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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. LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
  2. GRB 250101A: Swift-BAT refined analysis
  3. IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event
  4. GRB 250101A: further SAO RAS optical observations
  5. GRB 250101A: LCO optical counterpart detection
  6. EP241231b and EP250101a: EP-WXT detection of two X-ray transients
  7. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  8. GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
  9. GRB 250101A: Swift/UVOT Detection
  10. GRB 250101A: 1.6m Mephisto multi-band optical followup
  11. GRB 250101A: Swift-XRT refined Analysis
  12. Fermi Gamma-ray Burst Monitor trigger 757464861/250101954 is not a GRB
  13. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  14. IceCube-250101A - IceCube observation of a high-energy neutrino candidate track-like event
  15. GRB 250101A: LCOGT optical afterglow detection
  16. GRB 250101A: OASDG optical observations
  17. Fermi GRB 250101B: Global MASTER-Net observations report
  18. GRB 250101B: Fermi GBM Final Real-time Localization
  19. GRB 250101A: SAO RAS observations of optical brightening
  20. GRB 250101A: BOOTES-4/MET optical afterglow detection
  21. GRB 250101A: AKO Optical Afterglow Detection
  22. GRB 250101A: SAO RAS optical observations
  23. GRB 250101A: Enhanced Swift-XRT position
  24. LIGO/Virgo/KAGRA S250101k: Updated Sky localization and Source Classification
  25. GRB 250101A: Xinglong-2.16m spectroscopic redshift
  26. GRB 250101A: SVOM/C-GFT early optical observations
  27. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
  28. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  29. GRB 250101A: Nanshan/HMT optical observations
  30. GRB 250101A : GIT optical detection
  31. GRB 250101A: GMG Optical Observation
  32. GRB 250101A: Swift detection of a burst with an optical counterpart
  33. Swift GRB250101.56: Global MASTER-Net observations report
  34. GRB 241217a/EP241217b: ATCA Radio Detection
  35. EP241217a: VLA Radio Detection

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

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