# Multiwavelength Observations of A0620-00 ††slugcomment: [current draft: May 23, 2017]

Abstract

[still needed]

black hole physics, stars: individual: A0620-00, X-rays: binaries

## \label{sect:intro}Introduction

[still needed]

This paper presents observations of the X-ray Binary A0620-00 taken simultaneously in X-rays with the Chandra Observatory, in radio with the Jansky VLA, and in optical and infrared with the SMARTS 1.3m telescope. Section \ref{sect:obs} describes our observations in detail, Section \ref{sect:sed} discusses the Spectral Energy Distribution for A0620-00, Section \ref{sect:correlation} discusses these results in the context of the radio/X-ray correlation for X-ray Binaries, and Section \ref{sect:concl} contains our conclusions.

## \label{sect:obs}Observations

### X-ray Observations

\label{sect:obs-xray}

We observed A0620-00 using the ACIS detector on board the Chandra X-ray Observatory [ADS/Sa.CXO#obs/14656 (catalog ObsId 14656)] on 2013 December 9, starting at 00:52 UT, for $$\sim$$30 ks. Standard level-2 data products were used, and were processed and calibrated with the most current version of the CIAO software (4.7, CALDB 4.6.5).

Since A0620-00 is known to vary over time, we wanted to determine whether this most recent X-ray observation differed significantly from previous ones. We therefore downloaded the two previous observations of this source from the Chandra Data Archive: ADS/Sa.CXO#obs/00095 (catalog ObsId 95) (2000 February 29), and ADS/Sa.CXO#obs/05479 (catalog ObsId 5479) (2005 August 20). These older observations were reprocessed using the same calibration information, software versions, tasks, and parameters as our most recent observation.

The high energy particle background is known to increase rapidly on the ACIS detectors below 0.3 keV and above 8 keV. We therefore restricted most analysis to the energy range $$0.3-8$$ keV to minimize this background. Background flares were removed from our observations by examining all data within the energy range $$0.3-10$$ keV, and removing time periods with count rates more than one sigma away from the mean. In this manner 0.25 ks were removed from ObsID 14656, leaving 29.4 ks for our analysis.

Total counts and count rates for A0620-00 were calculated using a circular aperture with radius 10 pixels. Background counts and rate were measured in an annulus centered on A0620-00 with inner radius 11 pix and outer radius 20 pix. The source had 434 total counts, 0.0148 ct