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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. EPWXT01709129925: Xinglong optical observations
  2. GRB 250106A: NOT optical observations
  3. LIGO/Virgo/KAGRA S250104v: Updated Sky localization
  4. GRB 250103B: REM optical/NIR upper limits
  5. GRB 250101A: REM optical/NIR counterpart detection
  6. GRB 250106A: Swift-XRT observations
  7. GRB 250106A: SVOM/VT optical candidate
  8. GRB 250106A: Swift ToO observations
  9. The EP-WXT trigger 01709129925 is likely a flaring star
  10. GRB 250106A: SVOM detection of a long burst
  11. Fermi trigger No 757753930: Global MASTER-Net observations report
  12. GRB 241229A: SVOM/VT optical upperlimit
  13. GRB 250103B: Swift-XRT refined Analysis
  14. GRB 250103B: LCO/1m optical afterglow candidate detection
  15. GRB 250103A: Bassano Bresciano Observatory upper limit
  16. GRB 250103B: VLT/X-shooter spectroscopic redshift z = 1.416
  17. GRB 250103A: Swift-XRT observations
  18. GRB 250101A: 1.3m DFOT optical afterglow detection
  19. GRB 241229A: 1.3m DFOT upper limit
  20. GRB 241228B: 1.3m DFOT Optical observations
  21. GRB 241228A: 1.3m DFOT upper limit
  22. GRB 250103A: NOT spectroscopic redshift
  23. GRB 250103B：SVOM/VT optical counterpart
  24. LIGO/Virgo/KAGRA S250104v: Identification of a GW compact binary merger candidate
  25. GRB 250103A: Montarrenti Observatory optical detection
  26. GRB 250101A: further LCOGT optical afterglow observations
  27. GRB 250103A: Redshift 4.01 from OSIRIS+/GTC
  28. GRB 250103A: NOT optical observations
  29. GRB 250103A: TSHAO optical upper limit
  30. GRB 250103A: Fermi GBM Observation
  31. GRB 250103B: LCOGT Optical Upper Limit
  32. IceCube-250102A: Upper limits from a search for additional neutrino events in IceCube
  33. Swift GRB 250103B: Global MASTER-Net observations report
  34. GRB 250103A: SVOM/VT optical counterpart confirmation
  35. EP250101a: Liverpool Telescope optical upper limit
  36. GRB 250103A: Swift ToO observations
  37. IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
  38. GRB 250101a: Liverpool Telescope optical follow-up
  39. GRB 250103B: SVOM detection of a long burst
  40. GRB 250103B: Swift detection of a burst
  41. GRB 250103A: Xinglong 2.16m Optical Candidate
  42. Fermi GRB 250102A: Global MASTER-Net observations report
  43. GRB 250101B: SVOM/GRM observation
  44. GRB 250103A: GOTO optical upper limit
  45. GRB 250103A: SVOM/C-GFT optical upper limit
  46. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  47. IceCube Alert 250102.58: Global MASTER-Net observations report
  48. EP241231b: optical upper limit with the Liverpool Telescope
  49. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  50. GRB 250103A: SVOM detection of a long burst
  51. EP250101a: Xinglong optical upper limit
  52. GRB 250102A: Fermi GBM Final Real-time Localization
  53. LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
  54. GRB 250101A: Swift-BAT refined analysis
  55. IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event
  56. GRB 250101A: further SAO RAS optical observations
  57. GRB 250101A: LCO optical counterpart detection
  58. EP241231b and EP250101a: EP-WXT detection of two X-ray transients
  59. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  60. GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
  61. GRB 250101A: Swift/UVOT Detection
  62. GRB 250101A: 1.6m Mephisto multi-band optical followup
  63. GRB 250101A: Swift-XRT refined Analysis
  64. Fermi Gamma-ray Burst Monitor trigger 757464861/250101954 is not a GRB
  65. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  66. IceCube-250101A - IceCube observation of a high-energy neutrino candidate track-like event
  67. GRB 250101A: LCOGT optical afterglow detection
  68. GRB 250101A: OASDG optical observations
  69. Fermi GRB 250101B: Global MASTER-Net observations report
  70. GRB 250101B: Fermi GBM Final Real-time Localization
  71. GRB 250101A: SAO RAS observations of optical brightening
  72. GRB 250101A: BOOTES-4/MET optical afterglow detection
  73. GRB 250101A: AKO Optical Afterglow Detection
  74. GRB 250101A: SAO RAS optical observations
  75. GRB 250101A: Enhanced Swift-XRT position
  76. LIGO/Virgo/KAGRA S250101k: Updated Sky localization and Source Classification
  77. GRB 250101A: Xinglong-2.16m spectroscopic redshift
  78. GRB 250101A: SVOM/C-GFT early optical observations
  79. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
  80. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  81. GRB 250101A: Nanshan/HMT optical observations
  82. GRB 250101A : GIT optical detection
  83. GRB 250101A: GMG Optical Observation
  84. GRB 250101A: Swift detection of a burst with an optical counterpart
  85. Swift GRB250101.56: Global MASTER-Net observations report
  86. GRB 241217a/EP241217b: ATCA Radio Detection
  87. EP241217a: VLA Radio Detection

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

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