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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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 250106A: SVOM/VT optical candidate
  2. GRB 250106A: Swift ToO observations
  3. The EP-WXT trigger 01709129925 is likely a flaring star
  4. GRB 250106A: SVOM detection of a long burst
  5. Fermi trigger No 757753930: Global MASTER-Net observations report
  6. GRB 241229A: SVOM/VT optical upperlimit
  7. GRB 250103B: Swift-XRT refined Analysis
  8. GRB 250103B: LCO/1m optical afterglow candidate detection
  9. GRB 250103A: Bassano Bresciano Observatory upper limit
  10. GRB 250103B: VLT/X-shooter spectroscopic redshift z = 1.416
  11. GRB 250103A: Swift-XRT observations
  12. GRB 250101A: 1.3m DFOT optical afterglow detection
  13. GRB 241229A: 1.3m DFOT upper limit
  14. GRB 241228B: 1.3m DFOT Optical observations
  15. GRB 241228A: 1.3m DFOT upper limit
  16. GRB 250103A: NOT spectroscopic redshift
  17. GRB 250103B：SVOM/VT optical counterpart
  18. LIGO/Virgo/KAGRA S250104v: Identification of a GW compact binary merger candidate
  19. GRB 250103A: Montarrenti Observatory optical detection
  20. GRB 250101A: further LCOGT optical afterglow observations
  21. GRB 250103A: Redshift 4.01 from OSIRIS+/GTC
  22. GRB 250103A: NOT optical observations
  23. GRB 250103A: TSHAO optical upper limit
  24. GRB 250103A: Fermi GBM Observation
  25. GRB 250103B: LCOGT Optical Upper Limit
  26. IceCube-250102A: Upper limits from a search for additional neutrino events in IceCube
  27. Swift GRB 250103B: Global MASTER-Net observations report
  28. GRB 250103A: SVOM/VT optical counterpart confirmation
  29. EP250101a: Liverpool Telescope optical upper limit
  30. GRB 250103A: Swift ToO observations
  31. IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
  32. GRB 250101a: Liverpool Telescope optical follow-up
  33. GRB 250103B: SVOM detection of a long burst
  34. GRB 250103B: Swift detection of a burst
  35. GRB 250103A: Xinglong 2.16m Optical Candidate
  36. Fermi GRB 250102A: Global MASTER-Net observations report
  37. GRB 250101B: SVOM/GRM observation
  38. GRB 250103A: GOTO optical upper limit
  39. GRB 250103A: SVOM/C-GFT optical upper limit
  40. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  41. IceCube Alert 250102.58: Global MASTER-Net observations report
  42. EP241231b: optical upper limit with the Liverpool Telescope
  43. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  44. GRB 250103A: SVOM detection of a long burst
  45. EP250101a: Xinglong optical upper limit
  46. GRB 250102A: Fermi GBM Final Real-time Localization
  47. LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
  48. GRB 250101A: Swift-BAT refined analysis
  49. IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event
  50. GRB 250101A: further SAO RAS optical observations
  51. GRB 250101A: LCO optical counterpart detection
  52. EP241231b and EP250101a: EP-WXT detection of two X-ray transients
  53. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  54. GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
  55. GRB 250101A: Swift/UVOT Detection
  56. GRB 250101A: 1.6m Mephisto multi-band optical followup
  57. GRB 250101A: Swift-XRT refined Analysis
  58. Fermi Gamma-ray Burst Monitor trigger 757464861/250101954 is not a GRB
  59. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  60. IceCube-250101A - IceCube observation of a high-energy neutrino candidate track-like event
  61. GRB 250101A: LCOGT optical afterglow detection
  62. GRB 250101A: OASDG optical observations
  63. Fermi GRB 250101B: Global MASTER-Net observations report
  64. GRB 250101B: Fermi GBM Final Real-time Localization
  65. GRB 250101A: SAO RAS observations of optical brightening
  66. GRB 250101A: BOOTES-4/MET optical afterglow detection
  67. GRB 250101A: AKO Optical Afterglow Detection
  68. GRB 250101A: SAO RAS optical observations
  69. GRB 250101A: Enhanced Swift-XRT position
  70. LIGO/Virgo/KAGRA S250101k: Updated Sky localization and Source Classification
  71. GRB 250101A: Xinglong-2.16m spectroscopic redshift
  72. GRB 250101A: SVOM/C-GFT early optical observations
  73. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
  74. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  75. GRB 250101A: Nanshan/HMT optical observations
  76. GRB 250101A : GIT optical detection
  77. GRB 250101A: GMG Optical Observation
  78. GRB 250101A: Swift detection of a burst with an optical counterpart
  79. Swift GRB250101.56: Global MASTER-Net observations report
  80. GRB 241217a/EP241217b: ATCA Radio Detection
  81. EP241217a: VLA Radio Detection

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

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