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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: OASDG optical observations
  2. Fermi GRB 250101B: Global MASTER-Net observations report
  3. GRB 250101B: Fermi GBM Final Real-time Localization
  4. GRB 250101A: SAO RAS observations of optical brightening
  5. GRB 250101A: BOOTES-4/MET optical afterglow detection
  6. GRB 250101A: AKO Optical Afterglow Detection
  7. GRB 250101A: SAO RAS optical observations
  8. GRB 250101A: Enhanced Swift-XRT position
  9. LIGO/Virgo/KAGRA S250101k: Updated Sky localization and Source Classification
  10. GRB 250101A: Xinglong-2.16m spectroscopic redshift
  11. GRB 250101A: SVOM/C-GFT early optical observations
  12. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
  13. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  14. GRB 250101A: Nanshan/HMT optical observations
  15. GRB 250101A : GIT optical detection
  16. GRB 250101A: GMG Optical Observation
  17. GRB 250101A: Swift detection of a burst with an optical counterpart
  18. Swift GRB250101.56: Global MASTER-Net observations report
  19. GRB 241217a/EP241217b: ATCA Radio Detection
  20. EP241217a: VLA Radio Detection

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

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