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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"

21957 results found.

  1. EP250108a / AT 2025kg: Swift UVOT detections
  2. EP250108a: optical follow-up observations with the Liverpool Telescope
  3. EP250111a: NOT likely optical counterpart
  4. EP250111a: a new X-ray transient detected by Einstein Probe
  5. EP250109a/GRB 250109A:SVOM/VT optical counterpart
  6. EP250108a: further NOT optical observations
  7. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  8. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  9. GRB 250108A: Swift/XRT afterglow fading
  10. EP-WXT trigger EP250108a：Xinglong optical follow-up observations
  11. GRB 250101A: CMO RC-500 optical observations
  12. EP250108a: NOT optical observations
  13. EP-WXT trigger EP250109a：Xinglong optical follow-up observations
  14. EP250109a: Swift/UVOT non-detection
  15. EP250108a: Liverpool Telescope likely optical counterpart
  16. GRB 250108B: Gemini-North likely redshift z = 2.197
  17. GRB 250108B: 1.3m DFOT upper limit
  18. GRB 250108B: REM optical/NIR upper limits
  19. EP250109a: SVOM/VT optical candidate
  20. EP250109a: Global MASTER-Net observations report
  21. GRB 250101A: Terskol K-800 optical observations
  22. EP250109a: GOTO optical upper limits
  23. GRB 250108A: Swift/UVOT Upper Limits
  24. EP250108a: Global MASTER-Net observations report
  25. EP250109a: EP-WXT detection of an X-ray transient
  26. GRB 250108A: NOT optical upper limit
  27. EP250108a: EP-WXT detection of an X-ray transient
  28. Swift GRB 250108B: Global MASTER-Net observations report
  29. GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
  30. GRB 250103A: 1.6m Mephisto optical observations
  31. GRB 250108A: Swift-XRT afterglow detection
  32. GRB 250108A:SVOM/VT optical candidate
  33. GRB 250108B: Swift/UVOT Upper Limits
  34. GRB 250103A: Swift-XRT afterglow detection
  35. GRB 250108A: Swift ToO observations
  36. Fermi GRB 250107B: Global MASTER-Net observations report
  37. GRB 250107A: Swift ToO observations
  38. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  39. GRB 250106A: SVOM/VT 2nd optical deep observation
  40. GRB 250101A: J band upper limit by SYSU 80cm telescope
  41. EPWXT01709129925: Xinglong optical observations
  42. GRB 250106A: NOT optical observations
  43. GRB 250103B: REM optical/NIR upper limits
  44. GRB 250101A: REM optical/NIR counterpart detection
  45. GRB 250106A: Swift-XRT observations
  46. GRB 250106A: SVOM/VT optical candidate
  47. GRB 250106A: Swift ToO observations
  48. GRB 250106A: SVOM detection of a long burst
  49. Fermi trigger No 757753930: Global MASTER-Net observations report
  50. GRB 241229A: SVOM/VT optical upperlimit
  51. GRB 250103A: Bassano Bresciano Observatory upper limit
  52. GRB 250103B: VLT/X-shooter spectroscopic redshift z = 1.416
  53. GRB 250103A: Swift-XRT observations
  54. GRB 250101A: 1.3m DFOT optical afterglow detection
  55. GRB 241229A: 1.3m DFOT upper limit
  56. GRB 241228B: 1.3m DFOT Optical observations
  57. GRB 241228A: 1.3m DFOT upper limit
  58. GRB 250103A: NOT spectroscopic redshift
  59. GRB 250103B：SVOM/VT optical counterpart
  60. GRB 250103A: Montarrenti Observatory optical detection
  61. GRB 250101A: further LCOGT optical afterglow observations
  62. GRB 250103A: Redshift 4.01 from OSIRIS+/GTC
  63. GRB 250103A: NOT optical observations
  64. Swift GRB 250103B: Global MASTER-Net observations report
  65. GRB 250103A: SVOM/VT optical counterpart confirmation
  66. GRB 250103A: Swift ToO observations
  67. GRB 250101a: Liverpool Telescope optical follow-up
  68. Fermi GRB 250102A: Global MASTER-Net observations report
  69. GRB 250103A: GOTO optical upper limit
  70. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  71. IceCube Alert 250102.58: Global MASTER-Net observations report
  72. EP241231b: optical upper limit with the Liverpool Telescope
  73. LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
  74. GRB 250101A: further SAO RAS optical observations
  75. GRB 250101A: LCO optical counterpart detection
  76. EP241231b and EP250101a: EP-WXT detection of two X-ray transients
  77. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  78. GRB 250101A: Swift/UVOT Detection
  79. GRB 250101A: 1.6m Mephisto multi-band optical followup
  80. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  81. GRB 250101A: LCOGT optical afterglow detection
  82. GRB 250101A: OASDG optical observations
  83. Fermi GRB 250101B: Global MASTER-Net observations report
  84. GRB 250101A: SAO RAS observations of optical brightening
  85. GRB 250101A: SAO RAS optical observations
  86. GRB 250101A: SVOM/C-GFT early optical observations
  87. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
  88. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  89. GRB 250101A: Nanshan/HMT optical observations
  90. GRB 250101A : GIT optical detection
  91. Swift GRB250101.56: Global MASTER-Net observations report
  92. GRB 241217a/EP241217b: ATCA Radio Detection
  93. EP241217a: VLA Radio Detection

  94. LIGO/Virgo/KAGRA S241231du: Coverage and upper limit from MAXI/GSC observations
  95. GRB 241229B: Continued CrAO ZTSh observations
  96. LIGO/Virgo/KAGRA S241231bg: Updated NED Galaxies in the Localization Volume
  97. LIGO/Virgo/KAGRA S241231bg: NED Galaxies in the Localization Volume
  98. GRB 241229A: EP-FXT X-ray afterglow confirmation
  99. GRB 241228B: Multiband optical monitoring with 1.6m Mephisto
  100. EP241217A: J band upper limit by SYSU 80cm telescope

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