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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"

20538 results found.

  1. GRB 250101A: CMO RC-500 optical observations
  2. EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
  3. EP250108a: NOT optical observations
  4. EP-WXT trigger EP250109a：Xinglong optical follow-up observations
  5. GRB 250109a: GMG Optical Upper Limit
  6. EP250109a: Swift/UVOT non-detection
  7. IPN triangulation of GRB 250107D (short/hard)
  8. EP250108a: Liverpool Telescope likely optical counterpart
  9. GRB 250108B: 1.3m DFOT upper limit
  10. GRB 250108B: REM optical/NIR upper limits
  11. GRB 250107C: SVOM/GRM observation
  12. GRB 250101A: Terskol K-800 optical observations
  13. EP250109a: Swift/XRT non-detection
  14. GRB 250108A: Swift/UVOT Upper Limits
  15. LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
  16. GRB 250108A: NOT optical upper limit
  17. EP250108a: EP-WXT detection of an X-ray transient
  18. LIGO/Virgo/KAGRA S250109f: Identification of a GW compact binary merger candidate
  19. GRB 250103A: 1.6m Mephisto optical observations
  20. GRB 250108A: Swift-XRT afterglow detection
  21. LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate
  22. GRB 250108B: Swift/UVOT Upper Limits
  23. GRB 250103A: Swift-XRT afterglow detection
  24. GRB 250108B: Enhanced Swift-XRT position
  25. GRB 250108B: Swift detection of a burst
  26. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  27. GRB 250101A: J band upper limit by SYSU 80cm telescope
  28. EPWXT01709129925: Xinglong optical observations
  29. GRB 250106A: NOT optical observations
  30. GRB 250103B: REM optical/NIR upper limits
  31. GRB 250101A: REM optical/NIR counterpart detection
  32. GRB 250106A: Swift-XRT observations
  33. GRB 250103B: Swift-XRT refined Analysis
  34. GRB 250103B: LCO/1m optical afterglow candidate detection
  35. GRB 250103A: Bassano Bresciano Observatory upper limit
  36. GRB 250103B: VLT/X-shooter spectroscopic redshift z = 1.416
  37. GRB 250101A: 1.3m DFOT optical afterglow detection
  38. GRB 241229A: 1.3m DFOT upper limit
  39. GRB 241228B: 1.3m DFOT Optical observations
  40. GRB 241228A: 1.3m DFOT upper limit
  41. LIGO/Virgo/KAGRA S250104v: Identification of a GW compact binary merger candidate
  42. GRB 250103A: Montarrenti Observatory optical detection
  43. GRB 250101A: further LCOGT optical afterglow observations
  44. GRB 250103A: Redshift 4.01 from OSIRIS+/GTC
  45. GRB 250103A: TSHAO optical upper limit
  46. GRB 250103A: Fermi GBM Observation
  47. GRB 250103B: LCOGT Optical Upper Limit
  48. IceCube-250102A: Upper limits from a search for additional neutrino events in IceCube
  49. EP250101a: Liverpool Telescope optical upper limit
  50. IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
  51. GRB 250101a: Liverpool Telescope optical follow-up
  52. GRB 250103B: Swift detection of a burst
  53. GRB 250103A: Xinglong 2.16m Optical Candidate
  54. GRB 250101B: SVOM/GRM observation
  55. GRB 250103A: GOTO optical upper limit
  56. GRB 250103A: SVOM/C-GFT optical upper limit
  57. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  58. EP241231b: optical upper limit with the Liverpool Telescope
  59. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  60. GRB 250103A: SVOM detection of a long burst
  61. EP250101a: Xinglong optical upper limit
  62. GRB 250101A: further SAO RAS optical observations
  63. GRB 250101A: LCO optical counterpart detection
  64. EP241231b and EP250101a: EP-WXT detection of two X-ray transients
  65. GRB 250101A: Swift/UVOT Detection
  66. GRB 250101A: 1.6m Mephisto multi-band optical followup
  67. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  68. GRB 250101A: LCOGT optical afterglow detection
  69. GRB 250101A: OASDG optical observations
  70. GRB 250101A: BOOTES-4/MET optical afterglow detection
  71. GRB 250101A: AKO Optical Afterglow Detection
  72. GRB 250101A: SAO RAS optical observations
  73. GRB 250101A: Enhanced Swift-XRT position
  74. LIGO/Virgo/KAGRA S250101k: Updated Sky localization and Source Classification
  75. GRB 250101A: SVOM/C-GFT early 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. EP241217a: VLA Radio Detection

  80. LIGO/Virgo/KAGRA S241231du: Coverage and upper limit from MAXI/GSC observations
  81. LIGO/Virgo/KAGRA S250101k: Identification of a GW compact binary merger candidate
  82. GRB 241229B: Continued CrAO ZTSh observations
  83. LIGO/Virgo/KAGRA S241231bg: Updated NED Galaxies in the Localization Volume
  84. GRB 241228B: Multiband optical monitoring with 1.6m Mephisto
  85. GRB 241229B: SVOM/GRM observation
  86. LIGO/Virgo/KAGRA S241231bg: Identification of a GW compact binary merger candidate
  87. EP241217A: J band upper limit by SYSU 80cm telescope
  88. LIGO/Virgo/KAGRA S241230ev: Identification of a GW compact binary merger candidate
  89. GRB 241229B: SAO RAS optical upper limit
  90. GRB 241228B: SAO RAS optical observations
  91. IceCube-Cascade 241228A: Upper limits from a search for additional neutrino events in IceCube
  92. EP240702a: 7DT Optical upper limits
  93. GRB 240606B: 7DT Optical upper limits
  94. GRB241229B: UVOT upper limits
  95. GRB 241228B: Swift-XRT afterglow detection
  96. GRB 241228A: Mondy optical afterglow observations
  97. GRB 241229A: GOTO optical upper limits
  98. GRB 241228B: VLT/X-shooter redshift of z = 2.674
  99. GRB 241228A: NOT optical upper limits
  100. GRB 241228B: LCO optical observation

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