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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').

14251 results found.

  1. GW170817: VLA observations at ~5.5 yrs since merger
  2. GRB 240415A 1.3m DFOT Optical upper limit
  3. MeerKAT Discovery of a Probable Radio Counterpart to EP240414a
  4. LIGO/Virgo/KAGRA S240422ed: GECKO/7DT ToO observations
  5. Fermi-LAT gamma-ray observations of IceCube-240424A
  6. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limit for EP240426a
  7. LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet ToO observations
  8. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of J-GEM24a
  9. LIGO/Virgo/KAGRA S240422ed: DDOTI Optical Upper Limit for J-GEM24a
  10. EP240426b: AST3-2 optical upper limit
  11. LIGO/Virgo/KAGRA S240422ed: Observations with 1.6m Mephisto
  12. LIGO/Virgo/KAGRA S240422ed: NOT optical observations of EP240426a
  13. EP240426b: EP-WXT detection of a new fast X-ray transient
  14. LIGO/Virgo/KAGRA S240422ed: Archival radio detection of EP240426a
  15. LIGO/VIRGO/KAGRA S240422ed: Historical variability for EP240426a
  16. XMM-Newton observation of EP240426a
  17. LIGO/Virgo/KAGRA S240422ed: EP-FXT Detection of the Potential Opitcal Electromagnetic Counterpart AT 2024hfq Reported by DECam
  18. GRB 240414A: NOEMA detection
  19. LIGO/Virgo/KAGRA S240422ed: EP240426a possible optical detection
  20. EP240426a: GMG optical upper limit
  21. LIGO/Virgo/KAGRA S240422ed: EP-FXT detection of a candidate counterpart EP240426a
  22. LIGO/Virgo/KAGRA S240422ed: Zwicky Transient Facility contuinued observations of S240422ed and candidate analysis
  23. LIGO/Virgo/KAGRA S240422ed: PRIME near-infrared observations
  24. LIGO/Virgo/KAGRA S240422ed: 2.5m PRL Telescope follow-up of the Swift/XRT source S240422ed_X190
  25. LIGO/Virgo/KAGRA S240422ed: Further near-infrared observations with Subaru/MOIRCS by J-GEM Collaboration
  26. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-FXT for the Potential Electromagnetic Counterparts Reported by Swift and DECam
  27. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limits for Swift/XRT candidates
  28. GRB 240422A: Glowbug gamma-ray detection
  29. LIGO/Virgo/KAGRA S240422ed: Himalayan Chandra Telescope follow-up of the Swift/XRT source S240422ed_X101
  30. LIGO/Virgo/KAGRA S240422ed: No significant counterpart candidates in HAWC observations
  31. LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA/FRAM Observations
  32. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Potential Electromagnetic Counterparts Reported by Swift and DECam
  33. LIGO/Virgo/KAGRA S240422ed: ATCA follow-up of candidate counterparts
  34. LIGO/Virgo S240422ed: Swift-XRT detection of 3 possible counterparts
  35. LIGO/Virgo/KAGRA S240422ed: Early X-ray Upper Limits from EP-WXT for the LVK Sky Localization Region
  36. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of Mag24a
  37. LIGO/Virgo/KAGRA S240422ed: Archival DECaPSs2 observations of the field of Mag24a
  38. LIGO/Virgo/KAGRA S240422ed: NOT J-band upper limit on the Swift/XRT source S240422ed_X61
  39. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Three Potential Electromagnetic Counterparts Reported So Far
  40. LIGO/Virgo/KAGRA S240422ed: Magellan Detection of a Potential Electromagnetic Counterpart
  41. LIGO/Virgo/KAGRA S240422ed: Subaru/MOIRCS near-infrared observations by J-GEM Collaboration
  42. LIGO/Virgo/KAGRA S240422ed: WINTER J-band upper limits on the Swift/XRT source S240422ed_X61
  43. LIGO/Virgo/KAGRA S240422ed: No Counterparts in DDOTI/OAN Optical Observations
  44. LXT240402A/GRB240402B: Chandra X-ray detection
  45. GRB 240419A: Possible ATCA radio detection
  46. GRB 240421B: ATCA radio observations
  47. LIGO/Virgo/KAGRA S240422ed: WINTER near-infrared J-band observations
  48. LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam observations
  49. GRB 240421A: Glowbug gamma-ray detection
  50. GRB 240414A: radio detection with the VLA
  51. GRB 240414A: AMI-LA radio observations
  52. GRB 240414A: LBT optical detection
  53. GRB 240419B : MITSuME Akeno optical upper limits
  54. GRB240421B: Zadko Observations
  55. GRB 240421B: Swift-XRT refined Analysis
  56. GRB 240421B: J-band upper limits from WINTER
  57. GRB 240421B: Swift/UVOT Upper Limits
  58. GRB 240421B: Enhanced Swift-XRT position
  59. EP240417a: no counterpart detection by SOAR
  60. EP240420a: Xinglong decaying optical counterpart
  61. GRB 240421B: Swift detection of a burst
  62. EP240420a: Nanshan optical counterpart observations
  63. EP240420a: GWAC-F50A optical upper limit
  64. EP240420a: detection of fading X-ray emission with refined position by EP-FXT
  65. EP240420a: NOT optical counterpart candidate and potential host
  66. GRB240419A: Skynet Optical Afterglow Analysis
  67. GRB240418A - Candidate afterglow from NIRES
  68. GRB 240419B: Swift/UVOT Upper Limits
  69. EP240420a: EP-WXT detection of a fast X-ray transient
  70. GRB 240419A: Swift/UVOT Upper Limits
  71. GRB 240419B: optical afterglow from the NOT
  72. GRB 240419B: Enhanced Swift-XRT position
  73. GRB 240418A: Swift/UVOT Upper Limits
  74. GRB 240419A: REM NIR afterglow detection
  75. GRB 240419B: Swift detection of a burst
  76. GRB 240411B: Swift/UVOT Detection
  77. GRB 240419A: VLT optical afterglow detection
  78. GRB 240419A: Enhanced Swift-XRT position
  79. EP240416a: J-band observations with WINTER
  80. EP240414a: GMG observation
  81. GRB 240419A: Swift detection of a burst
  82. GRB 240418A: TSHAO Zeiss-1000 optical upper limit
  83. GRB 240418A: NOT optical upper limits
  84. GRB 240418A: Enhanced Swift-XRT position
  85. GRB 240418A: AKO Upper Limit
  86. GRB 240418A: Swift detection of a burst
  87. EP240417a: EP-WXT detection of a fast X-ray transient
  88. LIGO/Virgo/KAGRA S240413p: X-ray upper limits from EP-WXT for the candidate AGN counterpart
  89. LIGO/Virgo/KAGRA S240413p: DECam GW-MMADS candidates
  90. GRB 240415A: Glowbug gamma-ray detection
  91. GRB 240414A: Glowbug gamma-ray detection
  92. LIGO/Virgo/KAGRA S240413p: STEP - T80S Search and Candidate Counterpart Identification
  93. EP 240416a: Xinglong and NOT decaying optical counterpart
  94. GRB 240411A: Glowbug gamma-ray detection
  95. EP240416a: Kinder optical counterpart candidate
  96. EP240416a: EP-WXT detection of a fast X-ray transient
  97. GRB 240414A: AbAO optical upprer limit
  98. GRB 240415A: Swift/UVOT Detection
  99. GRB 240414A: GAD Observatory, La Spezia, Italy ,upper limit
  100. GRB 240415A: Earliest optical followup with the Kinder observations

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