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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').
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"

20815 results found.

  1. EP250111a: NOT likely optical counterpart
  2. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  3. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  4. EP-WXT trigger EP250108a：Xinglong optical follow-up observations
  5. GRB 250101A: CMO RC-500 optical observations
  6. EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
  7. EP250108a: EP-FXT follow-up observation
  8. EP250108a: NOT optical observations
  9. EP-WXT trigger EP250109a：Xinglong optical follow-up observations
  10. GRB 250109a: GMG Optical Upper Limit
  11. EP250109a: Swift/UVOT non-detection
  12. Konus-Wind detection of GRB 250107D (short/hard)
  13. IPN triangulation of GRB 250107D (short/hard)
  14. IPN triangulation of GRB 250107C
  15. EP250108a: Liverpool Telescope likely optical counterpart
  16. GRB 250108B: 1.3m DFOT upper limit
  17. GRB 250108B: REM optical/NIR upper limits
  18. EP250109a: SVOM/VT optical candidate
  19. GRB 250101A: Terskol K-800 optical observations
  20. EP250109a: GOTO optical upper limits
  21. EP250109a: Swift/XRT non-detection
  22. GRB 250108A: Swift/UVOT Upper Limits
  23. EP250109a: EP-WXT detection of an X-ray transient
  24. LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
  25. GRB 250108A: NOT optical upper limit
  26. EP250108a: EP-WXT detection of an X-ray transient
  27. LIGO/Virgo/KAGRA S250109f: Identification of a GW compact binary merger candidate
  28. GRB 250103A: 1.6m Mephisto optical observations
  29. GRB 250108A: Swift-XRT afterglow detection
  30. GRB 250108A:SVOM/VT optical candidate
  31. LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate
  32. GRB 250108B: Swift/UVOT Upper Limits
  33. GRB 250103A: Swift-XRT afterglow detection
  34. GRB 250108B: Enhanced Swift-XRT position
  35. GRB 250108B: Swift detection of a burst
  36. GRB 250101A: J band upper limit by SYSU 80cm telescope
  37. EPWXT01709129925: Xinglong optical observations
  38. GRB 250106A: NOT optical observations
  39. GRB 250103B: REM optical/NIR upper limits
  40. GRB 250101A: REM optical/NIR counterpart detection
  41. GRB 250106A: Swift-XRT observations
  42. GRB 250106A: SVOM/VT optical candidate
  43. GRB 241229A: SVOM/VT optical upperlimit
  44. GRB 250103B: Swift-XRT refined Analysis
  45. GRB 250103B: LCO/1m optical afterglow candidate detection
  46. GRB 250103A: Bassano Bresciano Observatory upper limit
  47. GRB 250103A: Swift-XRT observations
  48. GRB 250101A: 1.3m DFOT optical afterglow detection
  49. GRB 241229A: 1.3m DFOT upper limit
  50. GRB 241228B: 1.3m DFOT Optical observations
  51. GRB 241228A: 1.3m DFOT upper limit
  52. LIGO/Virgo/KAGRA S250104v: Identification of a GW compact binary merger candidate
  53. GRB 250103A: Montarrenti Observatory optical detection
  54. GRB 250101A: further LCOGT optical afterglow observations
  55. GRB 250103A: TSHAO optical upper limit
  56. GRB 250103B: LCOGT Optical Upper Limit
  57. EP250101a: Liverpool Telescope optical upper limit
  58. GRB 250101a: Liverpool Telescope optical follow-up
  59. GRB 250103B: Swift detection of a burst
  60. GRB 250103A: Xinglong 2.16m Optical Candidate
  61. GRB 250101B: SVOM/GRM observation
  62. GRB 250103A: GOTO optical upper limit
  63. GRB 250103A: SVOM/C-GFT optical upper limit
  64. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  65. EP241231b: optical upper limit with the Liverpool Telescope
  66. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  67. GRB 250103A: SVOM detection of a long burst
  68. EP250101a: Xinglong optical upper limit
  69. GRB 250101A: further SAO RAS optical observations
  70. GRB 250101A: LCO optical counterpart detection
  71. GRB 250101A: Swift/UVOT Detection
  72. GRB 250101A: 1.6m Mephisto multi-band optical followup
  73. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  74. GRB 250101A: LCOGT optical afterglow detection
  75. GRB 250101A: OASDG optical observations
  76. GRB 250101A: AKO Optical Afterglow Detection
  77. GRB 250101A: SAO RAS optical observations
  78. GRB 250101A: Enhanced Swift-XRT position
  79. GRB 250101A: Xinglong-2.16m spectroscopic redshift
  80. GRB 250101A: SVOM/C-GFT early optical observations
  81. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM 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. EP241217a: VLA Radio Detection

  86. LIGO/Virgo/KAGRA S241231du: Coverage and upper limit from MAXI/GSC observations
  87. LIGO/Virgo/KAGRA S250101k: Identification of a GW compact binary merger candidate
  88. GRB 241229B: Continued CrAO ZTSh observations
  89. LIGO/Virgo/KAGRA S241231bg: Updated Sky localization and EM Bright Classification
  90. LIGO/Virgo/KAGRA S241231bg: NED Galaxies in the Localization Volume
  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: SVOM/VT optical candidate
  99. GRB 241229A: EP-FXT afterglow candidates
  100. EP240702a: 7DT Optical upper limits

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