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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 250103A: SVOM/C-GFT optical upper limit
  2. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  3. IceCube Alert 250102.58: Global MASTER-Net observations report
  4. EP241231b: optical upper limit with the Liverpool Telescope
  5. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  6. GRB 250103A: SVOM detection of a long burst
  7. EP250101a: Xinglong optical upper limit
  8. GRB 250102A: Fermi GBM Final Real-time Localization
  9. LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
  10. GRB 250101A: Swift-BAT refined analysis
  11. IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event
  12. GRB 250101A: further SAO RAS optical observations
  13. GRB 250101A: LCO optical counterpart detection
  14. EP241231b and EP250101a: EP-WXT detection of two X-ray transients
  15. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  16. GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
  17. GRB 250101A: Swift/UVOT Detection
  18. GRB 250101A: 1.6m Mephisto multi-band optical followup
  19. GRB 250101A: Swift-XRT refined Analysis
  20. Fermi Gamma-ray Burst Monitor trigger 757464861/250101954 is not a GRB
  21. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  22. IceCube-250101A - IceCube observation of a high-energy neutrino candidate track-like event
  23. GRB 250101A: LCOGT optical afterglow detection
  24. GRB 250101A: OASDG optical observations
  25. Fermi GRB 250101B: Global MASTER-Net observations report
  26. GRB 250101B: Fermi GBM Final Real-time Localization
  27. GRB 250101A: SAO RAS observations of optical brightening
  28. GRB 250101A: BOOTES-4/MET optical afterglow detection
  29. GRB 250101A: AKO Optical Afterglow Detection
  30. GRB 250101A: SAO RAS optical observations
  31. GRB 250101A: Enhanced Swift-XRT position
  32. LIGO/Virgo/KAGRA S250101k: Updated Sky localization and Source Classification
  33. GRB 250101A: Xinglong-2.16m spectroscopic redshift
  34. GRB 250101A: SVOM/C-GFT early optical observations
  35. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
  36. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  37. GRB 250101A: Nanshan/HMT optical observations
  38. GRB 250101A : GIT optical detection
  39. GRB 250101A: GMG Optical Observation
  40. GRB 250101A: Swift detection of a burst with an optical counterpart
  41. Swift GRB250101.56: Global MASTER-Net observations report
  42. GRB 241217a/EP241217b: ATCA Radio Detection
  43. EP241217a: VLA Radio Detection

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

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