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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 S241231du: Coverage and upper limit from MAXI/GSC observations
  2. LIGO/Virgo/KAGRA S250101k: Identification of a GW compact binary merger candidate
  3. GRB 241229B: Continued CrAO ZTSh observations
  4. LIGO/Virgo/KAGRA S241231bg: Updated NED Galaxies in the Localization Volume
  5. LIGO/Virgo/KAGRA S241231bg: Updated Sky localization and EM Bright Classification
  6. LIGO/Virgo/KAGRA S241230ev: Updated Sky localization
  7. LIGO/Virgo/KAGRA S241231bg: NED Galaxies in the Localization Volume
  8. LIGO/Virgo/KAGRA S241230bd: Updated Sky localization
  9. GRB 241229A: EP-FXT X-ray afterglow confirmation
  10. GRB 241228B: Multiband optical monitoring with 1.6m Mephisto
  11. GRB 241229B: SVOM/GRM observation
  12. LIGO/Virgo/KAGRA S241231bg: Identification of a GW compact binary merger candidate
  13. EP241217A: J band upper limit by SYSU 80cm telescope
  14. LIGO/Virgo/KAGRA S241230ev: Identification of a GW compact binary merger candidate
  15. GRB 241229B: SAO RAS optical upper limit
  16. GRB 241228B: SAO RAS optical observations
  17. GRB 241229B: CrAO ZTSh possible optical counterpart of SVOM/VT confirmation
  18. GRB 241229A: SAO RAS optical observations
  19. IceCube-Cascade 241228A: Upper limits from a search for additional neutrino events in IceCube
  20. GRB 241229B: SVOM/VT optical candidate
  21. GRB 241229A: Swift-XRT observations
  22. Konus-Wind detection of GRB 241228A
  23. GRB 241229A: EP-FXT afterglow candidates
  24. EP240702a: 7DT Optical upper limits
  25. GRB 240606B: 7DT Optical upper limits
  26. Fermi trigger No 757231333: Global MASTER-Net observations report
  27. LIGO/Virgo/KAGRA S241230bd: Identification of a GW compact binary merger candidate
  28. GRB 241229B: Swift-BAT refined analysis
  29. LIGO/Virgo/KAGRA S241225v: Updated Sky localization
  30. LIGO/Virgo/KAGRA S241225c: Updated Sky localization and EM Bright Classification
  31. Fermi Gamma-ray Burst Monitor trigger 757207662/241229978 (GRB 241229C) is not a GRB
  32. GRB241229B: UVOT upper limits
  33. GRB 241229C: Fermi GBM Final Real-time Localization
  34. GRB 241228B: D50 optical detection
  35. GRB 241228B: Fermi GBM Observation
  36. GRB 241228B: Swift-XRT afterglow detection
  37. GRB 241229B: Fermi GBM Observation
  38. GRB 241229A: Swift ToO observations
  39. GRB 241229B: NUTTelA-TAO / BSTI Optical Limits
  40. GRB 241228A: Mondy optical afterglow observations
  41. GRB 241229B: Swift-XRT refined Analysis
  42. IceCube-241224A: No transient candidates from the Zwicky Transient Facility
  43. Swift GRB 241229B: Global MASTER-Net observations report
  44. GRB 241229A: GOTO optical upper limits
  45. GRB 241228B: VLT/X-shooter redshift of z = 2.674
  46. GRB 241228A: NOT optical upper limits
  47. GRB 241228B: LCO optical observation
  48. GRB 241228A: Swift-BAT refined analysis
  49. GRB 241228B: Swift/BAT-GUANO localization skymap of a burst
  50. GRB 241229B: Swift detection of a burst
  51. GRB 241229B: Fermi GBM Final Real-time Localization
  52. GRB 241229A: SVOM detection of a long burst
  53. Fermi GRB 241228B: Global MASTER-Net observations report
  54. GRB 241228A: Fermi GBM Observation
  55. GRB241228B: GROWTH-India Telescope optical observations
  56. Swift GRB 241228A: Global MASTER-Net observations report
  57. GRB 241228B: LCOGT photometry of the likely optical counterpart GOTO24jmz
  58. GRB 241228B: GOTO24jmz optical follow-up observations
  59. GRB 241226A: Swift/BAT-GUANO localization skymap of a burst
  60. GRB 241228A: GROWTH-India telescope optical upper limit
  61. GRB 241228B: Swift ToO observations
  62. GRB 241228B: TRT optical counterpart confirmation
  63. GRB 241228A: Swift-XRT refined Analysis
  64. GRB 241228A: Swift/UVOT Upper Limits
  65. GRB 241228B: GOTO possible optical counterpart candidate
  66. GRB 241228A: Enhanced Swift-XRT position
  67. GRB 241228B: Fermi GBM Final Real-time Localization
  68. GRB 241228A: Swift detection of a burst
  69. IceCube-241224A: Upper limits from a search for additional neutrino events in IceCube
  70. LIGO/Virgo/KAGRA S241225c: Two counterpart neutrino candidates from IceCube neutrino searches
  71. GRB 241223A: GRBAlpha detection
  72. GRB 241212A: VZLUSAT-2 detection
  73. GRB 241217A/EP241217b: continued SOAR observations
  74. Fermi GRB 241226A: Global MASTER-Net observations report
  75. GRB 241226A: Fermi GBM Final Real-time Localization
  76. EP241223a: Mondy AZT-33IK optical observations
  77. GRB 241029A: LCO optical observation
  78. GRB 241223A: Swift-XRT observations
  79. LIGO/Virgo/KAGRA S241225v: Identification of a GW compact binary merger candidate
  80. GRB 241029A: AbAO AS-32 optical observations
  81. GRB 241223A: Fermi GBM Detection
  82. Fermi trigger No 756678579: Global MASTER-Net observations report
  83. LIGO/Virgo/KAGRA S241225c: Identification of a GW compact binary merger candidate
  84. EP241223a
  85. IceCube-241224A - IceCube observation of a high-energy neutrino candidate track-like event
  86. IceCube Alert 241224.30: Global MASTER-Net observations report
  87. GRB 241219A: SVOM/GRM observation
  88. EP241223a: Global MASTER-Net observations report
  89. EP241223a: EP-WXT detection of a fast X-ray transient
  90. EP241113a: Non-detection in Radio Follow-up Observations with eMERLIN
  91. GRB241113A: 7DT Optical upper limits
  92. Fermi Gamma-ray Burst Monitor trigger 756678579 / 241223854 is not a GRB
  93. Fermi GRB 241223A: Global MASTER-Net observations report
  94. GRB 241223A: GOTO optical observations summary
  95. GRB 241105A: JWST photometric observations of the host galaxy
  96. GRB 241223A: Swift ToO observations
  97. EP241217a: e-MERLIN radio observations
  98. GRB 241223A: BALROG localization (Fermi Trigger 756648531 / GRB 241223506)
  99. GRB 241223A: Fermi GBM Final Real-time Localization
  100. GRB 241217A / EP241217b: Non-detection in ATCA Radio Follow-up Observations

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