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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"

26363 results found.

  1. GRB 250108B: REM optical/NIR upper limits
  2. GRB 250101A: Terskol K-800 optical observations
  3. EP250109a: Swift/XRT non-detection
  4. GRB 250108A: Swift/UVOT Upper Limits
  5. LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
  6. GRB 250108A: NOT optical upper limit
  7. EP250108a: EP-WXT detection of an X-ray transient
  8. LIGO/Virgo/KAGRA S250109f: Identification of a GW compact binary merger candidate
  9. GRB 250108B: Swift-XRT refined Analysis
  10. GRB 250103A: 1.6m Mephisto optical observations
  11. GRB 250108A: Swift-XRT afterglow detection
  12. GRB 250108A:SVOM/VT optical candidate
  13. LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate
  14. GRB 250108B: Swift/UVOT Upper Limits
  15. GRB 250103A: Swift-XRT afterglow detection
  16. GRB 250108B: Enhanced Swift-XRT position
  17. GRB 250108B: Swift detection of a burst
  18. GRB 250107A: Fermi GBM Observation
  19. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  20. GRB 250106A: SVOM/VT 2nd optical deep observation
  21. GRB 250101A: J band upper limit by SYSU 80cm telescope
  22. EPWXT01709129925: Xinglong optical observations
  23. GRB 250106A: NOT optical observations
  24. LIGO/Virgo/KAGRA S250104v: Updated Sky localization
  25. GRB 250103B: REM optical/NIR upper limits
  26. GRB 250101A: REM optical/NIR counterpart detection
  27. GRB 250106A: Swift-XRT observations
  28. GRB 250106A: SVOM/VT optical candidate
  29. The EP-WXT trigger 01709129925 is likely a flaring star
  30. GRB 250103B: Swift-XRT refined Analysis
  31. GRB 250103B: LCO/1m optical afterglow candidate detection
  32. GRB 250103A: Bassano Bresciano Observatory upper limit
  33. GRB 250103A: Swift-XRT observations
  34. GRB 250101A: 1.3m DFOT optical afterglow detection
  35. GRB 241229A: 1.3m DFOT upper limit
  36. GRB 241228B: 1.3m DFOT Optical observations
  37. GRB 241228A: 1.3m DFOT upper limit
  38. LIGO/Virgo/KAGRA S250104v: Identification of a GW compact binary merger candidate
  39. GRB 250103A: Montarrenti Observatory optical detection
  40. GRB 250101A: further LCOGT optical afterglow observations
  41. GRB 250103A: TSHAO optical upper limit
  42. GRB 250103A: Fermi GBM Observation
  43. GRB 250103B: LCOGT Optical Upper Limit
  44. IceCube-250102A: Upper limits from a search for additional neutrino events in IceCube
  45. EP250101a: Liverpool Telescope optical upper limit
  46. IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
  47. GRB 250101a: Liverpool Telescope optical follow-up
  48. GRB 250103B: Swift detection of a burst
  49. GRB 250103A: Xinglong 2.16m Optical Candidate
  50. GRB 250101B: SVOM/GRM observation
  51. GRB 250103A: GOTO optical upper limit
  52. GRB 250103A: SVOM/C-GFT optical upper limit
  53. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  54. EP241231b: optical upper limit with the Liverpool Telescope
  55. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  56. GRB 250103A: SVOM detection of a long burst
  57. EP250101a: Xinglong optical upper limit
  58. LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
  59. GRB 250101A: Swift-BAT refined analysis
  60. GRB 250101A: further SAO RAS optical observations
  61. GRB 250101A: LCO optical counterpart detection
  62. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  63. GRB 250101A: Swift/UVOT Detection
  64. GRB 250101A: 1.6m Mephisto multi-band optical followup
  65. GRB 250101A: Swift-XRT refined Analysis
  66. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  67. GRB 250101A: LCOGT optical afterglow detection
  68. GRB 250101A: OASDG optical observations
  69. GRB 250101B: Fermi GBM Final Real-time Localization
  70. GRB 250101A: SAO RAS observations of optical brightening
  71. GRB 250101A: BOOTES-4/MET optical afterglow detection
  72. GRB 250101A: AKO Optical Afterglow Detection
  73. GRB 250101A: SAO RAS optical observations
  74. GRB 250101A: Enhanced Swift-XRT position
  75. LIGO/Virgo/KAGRA S250101k: Updated Sky localization and Source Classification
  76. GRB 250101A: SVOM/C-GFT early optical observations
  77. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
  78. GRB 250101A: Nanshan/HMT optical observations
  79. GRB 250101A : GIT optical detection
  80. GRB 250101A: GMG Optical Observation
  81. GRB 250101A: Swift detection of a burst with an optical counterpart
  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 241228B: Multiband optical monitoring with 1.6m Mephisto
  91. GRB 241229B: SVOM/GRM observation
  92. LIGO/Virgo/KAGRA S241231bg: Identification of a GW compact binary merger candidate
  93. EP241217A: J band upper limit by SYSU 80cm telescope
  94. LIGO/Virgo/KAGRA S241230ev: Identification of a GW compact binary merger candidate
  95. GRB 241229B: SAO RAS optical upper limit
  96. GRB 241228B: SAO RAS optical observations
  97. GRB 241229A: SAO RAS optical observations
  98. IceCube-Cascade 241228A: Upper limits from a search for additional neutrino events in IceCube
  99. GRB 241229A: Swift-XRT observations
  100. EP240702a: 7DT Optical upper limits

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