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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 250106A: SVOM detection of a long burst
  2. Fermi trigger No 757753930: Global MASTER-Net observations report
  3. GRB 241229A: SVOM/VT optical upperlimit
  4. GRB 250103B: Swift-XRT refined Analysis
  5. GRB 250103B: LCO/1m optical afterglow candidate detection
  6. GRB 250103A: Bassano Bresciano Observatory upper limit
  7. GRB 250103B: VLT/X-shooter spectroscopic redshift z = 1.416
  8. GRB 250103A: Swift-XRT observations
  9. GRB 250101A: 1.3m DFOT optical afterglow detection
  10. GRB 241229A: 1.3m DFOT upper limit
  11. GRB 241228B: 1.3m DFOT Optical observations
  12. GRB 241228A: 1.3m DFOT upper limit
  13. GRB 250103A: NOT spectroscopic redshift
  14. GRB 250103B：SVOM/VT optical counterpart
  15. LIGO/Virgo/KAGRA S250104v: Identification of a GW compact binary merger candidate
  16. GRB 250103A: Montarrenti Observatory optical detection
  17. GRB 250101A: further LCOGT optical afterglow observations
  18. GRB 250103A: Redshift 4.01 from OSIRIS+/GTC
  19. GRB 250103A: NOT optical observations
  20. GRB 250103A: TSHAO optical upper limit
  21. GRB 250103A: Fermi GBM Observation
  22. GRB 250103B: LCOGT Optical Upper Limit
  23. IceCube-250102A: Upper limits from a search for additional neutrino events in IceCube
  24. Swift GRB 250103B: Global MASTER-Net observations report
  25. GRB 250103A: SVOM/VT optical counterpart confirmation
  26. EP250101a: Liverpool Telescope optical upper limit
  27. GRB 250103A: Swift ToO observations
  28. IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
  29. GRB 250101a: Liverpool Telescope optical follow-up
  30. GRB 250103B: SVOM detection of a long burst
  31. GRB 250103B: Swift detection of a burst
  32. GRB 250103A: Xinglong 2.16m Optical Candidate
  33. Fermi GRB 250102A: Global MASTER-Net observations report
  34. GRB 250101B: SVOM/GRM observation
  35. GRB 250103A: GOTO optical upper limit
  36. GRB 250103A: SVOM/C-GFT optical upper limit
  37. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  38. IceCube Alert 250102.58: Global MASTER-Net observations report
  39. EP241231b: optical upper limit with the Liverpool Telescope
  40. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  41. GRB 250103A: SVOM detection of a long burst
  42. EP250101a: Xinglong optical upper limit
  43. GRB 250102A: Fermi GBM Final Real-time Localization
  44. LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
  45. GRB 250101A: Swift-BAT refined analysis
  46. IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event
  47. GRB 250101A: further SAO RAS optical observations
  48. GRB 250101A: LCO optical counterpart detection
  49. EP241231b and EP250101a: EP-WXT detection of two X-ray transients
  50. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  51. GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
  52. GRB 250101A: Swift/UVOT Detection
  53. GRB 250101A: 1.6m Mephisto multi-band optical followup
  54. GRB 250101A: Swift-XRT refined Analysis
  55. Fermi Gamma-ray Burst Monitor trigger 757464861/250101954 is not a GRB
  56. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  57. IceCube-250101A - IceCube observation of a high-energy neutrino candidate track-like event
  58. GRB 250101A: LCOGT optical afterglow detection
  59. GRB 250101A: OASDG optical observations
  60. Fermi GRB 250101B: Global MASTER-Net observations report
  61. GRB 250101B: Fermi GBM Final Real-time Localization
  62. GRB 250101A: SAO RAS observations of optical brightening
  63. GRB 250101A: BOOTES-4/MET optical afterglow detection
  64. GRB 250101A: AKO Optical Afterglow Detection
  65. GRB 250101A: SAO RAS optical observations
  66. GRB 250101A: Enhanced Swift-XRT position
  67. LIGO/Virgo/KAGRA S250101k: Updated Sky localization and Source Classification
  68. GRB 250101A: Xinglong-2.16m spectroscopic redshift
  69. GRB 250101A: SVOM/C-GFT early optical observations
  70. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
  71. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  72. GRB 250101A: Nanshan/HMT optical observations
  73. GRB 250101A : GIT optical detection
  74. GRB 250101A: GMG Optical Observation
  75. GRB 250101A: Swift detection of a burst with an optical counterpart
  76. Swift GRB250101.56: Global MASTER-Net observations report
  77. GRB 241217a/EP241217b: ATCA Radio Detection
  78. EP241217a: VLA Radio Detection

  79. LIGO/Virgo/KAGRA S241231du: Coverage and upper limit from MAXI/GSC observations
  80. LIGO/Virgo/KAGRA S250101k: Identification of a GW compact binary merger candidate
  81. GRB 241229B: Continued CrAO ZTSh observations
  82. LIGO/Virgo/KAGRA S241231bg: Updated NED Galaxies in the Localization Volume
  83. LIGO/Virgo/KAGRA S241231bg: Updated Sky localization and EM Bright Classification
  84. LIGO/Virgo/KAGRA S241230ev: Updated Sky localization
  85. LIGO/Virgo/KAGRA S241231bg: NED Galaxies in the Localization Volume
  86. LIGO/Virgo/KAGRA S241230bd: Updated Sky localization
  87. GRB 241229A: EP-FXT X-ray afterglow confirmation
  88. GRB 241228B: Multiband optical monitoring with 1.6m Mephisto
  89. GRB 241229B: SVOM/GRM observation
  90. LIGO/Virgo/KAGRA S241231bg: Identification of a GW compact binary merger candidate
  91. EP241217A: J band upper limit by SYSU 80cm telescope
  92. LIGO/Virgo/KAGRA S241230ev: Identification of a GW compact binary merger candidate
  93. GRB 241229B: SAO RAS optical upper limit
  94. GRB 241228B: SAO RAS optical observations
  95. GRB 241229B: CrAO ZTSh possible optical counterpart of SVOM/VT confirmation
  96. GRB 241229A: SAO RAS optical observations
  97. IceCube-Cascade 241228A: Upper limits from a search for additional neutrino events in IceCube
  98. GRB 241229B: SVOM/VT optical candidate
  99. GRB 241229A: Swift-XRT observations
  100. Konus-Wind detection of GRB 241228A

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