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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').
  1. GRB 250101A: Enhanced Swift-XRT position
  2. LIGO/Virgo/KAGRA S250101k: Updated Sky localization and Source Classification
  3. GRB 250101A: Xinglong-2.16m spectroscopic redshift
  4. GRB 250101A: SVOM/C-GFT early optical observations
  5. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
  6. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  7. GRB 250101A: Nanshan/HMT optical observations
  8. GRB 250101A : GIT optical detection
  9. GRB 250101A: GMG Optical Observation
  10. GRB 250101A: Swift detection of a burst with an optical counterpart
  11. Swift GRB250101.56: Global MASTER-Net observations report
  12. GRB 241217a/EP241217b: ATCA Radio Detection
  13. EP241217a: VLA Radio Detection

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

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