observations
  48. IceCube-Cascade 241228A: Upper limits from a search for additional neutrino events in IceCube
  49. GRB 241229B: SVOM/VT optical candidate
  50. GRB 241229A: Swift-XRT observations
  51. Konus-Wind detection of GRB 241228A
  52. GRB 241229A: EP-FXT afterglow candidates
  53. EP240702a: 7DT Optical upper limits
  54. GRB 240606B: 7DT Optical upper limits
  55. Fermi trigger No 757231333: Global MASTER-Net observations report
  56. LIGO/Virgo/KAGRA S241230bd: Identification of a GW compact binary merger candidate
  57. GRB 241229B: Swift-BAT refined analysis
  58. LIGO/Virgo/KAGRA S241225v: Updated Sky localization
  59. LIGO/Virgo/KAGRA S241225c: Updated Sky localization and EM Bright Classification
  60. Fermi Gamma-ray Burst Monitor trigger 757207662/241229978 (GRB 241229C) is not a GRB
  61. GRB241229B: UVOT upper limits
  62. GRB 241229C: Fermi GBM Final Real-time Localization
  63. GRB 241228B: D50 optical detection
  64. GRB 241228B: Fermi GBM Observation
  65. GRB 241228B: Swift-XRT afterglow detection
  66. GRB 241229B: Fermi GBM Observation
  67. GRB 241229A: Swift ToO observations
  68. GRB 241229B: NUTTelA-TAO / BSTI Optical Limits
  69. GRB 241228A: Mondy optical afterglow observations
  70. GRB 241229B: Swift-XRT refined Analysis
  71. IceCube-241224A: No transient candidates from the Zwicky Transient Facility
  72. Swift GRB 241229B: Global MASTER-Net observations report
  73. GRB 241229A: GOTO optical upper limits
  74. GRB 241228B: VLT/X-shooter redshift of z = 2.674
  75. GRB 241228A: NOT optical upper limits
  76. GRB 241228B: LCO optical observation
  77. GRB 241228A: Swift-BAT refined analysis
  78. GRB 241228B: Swift/BAT-GUANO localization skymap of a burst
  79. GRB 241229B: Swift detection of a burst
  80. GRB 241229B: Fermi GBM Final Real-time Localization
  81. GRB 241229A: SVOM detection of a long burst
  82. Fermi GRB 241228B: Global MASTER-Net observations report
  83. GRB 241228A: Fermi GBM Observation
  84. GRB241228B: GROWTH-India Telescope optical observations
  85. Swift GRB 241228A: Global MASTER-Net observations report
  86. GRB 241228B: LCOGT photometry of the likely optical counterpart GOTO24jmz
  87. GRB 241228B: GOTO24jmz optical follow-up observations
  88. GRB 241226A: Swift/BAT-GUANO localization skymap of a burst
  89. GRB 241228A: GROWTH-India telescope optical upper limit
  90. GRB 241228B: Swift ToO observations
  91. GRB 241228B: TRT optical counterpart confirmation
  92. GRB 241228A: Swift-XRT refined Analysis
  93. GRB 241228A: Swift/UVOT Upper Limits
  94. GRB 241228B: GOTO possible optical counterpart candidate
  95. GRB 241228A: Enhanced Swift-XRT position
  96. GRB 241228B: Fermi GBM Final Real-time Localization
  97. GRB 241228A: Swift detection of a burst
  98. IceCube-241224A: Upper limits from a search for additional neutrino events in IceCube
  99. LIGO/Virgo/KAGRA S241225c: Two counterpart neutrino candidates from IceCube neutrino searches
  100. GRB 241223A: GRBAlpha detection

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